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Are there connections between the Earth's magnetic field and climate?
Abstract
Understanding climate change is an active topic of research. Much of the observed increase in global surface temperature over the past 150 years occurred prior to the 1940s and after the 1980s. The main causes invoked are solar variability, changes in atmospheric greenhouse gas content or sulfur due to natural or anthropogenic action, or internal variability of the coupled ocean–atmosphere system. Magnetism has seldom been invoked, and evidence for connections between climate and magnetic field variations have received little attention. We review evidence for correlations which could suggest such (causal or non-causal) connections at various time scales (recent secular variation ∼ 10–100 yr, historical and archeomagnetic change ∼ 100–5000 yr, and excursions and reversals ∼ 103–106 yr), and attempt to suggest mechanisms. Evidence for correlations, which invoke Milankovic forcing in the core, either directly or through changes in ice distribution and moments of inertia of the Earth, is still tenuous. Correlation between decadal changes in amplitude of geomagnetic variations of external origin, solar irradiance and global temperature is stronger. It suggests that solar irradiance could have been a major forcing function of climate until the mid-1980s, when “anomalous” warming becomes apparent. The most intriguing feature may be the recently proposed archeomagnetic jerks, i.e. fairly abrupt (∼ 100 yr long) geomagnetic field variations found at irregular intervals over the past few millennia, using the archeological record from Europe to the Middle East. These seem to correlate with significant climatic events in the eastern North Atlantic region. A proposed mechanism involves variations in the geometry of the geomagnetic field (f.i. tilt of the dipole to lower latitudes), resulting in enhanced cosmic-ray induced nucleation of clouds. No forcing factor, be it changes in CO2 concentration in the atmosphere or changes in cosmic ray flux modulated by solar activity and geomagnetism, or possibly other factors, can at present be neglected or shown to be the overwhelming single driver of climate change in past centuries. Intensive data acquisition is required to further probe indications that the Earth's and Sun's magnetic fields may have significant bearing on climate change at certain time scales.
... Dynamic climate changes recorded at sites worldwide are one of the characteristic features of the M/B transition (Cuenca-Bescós et al., 2011;Ferretti et al., 2015;Hyodo and Kitaba, 2015). These changes were coincident with changes in the intensity of the Earth's magnetic field and polarity reversals (Bassinot et al., 1994;Courtillot et al., 2007;Kitaba et al., 2012Kitaba et al., , 2017. Strong penetration of the atmosphere by cosmic rays and their potential influence on global climate can be expected due to the weakness of the geomagnetic field, e.g., during magnetic reversals, such as at the M/B transition (Railsbeck et al., 2006;Kitaba et al., 2017). ...
... Weakening of the Earth's magnetic field during the transition permits a galactic cosmic ray flux into the atmosphere and promotes more cloud formation (Svensmark and Friis-Christensen, 1997;Carslaw et al., 2002). This, in turn, increases albedo, reduces insolation and thus decreases Earth surface temperatures (Courtillot et al., 2007). The climate changes reconstructed by multiproxy analyses of the RP66 flowstone are not contradictory to this hypothesis. ...
A flowstone section in the Račiška pečina Cave (Classical Karst, SW Slovenia) records multiple chronostratigraphic and palaeoclimatic proxies that can be correlated with other records on the global scale (Mediterranean region, Japan). Its upper part has an excellent record of the Matuyama/Brunhes (M/B) magnetic reversal. The M/B reversal zone, which is 6 mm in thickness, was detected by a high-resolution palaeomagnetic analysis of the sequence. An age model based on oxygen isotopic stratigraphy locates this quick transition in mid-MIS 19, between 777.9 and 777.2 ka, with the midpoint at 777.7 ka. The transition is marked by abrupt changes in stable isotopic compositions, trace element concentrations and flowstone fabrics that point to temperature and precipitation changes. Two distinct maxima in trace element concentrations at the beginning and the end of the M/B transition indicate two periods of higher precipitation, with increased washes of clay minerals into the cave. In addition, the stable isotopic (δ13C and δ18O) compositions indicate that significant cooling and high precipitation occurred during the M/B reversal within the generally warm MIS 19.
... For this reason, in Sec-37 tion 4 we attempt to propose a more rigorous and consistent definition of climate, based 38 on stochastics. We illustrate the definition by real-world data, which also exemplify the 39 large variability of climate. Given this variability, the term climate change turns out to be 40 scientifically unjustified. ...
... 422 423 As evident in its definition, the climatic system is subject to external influences and 424 particularly those determining the solar radiation reaching the Earth, such as the solar 425 activity, the Earth's motion and the volcanic activity. Changes in the solar irradiance 426 (which is reflected in the sunspot number and is maximum and minimum when the 427 sunspot number is maximum and minimum, respectively), as well as in the solar and 428 terrestrial magnetic fields, are known to influence climate [39,40]. It has been suggested 429 that even the galactic cosmic ray flux may be a climate driver via solar wind modulation 430 [41,42]. ...
We revisit the notion of climate, along with its historical evolution, tracing the origin of the modern concerns about climate. The notion (and the scientific term) of climate has been established during the Greek antiquity in a geographical context and it acquired its statistical content (average weather) in modern times, after meteorological measurements had become common. Yet the modern definitions of climate are seriously affected by the wrong perception of the previous two centuries that climate should regularly be constant, unless an external agent acted. Therefore, we attempt to give a more rigorous definition of climate, consistent with the modern body of stochastics. We illustrate the definition by real-world data, which also exemplify the large climatic variability. Given this variability, the term “climate change” turns out to be scientifically unjustified. Specifically, it is a pleonasm as climate, like weather, has been ever-changing. Indeed, a historical investigation reveals that the aim in using that term is not scientific but political. Within the political aims, water issues have been greatly promoted by projecting future catastrophes while reversing the true roles and causality directions. For this reason, we provide arguments that water is the main element that drives climate and not the opposite.
... Condition 1 is obviously not met in the context of climatically modulated records of the geomagnetic field, because of the multiplicative term in Equation 2. Condition 2 holds in the case of sufficiently long geomagnetic records, if climatic variations are statistically uncorrelated to the Earth's magnetic field. Connections between climate and magnetic field variations, for example, through Milankovic orbital cycles, have been proposed, but evidence is tenuous and highly debated (Courtillot et al., 2007). A recent claim (Zhou et al., 2023) was based on the separation of paleomagnetic and climatic signals in 10 Be records from the Chinese Loess Plateau (Zhou et al., 2007). ...
Continuous reconstructions of past variations of the Earth's magnetic field are based mainly on paleomagnetic and cosmogenic ¹⁰Be records in marine sediments. In both cases, the recording mechanisms can be affected by environmental processes. Climatic overprints are only partially removed by normalization procedures, so that stacking is used to further remove site‐specific effects. Regionally or globally correlated artifacts, however, cannot be removed by stacking. Here we present a modified approach where geomagnetic records are complemented by environmental proxies representing processes that might affect the field recording mechanism. Geomagnetic and environmental records are jointly processed with principal component analysis to obtain a set of components supposed to represent true variations of the geomagnetic field and climatic overprints, respectively. After discussing the theoretical background of this new approach and its underlying assumptions, a practical example is presented, using a worst‐case scenario based on a single ¹⁰Be record from the North Atlantic with strong climatic overprints, covering the last 600 ka. The first two principal components, which represent the modulation of ¹⁰Be by global climatic variations and by the geomagnetic field, respectively, explain 66.3% of the signal variance. Comparison of the geomagnetic principal component with global relative paleointensity stacks shows that the original climatic overprint can be reduced by a factor of 2, outperforming a ¹⁰Be/⁹Be stack obtained from two sites with little glacial‐interglacial variability. The proposed method for removing climatic overprints can be applied to multiple sites more efficiently than conventional stacking.
... Increased GCRs flux leads to increased atmosphere ionization and the nucleation rates of nanoscale particles, which can influence cloud formation when these nano-aerosols grow into CCN size (Carslaw et al., 2002;Kirkby et al., 2016;Svensmark et al., 2016;Svensmark et al., 2017;Cooper et al., 2021). However, the EMF modulation of climate on geological time scales has not been demonstrated and has long been debated due to the uncertainty of the forcing mechanism between them (Courtillot et al., 2007;Kirkby, 2007;Kerton, 2009;Knudsen and Riisager, 2009). Resolving Holocene hydroclimatic variations in coastal southern China will provide valid insights into the potential links among the EMF, cloud cover, and climate variation. ...
The variations in precipitation have displayed a complex pattern in different regions since the mid-to-late-Holocene. Cloud formation processes may have a significant impact on precipitation, especially during the tropical marine processes and summer monsoon which convey abundant water vapor to coastal southern China and inland areas. Here, we use two 7500 year sedimentary records from the Pearl River Delta and the closed Maar Lake, respectively, in coastal southern China to reconstruct the mid-to-late-Holocene humidity variability and explore its possible relationship with cloud cover modulated by the Earth’s magnetic fields (EMF). Our proxy records document an apparent increase in wetness in coastal southern China between 3.0 and 1.8 kyr BP. This apparent increase in humidity appears to be consistent with the lower virtual axial dipole moments and, in turn, with a lower EMF. This correlation suggests that the EMF might have been superimposed on the weakened monsoon to regulate the mid-to-late-Holocene hydroclimate in coastal southern China through the medium of galactic cosmic rays, aerosols, and cloud cover. However, further investigations are needed to verify this interaction.
... The intensity of the ancient Earth's magnetic field (commonly called "paleointensity") is a crucial factor for understanding the geodynamo evolution (particularly during the early Earth's history) (Tarduno et al. 2015;Zhang et al. 2022), deep interior evolution (Bono et al. 2019;Zhou et al. 2022), and its links with surface climate, environment, and possibly other integral parts of the Earth's system (Courtillot et al. 2007; Knudsen and Riisager 2009;Lee and Kodama 2009;Kitaba et al. 2012Kitaba et al. , 2017Suter et al. 2014;Cooper et al. 2021). The absolute estimate of paleointensity (i.e., absolute paleointensity, API) can be used in the numerical dating of volcanic activities, archeological artefacts, and remains (Pérez-Rodríguez et al. 2019;Nitta et al. 2020;Genevey et al. 2021). ...
Despite being essential in determining absolute paleomagnetic field intensity (API) with high fidelity over Earth science research topics, API determination still suffers little quantitative success. This is due to common nonideal magnetic behaviors in experiments using natural rocks caused by physiochemical changes in the magnetic minerals contained. Although linking rock-magnetic parameters to API results may be fundamental, negligible effort has been made using the Tsunakawa–Shaw (TS) API method despite its potentially high experimental success rate in overcoming nonideal magnetic effects. Here, we explore the relationships between rock-magnetic parameters retrieved using relatively rapid and widely pre-conducted measurements and TS API results from late Cenozoic basaltic rocks. We selected rock-magnetic parameters quantified from strong-field high-temperature thermomagnetic curves, magnetic hysteresis loops, and back-field isothermal remanent magnetization demagnetizations. We provide new data pairs of rock-magnetic parameters and TS API results for 41 basaltic rock samples from 8 sites (cooling units) in Northeast China. Then, by compiling them with published data of similar quality, we compiled 133 pairs of rock-magnetic and TS API data at the sample level (38 sites). Using this data compilation, the following topics of interest were identified: Magnetic coercivity (B c ) and remanence coercivity (B cr ) among the hysteresis parameters, and the thermomagnetic parameter ITC |m| (an index of thermal change quantifying an average of the differences in saturation magnetization at a full temperature range of during a single heating–cooling run) allow meaningful and efficient discrimination between data subsets divided by “success” or “failure” in the API results. We propose sample preselection criteria for the TS experiment: a minimal set of B c ≥ 13 mT (or B cr ≥ 26 mT) and ITC |m| ≤ 0.15. Moreover, extended consideration based on the preselection criteria may allow the screening of potentially biased specimen/sample-level API estimates in the site-averaged determination of such a site with a large within-site API dispersion.
Graphical Abstract
... Also, the solar activity does not necessarily play only through the Total Solar Irradiancy 423 (TSI), but also its spectral distribution. Let us mention also the variations of the solar 424 magnetism (Courtillot, 2007), its shield effects towards cosmic radiation, impacting the 425 genesis of clouds (Svensmark, 2017(Svensmark, , 2021, the solar wind generated by solar flares 426 (Landscheidt 2000), etc. See Soon (2015) and Conolly (2021) for comprehensive reviews. 427 ...
Context. The anthropogenic principle, usually referred to as AGW (Anthropogenic Global Warming), is based on thousands of climate simulations that indicate that human activity is virtually solely responsible for the recent global warming. The climate models used are derived from the meteorological models used for short-term predictions. They are based on the fundamental and empirical physical laws that govern the myriad of atmospheric and oceanic cells integrated by the finite element technique. Numerical approximations, empiricism and the inherent chaos of fluid circulations make these models questionable for validating the anthropogenic principle, given the accuracy required (better than one per thousand) in determining the Earth energy balance.
Aims. The objective is to quantify and simulate behavioral models of weak complexity, without explicitly referring to the parameters of underlying physical laws, but relying exclusively on generally accepted historical and paleoclimate series.
Results. These models perform global temperature simulations that are consistent with those from the more complex physical models. However, the repartition of contributions in the current warming depends strongly on the retained temperature reconstructions, in particular the magnitudes of the Medieval Climate Anomaly and the Little Ice Age. It also depends on the level of solar activity series. It follows from these observations and climate reconstructions that the anthropogenic principle holds only for climate profiles assuming the absence of any significant Preindustrial Climate Oscillation (PCO) and variations in solar activity. Otherwise, it reduces to a weak principle where global warming is not only the result of human activity, but is largely due to solar activity.
... These perturbations affect solar activity, therefore sunspots [15], as well as the rotation axis [16], and therefore Earth's climate. This could explain the links between geomagnetism and climate (e.g., [20,21]). ...
