Climate Change 1995. The second IPCC Assessment of Climate Change
... J.P. PEIXOTO, na sua obra de divulgação sobre as variações climáticas ( 1987) descreve-as pormenorizadamente. Nosegundorelatóriodesíntesedo/PCC (HOUGHTON et al., 1996), é já mais desenvolvido o estudo das causas naturais das variações climáticas e é dada ênfase à influência dos aerossóis de origem antrópica, que podem retardar a intensificação do efeito de estufa. ...
... A pesquisa científica prossegue em várias frentes, citando-se algumas, a título de exemplo: a) Investigação da diversidade espaço-temporal das variações climáticas recentes , mascaradas pelos valores "globais" ou "hemisféricos". Esta imprescindível tarefa foi empreendida por diversos autores em HOUGHTON et al., (1996), onde são apresentados planisférios de valores observados e previstos por diversos modelos . Num estudo na escala regional, SCHONWIESE e RAPP (1997) apresentaram um muito interessante atlas da Europa, com as particularidades espaciais das alterações de temperatura, pressão, precipitação e h umidade, no decurso do último século (recensão em ALCOFORADO, no prelo). ...
... b) Desenvolvimento das previsões estacionais do clima Europeu e da sua relação com aNAO (WANNER, 1999). c)Aprofundamento do estudo das relações de interdependência entre a atmosfera e os outros subsistemas do sistema climático, nomeadamente a Hidrosfera (WANNER, 1997(WANNER, e 1999JOUSSAUME e GUIOT, 1999;HEGERL, 1999), a Biosfera (JOUSSAUME e GUIOT, 1999), a Litosfera e a Criosfera (HOUGHTON et al., 1996). Os resultados permitirão aperfeiçoar os modelos de previsão que, não raro, apenas incluem a atmosfera, ignorando, por dificuldade de quantificação, as retro-acções no sistema climático. ...
... The first concerns about the ongoing changes in the hydrological cycle were assessed by Budyko and Drozdov (1976), Wigley et al. (1980), Manabe et al. (1981), and recently by Houghton et al. (1996). ...
... Observational analyses have been made by Bradley et al. (1987), Groisman and Legates (1995), Iwashima and Yamamoto (1993), and Karl and Knight (1998). Model projections of a greenhouse-enriched atmosphere (Houghton et al. 1996) and the empirical evidence from the period of instrumental observations (Easterling et al. 2000) indicate an increasing probability of heavy precipitation events for many extratropical regions including the United States as global temperature increases. These projections and the observed increase of heavy precipitation raise the possibility of increased flooding, but snow cover changes induced by increasing temperature tend to smooth the seasonal cycle of streamflow, especially in high latitudes and elevations, thus reducing the intensity of spring snowmelt (Arnell et al. 1996;Georgievsky et al. 1996). ...
... Analyses of snow cover information from satellite and in situ sources indicate a significant retreat of spring snow cover over the Northern Hemisphere and the United States during the past several decades (Houghton et al. 1996;Frei et al. 1999). Groisman et al. (1999a) reprocessed the U.S. cooperative daily measurements of snow depth since 1949 (NCDC 1998). ...
Changes in several components of the hydrological cycle over the contiguous United States have been documented during the twentieth century: an increase of precipitation, especially heavy and very heavy precipitation, and a significant retreat in spring snow cover extent over western regions during the last few decades. These changes have affected streamflow, including the probability of high flow. In the eastern half of the United States a significant relationship is found between the frequency of heavy precipitation and high streamflow events both annually and during the months of maximum streamflow. Two factors contributed to finding such a relation: 1) the relatively small contribution of snowmelt to heavy runoff in the eastern United States (compared to the west), and 2) the presence of a sufficiently dense network of streamflow and precipitation gauges available for analysis. An increase of spring heavy precipitation events over the eastern United States indicates with high probability that during the twentieth century an increase of high streamflow conditions has also occurred. In the West, a statistically significant reduction of snow cover extent has complicated the relation between heavy precipitation and streamflow. Increases in peak stream flow have not been observed here, despite increases in heavy precipitation events, and less extensive snow cover is the likely cause.
... Sumerians obviously belonged to R1b haplogroup. Following the emergence of Neolithic agricultural societies resulting in permanent settlements and prolonged interactions and specializations throughout central Asia "Original Sumerian Homeland" became one of the Arbins regroupings throughout this long 8000 -10,000 years of history, before climate change forced them to make the maiden migration and resettle in the fertile lands of the Middle East between the Tigris and Euphrates Rivers around 4000 BC (Paleoclimatology, 2012;Houghton, et al., 1990), and eventually further south on the banks of Nile River in north east Africa. ...
... The archeological artifacts of a very similar culture,the traditions of these people, geological and climatological evidence of the already well documented climate change around 4000 BC (Holocene Maximum) in this region (Paleoclimatology, 2012;Houghton, et al., 1990) and ultimately the mass migration from their settlements around Gonur Tepe, Anau Türkmenistan further support this very logical proof of the origin of the Sumerians. (Hiebert, 2003;Raphael, 1908). ...
ABSTRACT
Who were the Sumerians? Where did they originate? For those who are not familiar with this remarkable, resourceful and intelligent people, who not only invented writing but also established the true mythological foundations of all main religions of the world, simply put, they taught us almost everything. Four different points regarding the current known archeological evidence are evaluated separately, and the Sumerians’ unique and strongly sacred mythological beliefs related to the lapis lazuli stone and the myth’s origin are analyzed. The uniqueness of the lapis mine location in the Hindu Kush Mountains and the unique (fingerprint) trace element and other physical characteristics of this metamorphic sacred blue stone of the Sumerians are the primary points of focus. The only possible and provable location of their original homeland, “based on the analysis” is; between the Caspian Sea and the Hindu Kush and Kopet Mountains, which is in Turkmenistan. This analysis and conclusion are based on “multiple independent factors”: current archeological excavations, the uniqueness of metamorphic lapis lazuli as a stone and over 6000 years of lapis lazuli mining at a fixed location (absolutely necessary requirements for the origin of strong lapis mythology) and current credible biogeographic DNA evidence and the distribution of R1b haplogroup of “Arbins”, as recently described by Dr. Anatole A. Klyosov. The Sumerians initial migration presumably began with a persistent drought in their original homeland, that eventually forced them to abandon their home migrate and resettle in the southern fertile lands of the Middle East between the Tigris and Euphrates Rivers and eventually further south near the banks of Nile River in north east Africa.KEYWORDS
Sumerian Origins, Lapis Lazuli, Location-Location-Location
... Quand l'intérêt politique pour la question augmente à la fin des années 1970, un premier rapport exhaustif est demandé à l'Académie des sciences américaine. Cette étude de 1979 préfigure les travaux du GIEC en offrant une synthèse des savoirs dans le domaine de la climatologie (Charney et al., 1979Bolin et al., 1995) 1939th Environment Council Meeting, Brussels, 25 June, §Meinshausen et al., 2009 ; Schmidt et Archer, 2009). Il a été repris et affiné dans deux rapports, ainsi que par Nicolas Stern dans son dernier ouvrage (IEA, 2009 ; WBGU, 2009 ; Stern, 2009).Sarewitz et Pielke, Jr., 2000 ; Pielke, Jr., 2007). ...
