Conference PaperPDF Available

Global warming and cooling for last 2,000 years mimic Sun's magnetic activity, not CO2: scientific literature synthesis

  • Geoclastica Ltd


INTRODUCTION. In the abstract book (below, or download) of the 2021 'Climate Change in the Geological Record' conference of the Geological Society of London, please search 'Higgs' for my 500-WORD ABSTRACT. For my ACCOMPANYING POSTER (pdf, 10 slides, 10-minutes) & 60-second VIDEO introducing it (MP4, 2MB), click on 'Linked data''. The conference webpage at says"This symposium is arranged in conjunction with the Geological Society’s scientific statement on climate change". My January 2021 critique of that appallingly flawed December 2020 'scientific statement' is at & at … The anti-CO2 bias of the programme is discussed here … … Please forward this ResearchGate link to colleagues, friends, family, teachers and politicians. The more people that learn the climate truth the better for society. Please see also my 1st August 2021 invited letter to John Kerry, United States Special Presidential Envoy for Climate …
26-27 May
What the geological record tells us about our
present and future climate
By reconstructing past climate changes, we can better
understand the dynamics of the climate system and
hence the range of impacts possible under current
warming. This symposium will address key questions
about past climate change and what those past changes
tell us about the future.
Climate change in the
geological record
(c) Ingrid Demaerschalk
May 26, 2021
Climate change in the geological record
What the geological record tells us about our past and future
Conference Programme
26 May 2021
Welcome address
Paul Valdes
Invited: Why has climate changed in the past?
Aidan Starr
ECR Flash talk: Antarctic icebergs reorganize ocean
circulation during Pleistocene glacials
Anna von der
Invited: How does the geological record inform our
quantification of climate sensitivity?
ECR Flash talk: Mechanisms of South American Monsoon
System response to external variability over the last
Darrell Kaufman
Invited: Is our current warming unusual?
Bette Otto
Invited: How can the geological record be used to evaluate
climate models?
Pam Vervoort
ECR Flash Talk: Negative carbon isotope excursions: an
interpretative framework
Maureen Raymo
Plenary Lecture: What the geological record tells us about
our present and future climate
27 May 2021
Welcome address
Daniela Schmidt
Invited: When Earth's temperature changed in the past,
what were the impacts?
Rachel Brown
ECR Flash talk: Late Miocene CO
and climate: divorced or
an old married couple?
Alan Haywood
Invited: Are there past climate analogues for the future?
ECR Flash talk: Strongly reduced meridional gradients in
water isotopes in the early Eocene hothouse
Jess Tierney
Invited: What does the geological record of climate change
look like?
Invited: What does the geological record indicate about
global v. regional change?
Poster talks
One minute flash talks from the poster authors
Rachael James
Invited: What is the role of geology in dealing with the
climate emergency for a sustainable future?
Poster breakouts
May 26, 2021
Poster presentations
Brian Richard Lewis
Howard Dewhirst
Ashley Francis
using glacier, sea level and HadCRUT4 surface temperature
Thomas Gernon
William R Gray
Roger Higgs
Gordon Inglis
Amy Jewell
Olaf K Lenz
Paleogene greenhouse on a coastal wetland in Northern
Valeria Luciani
Alan Maria Mancini
cyclical climatic and environmental changes during the
Messinian: a possible analogue for the future impact on the
Christopher John
Peter Francis Owen
Benjamin Petrick
Ellie Pryor
James Rae
Tammo Reichgelt
Marci Robinson
Matthew L Staitis
Douwe George van
der Meer
Aja Watkins
May 26, 2021
May 26, 2021
Climate change in the geological record
What the geological record tells us about our past and future
Flash talk and poster abstracts by theme
1. What does the geological record of climate change look like?
Understanding provenance changes in sediments supplying the South East
African Margin
Ellie Pryor* (School of Earth and Environmental Sciences, Cardiff University, Cardiff, CF10 3AT,
United Kingdom), Ian Hall (School of Earth and Environmental Sciences, Cardiff University, Cardiff,
CF10 3AT, United Kingdom), Morten Andersen (School of Earth and Environmental Sciences, Cardiff
University, Cardiff, CF10 3AT, United Kingdom), Daniel Babin (Department of Earth and
Environmental Sciences, Lamont-Doherty Earth Observatory, Columbia University, USA), Sidney
Hemming (Department of Earth and Environmental Sciences, Lamont-Doherty Earth Observatory,
Columbia University, USA), Jeroen van der Lubbe (Department of Earth Sciences, Cluster
Geochemistry & Geology, VU University Amsterdam), and Margit Simon (NORCE Norwegian
Research Centre, Bjerknes Centre for Climate Research, Bergen, Norway).
The South African region provides abundant archaeological evidence of cultural and
technological innovations of anatomically modern humans during the Middle Stone Age
(MSA), 100-50ka BP. It has been widely speculated that these industries were facilitated by
specific climatological and environmental conditions in this region. In order to reconstruct
these MSA environmental settings, a multiproxy study is being completed utilising modern-
day river sediments collected along the South East coast of South Africa (29°48.583 S -
34°18.8 S) as well as long marine sediment cores retrieved from the adjacent offshore
Agulhas Current System.
Marine sediment core MD20-3591 (36°43.707 S; 22°9.151 E, 2464m water depth) which
spans 450 ka was retrieved from the Agulhas Passage, ~ 150 km offshore of Blombos Cave,
a key MSA archaeological site. This marine core has the potential to record both marine
(Agulhas Current) and terrestrial hydrological (river discharge) variability.
During the last glacial low stand, the wide continental shelf South of Africa was sub-aerially
exposed, and rivers flowed across this plain within a subdued incised valley delivering their
sediments to the ocean.
Understanding the provenance of these deposited sediments could play an important role in
reconstructing sediment delivery by different rivers related to terrestrial hydrology. This is of
key importance for understanding transport history and characterising sediment source
regions in the marine and terrestrial environment.
Here, we present initial results of the present-day radiogenic isotopic fingerprints
(Neodymium and Strontium isotopes and clay mineralogy) of South African river catchment
signals from river sediment samples with the aim to gain a broad spatial coverage of the
source rock geology in the region and their relative contributions of terrigenous sediment
delivered to the ocean. This information will be applied to MD20-3591 which likely received a
May 26, 2021
significant amount of terrigenous material from the African continents via riverine input. Of
particular interest is the sensitivity of the radiogenic isotopic signatures to grain size
variabilities and how this relationship can help to define local vs distal sediment sources.
Finer lithogenic sediments originating from more distal river catchments might be transported
by the strong flowing Agulhas Current to the core site, whereas the coarser material may
represent a more local signature.
These records will allow us to explore variability in regional hydroclimate in relation to the
archaeological record during the MSA of southern Africa.
May 26, 2021
1. What does the geological record of climate change look like?
Plant proxy evidence for terra viridis australis: high rainfall and productivity in
the Australian early Eocene
Tammo Reichgelt* (University of Connecticut), David R. Greenwood (Brandon University), John G.
Conran (University of Adelaide), Leonie J. Scriven (Botanic Gardens and State Herbarium of South
During the early to middle Eocene, Australia occupied latitudes 4070° S, as opposed to its
position at 1040° S today. Enhanced latitudinal transport of moisture, in addition to a
generally more active hydrological cycle in the globally warmer early to middle Eocene world
would have likely increased water supply on land and contribute to a “greener” Australian
continent than today. Here, we revisit twelve plant megafossil sites from the early to middle
Eocene of Australia to generate ensemble temperature, precipitation and seasonality
paleoclimate estimates based on three leaf morphological proxies and one plant taxonomical
paleoclimate proxy. Additionally, we compare megafossil to modern-day Southern
Hemisphere leaf morphology and apply a novel approach to cross-correlate leaf morphology
to net primary productivity (NPP) in order to reconstruct the vegetation type and its carbon
sequestration capacity at this time. The early to middle Eocene temperature reconstructions
from Australian megafloras are uniformly subtropical with mean annual temperatures of
18.920.3 °C, mean summer temperatures of 22.526.5 °C and mean winter temperatures
of 13.516.9 °C. Precipitation was less homogeneous, with inland sites of the Lake Eyre
Basin mean annual precipitation of ~600 mm and sites <100 km from the Australo-Antarctic
Gulf or the Tasman Sea with > 1000 mm. Precipitation may have been seasonal, close to
monsoonal, with the driest month receiving between 27× less precipitation as mean
monthly precipitation. NPP estimates were 11001500 gC m-2 yr-1, which suggests much
higher productivity than modern, in particular for Lake Eyre Basin and South Australia sites,
where modern NPP is -200200 gC m-2 yr-1. The most similar modern vegetation type was
shown to be modern-day eastern Australian subtropical forest, although some distance from
coast and latitude may have led to vegetation heterogeneity.