The Earth’s revolution is modified by changes in inclination of its rotation axis. Its trajectory is not closed and the equinoxes drift. Changes in polar motion and revolution are coupled through the Liouville–Euler equations. Milanković (1920) argued that the shortest precession period of solstices is 20,700 years: the summer solstice in one hemisphere takes place alternately every 11,000 year at perihelion and at aphelion. Milanković assumed that the planetary distances to the Sun and the solar ephemerids are constant. There are now observations that allow one to drop these assumptions. We have submitted the time series for the Earth’s pole of rotation, global mean surface temperature and ephemeris to iterative Singular Spectrum Analysis. iSSA extracts from each a trend a 1 year and a 60 year component. Both the apparent drift of solstices of Earth around the Sun and the global mean temperature exhibit a strong 60 year oscillation. We monitor the precession of the Earth’s elliptical orbit using the positions of the solstices as a function of Sun–Earth distance. The “fixed dates” of solstices actually drift. Comparing the time evolution of the winter and summer solstices positions of the rotation pole and the first iSSA component (trend) of the temperature allows one to recognize some common features. A basic equation from Milankovic links the derivative of heat received at a given location on Earth to solar insolation, known functions of the location coordinates, solar declination and hour angle, with an inverse square dependence on the Sun–Earth distance. We have translated the drift of solstices as a function of distance to the Sun into the geometrical insolation theory of Milanković. Shifting the inverse square of the 60 year iSSA drift of solstices by 15 years with respect to the first derivative of the 60 year iSSA trend of temperature, that is exactly a quadrature in time, puts the two curves in quasi-exact superimposition. The probability of a chance coincidence appears very low. Correlation does not imply causality when there is no accompanying model. Here, Milankovic’s equation can be considered as a model that is widely accepted. This paper identifies a case of agreement between observations and a mathematical formulation, a case in which an element of global surface temperature could be caused by changes in the Earth’s rotation axis. It extends the range of Milankovic cycles and resulting global temperature variations to shorter periods (1–100 year range), with a major role for the 60-year oscillation).
... Numerous attempts have been made to find the connection between solar activity and terrestrial phenomena, depending on the means and stages of knowledge [1,[3][4][5][6][7][8][9][10] and resulting in some disputes [11][12][13]. Solar activity has been found to be correlated with climate during the 20th century; more precisely the geomagnetic trend, in general, correlates with the evolution of the global temperature, except in the last decade [14][15][16]. ...
The influence of solar/geomagnetic activity on climate variables still remains a fully unclarified problem, although many scientific efforts have been made to better understand it. In order to bring more information to this open problem, in the present study, we analyze the connection between solar/geomagnetic activity (predictors) and climate variables (predictands) by applying elements from information theory and wavelet transform analysis. The solar activity was highlighted by the Wolf number and geomagnetic activity was quantified by the aa index. For the climate variables, we considered seven Climate Indices (CIs) that influence atmospheric circulation on regional or global scales, such as the Greenland-Balkan Oscillation Index (GBOI), North Atlantic Oscillation Index (NAOI), Arctic Oscillation (AO), Atlantic Multidecadal Oscillation (AMO), Southern Oscillation Index (SOI), Bivariate ENSO Timeseries (BEST) and Trans-Niño Index (TNI). By using the difference between synergy and redundancy, a few cases were found where the two predictors can be considered together for CIs’ estimation. Coherence analysis through the wavelet transform for three variables, both through multiple and partial analysis, provides the time intervals and bands of periods, where the two considered predictors can be used together or separately. The results differ depending on the predictand, the season and the considered lags. Significant information is brought out by using the two predictors together, namely the summer season, for GBOI and NAOI, when the predictors were taken 2 years before, and the winter season, as AMO responds to the variations of both solar and geomagnetic activity after 4 years.
... Gosse & Phillips, 2001), although other studies indicated that the non-dipole field is also important for cosmogenic isotope production rate estimation (Nishiizumi et al., 1989;Dunai, 2000Dunai, , 2001. A growing number of studies argued that the high cosmic ray flux during excursions enhanced the cosmic radiation dose and the nucleation of clouds and may cause climatic and environmental changes (e.g., Carslaw et al., 2002;Courtillot et al., 2007;Cooper et al., 2021). High cosmic ray ionization may result in a high nucleation rate of sulfuric acid aerosols in the atmosphere, which could, in turn, act as cloud condensation nuclei (see review by Reid, 2000). ...
The geomagnetic field prevents energetic particles, such as galactic cosmic rays, from directly interacting with the Earth's atmosphere. The geomagnetic field is not static but constantly changing, and over the last 100,000 years several geomagnetic excursions occurred. During geomagnetic field excursions, the field strength is significantly decreased and the field morphology is strongly influenced by non-dipole components, and more cosmic ray particles can access the Earth's atmosphere. Paleomagnetic field models provide a global view of the long-term geomagnetic field evolution, however, with individual spatial and temporal resolution and uncertainties. Here, we reconstruct the geomagnetic shielding effect over the last 100,000 years by calculating the geomagnetic field cutoff rigidity using four global paleomagnetic field models, i.e., the GGF100k, GGFSS70, LSMOD.2, and CALS10k.2 model. We compare results for overlapping periods and find that the model selection is crucial to constrain the cutoff rigidity variation. However, all models indicate that the non-dipole components of the geomagnetic field are not negligible for estimating the long-term geomagnetic shielding effect. We provide a combined record of global cutoff rigidities using the best available model for individual time intervals. Our results provide the possibility to estimate the cosmogenic isotope production rate and cosmic radiation dose rate covering the last 100,000 years according to the best current knowledge about geomagnetic field evolution, and will be useful in further long-term solar activity and climate change reconstruction.
... These periods are already known to be characteristic of the space-time evolution of the Earth's rotation axis: the rotation pole (RP) also undergoes periodic motions longer than 1 year, at least up to the Gleissberg ∼90 yr cycle (Chandler 1891a,b;Markowitz 1968;Kirov et al. 2002;Lambeck 2005;Zotov et Bizouard 2012;Chao et al. 2014;Zotov et al. 2016;Lopes et al. 2017;Le Mouël et al. 2021;Lopes et al. , 2022a. They are encountered in solar physics (Gleissberg 1939;Jose 1965;Coles et al. 2019;Charvatova et Strestik 1991;Scafetta 2010;Le Mouël et al. 2017;Usoskin 2017;Scafetta 2020;Courtillot et al. 2021;Scafetta 2021) and terrestrial climate (Wood et al. 1974;Mörth et Schlamminger 1979;Mörner 1984;Schlesinger et Ramankutty 1994;Lau and Weng 1995;Courtillot et al. 2007Courtillot et al. , 2013Le Mouël et al. 2019a;Scafetta et al. 2020;Connolly et al. 2021). ...
This paper proposes a joint analysis of variations of global sea-level pressure and of Earth's rotation (RP), expressed as the coordinates of the rotation pole and length of day. Sea-Level-Pressure (SLP) extracted components are a weak trend, eleven quasi-periodic or periodic components (130, 90, 50, 22, 15, 4, 1.8 yr), an annual cycle and its first three harmonics. These periods are characteristic of the space-time evolution of the Earth's rotation axis and are present in many characteristic features of solar and terrestrial physics. We focus mainly on the annual and to a lesser extent semi-annual components. Maps of the first three components of SLP (that together comprise more than 85% of the data variance) reveal interesting symmetries. The trend is very stable and forms a triskel structure that can be modeled as Taylor-Couette flow of mode 3. The annual component is characterized by a large negative anomaly extending over Eurasia in the NH Summer (and the opposite in the NH Winter) and three large positive anomalies over Australia and the southern tips of South America and South Africa in the SH Spring (and the opposite in the SH Autumn) forming a triskel. The semi-annual component is characterized by three positive anomalies (an irregular triskel) in the NH Spring and Autumn (and the opposite in the NH Summer and Winter), and in the SH Spring and Autumn by a strong stable pattern consisting of three large negative anomalies forming a clear triskel within the 40-60 annulus formed by the southern oceans. A large positive anomaly centered over Antarctica, with its maximum displaced toward Australia, and a smaller one centered over Southern Africa complement the pattern.
... On the other hand, numerous researchers have tried to link the Geomagnetic Field (GF) and its oscillations with paleoclimatic changes (Courtillot et al. 2007;Kitaba et al. 2013Kitaba et al. , 2017Orgeira et al. 2016, among others), that is, they consider GF an additional forcing of the climate. This relationship has been defined as a process known as the "umbrella effect"; the hypothesis suggests that the decrease in the intensity of the GF allows a higher input of Galactic Cosmic Rays (GCRs) and consequently leads to cooling due to low cloud promotion. ...
A significant change in the Earth's climate occurred during the Pliocene-Pleistocene transition. Different external and internal forcings were interrelated in such a way that they promoted the cooling of the climate and environmental changes. We analyzed these changes using a mathematical and statistical approach based on a new algorithm combining Artificial Intelligence and the new multiple cross-wavelet analysis. Although the geomagnetic field (GF) paleointensity showed oscillations over time and not a uniform decay, the results of the Radial Basis Function Artificial Neural Networks showed a long periodicity oscillation with a downward trend practically throughout the Plio-Pleistocene transition. A weakened GF could have allowed an increase in the flux of galactic cosmic rays (GCR) penetrating the Earth's atmosphere. This led us to hypothesize that, during the Plio-Pleistocene transition, the increase in GCR could have induced a gradual increase in clouds and, therefore, the albedo intensified, causing a progressive decrease in the Earth's surface temperature, as recorded in different paleoclimatic reconstructions of the Plio-Pleistocene. In addition to the known variations in orbital parameters, the GF behavior (the Gauss-Matuyama reversal) and a feasible influence of a coetaneous near supernova event (at less than 100 pc), could have reinforced the climatic forcings towards glacial conditions during the Plio-Pleistocene transition (~ 2.5 Ma).
... Intriguing relations have also been found between the geomagnetic field and climate in the past at different temporal and spatial scales (e.g., Gallet et al. 2005;Courtillot et al. 2007;Usoskin et al. 2008). A recent work regarding this topic is linked with the evolution of the SAA over the last 300 years (Campuzano et al. 2018). ...
This paper reviews current knowledge about the Earth’s core and the overlying deep mantle in terms of structure, chemical and mineralogical compositions, physical properties, and dynamics, using information from seismology, geophysics, and geochemistry. High-pressure experimental techniques that can help to interpret and understand observations of these properties and compositions in the deep interior are summarized. The paper also examines the consequences of core flows on global observations such as variations in Earth’s rotation and orientation or variations in the Earth’s magnetic field. Processes currently active at the core-mantle boundary and the various coupling mechanisms between the core and the mantle are discussed, together with some evidence from magnetic field observations.
... However, even the very TSI is suspected [7,[25][26][27] to have risen much more steeply since the Little Ice Age than assumed in conservative estimations [28][29][30]. While neither of those mechanisms can presently be considered as conclusively proven [8,31,32], they all together entail significantly more potential for solar influence on the terrestrial climate than what is usually discussed [33]. Any resonance-like interaction of solar forcing with the intrinsic dynamics of the climate system (cf. ...
The paper aims to quantify solar and anthropogenic influences on climate change, and to make some tentative predictions for the next hundred years. By means of double regression, we evaluate linear combinations of the logarithm of the carbon dioxide concentration and the geomagnetic aa index as a proxy for solar activity. Thereby, we reproduce the sea surface temperature (HadSST) since the middle of the 19th century with an adjusted R2 value of around 87 percent for a climate sensitivity (of TCR type) in the range of 0.6 K until 1.6 K per doubling of CO2. The solution of the double regression is quite sensitive: when including data from the last decade, the simultaneous occurrence of a strong El Niño and of low aa values leads to a preponderance of solutions with relatively high climate sensitivities around 1.6 K. If these later data are excluded, the regression delivers a significantly higher weight of the aa index and, correspondingly, a lower climate sensitivity going down to 0.6 K. The plausibility of such low values is discussed in view of recent experimental and satellite-borne measurements. We argue that a further decade of data collection will be needed to allow for a reliable distinction between low and high sensitivity values. In the second part, which builds on recent ideas about a quasi-deterministic planetary synchronization of the solar dynamo, we make a first attempt to predict the aa index and the resulting temperature anomaly for various typical CO2 scenarios. Even for the highest climate sensitivities, and an unabated linear CO2 increase, we predict only a mild additional temperature rise of around 1 K until the end of the century, while for the lower values an imminent temperature drop in the near future, followed by a rather flat temperature curve, is prognosticated.
... Over the years, numerous studies have reported on the similarities between the timings and magnitudes of the peaks and troughs of various climate proxy records and equivalent solar proxy records [28,30,[37][38][39]54,55,80,182,186,189,209,262,[268][269][270][271][272][273][274][275][276][277]. Most climate proxy records are taken to be representative of regional climates, and so these studies are often criticised for only representing regionalised trends and/or that there may be reliability issues with the records in question [12,18,100,278] (see also Section 2.6.3). However, others note that similar relationships can be found at multiple sites around the world [30, 38,39,54,55,189,262,275,277]. ...
To evaluate the role of Total Solar Irradiance (TSI) on Northern Hemisphere (NH) surface air temperature trends it is important to have reliable estimates of both quantities. 16 different TSI estimates were compiled from the literature. 1/2 of these estimates are low variability and 1/2 are high variability. 5 largely-independent methods for estimating NH temperature trends were evaluated using: 1) only rural weather stations; 2) all available stations whether urban or rural (the standard approach); 3) only sea surface temperatures; 4) tree-ring temperature proxies; 5) glacier length temperature proxies. The standard estimates using urban as well as rural stations were anomalous as they implied a much greater warming in recent decades than the other estimates. This suggests urbanization bias might still be a problem in current global temperature datasets despite the conclusions of some earlier studies. Still, all 5 estimates confirm it is currently warmer than the late 19th century, i.e., there has been some global warming since 1850. For the 5 estimates of NH temperatures, the contribution from direct solar forcing for all 16 estimates of TSI was evaluated using simple linear least-squares fitting. The role of human activity in recent warming was then calculated by fitting the residuals to the UN IPCC's recommended anthropogenic forcings time series. For all 5 NH temperature series, different TSI estimates implied everything from recent global warming being mostly human-caused to it being mostly natural. It seems previous studies (including the most recent IPCC reports) that had prematurely concluded the former failed to adequately consider all the relevant estimates of TSI and/or to satisfactorily address the uncertainties still associated with NH temperature trend estimates. Several recommendations are provided on how future research could more satisfactorily resolve these issues.
... Over the years, numerous studies have reported on the similarities between the timings and magnitudes of the peaks and troughs of various climate proxy records and equivalent solar proxy records [28,30,[37][38][39]54,55,80,182,186,189,209,262,[268][269][270][271][272][273][274][275][276][277]. Most climate proxy records are taken to be representative of regional climates, and so these studies are often criticised for only representing regionalised trends and/or that there may be reliability issues with the records in question [12,18,100,278] (see also Section 2.6.3). However, others note that similar relationships can be found at multiple sites around the world [30, 38,39,54,55,189,262,275,277]. ...