... Quand l'intérêt politique pour la question augmente à la fin des années 1970, un premier rapport exhaustif est demandé à l'Académie des sciences américaine. Cette étude de 1979 préfigure les travaux du GIEC en offrant une synthèse des savoirs dans le domaine de la climatologie (Charney et al., 1979)Bolin et al., 1995). Avec cette « meilleure estimation » du réchauffement jusqu'à l'an 2100, le second rapport du GIEC est plus prudent à fois que le précédent et que le suivant. ...
Cet article passe en revue les resultats politiques de la conference de Copenhague et les evolutions que l'on decele dans les rapports de force geopolitiques, dans les thematiques et dans la cartographie des principaux acteurs. Partant du constat que le regime climatique est aujourd'hui attaque tant sur sa gouvernance que sur la relation science-politique, il retrace la construction de l'arene climatique et le cadrage particulier du probleme au cours de ces vingt dernieres annees. Nous suggerons qu'il y a eu au cours des annees 2000 une convergence des approches " descendantes " (top-down) dans l'expertise et dans les politiques climatiques, articulee autour d'objectifs de reduction, de seuils de rechauffement et de " budgets carbone ". Ce cadrage a ete mis en echec a Copenhague, ou s'est affirme le caractere " ascendant " (bottom-up) des engagements volontaires. Un chiffre central dans ce contexte est le seuil de " rechauffement dangereux " de deux degres. L'accord de Copenhague - confirme officiellement dans le compromis de Cancun - consacre ce chiffre comme objectif officiel du processus onusien, accentuant ainsi la tension entre une realpolitik desormais assumee et une expertise alarmante. Nous analysons la construction de l'objectif des deux degres et le role qu'il joue dans le regime climatique. Finalement, nous proposons une revue critique des contributions recentes au debat post-Copenhague.
... Though such accounts typically are much more detailed than merely holding that one has the right to what one historically has acquired, we include in our set up the principle of grandfathering, holding that distribution of environmental impact rights should be based on the actual status quo distribution of environmental impact. This very simple view probably has no theoretical justification, but we include it because it is widespread in the environmental literature and regulation (Caney, 2009;Houghton, 1995). The selected principles have been translated into equations that allocate the SOS according to the principle as presented in Table 2. ...
In the light of increasing human pressures on the Earth system, the issue of sharing in the face of scarcity is more pressing than ever. The planetary boundary framework identifies and quantifies nine environmental boundaries and corresponding human pressures. However, when aiming to make the concept operational for decision support it is unclear how this safe operating space (SOS) within each of the planetary boundaries should be shared. This study proposes a two‐step approach, where the operating space is first downscaled to the individual level using ethical allocation principles and next scaled up to a higher organizational level using different upscaling methods. For the downscaling, three allocation principles are demonstrated: egalitarian (equal per capita); grandfathering (proportional to current share of the total impacts); and ability to pay (proportional to economic activity). For upscaling from the individual level final consumption expenditure is used as a proxy for the priority that the individual gives to the product or sector. In an alternative upscaling approach, an additional upscaling factor is based on the eco‐efficiency (ratio between turnover and environmental impact) of the product or sector. A demonstration of the method's application is given by applying the framework to two of the planetary boundaries, climate change and biogeochemical flows, with the Danish, Indian and global dairy sectors as cases. It is demonstrated how the choices of allocation and upscaling approaches influence the results differently in the three cases. The developed framework is shown to support an informed and transparent selection of allocation principles and upscaling methods and it provides a step toward standardization of distributing the SOS in absolute environmental sustainability assessments.
... Fires tend to be concentrated in summer when temperatures are high, and air humidity and fuel moisture are low ( Juli et al., 1999). Predictions on climate warming in the Mediterranean basin indicate an increase in air temperature and a reduction in summer rainfall ( Houghton et al. 1996). This might explain firing of thousands of hectares of wild forests including juniper trees in EL-Gabal EL-Akhdar area (Figure 8). ...
Shortage of rainfall in arid and semi-arid zones is one of the major factors that restrict the growth of plants, especially in the so-called critical period. The problem has been gaining in importance recently as climatic changes are bringing about more and more frequently long drought spells in the months of spring and summer. Preliminary studies have shown that determinate varieties of some plants are poorer yielders and are more sensitive to water deficit. Therefore, considerations on how weather conditions influenced those characteristics were based primarily on the analysis of the amount and distribution of precipitation over decades. The Phoenician juniper is a species occurring naturally and distributes in the east part of Libya at El-Gabel El-Akhdar (Cyrenica) and it constitutes about 80% of the total vegetation of this area. The pattern of weather conditions in the study area modified the emergence, growth and development as well as the production of Juniper plants. Amount and distribution of rainfall have a strong impact on the development of morphological characteristics in this plant species. Shortage or uneven distribution of rainfall events in the period of spring and summer and increasing the drought period depress plant growth characteristics.
... Fires tend to be concentrated in summer when temperatures are high, and air humidity and fuel moisture are low. Predictions on climate warming in the Mediterranean basin indicate an increase in air temperature and a reduction in summer rainfall (Houghton et al. 1996). Although there is uncertainty on the mean and variance of the precipitation changes, all predictions suggest a future increment in water deficit. ...
Fire is an integral part of many ecosystems, including the Mediterranean ones. However, in recent decades the general trend in number of fires and surface burnt in European Mediterranean areas has increased spectacularly. This increase is due to: (a) land-use changes (rural depopulation is increasing land abandonment and consequently, fuel accumulation); and, (b) climatic warming (which is reducing fuel humidity and increasing fire risk and fire spread). The main effects of fire on soils are: loss of nutrients during burning and increased risk of erosion after burning. The latter is in fact related to the regeneration traits of the previous vegetation and to the environmental conditions. The principal regeneration traits of plants are: capacity to resprout after fire and fire-stimulation of the establishment of new individuals. These two traits give a possible combination of four functional types from the point of view of regeneration after fire, and different relative proportions of these plant types may determine the post-fire regeneration and erosion risk. Field observations in Spain show better regeneration in limestone bedrock type than in marls, and in north-facing slopes than in south-facing ones. Models of vegetation dynamics can be built from the knowledge of plant traits and may help us in predicting post-fire vegetation and long-term vegetation changes under recurrent fires.