May 26, 2021
1. What does the geological record of climate change look like?
Paleoclimate signals in Atlantic Coastal Plain sediments
Marci Robinson* (US Geological Survey), Harry Dowsett (USGS), Kevin Foley (USGS), Jean Self-
Trail (USGS), Seth Sutton (University of Wisconsin - Madison) and Whittney Spivey (USGS)
Changes in climate over millennial and longer time intervals are best observed in deep sea
sediment cores where orbital resolution micropaleontologic and geochemical studies can
illuminate climate extremes and their transitions. Coastal plain outcrops and sediment cores,
however, can capture climate change data during warm intervals when sea levels were high
in higher resolution than in deep sea cores due to high nearshore sedimentation rates. While
marine coastal plain deposits are usually discontinuous, they contain excellent snapshots of
extreme climate states that capture the magnitude and speed of dynamic changes in shallow
water ecosystems.
We sampled marine outcrops and sediment cores from the Atlantic Coastal Plain of Virginia
and Maryland, USA, for the Paleocene-Eocene Thermal Maximum (PETM), Miocene
Climate Optimum (MCO), middle Miocene Climate Transition (MMCT) and mid-Piacenzian
Warm Period (MPWP). Specifically, we analyzed the sedimentology, micropaleontology and
geochemistry of the Paleocene Aquia Formation and Eocene Marlboro Clay in the South
Dover Bridge (SDB) and Mattawoman Creek-Billingsley Road (MCBR) cores, the middle
Miocene Calvert Formation in the Calvert Cliffs outcrops and the Baltimore Gas & Electric
(BG&E) core, and the mid-Piacenzian Yorktown Formation in the Rushmere outcrops and
the Holland Ball Park and Dory cores. Although high resolution age models are often difficult
to attain from coastal plain sediments using methods based on microfossil content (i.e.,
biostratigraphy, oxygen isotopes) due to the paucity of desired species, we were able to
generate age models for these sections by combining calibrated first and last appearances
of age-diagnostic species with alkenone biomarkers, used as a tool for stratigraphic
Results from the PETM, MCO/MMCT, and MPWP include improved age models as well as
estimates of sea surface temperature, relative degree of ocean acidification, productivity and
sea level. We have 1) documented surface ocean warming and acidification in two discrete
pulses at the PETM onset, 2) generated the first MCO and MMCT sea surface temperature
data and documented extremely high primary productivity associated with the MCO along
the US mid-Atlantic Coastal Plain, and 3) characterized benthic foraminifer community
changes associated with the PETM, MCO/MMCT, and MPWP, leading to a better
understanding of the mid-Atlantic shallow marine ecological response to different rates and
magnitudes of temperature and sea-level rise. Our results show that, though discontinuous,
marine sedimentary records from the Atlantic Coastal Plain contain valuable quantitative
paleoecological data. These data are especially useful to better understand regional and
global responses to climate change because the initial response is often first recorded on the
shallow shelf.
May 26, 2021
1. What does the geological record of climate change look like?
A tectonic and glacio-eustatic sea level reconstruction for the Phanerozoic
Douwe George van der Meer* (CNOOC), Benjamin J. W. Mills, Chris Scotese, Appy Sluijs, Aart-Peter
van den Berg van Saparoea
Global mean sea level variations are of interest to the earth sciences, biology, and
climatology. Traditionally sea level curves have been based on stratigraphic analyses.
However, the validity has remained controversial and the amplitude and time scales of global
Phanerozoic long-term sea level variability is poorly constrained and does not separate
tectonic and glacio-eustatic driving forces. To provide a novel method of sea level
reconstruction, using an independent dataset, recently a low-frequency sea-level curve was
reconstructed by estimating the effect of plate tectonics (i.e. mid-ocean ridge spreading)
from the strontium isotope record. However, changes in sea level from climatologic
variations in water volume (storage in land ice) were not previously incorporated. Here, we
use a recent compilation for global average paleo-temperature, which was derived from
δ18O data and paleo-Köppen zones. First, we estimate the volume of land ice as a function
of paleotemperature and combine this with paleogeographic reconstructions. Ice thickness is
calibrated with a recent paleoclimate model for the late Cenozoic ice-house. Sea level
variation as a result of glaciations reaches up to 100m, similar to and at times dominant over
plate tectonic derived eustasy. We superimpose the glacio-eustatic effect on to the plate
tectonically driven eustasy and compare our resulting sea level curve with stratigraphically
derived sea level estimates and continental flooding from paleogeographic mapping. We
thereby show how both plate tectonics and climate change contribute to sedimentation in
basins and therefore are critical factors for the geological record
May 26, 2021
2. Why has climate changed in the past?
Mobilization of lithospheric mantle carbon during the Palaeocene-Eocene
thermal maximum
Thomas Gernon* (University of Southampton), Ryan Barr (University of Southampton), Godfrey Fitton
(University of Edinburgh), Thea Hincks (University of Southampton), Jack Longman (University of
Oldenburg), Andrew Merdith (Universite of Lyon), Ross Mitchell (Chinese Academy of Sciences),
Martin Palmer (University of Southampton)
The early Cenozoic exhibited profound environmental change influenced by plume
magmatism, continental breakup, and opening of the North Atlantic Ocean. Global warming
culminated in the transient (170 thousand year, kyr) hyperthermal event, the Palaeocene-
Eocene thermal maximum (PETM) 56 million years ago (Ma). Although sedimentary
methane release has been proposed as a trigger, recent studies have implicated carbon
dioxide (CO2) emissions from the coeval North Atlantic igneous province (NAIP). However,
we calculate that volcanic outgassing from mid-ocean ridges and large igneous provinces
associated with the NAIP yields only one-fifth of the carbon required to trigger the PETM.
Rather, we show that volcanic sequences spanning the rift-to-drift phase of the NAIP exhibit
a sudden and 220-kyr-long intensification of volcanism coincident with the PETM, and
driven by substantial melting of the sub-continental lithospheric mantle (SCLM). Critically,
the SCLM is enriched in metasomatic carbonates and is a major carbon reservoir. We
propose that the coincidence of the Iceland plume and emerging asthenospheric upwelling
disrupted the SCLM and caused massive mobilization of this deep carbon. Our melting
models and coupled tectonicgeochemical simulations indicate the release of >10^4
gigatons of carbon, which is sufficient to drive PETM warming. Our model is consistent with
anomalous CO2 fluxes during continental breakup, while also reconciling the deficit of deep
carbon required to explain the PETM.
May 26, 2021
2. Why has climate changed in the past?
Poleward shift in the Southern Hemisphere westerly winds synchronous with
the deglacial rise in CO2
William R Gray* (Laboratoire des Sciences du Climat et de l’Environnement (LSCE/IPSL)), Casimir
deLavergne (LOCEAN), Robert Wills (University of Washington), Laurie Menviel (University of New
South Wales), Paul Spence (University of Sydney), Mark Holzer (University of New South Wales),
Masa Kageyama (LSCE/IPSL), Elisabeth Michel (LSCE/IPSL)
The Southern Hemisphere westerly winds strongly influence deep ocean circulation and
carbon storage. While the westerlies are hypothesised to play a key role in regulating
atmospheric CO2 over glacial-interglacial cycles, past changes in their position and strength
remain poorly constrained. Here, we use a compilation of planktic foraminiferal d18O from
across the Southern Ocean and constraints from an ensemble of climate models to
reconstruct changes in the westerlies over the last deglaciation. We find a 5±2° (95% CI)
equatorward shift and about a 25% weakening of the westerlies during the Last Glacial
Maximum (about 20,000 years ago) relative to the mid-Holocene (about 6,000 years ago).