In order to evaluate how much Total Solar Irradiance (TSI) has influenced Northern Hemisphere surface air temperature trends, it is important to have reliable estimates of both quantities. Sixteen different estimates of the changes in Total Solar Irradiance (TSI) since at least the 19th century were compiled from the literature. Half of these estimates are “low variability” and half are “high variability”. Meanwhile, five largely-independent methods for estimating Northern Hemisphere temperature trends were evaluated using: 1) only rural weather stations; 2) all available stations whether urban or rural (the standard approach); 3) only sea surface temperatures; 4) tree-ring widths as temperature proxies; 5) glacier length records as temperature proxies. The standard estimates which use urban as well as rural stations were somewhat anomalous as they implied a much greater warming in recent decades than the other estimates, suggesting that urbanization bias might still be a problem in current global temperature datasets - despite the conclusions of some earlier studies. Nonetheless, all five estimates confirm that it is currently warmer than the late 19th century, i.e., there has been some “global warming” since the 19th century. For each of the five estimates of Northern Hemisphere temperatures, the contribution from direct solar forcing for all sixteen estimates of TSI was evaluated using simple linear least-squares fitting. The role of human activity on recent warming was then calculated by fitting the residuals to the UN IPCC’s recommended “anthropogenic forcings” time series. For all five Northern Hemisphere temperature series, different TSI estimates suggest everything from no role for the Sun in recent decades (implying that recent global warming is mostly human-caused) to most of the recent global warming being due to changes in solar activity (that is, that recent global warming is mostly natural). It appears that previous studies (including the most recent IPCC reports) which had prematurely concluded the former, had done so because they failed to adequately consider all the relevant estimates of TSI and/or to satisfactorily address the uncertainties still associated with Northern Hemisphere temperature trend estimates. Therefore, several recommendations on how the scientific community can more satisfactorily resolve these issues are provided.
... As evident in its definition, the climatic system is subject to external influences (system inputs) and particularly those determining the solar radiation reaching the Earth, such as the solar activity, the Earth's motion and the volcanic activity. Changes in the solar irradiance (which is reflected in the sunspot number and is maximum and minimum when the sunspot number is maximum and minimum, respectively), as well as in the solar and terrestrial magnetic fields, are known to influence climate [39,40]. It has been suggested that even the galactic cosmic ray flux may be a climate driver via solar wind modulation [41,42]. ...
We revisit the notion of climate, along with its historical evolution, tracing the origin of the modern concerns about climate. The notion (and the scientific term) of climate was established during the Greek antiquity in a geographical context and it acquired its statistical content (average weather) in modern times after meteorological measurements had become common. Yet the modern definitions of climate are seriously affected by the wrong perception of the previous two centuries that climate should regularly be constant, unless an external agent acts upon it. Therefore, we attempt to give a more rigorous definition of climate, consistent with the modern body of stochastics. We illustrate the definition by real-world data, which also exemplify the large climatic variability. Given this variability, the term “climate change” turns out to be scientifically unjustified. Specifically, it is a pleonasm as climate, like weather, has been ever-changing. Indeed, a historical investigation reveals that the aim in using that term is not scientific but political. Within the political aims, water issues have been greatly promoted by projecting future catastrophes while reversing true roles and causality directions. For this reason, we provide arguments that water is the main element that drives climate, and not the opposite.
... In contrast, superchrons may be related to the relationship between the Earth's dynamo and the lower mantle (Glatzmaier et al., 1999;Larson & Olson, 1991;Olson et al., 2012) or they may be triggered by crustal/upper mantle events, such as the impingement of a subducted slab with the core-mantle boundary (Courtillot et al., 2007;Larson & Olson, 1991). If the long-term thermal effect of mantle convection on the core during the Cretaceous led to a gradual decrease of the reversal rate before the onset of the superchron, then its existence could be predicted (McFadden & McElhinny, 1984;McFadden & Merrill, 2000). ...
Constraining the long-term variability and average of the Earth’s magnetic field strength is fundamental to understanding the characteristics and behavior of the geomagnetic field. Questions remain about the strength of the average field, and the relationship between strength and reversal frequency, due to the dispersion of data from key time intervals. Here, we focus on the Cretaceous Normal Superchron (CNS; 121-84 Ma), during which there were no reversals. We present new intensity results from 41 submarine basaltic glass (SBG) sites collected on the Nicoya Peninsula and Murcièlago Islands,
Costa Rica. New and revised 40Ar/39Ar and biostratigraphic age constraints from previous studies indicate ages from 141 to 65 Ma. One site with an age of 135.1 ± 1.5 Ma (2σ) gave a reliable intensity result of 34 ± 8 μT (equivalent to a virtual axial dipole moment, VADM, value of 88 ± 20 ZAm2), three sites from 121 to 112 Ma, spanning the onset of the CNS, vary from 21 ± 1 to 34 ± 4 μT (53 ± 3 to 87 ± 10 ZAm2). These results from the CNS are all higher thanthe long-term average of ~42 ZAm2 and data from Suhongtu, Mongolia (46-53 ZAm2) and are similar to the Troodos Ophiolite, Cyprus (81 ZAm2,
reinterpreted in this study). Together with the reinterpreted data, the new Costa Rica results suggest that the strength of the geomagnetic field was approximately the same both before and after the onset of the CNS. Therefore, the data do not support a strict correlation between polarity interval length and the strength of the magnetic field.
... Torque exchange in the upper most atmosphere for the gas giants can qualitatively explain the high thermosphere temperatures of these planets which otherwise remains problematic to explain. For the Earth torque exchange between the atmosphere and magnetosphere might explain the observed and otherwise poorly understood correlation between magnetic variations and climate (Courtillot et al. 2007). The power generation from torque exchange in the Earth's upper atmosphere is capable of being partially balanced by thermospheric cooling (Mlynczak et al. 2016), however solar ux e ects likely dominate. ...
This work applies a previously suggested model of gravitational field propagation to various planetary bodies within the solar system. Primarily the goal has been to critically test the validity of this model by identifying observations which are in direct conflict with it. Specifically this model predicts a Doppler shift in gravitational acceleration (gD). Applying the model to the planets and the Sun gD acts to increase planetary spin, opposing various sources of drag. The model is seen not to be in conflict with a wide variety of observed parameters which have been treated here and is shown to quantitatively account for several observed phenomena previously thought to be unrelated and which have been di˚cult to explain conventionally. These phenomena include the internal heat generation and magnetospheric generation within the gas giants as well as super rotation which seen in most planetary atmospheres as well as the Sun as differential rotation. This model for the first time provides a quantitative prediction of the low internal heat generation seen in Uranus compared to Neptune. It also provides a novel mechanism for solar coronal heating, thermospheric heating in the gas giants and the correlation between climate and magnetosphere observed on Earth.
... Some researchers studied the possible connection of the geomagnetic field with cloud formation, precipitation, temperature, and climate [42][43][44]. Their achievements showed that the cosmic rays generate electrically charged particles when they hit the atmosphere. These particles absorb the water molecules from the air and cause them to clump together until they condense into clouds. ...
In this paper, the exerted electric and geomagnetic forces on the electrified hydrometeors in thunderclouds are compared. The parameters of geomagnetic field are acquired from International Geomagnetic Reference Field (IGRF) model. First, the calculations showed that the magnitude of the electric force exerted on a charged hydrometeor dominated the magnitude of the geomagnetic force in troposphere. These results revealed the significance of electric force in the formation of thunderclouds’ charge structure. Moreover, as the electric field increases in thunderstorm conditions, (regarding the dependence of the induction mechanism of cloud electrification to the intensity of the electric field), the increased electric field strengthens the induction mechanism of cloud electrification and influences the electrical properties of thunderstorm. Second, using satellite-based/ground-based data and reports, an inverse relation has been revealed between the total geomagnetic field and the mean annual lightning activity in most of the hot spots on the Earth. Moreover, a comparison between the global annual thunder days’ map and the map of global total geomagnetic field showed an inverse relation between these two maps. Furthermore, regarding the horizontal and vertical correlation coefficient matrices of the geomagnetic field and the global mean annual lightning activity (in the global tropics and subtropics), approximately in latitudes and longitudes with high lightning density, the reverse relation between the average annual lightning activity and the total geomagnetic field is stronger.
... But even the very TSI was claimed (Hoyt and Schatten, 1993;Scafetta and Willson, 2014;Egorova et al., 2018;Connolly et al., 2021) to have risen much more steeply since the Little Ice Age than assumed in the conservative estimations by Wang, Lean and Sheeley (2005); Steinhilber, Beer and Fröhlich (2009) ;Krivova, Vieira and Solanki (2010). While neither of those mechanism can presently be considered as conclusively proven (Solanki et al., 2002;Courtillot et al., 2007;Gray et al., 2010), they all together entail significantly more potential for solar influence on the terrestrial climate than what was discussed on the corresponding one and a half pages of Bindoff et al. (2013). ...
The two main drivers of climate change on sub-Milankovic time scales are re-assessed by means of a multiple regression analysis. Evaluating linear combinations of the logarithm of carbon dioxide concentration and the geomagnetic aa-index as a proxy for solar activity, we reproduce the sea surface temperature (HadSST) since the middle of the 19th century with an adjusted value of around 87 per cent for a climate sensitivity (of TCR type) in the range of 0.6 K until 1.6 K per doubling of CO. The solution of the regression is quite sensitive: when including data from the last decade, the simultaneous occurrence of a strong El Ni\~no on one side and low aa-values on the other side lead to a preponderance of solutions with relatively high climate sensitivities around 1.6 K. If those later data are excluded, the regression leads to a significantly higher weight of the aa-index and a correspondingly lower climate sensitivity going down to 0.6 K. The plausibility of such low values is discussed in view of recent experimental and satellite-borne measurements. We argue that a further decade of data collection will be needed to allow for a reliable distinction between low and high sensitivity values. Based on recent ideas about a quasi-deterministic planetary synchronization of the solar dynamo, we make a first attempt to predict the aa-index and the resulting temperature anomaly for various typical CO scenarios. Even for the highest climate sensitivities, and an unabated linear CO increase, we predict only a mild additional temperature rise of around 1 K until the end of the century, while for the lower values an imminent temperature drop in the near future, followed by a rather flat temperature curve, is prognosticated.
... Space Weather includes a lot of physical processes and parameters, starting from the Sun and ultimately affecting the Sun-Earth space as well as human activities on Earth. The sun emits energy, in the form of electromagnetic radiation and electrically charged energy particles through coronal mass ejections (CME) and plasma fluxes [1][2][3][4][5]. The Sun releases a continuous stream of charged particles made up of energized electrons and protons. ...
The continuous development of data acquisition and processing techniques in planetary geomagnetic observatories and satellite data, allows at this time to extract as complete information about the morphology and evolution over time of the terrestrial geomagnetic field. The Sun, the source of all energy on Earth, heat the planet and drive the motions of atmosphere. The brightness of the Sun with 11-years solar cycles with 0.1% variation may be explaining the major driving changes in weather patterns on Earth. At the same time, solar activity is the only cause of the Earth's external geomagnetic variations. In the paper we did a study on a period of four solar cycles, regarding the correlation mode of the solar activity, the geomagnetic variations recorded in the Surlari Geomagnetic Observatory and the climatic data available from external sources. The techniques used in this study use algorithms for spectral and wavelet analysis, phenomenological extrapolation and comparative analysis between parameters.The geomagnetic data used in this study are the hourly averages during 1962-2006, as well as the calculated indices regarding the geomagnetic activity corroborated with the climatic data. INTRODUCTION Space Weather includes a lot of physical processes and parameters, starting from the Sun and ultimately affecting the Sun-Earth space as well as human activities on Earth. The sun emits energy, in the form of electromagnetic radiation and electrically charged energy particles through coronal mass ejections (CME) and plasma fluxes [1-5]. The Sun releases a continuous stream of charged particles made up of energized electrons and protons. The particles travel outward like the solar wind, carrying parts of the Sun's magnetic field with them. Electromagnetic radiation travels at the speed of light and takes about 8 minutes to move from Sun to Earth, while charged particles travel slower, taking from several hours to several days to move from Sun to Earth. The solar wind speed is about few millions of km/hour near the Sun, decreasing along the way, when interacting with the Earth's magnetosphere. Radiation and particles interact with the geomagnetic field [6-8] and with the outer atmosphere in complex modes, determining the collection of energy particle concentrations and the flow of electric currents in the regions of the outer atmosphere (magnetosphere and ionosphere). These can result in geomagnetic, auroral variations and affect a number of infrastructures and technologies on Earth. Also, can affect climatic change on the Earth. As the solar wind gets close to our planet, it is deflected by the Earth's magnetic field. Three kinds of solar phenomena can have major impacts on Earth by disturbing our space environment. The first is a coronal mass ejection (CME), a large explosion that hurls superheated plasma (electrified gas) into interplanetary space. The second is coronal holes that release high-speed streams of plasma that boost the solar wind. The third is a solar flare, an intense burst of radiation coming from the release of magnetic energy. CMEs and coronal holes can trigger geomagnetic storms in our magnetosphere (the region surrounding a planet where its magnetic field dominates) [9-10]. VARIATIONS OF THE EARTH'S ELECTROMAGNETIC FIELD Knowing the structure of the magnetosphere is based on the abundant data provided by satellite and land observations. The complicated problems of the structure of the magnetosphere and the nature of the geomagnetic variations have been largely dealt with in many publications and many authors (. Also, crustal magnetism is in relation with magnetics properties of geological formations. Figures 1 and 2 show two representative schemes for the main source areas of the magnetosphere for different types of observed phenomena as well as the main components of the magnetosphere current systems.
... It is fundamental for constraining core-mantle dynamics, cosmogenic isotope production and solar activity and, in turn, is relevant to climate change, human history and life on Earth (Doglioni et al., 2016). Indeed, geomagnetic field variations can be correlated with climate change (e.g., Courtillot et al., 2007) in terms of total solar irradiance (TSI) and cosmogenic isotope ( 10 Be and 36 Cl) production, where 10 Be/ 9 Be ratios in sediments or 36 Cl and 10 Be flux in ice cores are correlated with (and are indications of) past minima of the intensity of the geomagnetic field (e.g. Muscheler et al., 2005;Simon et al., 2016). ...
