1. Open Session on past global changes
Co-conveners: Lucien von Gunten, Marie-France Loutre, Hubertus Fischer and Sherilyn Fritz
This open session invites contributions in the various fields of past global changes which do not fit into the specialized sessions. It welcomes presentations of modeling studies as well as (paleo)-reconstructions. Papers from sessions that attracted too few contributions will also be collected here. Therefore, we offer all authors an appropriate place for displaying their work.
2. Quaternary climate and environmental change in the Southern Hemisphere
Co-conveners: Sebastien Bertrand, Andrew M. Lorrey, Maisa Rojas and Krystyna Saunders
This session will showcase the diverse climate and environmental change research being conducted within the terrestrial, marine, and cryospheric environments of the Southern Hemisphere. Presentations are welcome on Quaternary paleoclimate reconstruction, geochronology, paleoecology, and climate modeling.
Particular foci of the session will be:
- changes in the Southern Hemisphere atmospheric and oceanic circulation, including their environmental impacts;
- atmosphere-biosphere-cryosphere-marine connections;
- regional and hemispheric linkages; and
- the drivers of climate variability and change, including tipping points and abrupt events.
Contributions that focus on inter-archive and data-model comparisons, explore new analytical techniques and/or combine proxy records with historical evidence are particularly encouraged.
3. Regional and transregional climate variability over the last 2000 years
Co-conveners: Hugues Goosse and Nerilie Abram
The past 2000 years is a key period to understanding the dominant modes of internal variability and the response of the climate system to various natural forcings. It also provides a baseline to estimate the magnitude and regional patterns of climate changes associated with anthropogenic greenhouse gas emissions. The relatively small signals, heterogeneous data availability and the complex spatio-temporal structure of the climate changes observed during this period provide clear challenges on the methodologies, and also opportunities, to better understand the dynamics of the climate system at decadal to centennial timescales. In this framework, we welcome submissions discussing new records, interpretations or compilations of existing records, model-data comparisons and data assimilation experiments covering the past 2000 years or parts of this period.
4. From the Mediterranean to the Caspian: palaeoclimate variability, environmental responses and human adaptive strategies
Co-conveners: Ana Moreno, Valentina Yanko-Hombachmand William Fletcher
The Mediterranean region and adjacent intercontinental basins of the Marmara, Black and Caspian Seas represent climatically-sensitive regions where the signals of past climate variability can be traced in a range of archives. The reconstruction of past climate changes and their impacts is increasingly important for understanding climatic and cultural connections within and beyond these regions, past transformations in terms of cultural and biological diversity, and future implications in a changing world. In this multidisciplinary session, we aim to bring together recent advances in palaeoclimatic, palaeoenvironmental and palaeoanthropological approaches contributing to an improved understanding of past climate variability and human-climate-environment interactions in the Mediterranean, Marmara, Black and Caspian Sea regions.
Contributions relating to, but not limited to, the following topics are welcomed:
- terrestrial and oceanic records of climate variability at timescales from decadal to millennial;
- climate forcings and teleconnections to Atlantic and tropical regions;
- environmental impacts of past climate changes including vegetation dynamics, hydrological fluctuations and geomorphological activity;
- archaeological and palaeoanthropological records of human adaptive strategies and migrations; and
- modelling/GIS approaches to past climates, landscape evolution and human activity.
5. Disturbance dynamics across spatial and temporal scales: fire, wind, pathogens and post-disturbance run off as drivers of environmental change
Co-conveners: Graciela Gil-Romera, Jennifer Clear, Daniele Colombaroli, Richard Chiverrell, Angelica Feurdean and Jesse Morris
Disturbance dynamics (fire, wind, pathogens, post-disturbance sediment runoff) drive an array of ecological functioning: fire regulates the carbon cycle and drives vegetation dynamics, but is also a threatening risk in many populated areas; wind is an essential natural function delivering perception, however severe windstorms alter forest composition and cause severe structural damage to plantations and settlements; pathogens are an integrative part of the forested system, yet cause widespread tree mortality and consequently loss in ecosystem functioning, aesthetic and property value; flood events are a primary source of post-disturbance sediment runoff, with long-term ecological impacts over soils, vegetation and nutrient stocks. These disturbances are not mutually exclusive and often self-reinforcing across space and time e.g. wind may intensify the area burnt during a fire or a sever windstorm may initiate a pathogen outbreak, while a post-disturbed landscape will become more susceptible to sediment runoff.