Our reconstruction shows that the poleward shift in the westerlies over deglaciation closely
mirrors the rise in atmospheric CO2. Experiments with a 0.25° resolution ocean-sea-ice-
carbon model demonstrate that shifting the westerlies equatorward substantially reduces the
overturning rate of the abyssal ocean, leading to a suppression of CO2 outgassing from the
Southern Ocean. Our results establish a central role for the westerly winds in driving the
deglacial CO2 rise, and suggest natural CO2 outgassing from the Southern Ocean is likely
to increase as the westerlies shift poleward due to anthropogenic warming.
May 26, 2021
2. Why has climate changed in the past?
Global warming and cooling for last 2,000 years mimic Sun's magnetic activity,
not CO2: scientific literature synthesis
Roger Higgs* (Geoclastica Ltd)
Most scientists urge shifting to nuclear and/or renewable energy, amply justified by air
pollution, dwindling fossil fuels and, many believe, global warming by CO2.
For the last 2,000 years Earth's average surface temperature (by proxies and post-1750
thermometers) closely matches solar-magnetic output (SMO) (ice-core proxies, sunspots,
neutron detectors, magnetometers), after applying a ~100-year temperature lag. Both fell for
1,000 years from ~400AD into the Little Ice Age (LIA; ~1400-1900). Then SMO surged from
~1700AD (Maunder Minimum), the largest rise in 9,000 (sic) years, growing 130% in the
20th Century alone, reaching the strongest solar 'grand maximum' (1937-2004; peak 1991).
(Contrast <0.5% parallel increase in total solar irradiance [TSI].) Temperature surged too,
from the final LIA nadir ~1830 (Berkeley-HadCRUT data) to 2016, the largest warming
(~1.3C) and highest peak in 2,000 years. The temperature and SMO graphs share two
further characteristics, besides overall 'hockey-stick' shape: (A) multi-decadal up-down
'sawteeth', with superimposed 3-to-20-year sawteeth (longer than ENSO); and (B) surge
amplitude about twice the 1,000-year decline. Three simple cross-matches confirm the
~100-year lag: (1) LIA's three coldest peaks (~1470, 1610, 1830) mimic three SMO extreme
minima (~1330, 1450, 1700); (2) the Sun's 310AD peak (second-highest) aligns with a
prominent ~450AD warm peak (with abundant geological-archaeological evidence for a ~3-
metre sea-level rise in <100 years); (3) successive HadCRUT sawteeth cusps at 1910, 1945
and 1975 correspond to 1810, 1840 and 1890 (sunspot 30-year-smoothed chart).
In contrast CO2 has six mismatches with the 2,000-year temperature profile: (1) CO2 was
trendless before its modern rise from ~1850 by industrial emissions; (2) warming began
(~1830, above) before CO2's rise; (3) CO2's rise was continuous (except seasonal sawteeth
[Keeling Curve] and slight decline 1940-44), unlike very punctuated warming (supra-annual
sawteeth, above; 30-year coolings 1880-1910, 1945-75; pause 1998-2013); (4) CO2 has
steadily accelerated from 1944, but warming has not (after its 1975 resumption); (5) the
1975-2016 warming episode had the same gradient as the previous one (1910-45), while the
CO2 gradient increased fourfold; (6) the Berkeley-HadCRUT dataset includes solar
frequencies, unlike CO2. Evidently, CO2 and temperature are uncorrelated.
The foregoing evidence collectively indicates that the Sun governs global temperature,
consistent with Svensmark's SMO-cosmic ray-cloudiness theory. Volcanic mega-eruptions,
commonest during exceptional SMO minima, augment solar-driven cooling (LIA "volcanic-
solar downturns"). The ~100-year temperature lag is attributable to oceanic thermal inertia
(high heat capacity, slow mixing). This 'ocean-lag', variably estimated by previous authors as
10-100 years, explains why warming persists today, despite solar weakening since 1991.
The logical conclusion is that negative feedbacks cancel CO2's greenhouse effect. A
"potentially very important" but poorly constrained natural feedback acknowledged by IPCC
but omitted in their climate models is rising 'BVOC' aerosol emissions from forests growing
faster by enhanced photosynthesis ('CO2 fertilization'). Other IPCC climate-model errors
include: assuming negligible solar influence because TSI changes are trivial (ignores SMO);
and disregarding ocean lag. Further Sun-driven warming is predictable, ending ~100 years
May 26, 2021
(lag) after the 1991 solar peak. Reviewers: Drs Gary Couples and Tom Moslow. Literature
sources (dozens) in ResearchGate papers 348689944, 348369922, 346792725 and
May 26, 2021
2. Why has climate changed in the past?
Mechanisms of South American Monsoon System response to external
variability over the last millennium
Rebecca Orrison* (University at Albany; SUNY), Mathias Vuille [University at Albany; SUNY]
Constraints on climate variability in the Last Millennium (LM) help to define the climatic
context of the current warm period. Sufficiently detailed evidence in the geologic record,
such as from stable oxygen isotopes, can provide insight into both how the climate responds
to external forcings as well as the influence of internal variability. On a regional scale,
characterizing the range of variability is aided when paleoclimatic records can be sampled at
high-density. Estimating regional climate processes and feedbacks, particularly on a
relatively short timescale such as the LM is important to fill in the details of globally
imhomogenous change. Moreover, some regional changes can be subtle, but important
nevertheless in detailing impacts of modern global warming on regional systems. Monsoon
systems, characterized by interannual changes in regional circulation and hydroclimate, are
sensitive to both global external forcings and local modulation of internal variability.
Understanding how they will respond to climate change will require a detailed estimation of
the envelope of current variability as established during the LM.
In this work, we evaluate the modes of variability drawn from a network of stable oxygen
isotope records influenced by the South American Monsoon System (SAMS), disentangling
the signals that influence regional hydroclimate from those of local variability. Stable isotope
proxies in South America are more spatially representative of hydroclimate than proxies
strictly for precipitation, providing insight into various environmental characteristics which
modulate and drive hydroclimate such as atmospheric circulation variability and changes in
the regional energy budget. Though the application of a Monte Carlo Empirical Orthogonal
Function (MCEOF) decomposition of a network of 14 stable isotope records from the Last
Millennium, we are able to characterize the modes of regional isotopic variability associated
with the SAMS. The physical underpinnings of these statistical modes are explored through
comparison with spatiotemporal features of the SAMS. The first three mode of variability
correspond to 1) an upper-tropospheric Rossby wave response to condensational heating
over the Amazon basin during the mature phase of the monsoon, 2) the monsoon trough
region and local precipitation, and 3) SAMS variability modulated by the El Niño-Southern
Oscillation. Reconstructing how these modes vary through time establishes a baseline
envelope of variability against which future change can be compared and highlights key
processes in the system. This enhances our understanding of how different components of
the SAMS may respond to future changes in internal variability and external forcings.
May 26, 2021
2. Why has climate changed in the past?
Cycles of Climate Change
Peter Francis Owen* (Retired)
The geological record demonstrates that there has never been a stable climate on Earth,
based on various measurements of proxies for temperatures. In the very recent past, both
temperatures, and dates have been measured accurately. Ice cores, recovered from both
North and South Polar regions, are subject to dating uncertainty, both due to the coarseness
of depth sampling (1m. corresponds to several hundred years) and to variations in absolute
timing. In the stratigraphic record, an unusual level of chronological accuracy has been
achieved from a detailed investigation of Eocene lake sediments, but further back in time the
precision of dating is limited.
Analyses of the nature of the varves, and their biological content, from the sediments in Lake
Messel (Lenz, et al,2011) demonstrated cyclical variations, with periods corresponding with
the Schwabe, (11years), Hale (22 years), Yoshimura (66 years) and Gleissberg (84 years)
cycles. A later palynological study of the sediments (Lenz. et al. 2017) found evidence of
longer period solar cycles in plant populations around the margin of the lake. They were the
De Vries/Suess (210 years) and the Eddy (950 years) cycles; their “Cycle 5” contains
components that are close to the Bond cycle (1400 years).