In the last decades, palaeomagnetic research has provided us with a picture of the temporal and spatial behaviour of the Earth's magnetic field (EMF) from its origin up to the present day. Well-dated palaeomagnetic data offer important sources of information about the past variation of the geomagnetic field and have shown that it is characterized by temporal fluctuations such as reversals, excursions and spikes. Despite the advances in our understanding of EMF behaviour, the current dataset is biased towards high and northern latitudes and, therefore, several questions remain open to debate, such as the origin and evolution of the EMF and the frequency and spatial distribution of its variations. This Special Publication focuses on the study of the temporal and spatial evolution of the EMF in the past through new data from palaeomagnetic and rock magnetic studies of archaeological materials, sediments and lavas from Europe, Africa, Australia, New Zealand, India and Baltic Sea, and their applications in archaeology, stratigraphy and climate. This paper summarizes our current knowledge on geomagnetic field variations in the past, open questions and future challenges and gives an overview of the volume's context, which aims to disclose fundamental properties of the Earth's magnetic field evolution.
... The relationship between the paleoclimate and Earth's Magnetic field, however, is still matter of debate (Campuzano et al., 2018). As evidenced by Gallet et al. (2005) (see also Courtillot et al., 2007) these variations may be correlated to moderate to large scale climate changes. The cooling (warming) periods are apparently correlated to the intensity increase (decrease) and seem to be influenced by the geomagnetic field trough the modulation of cosmic ray flux interacting with the atmosphere (see also discussion in Goguitchaichvili et al., 2011). ...
... Some researchers studied the possible connection of the geomagnetic field with cloud formation, precipitation, temperature, and climate [42][43][44]. Their achievements showed that the cosmic rays generate electrically charged particles when they hit the atmosphere. These particles absorb the water molecules from the air and cause them to clump together until they condense into clouds. ...
... Fluctuations of the Earth's Magnetic Field elements are of great interest in geophysics and almost unique source to elucidate the coremantle conditions of our planet. Geomagnetic secular variation over the last millennia's may be potentially connected to the long-term climate changes (Courtillot et al., 2007) and collapse of ancestral cultures (Haug et al., 2003, see also Glabmeier et al., 2009). Recently, some relationship between the health issues of human populations and fine fluctuations of the geomagnetic field are also matter of debate (Palmer et al., 2006). ...
Historical documents, archives and old photographic collections allowed to analyze 877 direct geomagnetic measurement data obtained by sailors (including pirates), United States Coast and Geodetic Survey and National Astronomical Observatory since 1587. The updated catalogue includes 844 values of magnetic declination, 495 of inclination, 467 of the horizontal intensity component (H) and 455 of the vertical intensity component (Z). All data were relocated to Mexico City through the pole conversion method in order to build a reference secular variation curve for Mexico and surrounding area using bootstrap method to mitigate the effect of outliers and estimate the probability of density functions. The directional variation patterns obtained in this investigation were compared to the curves retrieved from Sha.Dif.14k, GUFM1and IGRF-12 models while VADM fluctuations were confronted to similar quality determinations from other localities worldwide as well as archaeomagnetic curves from Mesoamerica.
... The history of Earth can be investigated by seeking its magnetic field evolution, which is associated with the evolution of its deep interior (Gubbins and Richards 1986;Gubbins 1988;Glatzmaier et al. 1999;Roberts and Glatzmaier 2000;Costin and Buffett 2004;Biggin et al. 2015;Tarduno et al. 2015) but may also interact with other integral parts of the Earth system on variable geological time scales (Courtillot et al. 2007;Tarduno et al. 2007; Lee and Kodama 2009;Tarduno et al. 2010;Kitaba et al. 2012Kitaba et al. , 2017. For a complete picture of the geomagnetic field over time, it is clearly useful to acquire directions and intensities of the surface paleomagnetic field from geological materials (paleomagnetic full-vector data). ...
Abstract Finding the statistical intensity signatures of the Earth’s magnetic field over geologic time has helped understanding of the evolution of the Earth’s interior and its interactions with other integral parts of Earth systems. However, this has been often hampered by a paucity of absolute paleointensity (API) data, which are difficult to obtain primarily because of non-ideal magnetic behaviors of natural materials. Here, we present new API determination data with paleodirectional and rock magnetic analyses from basaltic rocks probably aged ~ 4‒5 Ma in Baengnyeong Island, Korea. Paleodirectional analysis obtained an overall mean direction of D = 347.3° and I = 38.3° (α 95 = 4.9°, k = 113.4) corresponding to a virtual geomagnetic pole at 342.1° E and 70.2° N. Comprehensive rock magnetic analyses identified Ti-poor titanomagnetite with, in part, multi-domain (MD) particles as a main carrier of remanent magnetization. The Tsunakawa–Shaw (TS) method yielded 12 qualified API estimates with a high success rate, efficiently removing possible MD influences, and resulted in a mean value of 13.1 μT with good precision (1.7 μT, standard deviation). The Thellier method of the IZZI protocol with pTRM checks, coupled with the use of a bootstrap approach instead of the “conventional best-fitting” in API determination, gave 6.6‒19.7 μT as a 95% confidence interval of its mean API estimate, which supports the reliability of our TS-derived API mean estimate; but it is not considered in the final mean value because of the relatively large uncertainty. The virtual dipole moment corresponding to the TS-derived API mean, 2.9 (± 0.4) × 1022 Am2, is somewhat lower than the expectations of the past few Myr averages. Combined with a global API database, our new data implies a larger dispersion in the dipole moment during the early Pliocene than previously inferred. This also suggests that the issue of whether the early Pliocene average dipole strength was moderately high (> 5 × 1022 Am2) or consistent (4‒5 × 1022 Am2) should be discussed further.
... For many decades, astronomers and meteorologists have looked for clues to a causal connection between solar activity and climate (Centre National d'Etudes Spatiales, 1980;Roberts and Olson, 1973;Pecker and Runcorn, 1990;Stauning, 2011). Links between climate and geomagnetism have also been sought (Abrahamsen, 1986;Courtillot et al., 2007;Doake, 1977;Flohn, 1974;Gnevyshev and Ol, 1971). ...
Liritzis, I.; Westra, A., and Miao, C., 2019. Disaster geoarchaeology and natural cataclysms in world cultural evolution: An overview. Journal of Coastal Research, 35(6), 1307–1330. Coconut Creek (Florida), ISSN 0749-0208.
Human records of short-term, catastrophic, geological processes, mainly in coastal or fluvial environments, and related phenomena in historic and prehistoric times have to be considered as functions of event intensities and impacts (and damages) caused on ancient human settlements and lives. Catastrophic events, such as, floods, earthquakes, volcanic eruptions, tsunamis, and the collapse of ancient cultures, in particular, those allied to the birth of myths and legends, are the subject of long-lasting, vivid debate. Longer-term, more-or-less consecutive, geological processes and climatic fluctuations have a more pronounced effect on human history. Historical accounts provide many descriptions about cultural evolution in a recurrent manner. The geoarchives (geology, sedimentology, and geomorphology) and the human record (archaeology and history) are considered documentary evidence of these past events. Astronomical causes have introduced severe phenomena (warming, heavy precipitation, monsoons, droughts) imposed on ancient societies, including catastrophic meteor impact. Terrestrial upheavals and astronomical impacts have introduced a nonlinear character of a quasiperiodic nature in transforming human cultural evolution and reshaping the earth's surface. The transient nature of geological, geophysical, and proxy climatic indices, as well as, astronomical phenomena within the solar system, exhibit a wide spectrum of quasiperiodic frequencies as variable and effective environmental factors, which, in addition to anthropogenic factors, reshape the human context. Several conspicuous examples have been reported on mythological deluges and their relation to natural catastrophes. The Anthropocene sea level rise and climatic episodes have had a decisive and prominent role on coastlines and human settlements. Alluvial sediments, sedimentary deposits, and land modifications have drastic effects on settlements. These effects were memorized as floods, deluges, and fallen sky. World examples of disasters derived from the coastal Mediterranean, the Great Flood of Gun-Yu in China, and those from South America, Mesopotamia, and the Middle East and others, were critically assessed with scientific methods.
... The WM intensification interval correlates with the cooling event in Osaka Bay 6,37 , ascribable to the major decrease in the earth's magnetic dipole field to <25% of the present strength from 783 to 776 ka ( Fig. 4i) 38 , from which large increases in GCR flux, by 50-80%, can be estimated (Fig. 4j) 39 . The increased GCR flux would have induced an increase in low-cloud cover [6][7][8] , possibly resulting in intensification of the WM through an umbrella effect. ...
The strength of Earth’s magnetic dipole field controls galactic cosmic ray (GCR) flux, and GCR-induced cloud formation can affect climate. Here, we provide the first evidence of the GCR-induced cloud effect on the East-Asian monsoon during the last geomagnetic reversal transition. Bicentennial-resolution monsoon records from the Chinese Loess Plateau revealed that the summer monsoon (SM) was affected by millennial-scale climate events that occurred before and after the reversal, and that the winter monsoon (WM) intensified independently of SM variations; dust accumulation rates increased, coinciding with a cooling event in Osaka Bay. The WM intensification event lasted about 5000 years across an SM peak, during which the Earth’s magnetic dipole field weakened to <25% of its present strength and the GCR flux increased by more than 50%. Thus, the WM intensification likely resulted from the increased land–ocean temperature gradient originating with the strong Siberian High that resulted from the umbrella effect of increased low-cloud cover through an increase in GCR flux.
... The monotonic decrease of absolute geomagnetic intensity for relatively recent periods seems to be a most common feature for all these curves obtained at very different locations. Courtillot et al. (2007) suggested that the fluctuations of absolute geomagnetic field strength may be correlated with climate changes over multi-decadal time scales. The cooling (warming) episodes are synchronous with the intensity increase (decrease) and seem to be influenced by the geomagnetic field through the modulation of the cosmic ray flux First archaeointensity reference paleosecular variation curve for South America 9 ...
We report comprehensive rock-magnetic and archaeointensity investigations from 21 well-constrained pottery fragments from the Catamarca province of northwest Argentina. The absolute ages of the studied sites are ascertained by several high-quality radiometric ages and range between 1940 to 1140 ¹⁴ C yr BP. Magnetic mineralogy experiments indicates that the remanence is carried by thermally stable Ti-poor titanomagnetites. Forty-seven samples belonging to 11 out of 98 studied potsherds yielded reliable absolute intensity determinations judging from the quality parameters associated with the Thellier double-heating experiments. Moreover, we analyzed the available absolute geomagnetic intensities associated with the radiometric ages to construct the first intensity paleosecular variation curve (PSVC) for South America using thermoremanent magnetization carried by burned archaeological artifacts obtained in the present investigation and 79 other selected archaeointensities (out of 213 published in the literature). The dataset is used to build the PSVC reference curve by combined bootstrap and temporal P-spline methods. The variation curve shows significant differences with the global prediction model SHA.DIF.14k mainly based on the GEOMAGIA database. This intensity PSVC curve shows reasonably good agreement with paleosecular variation curves for Europe between 850 through 1150 BC and for Asia between 1000 and 1500 BC. This regional curve may be used as most reliable archaeomagnetic dating tool for the major part of South America (Peru, Brazil, Argentina, Chile, and Bolivia) for the last two millennia.
... The authors Zhang, G. Q., Dorman, L. I. and Gerontidou [1,7,8] found that internal effects such as subsidence, volcanic and tectonic effects are not the only reason of earthquake but also earthquakes can be triggered by some external effects such as cosmic rays, magnetic field and solar activity. The team led by Courtillot, V. [9] explained that the radiations emitted from the Sun not only have very serious effects on the Earth's atmosphere, but also affect the Earth's surface. Low level clouds, ocean temperatures, land temperatures, tropospheric temperatures, and earthquakes are shown as evidences. ...
The relations between sunspot number, sunspot areas, and solar 10.7 cm radio flux, solar proton events and earthquakes of magnitude M ≥ 5 and M ≥ 8 during the interval from 1996 to 2008 of the solar cycle 23 have been analyzed in this work. We have found that there is a direct relation between solar activity and Earth seismic activity for M ≥ 5 and M ≥ 8, near the maximum of the solar cycle 23, and an inverse relation between them at the descending phase of the cycle.
The hypothesis that the position of the magnetic North Pole (Dip Pole) (latitude) ought to be very highly correlated with global temperature change on Earth has been tested and shown to be correct. The probability of such a correlation happening by chance is close to zero. Moreover, this has likely been the dominant climate driver for the last 2000 years. A Granger causality test shows Pole Shift drives temperature the latter having up to a two-year lag (Figure1). Two new climate models with and without CO₂ are developed and tested. Both models successfully predict modern warming, the Medieval Warm Period (MWP), and the Roman Warm Period (RWP) in time (figures 3+4). The model excluding CO₂ (figure 4) predicts past warming with stronger amplitude. This model also predicts the Little Ice Age ( LIA) with a seamless transition into the Modern Warm Period using the real data sets (figure 5). As Pole swings Northwards, interacting region shifts to higher ionospheric altitudes and combined particle precipitation changes (EEP) reduce albedo, hence increase forcing (figure 2) by virtue of their changes to the world’s clouds, provide calculated values in the region of 81% of recent warming, with the rest (15%) mainly of solar origin. CO₂ at most could contribute 3.9% of all warming. The detail disclosed above represents a profound and crucial discovery for climate science and its future direction. We need no longer try to mitigate so much for CO2, but we will desperately have to understand our geomagnetic climate and possibly how anthropogenic factors such as ELF radio transmitters and power systems and aviation aerosol may also change EEP. Preliminary investigations indicate that because South dip-pole is not antipodal and moves at different rates and in different directions this accounts for different rates of Antarctic warming and Southern Hemisphere Cloud behaviour also.