... Average precipitation is expected to increase globally (IPCC, 2001), but the magnitude of regional precipitation changes varies among models: with the range 0-50% where the direction of change is strongly indicated, and around -30 to +30% where it is not. For some areas, it shows a positive trend in the daily intensity and a tendency toward higher frequencies of extreme rainfall in the last few decades (Houghton et al., 1996). Among them, the main areas where significant positive trends have been observed are USA (Karl et al., 1995;Trenberth, 1998;Kunkel et al., 1999), eastern and north-eastern Australia (Suppiah and Hennessey, 1998;Plummer et al., 1999), South International Seminar on Sustainable Tropical Environmental Design 2012 Faculty of Design &Architecture, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor, Malaysia: 26-27 November 2012 4 Africa (Mason et al., 1999), UK (Osborn et al., 2000), and northern and central Italy (Brunetti et al., 2000(Brunetti et al., , 2001. ...
Central Alborz protected area in northern Iran includes the unique Caspian forests. But, last
years, climate change caused by human activities, has reduced area and density of that.
Quantifying the historical forest and variability of landscape composition and structure using
simulation modeling is becoming an important means of assessing current landscape
condition and prioritizing landscapes for ecosystem restoration. However, most simulated
time series are generated using static climate conditions which fail to account for the
predicted major changes in future climate. In this paper, climate change was modeled by
using a stochastic weather generator (LARS-WG) and determines future climate change has
an effect on landscape dynamics. Thus, factors such as precipitation, minimum and maximum
daily temperatures in 1985-2005 entered and climate change during 2010 to 2039 has been
modeled. On the other hand, by using remote sensing tools, the destruction of the protected
area and landscape variability in this period is measured. Consequently, the reduction in
winter rainfall, increasing in heavy floods and rising temperature, lead to a reduction in forest
landscape, and pastures and residential areas is increasing dramatically. Forest landscape has
changed to grasslands and arid areas.
... The IPCC talked in its Second Assessment Report about three problems of sensibility, adaptability and vulnerability [25] Vulnerability was understood as the extent to which climate change could be harmful to a system, depending not only on the sensitivity of that system, but also on its ability to adapt to new climate conditions. Vulnerability can thus be defined as the susceptibility (understood in a similar way to probability) a system has to suffer changes. ...
Cost-benefit analysis (CBA) has emerged as one of the most widely used methodologies in environmental policy analysis, with many governments applying it in their decision-making procedures and laws. However, undertaking a full CBA is expensive, and conclusions must be drawn on which project or policy impacts to include in the analysis. Based on the ideas of resilience, vulnerability and risk, we suggest a method for prioritizing project impacts for inclusion in a CBA, which includes both expert assessment and citizen preferences. We then illustrate how the method can be applied in the context of land use change decisions, using a real application.
... Fires tend to be concentrated in summer when temperatures are high, and air humidity and fuel moisture are low. Predictions on climate warming in the Mediterranean basin indicate an increase in air temperature and a reduction in summer rainfall (Houghton et al. 1996). Although there is uncertainty on the mean and variance of the precipitation changes, all predictions suggest a future increment in water deficit. ...
Fire is an integral part of many ecosystems, including the Mediterranean ones. However, in recent decades the general trend in number of fires and surface burnt in European Mediterranean areas has increased spectacularly. This increase is due to: (a) land-use changes (rural depopulation is increasing land abandonment and consequently, fuel accumulation); and (b) climatic warming (which is reducing fuel humidity and increasing fire risk and fire spread). The main effects of fire on soils are: loss of nutrients during burning and increased risk of erosion after burning. The latter is in fact related to the regeneration traits of the previous vegetation and to the environmental conditions. The principal regeneration traits of plants are: capacity to resprout after fire and fire stimulation of the establishment of new individuals. These two traits give a possible combination of four functional types from the point of view of regeneration after fire, and different relative proportions of these plant types may determine the post-fire regeneration and erosion risk. Field observations in Spain show better regeneration in limestone bedrock type than in marls, and in north-facing slopes than in south-facing ones. Models of vegetation dynamics can be built from the knowledge of plant traits and may help us in predicting post-fire vegetation and long-term vegetation changes under recurrent fires.
... The source strength of these ecosystems are estimated to be in a range of 0.05-2.0 Tg N 2 O-N yr Ϫ1 [e.g., Schmidt et al., 1988;Davidson, 1991;Houghton et al., 1992] and 0.1-0.85 Tg NO-N yr Ϫ1 [Davidson, 1991;Potter et al., 1996;Lee et al., 1997]. ...
The process-oriented model PnET-N-DNDC describing biogeochemical cycling
of C- and N and N-trace gas fluxes (N2O and NO) in forest
ecosystems was tested for its sensitivity to changes in environmental
factors (e.g., temperature, precipitation, solar radiation, atmospheric
N-deposition, soil characteristics). Sensitivity analyses revealed that
predicted N-cycling and N-trace gas emissions varied within measured
ranges. For model validation, data sets of N-trace gas emissions from
seven different temperate forest ecosystems in the United States,
Denmark, Austria, and Germany were used. Simulations of N2O
emissions revealed that field observations and model predictions agreed
well for both flux magnitude and its seasonal pattern. Differences
between predicted and measured mean N2O fluxes were <27%.
An exception to this was the N-limited pine stand at Harvard Forest,
where predictions of fluxes deviated by 380% from field measurements.
This difference is most likely due to a missing mechanism in PnET-N-DNDC
describing uptake of atmospheric N2O by soils. PnET-N-DNDC
was also validated for its capability to predict NO emission from soils.
Predicted and measured mean NO fluxes at three different field sites
agreed within a range of ±13%. The correlation between modeled
and predicted NO emissions from the spruce and beech stand at the
Höglwald Forest was r2 = 0.24 (spruce) and r2
= 0.35 (beech), respectively. The results obtained from both sensitivity
analyses and validations with field data sets from temperate forest
soils indicate that PnET-N-DNDC can be successfully used to predict
N2O and NO emissions from a broad range of temperate forest
sites.
... Quand l'intérêt politique pour la question augmente à la fin des années 1970, un premier rapport exhaustif est demandé à l'Académie des sciences américaine. Cette étude de 1979 préfigure les travaux du GIEC en offrant une synthèse des savoirs dans le domaine de la climatologie (Charney et al., 1979Bolin et al., 1995) 1939th Environment Council Meeting, Brussels, 25 June, §Meinshausen et al., 2009 ; Schmidt et Archer, 2009). Il a été repris et affiné dans deux rapports, ainsi que par Nicolas Stern dans son dernier ouvrage (IEA, 2009 ; WBGU, 2009 ; Stern, 2009).Sarewitz et Pielke, Jr., 2000 ; Pielke, Jr., 2007). ...