For the Pleistocene, ice core sampling of 1m (corresponding to approximately 500 years) is
insufficient to resolve most of the solar cycles, but the effect of the Earth’s orbital cycles is
clear from them. The temperature changes recorded there precede, more often than not, the
changes in carbon dioxide (Gest et al. 2017).
For the last 170 years, the HADCRUT compilation of global temperatures is the most
dependable. It is possible to model those measurements closely by combining the effects of
the seven solar cycles named above, and adding a factor for ENSO events over the period
for which it has been recorded. Although this may be dismissed as a coincidence, a
peculiarity of the model is that the amplitude of the temperature scalar for each cycle is in
the same proportion to the square root of its wavelength. The match of the model is well
within the quoted uncertainty of the measurements.
The conclusion to be drawn from the geological record is that the same solar and orbital
cycles have dominated changes in climate for at least the last 50 million years. By
comparison, atmospheric carbon dioxide has negligible influence, as is clear from the lack of
correlation between ice extent and carbon dioxide in figure 1 of the “G.S.L. Scientific
Statement”, 2021.
May 26, 2021
2. Why has climate changed in the past?
New multi-million year records of climate change from the shelf of Australia
Benjamin Petrick* (CAU Kiel Institute of Geology), Lars Reuning (CAU Kiel), Gerald Auer (University
of Graz) , David De Vleeschouwer (MARUM), Alexandra Auderset (Max Planck Institute of
Chemistry), Alfredo Martinez-Garcia (Max Planck Institute of Chemistry).
The ITF is a gateway controlling the flow of heat and salt between the Pacific and Indian
Oceans and is thought to play an important role in modulating the meridional overturning
circulation. However, the behaviour of the ITF across the Mid-Pleistocene Climatic Transition
(MPT), is not well understood. IODP Site 1460 provides sea surface temperature (SST) and
aridity (Ti/Ca) records from the west coast of Australia, spanning the past 2.5 Ma. Our
records show a decrease in glacial temperatures around 1.5 Ma, and 0.6 Ma, suggesting a
restriction of the ITF during these intervals. These restrictions were caused by changes in
sea level during glacials. These SST drops coincide with changes in benthic d13C gradients
across the Atlantic and Pacific basins, suggesting that the restriction of the ITF could have
influenced the evolution of global ocean circulation. This is the first evidence of the possible
influence of the ITF on the thermohaline circulation over the MPT. Newer work has also
shown that there are significant changes in productivity at the site at the same time
suggesting an intensification of the local Leeuwin around 900ka. Furthermore, IODP Site
1460 fits with other cores taken from IODP expedition 356, which preserve shifts in the ITF
and local current systems over the last 5 Ma. These show that shifts in the ITF around 3.6-
3.3 impacted the entire eastern Indian Ocean. This confirms in greater detail that changes in
the ITF have an impact on a global scale. It also shows that like for the more recent
changes these might have been driven as much by changes in sea level as tectonics.
Finally, we hope to expand this project by reconstructing SSTs and nutrients from the nearby
Coral Sea. These records should help extend our understanding of this critical area back to
at least 12 Ma and help investigate the impact of oceanic changes during the mid to late
Miocene in the documented loss of coral reefs. Therefore, our work has enabled us to
provide a new understanding into the role of changes around Australia in global cooling
since the mid Miocene.
May 26, 2021
2. Why has climate changed in the past?
Antarctic icebergs reorganize ocean circulation during Pleistocene glacials
Aidan Starr* (Cardiff University), Ian R. Hall (Cardiff University), Stephen Barker (Cardiff University),
Thomas Rackow (Alfred Wegener Institute), Xu Zhang (Lanzhou University; Chinese Academy of
Sciences), Sidney R. Hemming (Lamont-Doherty Earth Observatory of Columbia University), H. J. L.
van der Lubbe (Vrije University Amsterdam), Gregor Knorr (Alfred Wegener Institute), Melissa A.
Berke (Notre Dame), Grant R. Bigg (University of Sheffield), Alejandra Cartagena-Sierra (Notre
Dame), Francisco J. Jiménez-Espejo (CSIC-UGR Armilla; JAMSTEC), Xun Gong (Alfred Wegener
Institute), Jens Gruetzner (Alfred Wegener Institute), Nambiyathodi Lathika (NCPOR Goa), Leah J.
LeVay (IODP Texas A&M), Rebecca S. Robinson (University of Rhode Island), Martin Ziegler (Utrecht
University) & Expedition 361 Science Party
The geometry and vigour of the Atlantic Meridional Overturning Circulation (AMOC)
influences global climate on various timescales. Palaeoceanographic evidence suggests that
during glacial periods of the past 1.5 million years the AMOC was markedly different from
today, however an absence of evidence on the origin of this phenomenon means that the
sequence of events leading to global glacial conditions remains unclear. Here, we show
multi-proxy evidence and iceberg trajectory model results demonstrating that northward
shifts in Antarctic iceberg melt in the IndianAtlantic Southern Ocean (050° E)
systematically preceded deep-water mass reorganizations during Pleistocene-era
glaciations, resulting in a considerable redistribution of freshwater in the Southern Ocean.
This, in concert with increased sea-ice cover, enabled positive buoyancy anomalies to
‘escape’ into the upper limb of the AMOC, providing a teleconnection between surface
Southern Ocean conditions and the formation of deep water in the North Atlantic. The coeval
increase in magnitude of the ‘southern escape’ and deep circulation perturbations implicate
this mechanism as a key feedback in the transition to the ‘100-kyr world’, in which glacial
interglacial cycles occur at roughly 100,000-year periods.
May 26, 2021
3. Is our current warming unusual?
The Physics of Climate Systems - Cause, Effect and Observations
Brian Richard Lewis Catt* (Institute of Physics)
My presentation comes in three main elements, that address your points of interest in the
round, as a total system, and is intended to give some big picture context of how the physics
works to the more specialist areas that geologists know best, in terms of both scale and
structure, and how that may have changed in the last 50 years in particular. The system is
explained and assessed in terms of the natural observations from well known proxy and
direct sources.
This presentation describes, holistically, and necessarily summarily in view of the time
available, the primary physical controls of the Earth’s climate system. It focusses on
describing this system by applying established physics and the most well known, recent,
direct and proxy data from 21st Century observations. The focus is on the last 10Ka plateau
of the short warm interglacial era, and in particular using the big picture and natural data to
assess the anomalies between the geological proxy data from pre-industrial civilisations and
the direct measurements of the recent industrial period. The presentation comes in three
inter related and inter dependent parts.
(i) The global climate system is described in macro level terms of the primary sources of
energy and the major factors controlling their delivery to the surface and return to space,
directly reflected and re radiated as infra red. In particular how the macro level planetary
climate control system within the surface environment adjusts itself to maintain a stable
equilibrium within the relatively narrow range of temperatures we observe. This will include
the range of cyclic effects that the proxy record shows, the natural response to perturbations
from internal end external causes, both cyclic and exceptional, that are further quantified for
scale, and hence how the observed stability is delivered, and the likelihood of tipping points
at the proximal extremes to today.
(ii) Within this system, the relative contribution to and cause of the various components of
the lapse rate are briefly described, and how the lapse rate creates higher surface
temperatures relative to space, compared to the theoretical "vacuum Earth” temperature,
with particular reference to the contribution of the greenhouse effect. This includes a
summary of the relative contributions of the physical mechanisms of radiation, convection
and conduction to heat transport to space, as regulated by the overall control system
introduced in the first section. The effects of the fundamental geological differences between
Northern and Southern hemispheres on the climates of their respective hemispheres are
briefly discussed, as they affect the observations in particular..