Magnetic anomaly pole transformation converts magnetic field data into an equivalent response at the true magnetic pole, eliminating shifts and distortions, simplifying the interpretation of subsurface magnetic bodies, and improving data interpretation and inversion accuracy. However, the main challenge in magnetic anomaly pole transformation lies in the non-linear nature of the signals, making traditional methods difficult to apply. The interaction between the shape, depth, and magnetic inclination of magnetic bodies, especially in high and low latitude regions, can cause distortion in the transformed signal, leading to unclear causal relationships. To address this, this paper proposes a deep learning-based approach that automatically extracts high-dimensional features and establishes nonlinear mappings to enhance the correlation between magnetic anomaly signals and geological structures. Deep learning does not require explicit physical models and, through training with large datasets, demonstrates stronger robustness and accuracy, especially in areas where traditional methods fail. The proposed method is validated using both synthetic and measured data. Synthetic data simulates magnetic bodies of various shapes, depths, and magnetic inclinations, confirming the method’s stability and accuracy in handling complex non-linear signals. The measured data evaluates its pole transformation advantages in typical ore deposit regions. The results indicate that the deep learning model significantly enhances the accuracy of pole transformation, particularly in areas with complex magnetic anomaly signals, effectively preventing signal distortion and demonstrating exceptional generalization capabilities.
The Milankovitch theory states that the orbital eccentricity, precession, and obliquity of the Earth influence our climate by modulating the summer insolation at high latitudes in the northern hemisphere. Despite considerable success of this theory in explaining climate change over the Pleistocene epoch (2.6 to 0.01 Myr ago), it is inconclusive with regard to which combination of orbital elements paced the 100 kyr glacial-interglacial cycles over the late Pleistocene. Here we explore the role of the orbital elements in pacing the Pleistocene deglaciations by modeling ice-volume variations in a Bayesian approach. When comparing models, this approach takes into account the uncertainties in the data as well as the different degrees of model complexity. We find that the Earth's obliquity (axial tilt) plays a dominant role in pacing the glacial cycles over the whole Pleistocene, while precession only becomes important in pacing major deglaciations after the transition of the dominant period from 41 kyr to 100 kyr (the mid-Pleistocene transition). We also find that geomagnetic field and orbital inclination variations are unlikely to have paced the Pleistocene deglaciations. We estimate that the mid-Pleistocene transition took place over a 220 kyr interval centered on a time 715 kyr ago, although the data permit a range of 600--1000 kyr. This transition, occurring within just two 100\,kyr cycles, indicates a relatively rapid change in the climate response to insolation.
Variations in daily mean solar irradiance at the top of atmosphere (SITOA) caused by the revolution of the Earth around the Sun were studied by analysing two 24-year datasets. The first one was provided by the NASA/GEWEX Surface Radiation Budget Release-3.0 data and the second was evaluated through the model proposed by Laskar and co-authors. It was found that the first two pairs of empirical orthogonal functions and corresponding principal components (PC) account for more than 99.9% of the spatio-temporal variance in SITOA. A quite good consistency among the analysed parameters extracted from considered datasets was noted. Six harmonics with periods from 2 months to 1 year and large differences among their magnitudes were recognised in PC1 and PC2 periodograms. PC1 turned out to be dominated by the annual oscillations, while the semi-annual variations play a prevailing role in PC2. In addition, a close similarity between the periodograms of PC2 and variations in the length of apparent solar day was noted, that assumes a common origin of both variability patterns. The lowest annual amplitude of SITOA variations was found to be slightly above the equator, at 2∘44′N and the amplitude at southern latitudes exceeds the amplitude at the corresponding northern latitudes by 20–40% in the tropical zone and by about 10% for the rest of the globe.
Whether there are links between geomagnetic field and Earth's orbital parameters remains unclear. Synchronous reconstructions of parallel long-term quantitative geomagnetic field and climate change records are rare. Here, we present 10Be-derived changes of both geomagnetic field and Asian monsoon (AM) rainfall over the last 870 kyr from the Xifeng loess-paleosol sequence on the central Chinese Loess Plateau. The 10BeGM flux (a proxy for geomagnetic field-induced 10Be production rate) reveals 13 consecutive geomagnetic excursions in the Brunhes chron, which are synchronized with the global records, providing key time markers for Chinese loess-paleosol sequences. The 10Be-derived rainfall exhibits distinct ~100 kyr glacial-interglacial cycles, and superimposed precessional (~23 kyr) cycles that match with those in Chinese speleothem δ18O record. We find that changes in the geomagnetic field and AM rainfall share a common ~100 kyr cyclicity, implying a likely eccentricity modulation of both the geomagnetic field and climate.
Благодарности.
Выражаю глубокую признательность своему научному руководителю А.А. Костерову, без которого эта работа бы не состоялась. Большое спасибо моим коллегам по Палеомагнитной лаборатории ГИН РАН и ее заведующему В.Ю. Водовозову за поддержку в трудные времена. Большое спасибо И. Галле, А. Женевей и М. Ле Гоффу, которые предоставили автору возможность провести исследования в Парижском институте физики Земли и оказали огромную помощь в интерпретации и обсуждении результатов, полученных с помощью протокола Триакс.
Большое спасибо коллективу лабораторий 105 и 106 ИФЗ РАН за дружественную творческую атмосферу и обсуждение проблем палео- и археомагнетизма, зам. директору ИФЗ РАН В.В. Погорелову за всестороннюю помощь и поддержку, П.А. Минаеву за помощь в совместных полевых работах. Спасибо Г.П. Маркову за внесение правок стилистического характера. Большое спасибо В.П. Щербакову, В.В. Щербаковой и Г.В. Жидкову за всегда теплый прием в ГО «Борок» и отдельное спасибо А.Н. Сычеву и М.А. Смирнову за создание аппаратурного комплекса «Орион». Выражаю особую благодарность И.В. Антипову (СПбГУ) и Д.Д. Елшину (музей Эрмитаж) за помощь в отборе образцов и предоставление археомагнитных коллекций.
Большое спасибо моим коллегам и учителям из ВНИГРИ и СанктПетербургского Государственного университета А.Г. Иосифиди, В.В. Попову, Е.С. Сергиенко, С.В. Шипунову, В.А. Михайловой и А.Н. Храмову, которые ввели меня в удивительный мир палеомагнетизма и научили меня правильно относится к получаемым результатам. Спасибо моей семье и близким!
This paper proposes a joint analysis of variations of global sea-level pressure (SLP) and of Earth’s rotation (RP), expressed as the coordinates of the rotation pole (m1, m2) and length of day (lod). We retain iterative singular spectrum analysis (iSSA) as the main tool to extract the trend, periods, and quasi periods in the data time series. SLP components are a weak trend, seven quasi-periodic or periodic components (∼130, 90, 50, 22, 15, 4, 1.8 years), an annual cycle, and its first three harmonics. These periods are characteristic of the space-time evolution of the Earth’s rotation axis and are present in many characteristic features of solar and terrestrial physics. The amplitudes of the annual SLP component and its three first harmonics decrease from 93 hPa for the annual to 21 hPa for the third harmonic. In contrast, the components with pseudo-periods longer than a year range between 0.2 and 0.5 hPa. We focus mainly on the annual and, to a lesser extent, the semi-annual components. The annual RP and SLP components have a phase lag of 152 days (half the Euler period). Maps of the first three components of SLP (that together comprise 85% of the data variance) reveal interesting symmetries. The trend is very stable and forms a triskeles structure that can be modeled as Taylor–Couette flow of mode 3. The annual component is characterized by a large negative anomaly extending over Eurasia in the NH summer (and the opposite in the NH winter) and three large positive anomalies over Australia and the southern tips of South America and South Africa in the SH spring (and the opposite in the SH autumn), forming a triskeles. The semi-annual component is characterized by three positive anomalies (an irregular triskeles) in the NH spring and autumn (and the opposite in the NH summer and winter), and in the SH spring and autumn by a strong stable pattern consisting of three large negative anomalies forming a clear triskeles within the 40–60∘ annulus formed by the southern oceans. A large positive anomaly centered over Antarctica, with its maximum displaced toward Australia, and a smaller one centered over Southern Africa, complement the pattern. Analysis of iSSA components of global sea level pressure shows a rather simple spatial distribution with the principal forcing factor being changes in parameters of the Earth’s rotation pole and velocity. The flow can probably best be modeled as a set of coaxial cylinders arranged in groups of three (triskeles) or four and controlled by Earth topography and continent/ocean boundaries. Flow patterns suggested by maps of the three main iSSA components of SLP (trend, annual, and semi-annual) are suggestive of Taylor–Couette flow. The envelopes of the annual components of SLP and RP are offset by four decades, and there are indications that causality is present in that changes in Earth rotation axis lead force pressure variations.
Relationships between geomagnetic field (GF) variations, paleoclimates, and Milankovitch cycles have increasingly attracted the attention of researchers mainly because of the assumption that GF may have acted as a climate forcing, suggesting that GF variations and orbital forcing may be linked in a complex synergistic way, especially, during interglacials and interstadials. We first performed an exhaustive analysis of the relationship between GF, a paleotemperature proxy, astroclimatic parameters, and the summer solstice mean daily insolation at 65 N over the last 500 kyr. We evaluated the relationship between the variables at the orbital scale, using wavelets, cross wavelets, and multiple cross wavelets. Our novel approach to the subject is the use of a new multiple cross wavelet algorithm, which allowed us to simultaneously analyze several data series and determine the relative phases between the signals. We confirm that the eccentricity modulates the GF behavior, and that the precession could have been related to some short-term GF variations. Both orbital parameters seem to be precursors of GF changes. Also, it is especially interesting to investigate the role of the GF reversion events because they could have acted as an indirect climate forcing, and we focused on the relationship among forcings during Marine Isotope Stage (MIS) 5. During this period, two GF reversions (Blake and post-Blake) could have been associated with relative climate cooling. The consequent lack or weakening of shielding associated with GF events and downward insolation, both influenced by orbital forcing, could finally have promoted a relative global climate cooling during MIS 5.
The direction and strength of geomagnetic field had been evolving continuously in the past. One of the few means of obtaining continuous reconstructions of this evolution relies on sedimentary records. The latter are therefore important for understanding the geodynamo and the underlying evolution of the Earth’s interior, as well as providing an important dating tool through magnetostratigraphy. Sedimentary records of geomagnetic field variations rely on two main recording mechanisms: the alignment of magnetic particles, which underlies continuous records of relative paleointensity (RPI), and the archivation of cosmogenic isotopes, in particular ¹⁰Be, whose production by cosmic ray spallation is modulated by the screening action of the dipole component of the Earth’s field. Previous studies reported similarities as well as significant differences between RPI and cosmogenic ¹⁰Be (expressed as ¹⁰Be/⁹Be) records. While a perfect match of the two records is not expected due to environmental contaminations present in both records, the similar changes during the periods characterised by significant decrease of the dipole moment are suggested owning to global field strength control of ¹⁰Be production and attenuation of non-dipolar features in RPI records measured within the sediments with the low sedimentation rates (<10 cm/ka). The aim of the present work was to improve our present knowledge on the field recording mechanisms of marine sediments, in particular: The environmental factors responsible for ¹⁰Be transport and removal from the water column, and the effect of source distributions on ⁹Be supply. The effect of post-depositional processes, in particular sediment mixing, on ¹⁰Be and RPI records. The mechanism by which a post-depositional magnetization is acquired near the bottom of the surface mixed layer. The causes of a systematic lag between ¹⁰Be and RPI records, and the environmental factors affecting RPI. In order to disentangle the environmental and magnetic contribution in sedimentary ¹⁰Be/9Be records, we analysed five records, covering the last geomagnetic reversal. Different recording characteristics at the five sites have been described in terms of additive and multiplicative climatic modulations, which depend essentially on water depth, location along large oceanic current systems, and distance to the coast. Simple criteria have been derived for the identification of most suited sites yielding minimal environmental contaminations. A new bioturbation model has been developed to explain sedimentary NRM in bioturbated sediment. This model includes a newly discovered phenomenon of size segregation in the surface mixed layer (SML), analogous to the well-known Brazil nut effect. Size segregation is responsible for the longer permanence of larger particles in the SML, up to the limit case of ferromanganese nodules and has important implications for sediment dating with benthic foraminifera. Calibration of the bioturbation model with microtektite profiles from two Indian Ocean cores enabled to reproduce the correct degree of delay between ¹⁰Be and RPI records, as well the environmental dependence of RPI in two cores from the North Atlantic and the Equatorial Pacific Oceans. The results obtained in this work can aid in developing integrated approaches for the correction of climatic contaminations in ¹⁰Be and RPI records. Furthermore, the predictive power of the bioturbation-based model for NRM acquisition can be used to design new laboratory experiments for the simulation of specific magnetic recording mechanisms. We have demonstrated the Brazilian-nut effect on the microtektite particles, that consists in size-dependent fragments segregation. The results of this research have significant importance not only for the sediment mixing response characterisation and reconstruction of affected by bioturbation processes records (e.g. ¹⁰Be /⁹Be),..
The present studies of temporal synchronization between geomagnetic and climatic time series are highly controversial. Some research reports a climate cooling in periods of geomagnetic strengthening. Other studies state the opposite: that geomagnetic field weakening and/or magnetic poles reversals are accompanied by climate cooling. Such a controversy is not supportive of the idea of any relation between geomagnetic field and climate variability. This chapter therefore shows contemporary evidence for existing coherence between geomagnetic field variations and some climate variables during the period 1900–2010. Statistical analyses reveal that the strength of geomagnetic–climate relation is unevenly distributed over the globe, with well-pronounced hemispherical asymmetry. Comparative analysis of geomagnetic and galactic cosmic rays (GCRs) intensity with climatic variables implies that the mediator of geomagnetic influence on climate is the intensity of GCRs and the depth of their penetration in Earth's atmosphere.
This chapter provides an overview of the factors having potential for influence on Earth's climate system. As with any dissipative system, the climate system crucially depends on the received energy—i.e. on solar electromagnetic radiation. Consequently, any attempt to explain the complexity of climate variability solely by the chaotic variations of its components illustrates the lack of knowledge about driving factors of climate variability. Considering that the substantial deviations of climate system from its equilibrium are due to external factors, the chapter provides a critical analysis of the existing hypothesis, offering an explanation of the external influence on climate. It is shown that none of the existing mechanisms is able to clarify the sophisticated temporal and spatial variability of Earth's climate. In addition, it is pointed out that regional specificity of climate variability is the main challenge for all current hypotheses.
The existing controversy regarding the climatic response to given changes in the geomagnetic field intensity (e.g. climate cooling or warming in periods of geomagnetic field strengthening) raises scepticism about the existence of any relationship between both variables. The main shortcomings of the recent understanding of the geomagnetic field–climate relationship are the expectations for: (i) its universal character over the globe; and (ii) the zonal homogeneity of this relationship. This paper offers a new conceptual framework aimed at resolving the existing controversy and explaining the mechanism for the appearance of geomagnetic footprints on climatic records.