In less than thirty years, climate change became a both scientific and geopolitical crucial stake, concerning a great variety of research groups, epistemic communities, and political actors. An international organisation of scientific assessment– the International Panel of Climate Change (IPCC)– played a key role in the domain and tends to become a paradigmatic model for other international scientific assessments. In this paper, we wanted to analyse this evolution of climate change regime, the IPCC, and the feedbacks of this evolution in France on the climate sciences community.
... E-mail: muthuvel.chelliah@ncep.noaa.gov tion of these trends to specific causes has been one of the most difficult, challenging, and contentious areas of climate research of this century (Houghton et al. 1996; Barnett et al. 1999 ). The conceptual and technical difficulties associated with developing, testing, and applying climate change detection and attribution methods are compounded by a scarcity of appropriate data to study the problem. ...
Uncertainties in estimates of tropospheric mean temperature were investigated in the context of climate change detection through comparisons of the National Centers for Environmental Prediction-National Center for Atmospheric Research (NCEP-NCAR) 40-yr reanalysis (1958-97), the National Aeronautics and Space Administration Data Assimilation Office (NASA/DAO) 14-yr reanalysis (1980-93), the European Centre for Medium-Range Weather Forecasts Reanalysis Project (ERA) 15-yr reanalysis (1979-94), and the satellite microwave sounding unit channel 2 (MSU Ch2) (1979-97) temperature data. The maximum overlap period for comparison among these datasets is the 14 full years January 1980 to December 1993. This study documents similar shifts in the relative bias between the MSU Ch2 and the ERA and the NCEP-NCAR reanalyses in the 1991-97 period suggesting changes in the satellite analysis. However, the intercomparisons were not able to rule out the changes in the reanalysis systems and/or the input data on which the reanalyses are based as prime factors for the changes in the relative bias between the MSU and ERA and NCEP-NCAR reanalyses.These temporal changes in the relative bias among the reanalyses suggest their limitations for global change studies. Nonetheless, the analysis also shows that the pattern correlations (r) between the MSU Ch2 monthly mean fields and each of the reanalyses are very high, r > 0.96, and remain relatively high for the anomaly fields, r > 0.8, generally >0.9. This result suggests that reanalysis may be used for comparisons to numerical model-generated forecast fields (from GCM simulation runs) and in conjunction with `fingerprint' techniques to identify climate change.In comparisons of the simple linear trends present in each dataset for the 1980-90 period, each of the reanalyses had spatial patterns similar to MSU Ch2 except that the NCEP-NCAR reanalysis showed smaller `positive' (warming) trends in comparison with the MSU while the ERA reanalysis showed larger positive trends. The NASA/DAO reanalysis showed a mixed pattern. Many regions of the globe are identified that showed consistent warming/cooling patterns among the major reanalyses and MSU, even though there were disagreements in the exact magnitude among the analyses. The spatial patterns of linear trends changed, however, with the addition of three years of data to extend the trend analysis to the 1980-93 period. This result suggests that such simple linear trend analyses are very sensitive to the temporal span in these relatively short datasets and thus are of limited usefulness in the context of climate change detection except, however, when the signal is large and shows consistency among all datasets.The long record (1958-96) of seasonal mean 2-m temperature anomalies from NCEP-NCAR reanalysis is well correlated with gridded analyses of station-based observed surface temperature, with correlations between 0.65 and 0.85. It is argued that these correlations might suggest an upper limit to the magnitudes of the pattern correlations that might be obtained by correlating observed surface temperature analyses with those from multiyear GCM simulation runs made in the context of fingerprint climate change detection.
... Recently, many studies have examined the impact of changed greenhouse-gas concentrations (e.g. Mitchell, 1989; Houghton et al., 1996 Houghton et al., , 2001 Yang et al., 2003) or changed land-cover (e.g. Sud et al., 1996; Chase et al., 1999; Bounoua et al., 2002; Mölders and Kramm, 2007) on water-cycle-relevant quantities (e.g. ...
The Community Climate System Model version 2.0.1 is running for 40 years under 355 ppm CO2 conditions, without and with natural and anthropogenic land-cover changes that are assumed in the inner core of four hydrothermally different, but similar-sized (≈3.27x106 km2) regions (Yukon, Ob, St. Lawrence, Colorado, and lands adjacent to them). A further set of simulations assumes 710 ppm CO2 conditions without and with these land-cover changes. Impacts of (1) doubled CO2, (2) changed land-cover, and (3) the interaction between doubled CO2 and changed land-cover on the four regional water cycles are elucidated using analysis of variance plus multiple testing. For the Yukon, Ob, and St. Lawrence regions, doubling CO2 significantly increases precipitation, evapotranspiration, and residence time nearly year-round; the opposite is true for precipitation and evapotranspiration in Colorado. In general, doubling CO2 slows down water cycles regardless of land-cover changes. Since land-cover changes occur locally, they more strongly affect regional than global water cycling. Sometimes land-cover changes alone reduce regional-scale precipitation and evapotranspiration. Water-cycle changes of comparable absolute magnitude can occur in response to either changed land-cover or doubled CO2. Significant interactions between the two treatments indicate that local land-cover changes, even if they have little impact under reference climate conditions, may have substantial regional impact in a warmer climate. Increased residence time after doubling CO2 indicates a generally increased influence of upwind regions on downwind regions. If land-cover changes occur concurrently with CO2 changes, they will have farther-reaching impact than under reference CO2 conditions. Thus, due to atmospheric transport the interaction between impact of land-cover changes and CO2 doubling on water-cycle-relevant quantities may occur even in regions with unchanged land-cover. A sensitivity study for tripled CO2 showed similar results, but more pronounced slowed-down regional water cycles and interaction of the two treatments. Copyright © 2008 Royal Meteorological Society
... Studies on climate change in the Mediterranean basin predict an increase in temperatures and a reduction in summer precipitation, with concomitant increases in potential evapotranspiration, water deficit and forest fire risk (Brotak and Reifsnyder, 1976;Houghton et al., 1996;Easterling, 1997;Piñol et al., 1998). In fact, in the ongoing discussion on climate change, summer temperatures are considered a parameter of interest and concern in so far as any hypothetical increase in the number of intense-heat situations and/or persistent heatwaves could affect areas as diverse as public health, energy consumption, fauna, flora and natural biodiversity, as well as simple climatic comfort (Austin Miller, 1982;Kalkstein and Valimont, 1986). ...