(iii) Finally, the reality of what the geological proxy temperature data from both hemispheres
tells us about the recent interglacial period, its extremes, natural ranges, cycles and trends,
closes with how the geological proxy data from the past compares to the direct and
pervasive observations of satellites since 1979, that has made reliable and consistent
temperature observations uniformly available across the entire surface of the Earth for 40
May 26, 2021
3. Is our current warming unusual?
The contribution of fossil fuel emissions and the Pause to Global Warming
Howard Dewhirst* (Fellow of the Geological Society of London)
The question posed in the Society’s latest position paper ‘Is the current warming unusual?’ is
a curious one, because the world’s average temperature, which increased markedly
between 1910 and 1942 and again from 1978 to the El Niño of 1998, began cooling from the
beginning of this century. This pause in warming was then interrupted by the 2016 El Niño
and 2019 ENSO-IOD warming events, and the world is now in the throes of a La Niña
cooling. It may be valid to claim that the 21st century contains some of the warmest
days/weeks/months on record since the Industrial Revolution began, but it is misleading, as
they are the temporary result of natural fluctuations in what is an overall cooling trend. The
AGW conjecture that rising human CO2 emissions are causing an increase in global
warming, is shown to be incorrect.
The annual increase in atmospheric CO2 appears to rise smoothly, but year-on-year
fluctuations of up to 3 ppm are too large to have been caused by fossil fuel emissions, which
show little-to-no change in rate over time. Such changes in rate that do occur, while large in
relative terms, are much too small volumetrically to impact global concentrations..
The data examined are primarily atmospheric CO2 records from a series of world-wide
measuring stations, fossil fuel CO2 emissions, from the BP Annual Energy Review 2020,
and a selection of global temperature data sets kept by NOAA, UAH, CSIRO and others.
Abundant geological data demonstrates that changes in atmospheric CO2 always follow
temperature changes, in accordance with Henry’s Gas Law, but with a variable time lag.
Importantly, results of the analysis are presented in graphical form, based not on models or
hypotheses, but on observations.
The IPCC once described the world’s climate as a “coupled non-linear chaotic system”, for
which “the long-term prediction of future climate states is not possible.” Yet they continue to
predict catastrophes that do not happen. Despite these repeated failures of fact, western
governments plan to replace fossil fuel-based energy with unreliable renewables.
The phrase Climate Change is not only a pleonasm, but is deeply confusing, because there
is not one single climate, but a number of very different types, all part of a global dynamical
system that is not in equilibrium, with multiple feedback processes involving several
spatiotemporal orders of magnitude. Such nonlinear, nonequilibrium systems
characteristically fluctuate, as witnessed from the disciplines of electronics and mechanical
engineering, simple population dynamics and the stock market; where long term linear
trends always overturn. With so many contributing and counteracting processes, the chance
that only one of them, human CO2 emissions could be the system’s mainspring, is
vanishingly small, a conjecture well supported by the climate data examined. Nevertheless,
the scientific view widely promulgated still appears to be that human emissions since around
1950, are fully responsible for all of the warming that has occurred since then. The data
presented here indicate that this is incorrect.
May 26, 2021
3. Is our current warming unusual?
Comparison of warming onset timing and warming rates post-LIA using
glacier, sea level and HadCRUT4 surface temperature observations
Ashley Francis* (Independent, Fellow of Royal Astronomical Society)
Surface temperature observations are used to construct global temperature averages. The
different versions available are based on the same underlying station data. HadCRUT4 is
selected as it has (a) the most stable change log with time and (b) is not spatially
interpolated. For consistency with CMIP5 climate models, output is used up to 2011.
HadCRUT4 time series can be roughly characterised into four time intervals defined as
general trends. These are: neutral or slightly cooling 1852 - 1910; warming 1910 - 1945;
neutral or slightly cooling 1945 - 1980 and stronger warming 1980 - 2011. The onset of
modern warming is circa 1900 - 1910. The ratio of the warming rates of the two periods is
CMIP5 (and CMIP6) climate models respond only to imposed prior forcing curves as a
function of time which are used as inputs. The net forcing follows the same trend pattern
described above for HadCRUT4. Like HadCRUT4 the climate model forcing input and
resultant temperature output also show the onset of warming from about 1900 - 1910. The
ratio of average net forcing 1975-2005 to 1910-1945 shows the later period is modelled with
3x the net forcing of the earlier period and this is also evident in the resultant climate model
temperature output. There is therefore a factor of two discrepancy between modelled and
observed warming rates.
Two other direct physical measurements are sensitive to temperature: global sea level (SL)
and glacier length (GL) data. Using the SL dataset of Jevrejeva (2014), the ratio of the SL
rate for the two C20th warming periods is 1.3x, consistent with HadCRUT4 observations but
not with climate models. The onset of the linear SL trend commences in 1856, but a cross-
correlation of the rate of change of the SL data and HadCRUT4 (30 year slope, 100 year
window) gives a cross-correlation peak of R=0.91 with a lag of 16.3 years. Adjusting for this
lag, the observed onset of SL rise would require the onset of a temperature trend no later
than about 1840. This finding contradicts both HadCRUT4 and the climate model results.
Glacier data is based on the comprehensive and exhaustive dataset of Leclercq et al (2014)
and the temperature reconstruction of Leclercq and Oerlemans (2011). The L&O2011
temperature reconstruction from GL data shows glacier response to a warming trend to have
started no later than 1850 and potentially as early as 1833. The ratio of the GL derived
warming rates for the two C20th century periods is 1.4x, close to the temperature
observations but also contradicting the climate model results.
Finally, the glacial retreat timing is also consistent with the Arctic sea ice reconstruction of
McKay &Kaufman (2014) which shows a likely warming onset 1810 - 1820. Arctic sea ice is
expected to be very sensitive to temperature changes and would be expected to have a
more sensitive/earlier response time than the glacier database which average around tor=60
May 26, 2021
3. Is our current warming unusual?
Consider the Hippopotamus, and The Eemian
Christopher John Matchette-Downes* (Fellow of the Geological Society of London)
This presentation discusses the previous and warmest of the current 100Ka series of ice age
cycle interglacials, the Eemian, in the context of the entire series of 41Ka and 100Ka period
ice age cycles over the last 3Million years. The discussion will relate this event to the current
Holocene interglacial, that is nearing its probable end, to assess how anomalous the current
interglacial is in terms of past interglacials, and what the Eemain can tell us about the natural
operation of the climate system.
The detail of the natural reality is presented in terms of the direct geological observations,
the available proxy climate data, and, in particular, the actual flora and fauna of Northern
Europe during the Eemian is discussed, relative to today.
The records presented include the well known and tested ice core and other proxy
temperature indicators, also other ice core data, including carbon dioxide levels throughout
the periods discussed, also the changes observed in the overall climate in terms of the range
and rate of change in global temperature observed in the record over the studied time.
In conclusion the presentation reviews the stability of the planetary control system under the
known range of natural conditions that have applied, and the apparent role of CO2 in this,
which is then contrasted with the recent observed change during the industrial period of the
Holocene. This poses interesting questions for discussion as regards the reality of tipping
points suggested as an existential threat, the actual relationship between surface
temperature and changing CO2 levels, and the actual observed extent of the anomalies
between today's temperature change and that of other interglacials. In particular the Eemian,
when Hippos and Elephants were native to the rivers of Northern Europe, and Lions roamed
the riverbanks.
May 26, 2021
4. What does the geological record indicate about global v. regional change?
Strongly reduced meridional gradients in water isotopes in the early Eocene
Margot J. Cramwinckel* (University of Southampton, UK), Jiang Zhu (National Center for Atmospheric
Research (NCAR) USA), Gordon Inglis (University of Southampton UK)
Projections indicate that together with global warming of Earth’s climate will come an
increase in global mean precipitation and extreme precipitation events. While these changes
are critical for both human societies and natural ecosystems, large uncertainty exists on the
specific shifts in regional and seasonal rainfall patterns in the future. While the general
paradigm holds that “wet areas gets wetter, dry areas get drier” under higher global
temperatures, the warm Miocene and Pliocene instead seem to record increased
precipitation in the arid subtropics. Here, we contrast this to hydrological cycling during the
warm early Eocene, characterised by CO2 levels and temperature distributions similar to
those expected for 2150 under high emission scenarios. We employ water isotopes of
precipitation (δD, δ18O) as a means of tracking the dynamics of the hydrological cycle.