We show that particles trapped in the Earth's radiation belts are subject to geomagnetic lensing in the parts of their trajectories closest to the surface, being focused or defocused at different regions over the world. The irregularly distributed ionization, created in such a way near the tropopause, activates various ion–molecular reactionships which affect the atmospheric composition there. Thus, the regional changes in the ozone and water vapour are furthermore projected onto the surface temperature and pressure. Consequently, the geomagnetic field–climate relationship is not a rigid but, rather, a flexible one because it is mediated by the near-tropopause ionization, ozone and humidity, with each of them being subject to the other's influence.
Este artigo constitui esforço teórico sobre o tema relacionado ao aumento do Nível Médio do Mar e seus impactos nos sistemas ambientais naturais e antrópicos nas zonas costeiras, tema que está presente tanto no meio acadêmico, quanto fora dele, como uma reflexão cotidiana da sociedade contemporânea. Tal desafio empreendeu a construção de uma base teórica estruturada nos conceitos de Mudanças Climáticas, Zona Costeira, Nível Médio do Mar, Antropoceno e Meios Geográficos associados ao contexto das mudanças climáticas atuais. Para tanto, foi fundamental a pesquisa em periódicos indexados, internacionais e nacionais, livros, teses e sites, o que totalizou 125 referências sobre o tema. De forma procedimental houve, inicialmente, um breve resgate histórico dessas discussões desde a Antiguidade Clássica até a Primeira Revolução Industrial. Posteriormente, foram inseridas, as informações mais recentes baseadas na linha científica do Painel Intergovernamental sobre Mudanças Climáticas (IPCC). A correlação entre as projeções do Quinto Relatório do IPCC AR5/2013 e a base de dados de altimetria por satélites, demostrou que o nível do mar tem aumentado na maior parte do Globo, provocando diversos impactos socioambientais advindos da erosão e inundação, principalmente na chamada Zona Costeira de Baixa Elevação.
In order to gain a more comprehensive picture on different mechanisms behind atmospheric particle formation, measurement results from QUEST 2-campaign are analyzed with an aid of an aerosol dynamic model. A special emphasis is laid on air ion and charged aerosol dynamics. Model simulations indicate that kinetic nucleation of ammonia and sulphuric acid together with condensation of sulphuric acid and low-volatile organic vapours onto clusters and particles explain basic features of particle formation events as well as ion characteristics. However, an observed excess of negative ions in the diameter range 1.5-3 nm and overcharge of 3-5 nm particles demonstrate that ions are also involved in particle formation. These observations can be explained by preferential condensation of sulphuric acid onto negatively charged clusters and particles and/or contribution of ion-induced nucleation on particle formation. According to model simulations, which assume that the nucleation rate is equal to the sulfuric acid collision rate, the relative contribution of ion-based particle formation seems to be smaller than kinetic nucleation of neutral clusters. Conducted model simulations also corroborate the recently-presented hypothesis according to which a large number of so-called thermodynamically stable clusters (TSCs) having a diameter between 1-3 nm exist in the atmosphere. TSCs were found to grow to observable sizes only under favorable conditions, e. g. when the pre-existing particle concentration was low.
The standard explanation for vagaries of our climate, championed by the IPCC (Intergovernmental Panel on Climate Change), is that greenhouse gases, particularly carbon dioxide, are its principal driver. Recently, an alternative model that the sun is the principal driver was revived by a host of empirical observations. Neither atmospheric carbon dioxide nor solar variability can alone explain the magnitude of the observed temperature increase over the last century of about 0.6°C. Therefore, an amplifier is required. In the general climate models (GCM), the bulk of the calculated temperature increase is attributed to "positive water vapour feedback". In the sun-driven alternative, it may be the cosmic ray flux (CRF), energetic particles that hit the atmosphere, potentially generating cloud condensation nuclei (CCN). Clouds then cool, act as a mirror and reflect the solar energy back into space. The intensity of CRF reaching the earth depends on the intensity of the solar (and terrestrial) magnetic field that acts as a shield against cosmic rays, and it is this shield that is, in turn, modulated by solar activity. Cosmic rays, in addition to CCN, also generate the so-called cosmogenic nuclides, such as beryllium-10, carbon-14 and chlorine-36. These can serve as indirect proxies for solar activity and can be measured e.g., in ancient sediments, trees, and shells. Other proxies, such as oxygen and hydrogen isotopes can reflect past temperatures, carbon isotopes levels of carbon dioxide, boron isotopes the acidity of ancient oceans, etc. Comparison of temperature records from geological and instrumental archives with the trends for these proxies may enable us to decide which one of the two alternatives was, and potentially is, primarily responsible for climate variability. This, in turn, should enable us to devise appropriate countermeasures for amelioration of human impact on air quality and climate.
The analysis of both paleo- and archeomagnetic data and magnetic properties of continental and marine sediments has shown that around 2700 BP, the geomagnetic Sterno-Etrussia excursion took place in 15 regions of the Northern Hemisphere. The study of magnetic properties of sediments of the Barents, Baltic, and White Seas demonstrates that the duration of this excursion was not more than 200–300 yr.
Paleoclimatic data provide extensive evidence for a sharp global cooling around 2700 B P. The causes of natural climate variation are discussed. Changes of the galactic cosmic ray intensity may play a key role as the causal mechanism of climate change. Since the cosmic ray intensity (reflected by the cosmogenic isotope level in the earth's atmosphere) is modulated by the solar wind and by the terrestrial magnetic field, this may be an important mechanism for long-term solar climate variability. The Sterno-Etrussia excursion may have amplified the climate shift, which, in the first place, was the effect of a decline of solar activity. During excursions and inversions, the magnetic moment decreases, which leads to an increased intensity of cosmic rays penetrating the upper atmosphere. Global changes in the electromagnetic field of the earth result in sharp changes in the climate-determining factors in the atmosphere, such as temperatures, total pressure field, moisture circulation, intensity of air flows, and thunderstorm activity. In addition, significant changes in the ocean circulation patterns and temperature regimes of oceans will have taken place.
Auroral specialists have suggested that in the Bible's Old Testament book of Ezekiel, the opening vision of a “storm cloud out of the north” depicts imagery inspired by a low‐latitude auroral display [ Link , 1967; Eather , 1980; Silverman , 1998]. Naturally, other interpretations have been suggested, including a true epiphany, a sandstorm, a thunderstorm, a tornado, a solar halo, a hallucination, and a UFO. Biblical scholars place the site of the Ezekiel's vision about 100 km south of Babylon near Nippur, latitude ˜32°, longitude ˜45°, and the date is within a year or two of 593 B.C., or about 2600 years ago.
An auroral interpretation of the vision is subject to possible refutation due to several geophysical considerations. Can auroras be seen at Ezekiel's latitude? More important, can they reach a coronal stage of development, which is what the vision requires? Was the tilt of the dipole axis favorable? Was the general level of solar activity favorable? And finally, What effect does a larger dipole moment in Ezekiel's time have on the question? All but the last question could have been answered on the basis of geophysical data a decade ago or earlier.
We construct a Galactic cosmic ray (CR) diusion model while considering that CR sources reside predominantly in the Galactic spiral arms. We nd that the CR ux (CRF) reaching the solar system should periodically increase each crossing of a Galactic spiral arm. We search for this signal in the CR exposure age record of Iron meteorites and conrm this prediction. We then check the hypothesis that climate, and in particular the temperature, is aected by the CRF to the extent that glaciations can be induced or completely hindered by possible climatic variations. We nd that although the geological evidence for the occurrence of IAEs in the past Eon is not unequivocal, it appears to have a nontrivial correlation with the spiral arm crossings|agreeing in period and phase. Thus, a better timing study of glaciations could either conrm this result as an explanation to the occurrence of IAEs or refute a CRF climatic connection. lar pattern speed which will soon be shown to t various data, the expected CRF changes from about 25% of the current day CRF to about 135%. Moreover, the average CRF obtained in units of today's CRF is 76%. This is consistent with measurements showing that the average CRF over the period 150-700 Myr before present (BP), was about 28% lower than the current day CRF (10).
We study the role of solar forcing on global surface temperature during four periods of the industrial era (1900-2000, 1900-1950, 1950-2000 and 1980-2000) by using a sun-climate coupling model based on four scale-dependent empirical climate sensitive parameters to solar variations. We use two alternative total solar irradiance satellite composites, ACRIM and PMOD, and a total solar irradiance proxy reconstruction. We estimate that the sun contributed as much as 45-50% of the 1900-2000 global warming, and 25-35% of the 1980-2000 global warming. These results, while confirming that anthropogenic-added climate forcing might have progressively played a dominant role in climate change during the last century, also suggest that the solar impact on climate change during the same period is significantly stronger than what some theoretical models have predicted.
The reliability of paleomagnetic records as proxies of the geomagnetic field intensity is still a matter of controversy since volcanic materials hardly provide continuous records, and marine sediments are suspected to carry a remanence biased by post-depositional realignments and/or by overprints. Such long standing debate emphasizes the need for the development of methods independent from paleomagnetism to decipher geomagnetic intensity variations. High resolution measurements of authigenic 10Be/9Be along with a detailed sedimentary record of directional and relative paleointensity variations evidence, over the 0.6-1.3 Ma time interval, frequent and recurrent excursions or short events in the late Matuyama and the early Brunhes epochs, among which two Brunhes-Matuyama reversal precursors and an intra-Jaramillo excursion. The results of this study confirm the idea of a highly unstable geomagnetic field as suggested by paleomagnetic evidences.
The standard explanation for vagaries of our climate, championed by the IPCC (Intergovernmental Panel on Climate Change), is that greenhouse gases, particularly carbon dioxide, are its principal driver. Recently, an alternative model that the sun is the principal driver was revived by a host of empirical observations. Neither atmospheric carbon dioxide nor solar variability can alone explain the magnitude of the observed temperature increase over the last century of about 0.6°C. Therefore, an amplifier is required. In the general climate models (GCM), the bulk of the calculated temperature increase is attributed to "positive water vapour feedback". In the sun-driven alternative, it may be the cosmic ray flux (CRF), energetic particles that hit the atmosphere, potentially generating cloud condensation nuclei (CCN). Clouds then cool, act as a mirror and reflect the solar energy back into space. The intensity of CRF reaching the earth depends on the intensity of the solar (and terrestrial) magnetic field that acts as a shield against cosmic rays, and it is this shield that is, in turn, modulated by solar activity. Cosmic rays, in addition to CCN, also generate the so-called cosmogenic nuclides, such as beryllium-10, carbon-14 and chlorine-36. These can serve as indirect proxies for solar activity and can be measured e.g., in ancient sediments, trees, and shells. Other proxies, such as oxygen and hydrogen isotopes can reflect past temperatures, carbon isotopes levels of carbon dioxide, boron isotopes the acidity of ancient oceans, etc. Comparison of temperature records from geological and instrumental archives with the trends for these proxies may enable us to decide which one of the two alternatives was, and potentially is, primarily responsible for climate variability. This, in turn, should enable us to devise appropriate countermeasures for amelioration of human impact on air quality and climate.
A high-resolution ice-core record of atmospheric CO2
concentration over the Holocene epoch shows that the global carbon cycle
has not been in steady state during the past 11,000 years. Analysis of
the CO2 concentration and carbon stable-isotope records,
using a one-dimensional carbon-cycle model,uggests that changes in
terrestrial biomass and sea surface temperature were largely responsible
for the observed millennial-scale changes of atmospheric CO2
concentrations.
High energy cosmic rays may influence the formation of clouds and thus impact weather and climate. Due to systematic solar wind changes, the intensity of cosmic rays incident on the magnetopause has decreased markedly during this century. The pattern of cosmic ray precipitation through the magnetosphere to the upper troposphere has also changed. Early in the century, the part of the troposphere open to cosmic rays of all energies was typically confined to a relatively small high-latitude region. As the century progressed the size of this region increased by over 25% and there was a 6.5° equatorward shift in the yearly averaged latitudinal position of the subauroral region in which cloud cover has been shown to be cosmic ray flux dependent. We suggest these changes in cosmic ray intensity and latitude distribution may have influenced climate change during the last 100 years.
Experimental studies of aerosol nucleation in air, containing trace amounts of ozone, sulphur dioxide and water vapour a concentrations relevant for the Earth's atmosphere, are reported. The production of new aerosol particles is found to be proportiona to the negative ion density and yields nucleation rates of the order of 0.1–1 cm−3 s−1. This suggests that the ions are active in generating an atmospheric reservoir of small thermodynamically stable clusters which are important for nucleation processes in the atmosphere and ultimately for cloud formation.
The purpose of this paper is to put forward a new estimate, in the context of previous assessments, of the annual global mean energy budget. A description is provided of the source of each component to this budget. The top-of-atmosphere shortwave and longwave flux of energy is constrained by satellite observations. Partitioning of the radiative energy throughout the atmosphere is achieved through the use of detailed radiation models for both the longwave and shortwave spectral regions. Spectral features of shortwave and longwave fluxes at both the top and surface of the earth's system are presented. The longwave radiative forcing of the climate system for both clear (125 W m-2) and cloudy (155 W m-2) conditions are discussed. The authors find that for the clear sky case the contribution due to water vapor to the total longwave radiative forcing is 75 W m-2, while for carbon dioxide it is 32 W m-2. Clouds alter these values, and the effects of clouds on both the longwave and shortwave budget are addressed. In particular, the shielding effect by clouds on absorption and emission by water vapor is as large as the direct cloud forcing. Because the net surface heat budget must balance, the radiative fluxes constrain the sum of the sensible and latent heat fluxes, which can also be estimated independently.
A first secular variation (SV) curve for the Iberian Peninsula was computed by hierarchical Bayesian
method using a total of 134 archaeomagnetic directions with ages ranging from �775 to 1959 A.D. A
general agreement is observed between the Iberian curve and the French and German SV curves, although
some interesting differences were found, such as the occurrence of lower inclinations between the 11th and
14th centuries in the Iberian curve. The analysis of these three reference curves indicates that SV in western
Europe is characterized by three major directional changes at �125, 200, and 1350 A.D. It is suggested
that these cusps are regional features of the geomagnetic field. The Iberian curve has been compared with
the predictions of the Jackson, CALSK7K.2, and Hongre global models. Despite large differences
recognized between these models, even for the dipolar terms, they predict reasonably well the Iberian
archaeomagnetic SV.