Within the area of climate change, summer temperatures are of special interest because of the economic, social and environmental consequences that can derive from their hypothetical increase. A number of recent studies have shown a worldwide trend towards increasing summer temperatures. In this work, we analyse summer temperatures (July and August) in the Valencia region of Spain from 1958 to the present, with the aim of characterising their evolution and detecting any trend towards a higher frequency of warmer days. First results indicate that in our study area there is indeed a higher frequency of days with tropical characteristics and persistent heat; in contrast, we found no tendency to exceed the records of absolute maximum temperatures. Copyright © 2006 Royal Meteorological Society.
... Currently developed scenarios of climate change within the next century indicate that water deficit in the Mediterranean basin would increase (Houghton et al. 1996; Piñol et al. 1998). This change would lead to an increment in water stress conditions for plants, changes in fuel conditions and, consequently, changes in the fire regime. ...
In the Mediterranean basin, the climate is predicted to be warmer and effectively drier, leading to changes in fuel conditions and fire regime. Land abandonment in the Mediterranean basin is also changing the fire regime through the increase in fuel loads. In the present study, two simulation models of vegetation dynamics were tested in order to predict changes in plant functional types due to changes in fire recurrence in eastern Spain. The two modelling approaches are the FATE-model (based on vital attributes) and the gap model BROLLA (based on the gap-phase theory). The models were arranged to simulate four functional types, based mainly on their regenerative strategies after disturbance: Quercus (resprouter), Pinus (non-resprouter with serotinous cones), Erica (resprouter), and Cistus (non-resprouter with germination stimulated by fire). The simulation results suggested a decrease in Quercus abundance, an increase in Cistus and Erica, and a maximum of Pinus at intermediate recurrence scenarios. Despite their different approaches, both models predicted a similar response to increased fire recurrence, and the results were consistent with field observations.
... Total annual rainfall ranges from <300 up to 900 mm, but irregularly distributed within and between years. Predictions for climatic change due to doubling CO 2 in the MB indicate an increase in air temperature and a reduction in summer rainfall (Houghton et al. 1996). Although there is uncertainty on the mean and variance of the precipitation changes, all predictions suggest a future increment in water deficit. ...
Gap models have been applied to a wide range of ecosystems, mainly temperate and boreal forests, but rarely have such models been applied to Mediterranean ecosystems. In the present review we address some problems of gap models for predicting the long-term dynamics of Mediterranean ecosystems, and we suggest plant functional types suitable for modelling based on responses to disturbance. Most gap models do not take into account different life forms, interactions with fire (e.g., resprouting and stimulation of the germination), and underground structures. Long term human impact on Mediterranean ecosystems has made a significant impact on the current landscapes. That intense land use, involving long-lived slow-growing species, has had long-term consequences. It is not possible to understand Mediterranean vegetation and to validate any model without considering these factors. The lack of data for Mediterranean species may be overcome by taking into account correlations of traits and trade-offs between different functional types. A simple disturbance-based functional group system is discussed.
... Amongst the various manifestations of global environmental change the issue of climatic changes, particularly those related to atmospheric accumulation of " greenhouse gases " , has attracted the attention of the research community, decision makers, and the public. It is now widely accepted that human-induced changes in climate are likely in the next century if not apparent already, and that they will have or are having significant implications for societies and economies (Houghton et al., 1996; Watson et al., 1996; Bruce rt al., 1996). International concerns over global climatic change and its consequences are reflected in the 1992 United Nations Conference on Environment and Development (UNCED) which developed the Framework Convention on Climate Change (FCCC) signed by 154 countries, many of whom now have national plans to address the " problem " of climate change. ...
Recent developments in both the policy arena and the climate impacts research community point to a growing interest in human adaptation to climatic variability and change. The Importance of adaptation in the climate change question is affirmed in the Intergovernmental Panel on Climate Change (IPCC) Technical Guidelines for Assessing Impacts and Adaptations and the IPCC's more recent Second Assessment Report. Yet, the nature and processes of human adaptation to climate are poorly understood and rarely investigated directly. Most often, human responses of one form or another are simply assumed in impacts research. Analyses that do address adaptation use a variety of interpretations and perspectives resulting in an Incomplete, and at times inconsistent, understanding of human adaptation to environmental variations. This paper reviews and synthesizes perspectives from an eclectic body of scholarship to develop a framework for characterizing and understanding human adaptation to climatic variability and change. The framework recognizes the characteristics of climatic events, the ecological properties of systems which mediate effects, and the distinctions which are possible among different types of adaptation. A classification scheme is proposed for differentiating adaptation strategies.
... The source strength of these ecosystems are estimated to be in a range of 0.05–2.0 Tg N 2 O-N yr 1 [e.g., Schmidt et al., 1988; Davidson, 1991; Houghton et al., 1992] and 0.1– 0.85 Tg NO-N yr 1 [Davidson, 1991; Potter et al., 1996; Lee et al., 1997]. These uncertainties are mainly due to (1) the limited number of field measurements; (2) the restricted temporal coverage of data sets to assess daily, seasonal, and interannual variations in fluxes Gasche and Papen, 1999] ; (3) limited information on the impact of anthropogenic influences (e.g., enhanced atmospheric N input into these ecosystems leading to changes in source strengths) [Butterbach-Bahl et al., 1998]; and (4) a lack of information about the effects of different forest types (e.g., coniferous, deciduous forests) on N-trace gas emissions from forest soils. ...
To predict emissions of nitrous oxide (N2O) and nitric oxide (NO) from forest soils, we have developed a process-oriented model by integrating several new features with three existing models, PnET, Denitrification-Decomposition (DNDC), and a nitrification model. In the new model, two components were established to predict (1) the effects of ecological drivers (e.g., climate, soil, vegetation, and anthropogenic activity) on soil environmental factors (e.g., temperature, moisture, pH, redox potential, and substrates concentrations), and (2) effects of the soil environmental factors on the biochemical or geochemical reactions which govern NO and N2O production and consumption. The first component consists of three submodels for predicting soil climate, forest growth, and turnover of soil organic matter. The second component contains two submodels for nitrification and denitrification. A kinetic scheme, a so-called ââ¬Åanaerobic balloon,ââ¬Â was developed to calculate the anaerobic status of the soil
... durch¨Anderungdurch¨ durch¨Anderung der Atmosphärenzusammensetzung massiv gestört. Erste Ergebnisse dieses globalen Experiments können im IPCC Report (Bolin et al., 1996) nachgelesen werden. Bei der Vorhersage solcher anthropogen induzierter Veränderungen stößt man immer wieder auf ein grundlegendes Problem: Experimente mit dem Erdsystem als ganzes sind nicht möglich. ...