Specifically, we present a new compilation of late Paleocene early Eocene (LPEE) δD of
precipitation, based on newly generated and compiled data of δD measured on fossil leaf
wax n-alkanes. In line with earlier work, our preliminary results indicate a strongly reduced
meridional gradient in δD of precipitation over land, with much less depleted high latitude
precipitation than at present. Regional variability is high in the subtropical band, which is
interesting in light of the proposed wet-wetter, dry-drier hypothesis and Miocene-Pliocene
reconstructions. In order to interpret our proxy-based δD patterns and meridional gradient in
a mechanistic sense, we employ early Eocene simulations using the water isotope-enabled
Community Earth System Model version 1.2 (iCESM).
May 26, 2021
4. What does the geological record indicate about global v. regional change?
Reconstructing regional North African aridity through the late Quaternary
Amy Jewell* (School of Ocean and Earth Science, University of Southampton), Anya J. Crocker
(School of Ocean and Earth Science, University of Southampton), Matthew J. Cooper (School of
Ocean and Earth Science, University of Southampton), J. Andy Milton (School of Ocean and Earth
Science, University of Southampton), Rachael H. James (School of Ocean and Earth Science,
University of Southampton), Chuang Xuan (School of Ocean and Earth Science, University of
Southampton), Alistair Pike (Department of Archaeology, University of Southampton), Paul A. Wilson
(School of Ocean and Earth Science, University of Southampton).
North Africa is home to millions of people living in nation states considered to be particularly
vulnerable to anthropogenically-driven climate change. The region is very likely to warm over
the 21st Century but there is fundamental disagreement among model projections about the
magnitude, and even sign, of the rainfall climate response. Geological records of wind-blown
Saharan dust accumulating in marine sediment cores in the North Atlantic Ocean provide a
way to assess the response of North African rainfall climate to past changes in global
Dust is transported to the North Atlantic Ocean from North Africa via two main routes, a
summer (northern) route and a winter (southern) route. Virtually everything we have learnt
so far from marine sediment cores about North African hydroclimate comes from drill sites
located beneath the summer (northern) dust plume. Here we report high resolution
geochemical records (radiogenic isotope (87Sr/86Sr and eNd) and XRF core scanning) from
ODP Site 662 in the eastern equatorial Atlantic. We show that ODP Site 662 is ideally
situated to study the palaeo-history of the winter dust route and present records of winter
dust provenance for the last glacial cycle.
Comparison of our late Holocene data to the geochemically fingerprinted preferential dust
source areas (PSA) of North Africa (Jewell et al., 2021, EPSL) shows that the central PSA is
the main source of terrigenous material to the winter plume today. The central PSA
encompasses palaeolake Megachad and the Bodélé Depression, Earth’s most productive
dust source today. Large downcore excursions in radiogenic isotope composition of the
silicate fraction at Site 662 show that the contribution of these central Sahelian palaeolakes
varied on precessional timescales over the last glacial cycle. Minima in dust supply from
these sources are suggested for all the insolation maxima of the last 100 kyrs, signifying
palaeolake high stands even when insolation forcing was comparatively modest. Our results
shed new light on the provenance of dust supply to the North Atlantic Ocean and on the
linearity and regionality of the response of African hydroclimate to insolation forcing.
May 26, 2021
5. When Earth's temperature changed in the past, what were the impacts?
Climate-biogeochemistry feedbacks during rapid warming events
Gordon Inglis* (University of Southampton), Megan Rohrssen (Central Michigan University), Elizabeth
M. Kennedy (GNS Science), Erica M. Crouch (GNS Science), J. Ian Raine (GNS Science), Dominic
P. Strogen (GNS Science), B. David A. Naafs (University of Bristol), Margaret E. Collinson (Royal
Holloway University London), and Richard D. Pancost (University of Bristol).
Anthropogenic warming is expected to trigger a cascade of terrestrial biogeochemical
feedbacks, which may weaken or strengthen the global temperature response. Warming is
expected to enhance methane emissions from wetlands, resulting in further warming.
However, this feedback was not fully assessed in the Intergovernmental Panel on Climate
Change Fifth Assessment Report.
The geological record can act as a platform to explore these changes and to provide insights
into the known (and unknown) biogeochemical feedbacks that may operate in the future.
Here we employ a novel geochemical approach to study wetland methane cycling during the
most rapid warming event of the last 66 million years (the Paleocene-Eocene Thermal
Maximum; ~56 million years ago). Our results confirm a major perturbation of the methane
cycle during the onset of the Paleocene-Eocene Thermal Maximum. If some of this methane
escaped into the atmosphere, it would have led to additional planetary warming. Intriguingly,
elevated methane cycling does not persist into the early Eocene, despite evidence for high
temperatures. This suggests it is the onset of rapid global warming that is particularly
disruptive to methane cycling in wetlands, a finding that is particularly concerning given the
rapid global warming we are experiencing now.
More information:
May 26, 2021
5. When Earth's temperature changed in the past, what were the impacts?
Impacts of long- and short-term climate variations during the Paleogene
greenhouse on a coastal wetland in Northern Germany
Olaf K. Lenz* (Senckenberg Research Institute and Natural History Museum Frankfurt, 60325
Frankfurt am Main, Germany), Volker Wilde (Senckenberg Research Institute and Natural History
Museum Frankfurt, 60325 Frankfurt am Main, Germany)
Walter Riegel (Senckenberg Research Institute and Natural History Museum Frankfurt, 60325
Frankfurt am Main, Germany)
A number of studies is devoted to the effects of the recent rise in CO2 in the atmosphere and
the resulting rise in global temperatures on plant communities because they act as important
sources and sinks for CO2. However, long-term effects of present global warming on plant
communities on timescales beyond those covered by the human record of the last few
centuries are still a matter of speculation. Since long-term greenhouse periods and short-
term warming events occurred repeatedly in the history of the earth, they may be the subject
for detailed studies on the reaction of plant communities to global warming on different
timescales. The Early Eocene Climatic Optimum (EECO) and its superposed short-term
warming events such as the Paleocene-Eocene Thermal Maximum (PETM) represent the
last greenhouse period before today which is especially suited for comparisons to the
presently developing greenhouse since fauna and flora had reached an evolutionary state
already similar to today.
The sedimentary succession of the former Helmstedt Lignite Mining District in northern
Germany, which includes the upper Paleocene to lower Eocene Schöningen Formation and
the middle Eocene Helmstedt Formation, covers the entire Paleogene greenhouse phase
and its gentle demise almost continuously in an estuarine situation at the southern edge of
the proto-North Sea. Due to the interaction between changes in sea level, salt withdrawal in
the subsurface and climate-related changes in runoff from the hinterland the area was
subject to frequent changes between marine and terrestrial conditions, repeatedly leading to
peat formation. Today, such near-coastal wetlands play a major role in the global carbon
cycle by storing large quantities of terrestrial organic carbon but also as a primary source of
methane emissions to the atmosphere. Therefore, peatlands are likely to contribute
significantly to the future balance of greenhouse gas emissions. The more than 200 m thick
succession of the Helmstedt Lignite Mining District with 13 up to 15 m thick lignites offers the
rare opportunity to study PaleoceneEocene near-coastal ecosystems and to trace the
effects of long- and short-term climate perturbations on the diversity and composition of the
plant communities across 10 million years during the Paleogene greenhouse. As far as
known, the succession at Schöningen is worldwide unique due to the completeness of the
record in time. The aim of an ongoing project is to study the response of the vegetation in
this paralic environment to the long-term event of the EECO but also to short-term events
such as the PETM by making use of pollen and spores as proxies. A new robust
stratigraphic framework for the succession is based on a combination of biostratigraphy and
eustatic sea-level changes. It now allows for an exact correlation of distinct carbon isotope
excursions in the bulk organic matter δ13CTOC record to the individual thermal events.
May 26, 2021
5. When Earth's temperature changed in the past, what were the impacts?
Biotic impact of past warm events: effects of Early Eocene Climatic Optimum
on planktic foraminifera
Valeria Luciani* (Dipartimento di Fisica e Scienze della Terra, University of Ferrara, Italy), Luciani V..