The main results of a transient climate simulation of the last 500 years with a coupled atmosphere-ocean model driven by estimated solar variability, volcanic activity and atmospheric concentrations of greenhouse gases are presented and compared with several empirical climate reconstructions. Along the last five centuries the climate model simulates a climate colder than mean 20th century conditions almost globally, and the degree of cooling is clearly larger than in most empirical reconstructions of global and North hemispheric near-surface air temperature (Mann et al., 1998; Jones et al., 1998). The simulated temperatures tend to agree more closely with the reconstruction of Esper et al. (2002) based on extratropical tree-ring chronologies. The model simulates two clear minima of the global mean temperature around 1700 A.D. (the Late Maunder Minimum) and around 1820 A.D. (the Dalton Minimum). The temperature trends simulated after the recovery from these minima are as large as the observed warming in the 20th century. More detailed results concerning the simulated Late Maunder Minimum, together with a spatially resolved historical reconstruction of the temperature field in Europe, are presented. It is found that the broad patterns of temperature deviations are well captured by the model, with stronger cooling in Central and Eastern Europe and weaker cooling along the Atlantic coast. However, the model simulates an intense drop of air-temperature in the North Atlantic ocean, together with an extensive sea-ice cover south of Greenland and lower salinity in North Atlantic at high latitudes, reminiscent of the Great Salinity Anomaly. Also, during the Late Maunder Minimum the intensities of the Golf Stream and the Kuroshio are reduced. This weakening is consistent with a reduced wind-stress forcing upon the ocean surface.
1] Svensmark and Friis-Christensen [1997] proposed a ''cosmic ray-cloud cover'' hypothesis that cosmic ray flux, modulated by solar activity, may modify global cloud cover and thus global surface temperature by increasing the number of ions in the atmosphere, leading to enhanced condensation of water vapor and cloud droplet formation. We evaluate this idea by extending their period of study and examining long-term surface-based cloud data (from national weather services and the Global Telecommunication System) as well as newer satellite data (International Satellite Cloud Climatology Project (ISCCP) D2, 1983–1993). No meaningful relationship is found between cosmic ray intensity and cloud cover over tropical and extratropical land areas back to the 1950s. The high cosmic ray-cloud cover correlation in the period 1983–1991 over the Atlantic Ocean, the only large ocean area over which the correlation is statistically significant, is greatly weakened when the extended satellite data set (1983– 1993) is used. Cloud cover data from ship observations over the North Atlantic, where measurements are denser, did not show any relationship with solar activity over the period 1953–1995, though a large discrepancy exists between ISCCP D2 data and surface marine observations. Our analysis also suggests that there is not a solid relationship between cosmic ray flux and low cloudiness as proposed by Marsh and Svensmark [2000].
In recent years the variability of the cosmic ray flux has become one of the main issues interpreting cosmogenic elements
and especially their connection with climate. In this review, an interdisciplinary team of scientists brings together our
knowledge of the evolution and modulation of the cosmic ray flux from its origin in the Milky Way, during its propagation
through the heliosphere, up to its interaction with the Earth’s magnetosphere, resulting, finally, in the production of cosmogenic
isotopes in the Earth’ atmosphere. The interpretation of the cosmogenic isotopes and the cosmic ray – cloud connection are
also intensively discussed. Finally, we discuss some open questions.
The recent completion of drilling at Vostok station in East Antarctica has allowed the extension of the ice record of atmospheric composition and climate to the past four glacial-interglacial cycles. The succession of changes through each climate cycle and termination was similar, and atmospheric;and climate properties oscillated between stable bounds. Interglacial periods differed in temporal evolution and duration. Atmospheric: concentrations of carbon dioxide and methane correlate well with Antarctic air-temperature throughout the record. Present-day atmospheric burdens of these two important greenhouse gases seem to have been unprecedented during the past 420,000 years.
Experiments lend support to the proposal that precessional torques drive the earth's dynamo.
During the past ∼120 years, Earth's surface temperature is correlated with both decadal averages and solar cycle minimum values of the geomagnetic aa index. The correlation with aa minimum values suggests the existence of a long-term (low-frequency) component of solar irradiance that underlies the 11-year cyclic component. Extrapolating the aa-temperature correlations to Maunder Minimum geomagnetic conditions implies that solar forcing can account for ∼50% or more of the estimated ∼0.7–1.5°C increase in global surface temperature since the second half of the 17th century. Our analysis is admittedly crude and ignores known contributors to climate change such as warming by anthropogenic greenhouse-gases or cooling by volcanic aerosols. Nevertheless, the general similarity in the time-variation of Earth's surface temperature and the low-frequency or secular component of the aa index over the last ∼120 years supports other studies that indicate a more significant role for solar variability in climate change on decadal and century time-scales than has previously been supposed. The most recent aa data for the current solar minimum suggest that the long-term component of solar forcing will level off or decline during the coming solar cycle.
The anisotropy of magnetic susceptibility (AMS) data presented herein underscore the resolving power magnetic anisotropy has in non-lithified poorly consolidated sediments. We turn our attention to primary aeolian sedimentary magnetic fabrics preserved along two coeval loess profiles in Central Alaska at the Halfway House (HH3) and Gold Hill Steps (GHS2) sites. We first demonstrate that published preliminary results along HH1 and HH2 are reproducible. Moreover, the new sample suite, the first ever at GHS, collected at a higher temporal resolution and statistical confidence permits a better evaluation of the significance of the inferred paleowind directions and their temporal variability. The data demonstrate that the resolvability of the magnetic lineation is independent of both the eccentricity of the AMS ellipsoid and the strength of the magnetic foliation. Furthermore, the orientations and temporal variability of the most significant magnetic lineations are not artifacts of the data filtering process developed to isolate them. We conclude that the temporal variations of inferred paleowind directions along HH3 track paleoclimatic glacial-interglacial cycles as well as provide additional constraints to the geochronology of the loess deposit. Along GHS2, the limited coeval primary magnetic fabrics suggest an influence from a local microclimate not present at the HH site, complicating the interpretation of small-scale variability in paleowind directions. However, the overall average paleowind directions are similar to those inferred along HH3 confirming a regional (spatial) consistency of past surface air circulation. (C) 2004 Elsevier B.V. All rights reserved.
A time-varying spherical harmonic model of the palaeomagnetic field for 0-7 ka is used to investigate large-scale global geomagnetic secular variation on centennial to millennial scales. We study dipole moment evolution over the past 7 kyr, and estimate its rate of change using the Gauss coefficients of degree 1 (dipole coefficients) from the CALS7K.2 field model and by two alternative methods that confirm the robustness of the predicted variations. All methods show substantial dipole moment variation on timescales ranging from centennial to millennial. The dipole moment from CALS7K.2 has the best resolution and is able to resolve the general decrease in dipole moment seen in historical observations since about 1830. The currently observed rate of dipole decay is underestimated by CALS7K.2, but is still not extraordinarily strong in comparison to the rates of change shown by the model over the whole 7 kyr interval. Truly continuous phases of dipole decrease or increase are decadal to centennial in length rather than longer-term features. The general large-scale secular variation shows substantial changes in power in higher spherical harmonic degrees on similar timescales to the dipole. Comparisons are made between statistical variations calculated directly from CALS7K.2 and longer-term palaeosecular variation models: CALS7K.2 has lower overall variance in the dipole and quadrupole terms, but exhibits an imbalance between dispersion in g12 and h12, suggestive of long-term non-zonal structure in the secular variations.
In the Eos article,“Ezekiel and the Northern Lights: Biblical Aurora Seems Plausible” (16 April 2002), Siscoe et al. presented arguments showing that coronal auroras can occur at low latitudes under the condition of increased geomagnetic dipole field strength. From this standpoint, they give an interpretation of the “reported” Ezekiel's vision (the Bible's Book of Ezekiel in the Old Testament). The site of the Ezekiel's vision was about 100 km south of Babylon (latitude ˜32° N, longitude ˜5°E), and the date of the vision was around 593 B.C.
Auroral specialists believe that Ezekiel's vision was inspired by a very strong magnetic storm accompanied by coronal auroras at low latitudes. However, as justly noted by Siscoe et al. [2002],to adopt this interpretation, several questions should be answered. Can auroras be seen at the latitude where Ezekiel reportedly was? More important, can they reach a coronal stage of development, which is what the vision requires? Was the tilt of the dipole axis favorable? Was the general level of solar activity favorable? The principal question is, no doubt, the second one.
Short-term variations in the strength and direction of the geomagnetic field have the potential to provide Quaternary chronologies with millennial and sub-millennial resolution. The variations, particularly in the form of large directional swings such as geomagnetic excursions and relative paleointensity highs and lows, can typically be correlated over large regions and, in many cases, worldwide. These attributes, in addition to the relative ease and speed with which high-resolution measurements can be made, provide a means for constructing chronologies that can be used at sites around the globe. When the paleomagnetic records are tied to a variety of climate and environmental proxies - stable isotope, cosmogenic isotope, lithology, sediment color, rock magnetic, and other records - they become a powerful tool for examining the synchroneity of climatic events. Besides being a passive chronologic tool, however, the geomagnetic field may also play a role in climate change or be influenced by such change. Paleomagnetic records from across the North Atlantic reveal the synchroneity of the geomagnetic variability across the region, including the occurrence of multiple geomagnetic excursions during the Brunhes chron (0-780,000 years). Intriguing relationships between the geomagnetic variability and both climate change and orbital forcing suggest a causal link.
The difference in the precessional torques on the core and mantle of the earth can produce a small relative rotation between the two. The magnitude of the relative rotation depends upon the inertial reaction resulting from the figure of the core-mantle boundary and upon the frictional torque caused by the shearing flow. It is concluded in this study that the frictional torque due to a turbulent hydromagnetic Ekman layer is the principal restraint on relative rotation. From the gross geophysical parameters of figure and density and the electrical conductivity of core material, the resulting magnetic fields, fluid velocities, and characteristic periods are found to compare favorably with the available information.
It is a widely accepted hypothesis that buoyancy in the fluid core powers the geodynamo. Estimates of the available power rest on assumptions about the material properties of the core, its composition and its history. By contrast, we know with much better accuracy the rotational motion of the Earth and its tidal deformation. We are thus prompted to inquire what effects precession and tides have on the core flow. If precession and tides are neglected, fluid particles in the core revolve once a day about the geographic axis on a circular path. Both precession and tides distort the stramlines into ellipses. From theory, simulations and experiments, it is known that this deformation can trigger an instability. Whether this actually happens inside the Earth is presently uncertain because of our insufficient knowledge about core viscosity. Assuming precession indeed leads to instability in the core, simulations have shown that the resulting flow is a dynamo by itself. But precession and tides could also interact with a dynamo driven by buoyancy and leave an observable signature in magnetic secular variation. This is in particular expected if "resonant collapses" occur, a phenomenon in which the flow cyclically traverses laminar and chaotic phases. This presentation will give an overview of our present knowledge of flows driven by precession and tides and point to some open questions.
Recent studies have shown that the Earth s cloud cover is strongly correlated with the galactic cosmic ray flux While this correlation is indicative of a possible physical connection there is until now no confirmation that a physical mechanism exists An experiment has therefore been set up in order to investigate the underlying microphysical processes Since any physical mechanism linking cosmic rays to clouds and climate is currently speculative there have been various suggestions of the role atmospheric ions may play These involve any one of a number of processes from the nucleation of aerosols up to the collection processes of cloud droplets Experimental studies of aerosol nucleation in air containing trace amounts of ozone sulfur dioxide and water vapor at concentrations relevant for the Earths lower atmosphere are reported The results suggest that the production rate of critical clusters is sensitive to ionization and indicate that ions act as a catalyst in the initial chemical reactions leading to a significant production rate of stable sulfuric acid clusters It is suggested that this nucleation process is a fundamental source of new aerosols in the Earths atmosphere and could be the physical link between cosmic ray ionization cloud cover and climate previously reported
A ∼41 Kyr periodic component has been reported in some sedimentary paleointensity records, allowing speculation that there may be some component of orbital control of geomagnetic field generation such as by obliquity modulation. However, no discernable tendency is found for astronomically-dated geomagnetic reversals in the Plio-Pleistocene (0 to 5.3 Ma) or excursions in the Brunhes (0 to 0.78 Ma) to occur at a consistent amplitude or phase of obliquity cyclicity, nor of orbital eccentricity. An implication is that paleointensity lows which are characteristically associated with these features are not distributed in a systematic way relative to obliquity and eccentricity, supporting the idea that orbital forcing does not power the geodynamo.
We studied 14 groups of French pottery fragments dated between the 4th and 16th centuries. The potsherds were analyzed using the Thellier and Thellier [1959] method, revised by Coe [1967]. Intensity values were corrected for thermoremanent magnetization (TRM) anisotropy and cooling rate dependence of TRM acquisition. We first analyzed modern ceramics produced following ancient techniques and fired in a wood-burning kiln inside of which field intensity was measured. The recovered mean intensity is within ∼3% of the expected value, which proves the reliability of our experimental procedure. Thermal experiments carried out at rapid and slow cooling rates clearly indicate that the cooling rate correction is critical in archeointensity studies. Our data indicate that large variations in intensity occurred in France over the last 2000 years. Two relative maxima in intensity are observed, one between the 8th and 10th centuries and the second between the 14th and 15th centuries. Similarities are observed between the archeointensity data from France and Ukraine, yielding some evidence for eastward drift of geomagnetic sources between western and eastern Europe from A.D. 800 to A.D. 1700. We also show that the dipole moment evolution proposed by McElhinny and Senanayake [1982] and Yang et al. [2000] for the last two millennia is likely biased toward higher values, mainly because of the absence of correction for the cooling rate dependence of TRM acquisition in most published archeointensity studies. We finally underline a possible relationship, valid at least in western Europe, between changes in direction and intensity of the geomagnetic field.
Differences in time- variation between total and ultraviolet solar irradiance could help in separating their influence on climate. We present the first models based on area measurements of magnetic plages from CaK spectroheliograms obtained between 1915–1999. Correlation of our time series of UV irradiance with global temperature, T, accounts for only 20% of the global temperature variance during the 20th century. Correlation of our total irradiance time series with T accounts statistically for 80% of the variance in global temperature over that period, although the irradiance variation amplitude is insufficient to influence global warming in present-day climate models. This interesting difference has been obscured in past modelling by additional components introduced to represent secular variations, which are no longer supported by current observational evidence. Future irradiance models emphasizing the more securely- based contributions of photospheric magnetic structures seem to provide better prospects for improved physical understanding of sun-climate links.