Thesis (doctoral)--Universität, Potsdam, 2000.
The Himalayan region, renowned for its magnificent beauty and ecological significance, has been severely impacted by disasters, with Himachal Pradesh emerging as one of the most affected states. In 2023, it was particularly impacted with heavy monsoon rains in three spells, leading to extensive flooding and landslides. The first spell took place on 7–11 July, while the second took place on 11–14 August, and the final spell occurred on 21–23 August. Due to intensive and heavy rainfall, Himachal Pradesh experienced numerous disasters, including flash floods, landslides, cloudbursts, and landslips. Himachal Pradesh suffered losses of approximately 12 000 crore rupees and over 500 lives, as stated by the state government, due to these calamities. A mixed method research approach (quantitative and qualitative research) was utilised using existing reports for present research. The main aim of this research paper is to emphasise the comprehensive analysis of disasters, encompassing various sectors such as housing, education, health, road and transportation, water and sanitation, power, agriculture, horticulture, animal husbandry, and fisheries. Mitigation measures for each sector are also discussed subsequently. This paper also highlights the urgent need for specific coordinated efforts at multiple levels to safeguard the Himalayan ecosystem.
Climate history is an important resource in the study of the Great Geophysical Experiment being performed on the planet, that is, the large-scale release of greenhouse gases (carbon dioxide and methane, and also others). Climate history is crucial in establishing that man-made global warming is an historic fact. The probability that recent warming has occurred independently of greenhouse gases derived from human activity is very small. The task is to make the best possible assessment of potential effects of global warming on regional agriculture and public health. The Great Experiment is a test of the response of the climate system to disturbance. It is also a test of the ability of human society to deal with environmental problems on a global scale.
In history there is a rich store of experience concerning climate change, which we need to mobilize to assess the risks of the future. Information can be derived on many different time scales: from the last 1000 years (containing the “Little Ice Age”), from deglaciation (containing the enigmatic “Younger Dryas” cold spell) and even from periods millions of years ago. Climate history is not supposed to deliver analogs, but to expand our thinking and make us ask pertinent questions. Perhaps the worst of the bad-case scenarios associated with global warming is the notion that ocean warming can lead to large-scale release of methane from the sea floor. Apparently it did in the distant past, at the end of the Paleocene, 55 million years ago. Venting of methane is proceeding right now. The question is, will it accelerate.
Traditional historians are reluctant to admit a strong role for climate in human history. However, as climate is becoming a product of human activities, it automatically becomes part of history; climate has entered the narrative of what humans do to each other.
Observational records from 1950 onwards and climate projections for the 21st century provide evidence that droughts are a recurrent climate feature in large parts of Europe, especially in the Mediterranean, but also in western, south-eastern and central Europe. Trends over the past 60 years show an increasing frequency, duration and intensity of droughts in these regions, while a negative trend has been observed in north-eastern Europe. With a changing climate, this tendency is likely to be reinforced during the 21st century, affecting a wide range of socioeconomic sectors.
Human activities such as conversion of natural ecosystem to croplands and urban-centers, deforestation and afforestation impact biophysical properties of land surface such as albedo, energy balance, and surface roughness. Alterations in these properties affect the heat and moisture exchanges between the land surface and atmospheric boundary layer. The objectives of this research were; (i) to quantitatively identify the High plains’ regional climate change in temperatures over the period 1895 to 2006, (ii) detect the signatures of anthropogenic forcing of LULC changes on the regional climate change of the High Plains, and (iii) examine the trends in evolving regional latent heat flux under the changing climate during the past thirty years.
We investigated the regional climate change by comparing two trend periods, the reference period (1895 – 1930) and the warming period (1971 – 2006), using the base period as 1935 – 1965. For the objective (ii) the study developed an enhanced signal processing procedure to maximize the signal to noise ratio by introducing a pre-filtering technique of ARMA modeling, before applying the optimal fingerprinting technique to detect the signals of LULC change. For the objective (iii), we estimated ETc using the widely accepted two-step approach. We developed a linear model to estimate spatial crop coefficient (Kc) from AVHRR-based NDVI. The Kc estimates were used to adjust spatial ETo estimates, thereby yielding spatial ETc estimates that are representative of the summer latent heat fluxes of years 1981 to 2006.
The results from the study show that, the overall warming trend in the High Plains was about 0.11oC/decade. The minimum temperature had the strongest warming at a rate of 0.19oC/decade. Due to LULC changes attributed to increase in irrigation application and vegetation surfaces, more surface energy in summer is being redistributed into latent heat flux. Therefore, there is a significant influence of evaporative cooling on regional temperatures during summer season. As a result, the greenhouse warming effect in the region is being surpassed.
The low frequency variability in the surface air pressure (SAP) field
is investigated using the NCEP/NCAR 40-year reanalysis data. The EOF1
(EOF2), which accounts for 36% (21%) of total variance of the zonal mean
anomalous SAP, corresponds to the air mass oscillation in the middle and
high latitudes of the Southern (Northern) Hemisphere. While the total
air mass is conserved globally, EOF3 (14.5%) represents the air mass
redistribution between the two hemispheres on time-scales ranging from
several months to a decade. This is referred to as the interhemispheric
oscillation (IHO). An index is defined to describe the IHO variability.
The EOF3 explains 65% of the total variance of the IHO index. Moreover
14.5% of the total variance of the zonal mean SAP anomalies represents
the variability of the IHO.
Simulations using global coupled climate models predict a climate change due to the increasing concentration of greenhouse gases and aerosols in the atmosphere. Both are associated with the burning of fossil fuels. There has been considerable debate if this postulated human influence is already evident. This paper gives an overview on some recent material on this question. One particular study using optimal fingerprints (Hegerl et al., 1996) is explained in more detail. In this study, an optimal fingerprint analysis is applied to temperature trend patterns over several decades. The results show the probability being less than 5% that the most recently observed 30 year trend is due to naturally occurring climate fluctuations. This result suggests that the present warming is caused by some external influence on climate, e.g. by the increasing concentrations of greenhouse gases and aerosols. More work is needed to address the uncertainties in the magnitude of naturally occurring climate fluctuations. Also, other external influences on climate need to be investigated to uniquely attribute the present climate change to the human influence.