(Dipartimento di Fisica e Scienze della Terra, University of Ferrara, Italy),Wade B. (Department of
Earth Sciences, University College London, UK), Dickens, J.R. (Trinity College Dublin, the University
of Dublin College, Ireland) Kirtland-Turner S. (Department of Earth Sciences, University of California,
Riverside, USA).
The Early Eocene Climatic Optimum (EECO; ~ 53-49 ma) impacted planktic foraminiferal
assemblages significantly with at least three different aspects. A first major change includes
the turnover between two dominant genera, the mixed-layer symbiont-bearing Morozovella
and Acarinina. This turnover occurred rapidly at multiple sites from diverse latitudes (Atlantic
and Pacific Oceans, Tethys) near the onset of EECO and very close to the “J” carbon
isotope excursion (CIE). Specifically, the abundance and diversity of Morozovella decreased
significantly and permanently while Acarinina concurrently increased in abundance and
diversity. Second, a reduction in morozovellid test-size occurred across EECO as recorded
from Atlantic ODP sites 1051, 1258 and 1263. Several potential stressors may explain both
the reduced size and the permanent morozovellid decline. These include algal
photosymbiont inhibition (bleaching), increase in temperature, decrease in pH and/or calcite
saturation state. Even though a bleaching test at Site 1051 revealed only a transient
reduction of algal-symbiont relationships just after the morozovellid abundance decline, a
general reduction in δ13C gradient (~ 0.5 ‰) between morozovellids and the thermocline
dweller Subbotina spp. through the EECO is recorded from the Atlantic sites. This suggests
that the former group became less reliant on photosymbionts and/or may have moved to
slightly deeper depth in the mixed-layer. Third, the coiling direction of Morozovella species
switched from predominantly dextral to mostly sinistral within the EECO, slightly after the K/X
CIE. This coiling switch is recorded at the three aforementioned Atlantic sites and at the
tropical Pacific Site 1209 (unpublished data) and may be somewhat related to the
morozovellid decline. Stable carbon isotopes on numerous sinistrally and dextrally coiled
morozovellids (that may represent cryptic species) from the Atlantic sites show that sinistral
morphotypes typically have lower δ13C values. The dominance of sinistral morphotypes that
survived, though in low abundance, at the expense of dextral forms within EECO, coupled
with the lower δ13C signatures of the former, suggests that the sinistral morphotypes were
less dependent on their photosymbiotic partnerships and thus able to tolerate
paleoceanographic changes. Preliminary Mg/Ca data from Site 1263 reveal that Morozovella
crater and M. subbotinae record a major warming across EECO, and more than that of
Acarinina coalingensis and A. soldadoensis. Increased temperature is considered a primary
cause of bleaching in present tropical larger benthic foraminifera. The higher rise in
temperature recorded by morozovellid may explain the reduced symbiotic relationship and
one reason for their reduction in abundance and size, even though other potential stressor
such as pH decrease should be explored. The virtual disappearance of the genus
Chiloguembelina at the EECO beginning in the Atlantic Ocean is an additional evidence of
the environmental stress induced by the ECCO interval. A combination of reduced food
supply, increase in thermocline temperature and oxygen content within the oxygen minimum
zone may explain the decline of chiloguembelinids in the early EECO.
May 26, 2021
5. When Earth's temperature changed in the past, what were the impacts?
Calcareous nannofossils and benthic foraminifers highlight the cyclical
climatic and environmental changes during the Messinian: a possible
analogue for the future impact on the Mediterranean ecosystem?
Alan Maria Mancini* (Department of Earth Science, University of Turin), Gennari R. (Department of
Earth Science, University of Turin), Pilade F. (Department of Earth Science, University of Turin),
Pellegrino L. ((Department of Earth Science, University of Turin), Lozar F. (Department of Earth
Science, University of Turin)
Huge anthropogenic CO2 emissions are altering the global biogeochemical cycles resulting
in an increase in the global temperature, that are expected to severely impact the marine
The marginal basins and restricted marine conditions are characterised by more fluctuating
environmental parameters compared to the open ocean, making them an excellent case
study for better constraining the timing and magnitude of the climate change and its impacts
on the marine biota. In this perspective, the Mediterranean Neogene sedimentary
succession represents an excellent record of the past climatic changes. The impact of the
current rising temperature on the marine ecosystem could be constrained from the
geological record analysing time interval characterised by similar pattern. The Messinian,
with warmer sea surface temperature compared to the present, may represents an ideal
candidate for this purpose, and a possible analogue for the near future impact scenarios of
the Mediterranean sea.
Here we present the calcareous nannofossil and benthic foraminifers response (changes in
the assemblage, absolute abundance and morphometry) to the climatic variation recorded in
the Messinian sediments of the marginal basin of Sorbas (S-E Spain) and spanning a 25 kyr
long time interval preceding the inception of the Messinian Salinity Crisis (~ 6 Ma). Our aim
is to better constrain the environmental changes associated with climatic instability and
suggests possible future impacts scenario on the Mediterranean ecosystem.
Variation in the Earth orbital parameters, mostly precession ( 21000 yrs), resulted in the
deposition of quadripartite sedimentary cycles composed of organic rich marls (e.g.
sapropel) and diatomite sandwiched between massive marls; each lithology was
characterised by peculiar micropaleontological content, reflecting the environmental
condition at the time of its deposition.
The sapropel deposition were triggered by enhanced primary productivity in the water
column starting at the precession maxima (insolation minima); this resulted in an increase in
the organic carbon rain to the sea floor and to the establishment of bottom anoxia and the
consequent organic carbon preservation in the sediments. The upper part of the sapropel
records a progressive shift toward a warmer/humid climate (insolation maxima); at this time,
the bottom anoxic condition was maintained by relatively high productivity and export from
the deep photic zone, where a Deep Chlorophyll Maximum (DCM) was established. When
the temperature and the freshwater input started to decrease, a weakening of the export to
the bottom from the DCM occurred, restoring bottom oxygenated conditions and promoting
the deposition of massive marl. This study highlights the ecosystem response to the cyclical
climatic variation that occurred in a context which was warmer than today. Our study reveals
that the rising temperature characterising the actual climate change may lead to a
May 26, 2021
deoxygenation and to an increase in carbon burial in the Mediterranean marginal basins.
This feedback in response to the rising temperature will significantly impact the
Mediterranean ecosystem, especially the benthic one.
May 26, 2021
5. When Earth's temperature changed in the past, what were the impacts?
Investigating Deccan-induced environmental changes, prior to the K/Pg mass
Matthew L. Staitis* (University of Edinburgh), Prof Dick Kroon (University of Edinburgh)
Dr James Barnet (University of St Andrews)
~66 million years ago, the Earth experienced two major events the Chicxulub bolide impact
and the eruption of the Deccan Traps Large Igneous Province. Whereas the Chicxulub
impact is widely implicated as the main driver of the Cretaceous-Paleogene (K/Pg) mass
extinction, the exact environmental and biotic impacts of the preceding Deccan trap
volcanism require further research focus. My MScR research project will use paired planktic
and benthic trace element (B/Ca, Mg/Ca) and stable isotope (δ11B, δ18O, δ13C) analyses to
quantify the changes in climate and carbonate chemistry (related to ocean acidification)
during the Late Maastrichtian Warming Event (LMWE) at ODP 1262. I will investigate; (a)
whether ocean acidification occurred during the Late Maastrichtian Warming Event (LMWE),
(b) the magnitude of temperature changes that occurred during the Latest Maastrichtian, and
(c) if similar trends in δ18O and δ13C occurred in both the surface and deep ocean during
Late Maastrichtian Warming Event (LMWE) in ODP 1262 samples. I anticipate: (1) a positive
correlation when the new B/Ca and δ11B data are compared to established % CaCO3
records, but a negative correlation when compared to established Fe intensity records at
ODP 1262. (2) A positive correlation between the new Mg/Ca trace element data and the
established δ18OBenthic record at ODP 1262. (3) A positive correlation between both the
planktic and benthic δ18O and δ13C records at ODP 1262. The results of my research project
will contribute to improving our understanding of the environmental response to Deccan
volcanism, prior to the K/Pg mass extinction.