At geologic timescales, many proxy data suggest a contrasting evolution of Asian and African monsoons since the Oligocene. The Asian summer monsoon increases drastically around 8 Ma, whereas the African summer monsoon gradually weakens during the Miocene. Using an atmospheric general circulation model, we simulate most of the spatial evolutions of both monsoons only accounting for the changes of paleogeography, including continental drift, orogeny, and sea level change. The paleogeographic changes modify drastically the climate over central and southern Asia between the Oligocene and the present. The retreat of an epicontinental sea warms central Eurasia in summer. The heating of this area and the uplifts of the Tibetan plateau and of the Himalayas deepen the Asian low-pressure cell and displace it northwest. This then shifts precipitation from Indochina toward the southern flank of the Himalayas. This is in good agreement with proxy data. Therefore our modeling studies support a shift and a strengthening of the Asian monsoon during the late Tertiary rather than a real ``onset.'' We suggest that the increase in seasonal precipitation and the strengthening of the number of days with heavy rainfall over the Himalayas from 30 Ma to the present may be of critical importance to explain the long-term evolution of physical erosion of this area. We also investigate the respective impact of the Paratethys shrinkage and of the Tibetan plateau uplift through sensitivity experiments and prove that the Paratethys retreat plays an important role in monsoon evolution. The northward drift of the African continent confines summer monsoon precipitation to a thin belt which favors the stretching of the subtropical desert, in good agreement with data. We finally show that during the Oligocene, the African and Asian monsoon systems are clearly separated by the Tethys seaway. The closure of this seaway and the evolution of the Asian monsoon induce a connection between both monsoon systems in the low and middle troposphere.
Normalized remanence (relative geomagnetic paleointensity) records for the last 500 kyr can be matched between two Iceland Basin Ocean Drilling Program (ODP) sites (984 and 983) and correlated with other high-resolution records. Directional secular variation is, however, not easily correlated between sites due to inadequate recording, at these mean sedimentation rates (12–15 cm/kyr), of the characteristic high frequency variability of the directional record. Both sites record the Iceland Basin event at ∼186–189 ka in which the characteristic magnetization component rotates through 180° and back, coincident with a paleointensity low that lasted about 3 kyr. Other Brunhes Chron geomagnetic excursions appear to be manifest as intervals of higher-amplitude secular variation during lows in paleointensity. There is a tendency for paleointensity lows to correlate with peak interglacials in the oxygen isotope records; however, this does not translate into a correlation between paleointensity and percent carbonate or between paleointensity and magnetic concentration or grain size parameters.
We are living in unusual times. Twentieth century climate was dominated by near universal warming with almost all parts of the globe experiencing tem-peratures at the end of the century that were signifi-cantly higher than when it began (Figure 6.1) (Parker et al. 1994; Jones et al. 1999). However the instrumental data provide only a limited temporal perspective on present climate. How unusual was the last century when placed in the longer-term context of climate in the centuries and millennia leading up to the 20, century? Such a perspective encompasses the period before large-scale contami-nation of the global atmosphere by human activities and global-scale changes in land-surface conditions. By studying the records of climate variability and forcing mechanisms in the recent past, it is possible to establish how the climate system varied under "natural" conditions, before anthropogenic forcing became significant. Natural forcing mechanisms will continue to operate in the 21, century, and will play a role in future climate variations, so regardless of how anthropogenic effects develop it is essential to understand the underlying background record of forcing and climate system response. Sources of information on the climate of the last millennium include: historical documentary records, tree rings (width, density); ice cores (isotopes, melt layers, net accumulation, glaciochemistry); corals (isotopes and other geochemistry, growth rate); varved lake and marine sediments (varve thickness, sedimentology, geochemistry, biological content) and banded speleothems (isotopes). These are all paleoclimatic proxies that can provide continuous
The Eurasian climates of today, 10 million and 3O million years ago are simulated using an atmospheric general circulation model that incorporates realistic continental geography and epicontinental sea distributions. The resulting climates compare well with various palaeoclimate records. The retreat of the Paratethys-an epicontinental sea-shifts the central Asian climate from temperate to continental conditions, and plays as important a role as uplift of the Himalayan/Tibetan plateau in driving the Asian monsoon changes.
During the last solar cycle Earth's cloud cover underwent a modulation more closely in phase with the galactic cosmic ray flux than with other solar activity parameters. Further it is found that Earth's temperature follows more closely decade variations in galactic cosmic ray flux and solar cycle length, than other solar activity parameters. The main conclusion is that the average state of the heliosphere affects Earth's climate.
The study of the physical processes that drive the variability of the Earth's climate system is one of the most fascinating and challenging topics of research today. Perhaps the largest uncertainties in our ability to predict climate change are the cloud formation process and the interaction of clouds with radiation. Here we show that in the southern Pacific Ocean cloud effects on the net radiative flux in the atmosphere are related to the intensity of the Earth's magnetic field through lower atmosphere cosmic ray effects. In the inner region of the Southern Hemisphere Magnetic Anomaly (SHMA) it is observed a cooling effect of approximately 18 W/m2 while in the outer region it is observed a heating effect of approximately 20 W/m2. The variability in the inner region of the SHMA of the net radiative flux is correlated to galactic cosmic rays (GCRs) flux observed in Huancayo, Peru (r = 0.73). It is also observed in the correlation map that the correlation increases in the inner region of the SHMA. The geomagnetic modulation of cloud effects in the net radiative flux in the atmosphere in the SHMA is, therefore, unambiguously due to GCRs and/or highly energetic solar proton particles effects.
Twenty new intensity determinations of the ancient geomagnetic field have been obtained from groups of potsherds and brick fragments from Syria. These artifacts, archeologically well dated from ∼6000 B.C. to approximately A.D. 1200, have been analyzed using the Thellier and Thellier [1959] method as modified by Coe [1967]. Intensity values have been corrected for the effects of anisotropy of thermal remanent magnetization and cooling rate. Our results indicate that field intensities were moderate in Syria from ∼6000 B.C. to ∼3500 B.C., with values of ∼30–40 μT. There was a significant increase in intensity by a factor of 2 from ∼3500 B.C. to ∼700 B.C., which was interrupted by a moderate decrease between ∼2550 B.C. and ∼1750 B.C. During more recent periods, our results show an intensity minimum approximately A.D. 200 and a maximum around the tenth century. Comparison with different data sets from the eastern Mediterranean and central Asia shows that geomagnetic field intensity variations were consistent at this large regional scale, at least over the last 5 millennia.
Based on a 16-year observation period (1980-1995), it was claimed
recently that Earth's climate was linked to variations in the flux of
cosmic rays penetrating into the atmosphere via their postulated effect
on global cloud cover. Data from three independent studies yield
information relevant to the ongoing discussion of the likelihood of the
existence of such a link. (1) Model calculations show that the relative
change in the ion production rate from a solar maximum to a solar
minimum is of the same order as, or even greater than, the corresponding
change in global cloud cover. (2) However, the smoothed combined flux of
10Be and 36Cl at Summit, Greenland, from 20-60 kyr
B.P. (proportional to the geomagnetically modulated cosmic ray flux) is
unrelated to the corresponding δ18O and CH4
data (interpreted as supraregional climate proxies). (3) Furthermore,
although a comparison of the incoming neutron flux with cloud cover in
Switzerland over the last 5 decades shows a significant correlation at
times during the 1980s and 1990s, this does not occur during the rest of
the period.
Information is presented on the existence of a large tropospheric and
stratospheric effect produced by the solar-cycle modulation of cosmic rays.
Consideration is given to climatological effects of solar-cycle period. (J.H.M.)
Historical observations document ~1100 km change in the position of the
North Magnetic Pole (NMP) over the last century. This movement has
accelerated over the last few decades to an astonishing 40 km/yr and
along with the diminishing intensity of the dipole field has led to
speculation of imminent reversal or excursion. Recently it has been
shown that movement of the NMP is sensitive to small and rapid
variations of the field known as Geomagnetic Jerks (Newitt et al., 2002;
Mandea and Dormy 2003). These observations indicate that tracking the
migration of the NMP provides a tracer of field variations allowing a
more complete understanding of geomagnetic field behavior prior to
historical observations. Reconstruction of the late Holocene
paleomagnetic record from the Canadian High Arctic has been undertaken
using u-channel paleomagnetic measurements from lakes in Ellesmere,
Devon, Cornwallis and Bathurst Islands. At present the most complete
records come from Ellesmere Island (Sawtooth Lake, 79°21 N,
83°56 W and Murray Lake, 81°34 N, 69°54 W) as these
sediments have excellent magnetic properties, and preserve a strong,
stable, single component magnetization. Multiple records have been
obtained from each of these lakes and they possess independent age
control based on varve chronologies. The paleomagetic record from
several other lakes support observations from Sawtook and Murray Lakes,
although they lack either independent age control or replicate-coring.
These data help to establish the characteristics of late Holocene
paleomagnetic secular variation (PSV) for the Canadian High Arctic for
the last 2600 yrs. Correlations between sediment PSV records and
historical observations demonstrate that the geomagnetic record is
influenced by the position of the NMP, and that Arctic sediment
magnetizations are sensitive to its movement. Over the last 2000 yrs,
the PSV record documents at least 3 rapid (< 100 yrs) high amplitude
NMP shifts that are much larger than anything observed in the historical
record (the last 400 yrs). Abrupt shifts in the position of the NMP by
thousands of kilometers appear to closely coincide with the three most
recent archeomagnetic "jerks" of Gallet et al., (2003).
New evidence from deep sea cores in the North Atlantic suggests that
recurring expansions of the subpolar surface circulation were influenced
by variations in solar output through the entire Holocene. Five
high-resolution records of drift ice from three widely separated sites
reveal a series of rapid, centennial time-scale oscillations that are
bundled into the millennial duration events of the "1500-year" cycle.
The centennial duration oscillations closely match prominent changes in
production rates of the cosmogenic nuclides 14C and
10Be as inferred from tree ring measurements and from
Greenland ice core records, respectively. Virtually every expansion of
the subpolar surface circulation is linked to reduced solar irradiance.
The most recent circulation cycle corresponds to the "Little Ice
Age-Medieval Warm Period". Each expansion of the subpolar circulation
was associated with cooler surface temperatures and probably with more
zonal surface winds. Those changes may reflect an intensified and
expanded Polar Cell and would be consistent with recent GCM models of
the atmosphere's dynamical response to solar forcing of stratospheric
ozone and temperature. The sense of the circulation-driven temperature
changes, though, does not exhibit the characteristic dipole pattern of
the NAO; rather the pattern resembles that of regional cooling
associated with reduced production of North Atlantic Deep Water (NADW),
such as during the Younger Dryas although with much lower amplitude. As
production of NADW is highly sensitive to changes in surface
hydrography, we suggest that the solar forced expansions of subpolar
circulation may have triggered a deep ocean response, which, through
reduced northern heat transport and increased sea ice, further amplified
the climate response to variations in solar output.
ICE ages and reversals of the Earth's magnetic field are two widely different geophysical phenomena; but they may be casually linked by the following mechanism. The moment of inertia of the Earth will be changed by variations in size of polar ice sheets and the resulting redistribution of water mass. To conserve angular momentum the Earth's rotation must therefore change. Calculations on the basis of a simple model then suggest that conditions at the core–mantle boundary may be perturbed in such a way as to affect the generation of the Earth's magnetic field.
More than 20 years ago, on the basis of data from a Pacific sediment core, it was suggested that geomagnetic field intensity may vary with the Earth's orbital obliquity (centred on a period of ~41 kyr) as a result of the effect of obliquity on precessional forces in the Earth's core. It had also been proposed that precession plays an important role in the energy budget of the Earth's geodynamo. But subsequent analyses indicated that the energy available from precession is at least an order of magnitude less than that required to drive the geodynamo. Here, however, we report a spectral analysis of sedimentary records of relative geomagnetic palaeointensity from two North Atlantic sites which shows significant power both at orbital eccentricity (~100 kyr) and obliquity (41 kyr). The eccentricity power is also present in bulk magnetic properties (such as susceptibility) and is therefore attributable to lithological variations controlled by eccentricity- driven climate change. The obliquity power, however, is not apparent in bulk magnetic properties, and seems to be a property of the geomagnetic field itself, thus providing evidence for the orbital forcing of geomagnetic field intensity.
Sami K Solanki presents the Harold Jeffreys Lecture on the links between our climate and the behaviour of the Sun, from the perspective of a solar physicist.
Radiation from the Sun makes Earth a habitable planet. Fluctuations in the solar output are therefore likely to affect the climate on Earth, but establishing both how the output of he Sun varies and how such variations influence Earth’s climate have proved tricky. But increased amounts of data from the Sun and about the climate on Earth over recent years mean that rapid progress is being made. In this paper, I review the current debate on the influence of the Sun and summarize the state of play in this area of solar physics.
We obtained new archeointensity data from French faience potsherds dated from the 17th to 19th century. These results further document the occurrence of sharp changes in geomagnetic field secular variation in Western Europe over the past three millennia. The intensity variation curve shows several maxima whose rising parts appear to coincide in time with the occurrence of cooling events documented in this region from natural and historical data. This coincidence suggests a causal link between enhanced secular variation of the geomagnetic field and climate change over centennial time scales, challenging the role of solar forcing as the sole factor provoking these climatic variations. We propose that the archeomagnetic jerks described by Gallet et al. [1] [Y. Gallet, A. Genevey, V. Courtillot, On the possible occurrence of archeomagnetic jerks in the geomagnetic field over the past three millennia, Earth Planet. Sci. Lett. 214 (2003) 237–242.] may engage the mechanism for centennial climate change.
The production of 10Be in the Earth’s atmosphere depends on the galactic cosmic ray influx that, in turn, is affected by the solar surface magnetic activity and the geomagnetic dipole strength. Using the estimated changes in 10Be production rate and the geomagnetic field intensity, variations in solar activity are calculated for the last 200 ka. Large variations in the solar activity are evident with the Sun experiencing periods of normal, enhanced and suppressed activity. The marine δ18O record and solar modulation are strongly correlated at the 100 ka timescale. It is proposed that variations in solar activity control the 100 ka glacial–interglacial cycles. However, the 10Be production rate variations may have been under-estimated during the interval between 115 ka and 125 ka and may have biased the results. Future tests of the hypothesis are discussed.