Twentieth century trends of precipitation are examined by a variety of methods to more fully describe how precipitation has changed or varied. Since 1910, precipitation has increased by about 10% across the contiguous United States. The increase in precipitation is reflected primarily in the heavy and extreme daily precipitation events. For example, over half (53%) of the total increase of precipitation is due to positive trends in the upper 10 percentiles of the precipitation distribution. These trends are highly significant, both practically and statistically. The increase has arisen for two reasons. First, an increase in the frequency of days with precipitation ]6 days (100 yr)1[ has occurred for all categories of precipitation amount. Second, for the extremely heavy precipitation events, an increase in the intensity of the events is also significantly contributing (about half) to the precipitation increase. As a result, there is a significant trend in much of the United States of the highest daily year-month precipitation amount, but with no systematic national trend of the median precipitation amount.These data suggest that the precipitation regimes in the United States are changing disproportionately across the precipitation distribution. The proportion of total precipitation derived from extreme and heavy events is increasing relative to more moderate events. These changes have an impact on the area of the United States affected by a much above-normal (upper 10 percentile) proportion of precipitation derived from very heavy precipitation events, for example, daily precipitation events exceeding 50.8 mm (2 in.).
A revised framework is presented that quantifies observed changes in the climate of the contiguous United States through analysis of a revised version of the U.S. Climate Extremes Index (CEI). The CEI is based on a set of climate extremes indicators that measure the fraction of the area of the United States experiencing extremes in monthly mean surface temperature, daily precipitation, and drought (or moisture surplus). In the revised CEI, auxiliary station data, including recently digitized pre-1948 data, are incorporated to extend it further back in time and to improve spatial coverage. The revised CEI is updated for the period from 1910 to the present in near–real time and is calculated for eight separate seasons, or periods.
Results for the annual revised CEI are similar to those from the original CEI. Observations over the past decade continue to support the finding that the area experiencing much above-normal maximum and minimum temperatures in recent years has been on the rise, with infrequent occurrence of much below- normal mean maximum and minimum temperatures. Conversely, extremes in much below-normal mean maximum and minimum temperatures indicate a decline from about 1910 to 1930. An increasing trend in the area experiencing much above-normal proportion of heavy daily precipitation is observed from about 1950 to the present. A period with a much greater-than-normal number of days without precipitation is also noted from about 1910 to the mid-1930s. Warm extremes in mean maximum and minimum temperature observed during the summer and warm seasons show a more pronounced increasing trend since the mid-1970s. Results from the winter season show large variability in extremes and little evidence of a trend. The cold season CEI indicates an increase in extremes since the early 1970s yet has large multidecadal variability.
This paper is concerned with identifying the spatial and temporal patterns in the annual maximum and minimum water level in the Pearl River Delta (PRD) region. The Mann–Kendall test and Pettitt test are used to detect trends and abrupt change points, and the Trend Free Pre-Whitening (TFPW) approach then eliminates the effect of serial correlation in data series with significant autocorrelation. Approximately fifty years of the annual hydrological variables from 18 stations in the three major rivers (the West River, the North River, and the East River) are examined. The changing trends of the extremes in water level show different features in different parts of the PRD region. Generally speaking, in the upper part of the delta, the water levels show a decreasing trend while in the middle and lower part there is an increasing trend. This spatial pattern of the extreme water level variation is unlikely to be due to a long-term change in stream flow in the PRD region because the water level changes do not always coincide with the extreme stream flow variations. Sand excavation initiated in the 1980s and continuing for more than 20years in almost all tributaries around the PRD region is one of the most serious intensive human activities affecting water levels. The result of the Pettitt test indicates that most abrupt change points occurred in 1980s–1990s, which reveals that sand excavation and channel regulation are likely to have been the most significant factors contributing to the change over this period. These anthropogenic activities modify the annual extreme water level dramatically in a way that affects the morphology of river channels and estuaries of the PRD and also the redistribution of discharge. However, there are differences in the geographic locations of significant trends for the water level investigated, which implies that these impacts are not spatially uniform.
As preparation of the IPCC's Third Assessment Report takes place, one of the many observed climate variables of key interest is cloud amount. For several nations of the world, there exist records of surface-observed cloud amount dating back to the middle of the 20th Century or earlier, offering valuable information on variations and trends. Studies using such databases include Sun and Groisman (1999) and Kaiser and Razuvaev (1995) for the former Soviet Union, Angel1 et al. (1984) for the United States, Henderson-Sellers (1986) for Europe, Jones and Henderson-Sellers (1992) for Australia, and Kaiser (1998) for China. The findings of Kaiser (1998) differ from the other studies in that much of China appears to have experienced decreased cloudiness over recent decades (1954-1994), whereas the other land regions for the most part show evidence of increasing cloud cover. This paper expands on Kaiser (1998) by analyzing trends in additional meteorological variables for Chi na [station pressure (p), water vapor pressure (e), and relative humidity (rh)] and extending the total cloud amount (N) analysis an additional two years (through 1996).
The effect of future climate variability combined with geographic and soil information from Sardinia island, Italy on agriculture in Mediterranean region, was investigated using a Land Capability for Agriculture (LCA) classification system. By the use of soil and land cover maps, the territory of Sardinia was classified in pedological LCA classes ranging from 1 to 8. The climatic LCA classification was extended to the whole island territory using temperature and precipitation data from about 200 weather stations. The results show that LCA classification is sensitive to weather variability and that the determination of climatic risk for agriculture requires climatic variability to be included into Land Evaluation models.
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This study investigates the temporal and spatial variation of soil moisture associated with global warming as simulated by long-term integrations of a coupled ocean-atmosphere model conducted earlier. Starting from year 1765, integrations of the coupled model for 300 years were performed for three scenarios: increasing greenhouse gases only, increasing sulfate-aerosol loading only and the combination of both radiative forcings. The integration with the combined radiative forcings reproduces approximately the observed increases of global mean surface air temperature during the 20th century. Analysis of this integration indicates that both summer dryness and winter wetness occur in middle-to-high latitudes of North America and southern Europe. These features were identified in earlier studies. However, in the southern part of North America where the percentage reduction of soil moisture during summer is quite large, soil moisture is decreased for nearly the entire annual cycle in response to greenhouse warming. A similar observation applies to other semi-arid regions in subtropical to middle latitudes such as central Asia and the area surrounding the Mediterranean Sea. On the other hand, annual mean runoff is greatly increased in high latitudes because of increased poleward transport of moisture in the warmer model atmosphere. An analysis of the central North American and southern European regions indicates that the time when the change of soil moisture exceeds one standard deviation about the control integration occurs considerably later than that of surface air temperature for a given experiment because the ratio of forced change to natural variability is much smaller for soil moisture compared with temperature. The corresponding lag time for runoff change is even greater than that of either precipitation or soil moisture for the same reason. Also according to the above criterion, the inclusion of the effect of sulfate aerosols in the greenhouse warming experiment delays the noticeable change of soil moisture by several decades. It appears that observed surface air temperature is a better indicator of greenhouse warming than hydrologic quantities such as precipitation, runoff and soil moisture. Therefore, we are unlikely to notice definitive CO2-induced continental summer dryness until several decades into the 21st century.