May 26, 2021
6. How does the geological record inform our quantification of climate sensitivity?
Late Miocene CO2 and Climate: divorced or an old married couple?
Rachel Brown* (University of Southampton), Thomas Chalk, Paul Wilson, Anya Crocker, Gavin Foster
Earth’s climate cooled markedly during the Late Miocene (12-5 million years ago, Ma) with
far-reaching consequences for global ecosystems, but the mechanistic driving forces of
these changes remain controversial. A major obstacle to progress is the uncertainty over the
role played by greenhouse gas radiative forcing. Here we present a new record of carbon
dioxide (CO2) change for the interval of most rapid cooling, the Late Miocene Cooling (LMC)
event (7 to 5 Ma) based on the boron isotope composition of planktic foraminifera. Our
record suggests that CO2 declined by ~100 ppm over this two million year-long interval to a
minimum at ~5.9 Ma. Comparing our record of radiative forcing from CO2 with a new record
of global mean average surface temperature change and after accounting for non-CO2
greenhouse gasses and slow climate feedbacks, we estimate Equilibrium Climate Sensitivity
(ECS, global mean surface temperature change for a doubling of CO2) to be 3.9˚C (1.8-6.7
˚C at 95% confidence). We conclude that changes in CO2 and climate were closely coupled
during the latest Miocene and that ECS was within the range of estimates for the Pliocene,
Pleistocene and the 21st century as presented by the Intergovernmental Panel on Climate
Change (IPCC).
May 26, 2021
6. How does the geological record inform our quantification of climate sensitivity?
Atmospheric CO2 over the Past 66 Million Years from Marine Archives
James Rae* (University of St Andrews), Yi Ge Zhang (Texas A&M University), Xiaoqing Liu (Texas
A&M University), Gavin L. Foster (University of Southampton), Heather M. Stoll (ETH Zürich), Ross D.
M. Whiteford (University of St Andrews)
Throughout Earth’s history, CO2 is thought to have exerted a fundamental control on
environmental change. Here we review and revise CO2 reconstructions from boron isotopes
in carbonates and carbon isotopes in organic matter over the major climate transition of the
last 66 million years. We find close coupling between CO2 and climate throughout the
Cenozoic, with peak CO2 levels of ~1,500 ppm in the Eocene greenhouse, decreasing to
~550 ppm in the Miocene, and falling further into ice age world of the PlioPleistocene.
Around two-thirds of Cenozoic CO2 drawdown is explained by an increase in the ratio of
alkalinity to dissolved inorganic carbon, likely linked to a change in the balance of weathering
to outgassing, with the remaining one-third due to changing ocean temperature and major
ion composition. Earth system climate sensitivity is explored and may vary between different
time intervals. The Cenozoic CO2 record highlights the truly geological scale of
anthropogenic CO2 change: Current CO2 levels were last seen around 3 million years ago,
and major cuts in emissions are required to prevent a return to the CO2 levels of the
Miocene or Eocene in the coming century.
May 26, 2021
6. How does the geological record inform our quantification of climate sensitivity?
Negative carbon isotope excursions: an interpretative framework
Pam Vervoort* (University of California, Riverside), Markus Adloff (University of Birmingham), Sarah
E. Greene (University of Birmingham), Sandra Kirtland Turner (University of California, Riverside)
Climate sensitivity is the greatest uncertainty in future climate predictions. Natural CO2-
release events of the past with evidence of simultaneous global warming offer crucial
insights into the CO2-temperature relationship at that time and help narrowing down the
uncertainty. Precise, high-resolution paleo-CO2 reconstructions are however difficult to
obtain. Beyond the age of ice-cores, negative carbon isotope excursions (nCIEs) in
sedimentary records can be used to identify episodes of carbon release and the nCIE
magnitude and duration inform us about the associated mass of carbon release, assuming
the carbon source and its isotopic signature are known. A simple isotopic mass balance
equation often serves as a first order estimate for the mass of carbon input, but this
approach ignores the effects of negative carbon cycle-climate feedbacks. Plus, translating
the mass of carbon input into an estimate for atmospheric CO2 change is not straightforward
due to intricate feedbacks related to ocean circulation and carbonate chemistry.
We present a framework of 432 carbon release experiments in an Earth system model that
includes the impacts of ocean circulation, carbonate compensation, and terrestrial
weathering on atmosphere-ocean carbonate chemistry. The framework is a tool to interpret
geologic nCIEs with sizes ranging from 0.5 to 6.0‰ and onset durations between 12.5 and
225 kyr. In combination with other environmental constraints such as temperature or ocean
pH, the mass and source of carbon release and the subsequent change in atmospheric CO2
can be reconstructed. For instance, a nCIE of 1.0‰ associated with an increase in sea
surface temperature of 0.8°C with an onset duration of 12.5 kyr requires 1,250 Pg of organic
(-22‰) carbon, resulting in a maximum rise of ~310 ppm CO2. On timescales greater than
thousands of years, long-term negative carbon cycle feedbacks play a notable role in the
removal of carbon from the atmosphere during CO2-release events. The relative rise in CO2
and the impact on global surface temperature, surface ocean pH and saturation state
decrease with the nCIE onset duration. E.g. a 1.0‰ nCIE over 50 kyr requires 250 Pg more
organic carbon but results in atmospheric CO2 90 ppm lower, and 0.3°C colder surface
temperatures than the shorter nCIE. The framework can thus not only be utilized to estimate
paleo-CO2 rise associated with a nCIE, but also to better constrain the duration of a geologic
event with additional constrains on environmental changes.
May 26, 2021
7. Are there past climate analogues for the future?
Using Temporal Scaling to Establish Paleoclimate Analogues
Aja Watkins* (Boston University)
It is commonly thought that one major barrier to establishing and using paleoclimate
analogues for contemporary climate change is that the rate of contemporary climate change
is unprecedentedly high. On this basis, many think that we need to restrict the use of
paleoclimate analogues to drawing analogies independent of rates of change. However,
others have argued that the conclusion that past and present rates are disanalogous is
erroneous, as it does not take into consideration the dependence of rates on the durations
over which they are measured. By using a process called “temporal scaling,” we can adjust
rates measured over vastly different durations to be comparable. If we do so, then past and
present rates can be more adequately compared, and we may find that past rates are more
similar to present rates than previously thought, as is suggested by some data.
This talk has two aims. First, I explain why temporal scaling is necessary for testing whether
the rates of particular past episodes of climate change are analogous to rates in the present.
In general, rates are not independent from the durations over which they are measured, but
there is a precise inverse relationship between rates and durations (longer durations
produce lower rates, and vice versa). This relationship applies in all cases where rates are
nonconstant, including rates of climate change, as well as sedimentation,
speciation/extinction, precipitation, and more. Luckily, we can use this relationship to
extrapolate from measured rates to what the rate would have been if measured over a
higher or lower duration. In the context of establishing paleoclimate episodes, this will either
involve scaling paleoclimate rate data (necessarily measured over long durations due to the
low temporal resolution of the historical record) to shorter durations, comparable with the
durations over which contemporary data are measured, or scaling contemporary rate data to
longer durations, comparable with the durations over which we collect paleodata.
Second, I give two recommendations for climate scientists who are interested in using
paleoclimate analogues to draw conclusions about the trajectory or effects of contemporary
climate change. Knowing that temporal scaling is necessary to compare rates, as will have
been established in the first half of the talk, is not sufficient for telling us how to use temporal
scaling in this way. Specifically, the particular duration over which rates should be compared
is underdetermined. I will argue that choosing a duration primarily depends on our purposes;
different sorts of climate projections are more or less useful over particular timescales.
Consequently, I give two recommendations: (1) that researchers choose a useful time
duration over which to establish analogy with paleoclimatic change, and (2) that researchers
use this same time duration consistently when making projections. For example, if
researchers determine that projections are useful only over fifty-year time scales, then they
will need to first use temporal scaling to look for paleoclimatic episodes that are analogous
over fifty-year time scales, and then use those paleoclimate analogues only to make
projections over fifty-year time scales.
[Type here]
ResearchGate has not been able to resolve any citations for this publication.
ResearchGate has not been able to resolve any references for this publication.