The vulnerability of grassland vegetation in Inner Mongolia to climate change and grazing was examined using an ecosystem model. Grazing is an important form of land use in this region, yet there are uncertainties as to how it will be affected by climate change. A sensitivity analysis was conducted to study the effects of increased minimum and maximum temperatures, ambient and elevated CO2, increased or decreased precipitation, and grazing on vegetation production. Simulations showed that herbaceous above ground net primary production was most sensitive to changes in precipitation levels. Combinations of increased precipitation, temperature, and CO2 had synergistic effects on herbaceous production, however drastic increases in these climate scenarios left the system vulnerable to shifts from herbaceous to shrub-dominated vegetation when grazed. Reduced precipitation had a negative effect on vegetation growth rates, thus herbaceous growth was not sustainable with moderate grazing. Shifts in temporal biomass patterns due to changed climate have potentially significant implications for grazing management, which will need to be altered under changing climate to maintain system stability.
A striking climate warming over the Tibetan Plateau during the last decades has been revealed by many studies, but evidence
linking it to human activity is insufficient. By using historical observations, here we show that the in situ climate warming is accompanied by a distinct decreasing trend of the diurnal range of surface air temperature. The ERA40
reanalysis further indicates that there seems to be a coherent warming trend near the tropopause but a cooling trend in the
lower stratosphere. Moreover, all these features can be reproduced in two coupled climate models forced by observed CO2 concentration of the 20th century but cannot be produced by the fixed external conditions before the industrial revolution.
These suggest that the recent climate warming over the Tibetan Plateau primarily results from the increasing anthropogenic
greenhouse gases emissions, and impacts of the increased greenhouse gases emissions upon the climate change in the plateau
are probably more serious than the rest of the world.
Sustainable water use in the piedmont region of the Taihang Mountains in the northern part of the North China Plain (NCP) is under serious crisis due to the rapid depletion of groundwater caused mainly by pumping for agricultural irrigation. The development of water-conserving agricultural practices is essential in order to limit agricultural water use. To find an effective way to save water in the wheat-growing season without markedly reducing wheat yield, DSSAT-wheat was calibrated, validated and used to simulate water use by winter wheat. The simulations suggest: (1) since a moderately low growth in the leaf area index (LAI) of wheat does not result in low yield, moderate water deficits in March can save water, and therefore, the aim should be to avoid irrigation in March. (2) Depending on the soil water condition, irrigation in mid November is recommended to obtain a good growth of LAI and to create a moderate condition for water stress in March. (3) After the start of the growth of the ears (around 15 April), water deficits should be avoided so as to ensure there is no influence on ear growth and grain filling. Simulation of a 12-year period showed that when irrigation practice follows the above three principles, 76 mm of evapotranspiration and 99.5 mm irrigation water can be saved without much reduction in the yield of winter wheat (only 4.5%). This is sufficient to decrease the drawdown of groundwater by 0.42 m a−1 and to improve water use efficiency from 1.27 to 1.45 kg m−3.
As climate change increases vegetation combustibility, humans are impacted by wildfires through loss of lives and property, leading to an increased emphasis on prescribed burning practices to reduce hazards. A key and pervading concept accepted by most environmental managers is that combustible ecosystems have traditionally burnt because plants are fire adapted. In this opinion article, we explore the concept of plant traits adapted to fire in Mediterranean climates. In the light of major threats to biodiversity conservation, we recommend caution in deliberately increasing fire frequencies if ecosystem degradation and plant extinctions are to be averted as a result of the practice.
The main intent of this paper is to present a review on the application of time series analysis techniques in hydrology and climatology. An overview of various statistical tests for detecting and estimating the hydrologic time series characteristics (i.e., homogeneity, stationarity, trend, periodicity, and persistence) is presented, together with their merits and demerits followed by comprehensive reviews of past studies (both basic and applied), and future research directions. The present review revealed that the climatologic time series of precipitation, air temperature, evapotranspiration and climatic change, and the hydrologic time series of streamflow and surface water quality have received a great deal of attention worldwide. Although the application areas of time series analysis techniques are expanding with growing concerns about climate change and global warming, their application is still very limited in groundwater hydrology as well as for non-traditional hydrologic time series. It is also apparent from this review that the detection of trend and stationarity by parametric and/or nonparametric tests has been a major focus in the past. Multiple comparison tests lack appreciation by the researchers for testing homogeneity in the hydrologic and climatologic time series. Furthermore, most studies have ignored the importance of testing periodicity and persistence in the time series, which are equally important properties of hydrologic and climatologic time series. Based on the comprehensive review, future research needs for time series studies in hydrology and climatology are discussed.
Anthropogenic, or human-induced, climate change is a critical issue in science and in the affairs of humankind. Though the target of substantial research, the conclusions of climate change studies remain subject to numerous uncertainties. This article presents a very brief review of the basic arguments regarding anthropogenic climate change with particular emphasis on uncertainty.
The humidity of the free troposphere is being increasingly scrutinized in climate research due to its central role in global warming theory through positive water vapor feedback. This feedback is the primary source of global warming in general circulation models (GCMs). Because the loss of infrared energy to space increases nonlinearly with decreases in relative humidity, the vast dry zones in the Tropics are of particular interest. These dry zones are nearly devoid of radiosonde stations, and most of those stations have, until recently, ignored the low humidity information from the sondes. This results in substantial uncertainty in GCM tuning and validation based on sonde data. While satellite infrared radiometers are now beginning to reveal some information about the aridity of the tropical free troposphere, the authors show that the latest microwave humidity sounder data suggests even drier conditions than have been previously reported. This underscores the importance of understanding how these low humidity levels are controlled in order to tune and validate GCMs, and to predict the magnitude of water vapor feedback and thus the magnitude of global warming.
One of the major concerns with a potential change in climate is that an increase in extreme events will occur. Results of
observational studies suggest that in many areas that have been analyzed, changes in total precipitation are amplified at
the tails, and changes in some temperature extremes have been observed. Model output has been analyzed that shows changes
in extreme events for future climates, such as increases in extreme high temperatures, decreases in extreme low temperatures,
and increases in intense precipitation events. In addition, the societal infrastructure is becoming more sensitive to weather
and climate extremes, which would be exacerbated by climate change. In wild plants and animals, climate-induced extinctions,
distributional and phenological changes, and species' range shifts are being documented at an increasing rate. Several apparently
gradual biological changes are linked to responses to extreme weather and climate events.
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