Understanding the effect of disturbance dynamics on ecosystem properties such as species diversity, community assembly, structure and resilience, over timescales ranging from decades to millennia is essential to establish adequate baselines to predict potential environmental threshold responses under future IPCC climate scenarios. The study of current disturbance dynamics and risks, including prevention and mitigation, requires the understanding of the relative drivers; climate, vegetation, landscape structure and human activities (such as plantations, farming, grazing and logging) and associated feedbacks.
This session aims to:
- identify fire, wind, pathogen and sediment fluxes in the palaeoecological, sedimentary and dendroecological records and their effect on vegetation structure, biodiversity and other ecosystem properties;
- identify the drivers (climate, vegetation, landscape structure and human activity) and interactions between disturbance regimes; and
- understand the Climate-Human-Disturbance nexus across time and space using multiproxy and modelling approaches
6. Before and after - climate contrasts across the MPT
Co-conveners: Eric Wolff, Erin McClymont, Michel Crucifix and Hubertus Fischer
The mid-Pleistocene Transition looks like a fundamental shift in the way the climate system worked. The regular 40 ka world gave way to a less regular pattern with a longer period; glacials became stronger (more ice). There is now a range of paleoceanographic and terrestrial records that span the MPT with reasonable resolution and improved dating, and there is the prospect of an ice core crossing the MPT in the next few years. It is therefore timely to ask again what are the climatic contrasts across the MPT, and how robust are the possible explanations for what caused it. The session will include new datasets and compilations, and conceptual and modelling studies examining mechanisms. Prospects and preparations for new records spanning the MPT will also be discussed.
7. Historical Climate Reconstruction and Impacts of the Common Era
Co-conveners: Rudolf Brázdil, Sam White and Dagomar Degroot
Both written sources and high-resolution climate proxies can provide valuable insights on past climate and its human consequences. For this session, we invite new research in climate reconstruction at timescales relevant to human history, as well as historical studies of societies undergoing climatic variability and extremes.
Relevant topics may include:
- new methods and findings of documentary-based climate reconstruction.
- high-resolution climate history combining documentary and proxy sources.
- the reconstruction of major events such as hurricanes from descriptive and early instrumental records.
- interdisciplinary investigations of human vulnerabilities, impacts, and adaptation during past climatic anomalies (e.g. the Maunder Minimum or “Late Antique Little Ice Age”).
8. Volcanic eruptions: the thread connecting climate records, societal change and future climate projections?
Co-conveners: Francis Ludlow, Nelia Dunbar, Siwan Davies, Davide Zanchettin, Michael Sigl and Sam White
This session aims to present new research from multiple disciplines and sources on the identification, dating, description, climatic impacts and human experiences of volcanic eruptions. Volcanic eruptions distribute tephra nearly instantaneously over large areas, creating isochrons in a wide range of paleo-archives and providing a powerful global research tool with multi-disciplinary applications ranging from archaeology and paleoclimatology to natural hazards and volcanology. Volcanic eruptions are also key drivers of climate variability, generating large-scale surface cooling and altering atmospheric circulation patterns, with complex consequences at the regional scale. The comparison of palaeoclimate records and model simulations of periods with strong volcanic activity can, moreover, yield important clues to the sensitivity of the climate system and as well as providing an important means to improve climate modeling and projections. Finally, the precise timing and rapid large-scale effects of volcanic eruptions make for powerful case studies in climate impacts, vulnerability and resilience in past societies, with potential lessons for the future. The conveners of this session seek presentations that can advance and connect these areas of study.
Topics may include:
- innovative methodological developments in volcanology (e.g. tephra detection, mapping, characterization, and statistical correlations) as well as cutting-edge approaches to reconstruct eruptive histories and tephra transport mechanisms.
- reconstruction of radiative aerosol forcing, global and regional climate impacts through proxy climate records, historical documents, and instrumental observations.
- climate model experiments involving volcanic forcing, especially in regard to comparative assessments of simulated and reconstructed impacts.
- studies of the human experience of volcanic eruptions and their associated climate anomalies, particularly contributions that combine historical, archaeological, instrumental, and/or proxy evidence in order to analyze agricultural, economic, and health impacts or public and private responses to volcanic-induced disasters.
This session is co-sponsored by the PAGES Volcanic Impacts on Climate and Society (VICS) working group, the VolMIP and PMIP initiatives of the 6th phase of the Coupled Model Intercomparison Project (CMIP6), INQUA INTAV (International focus group on Tephrochronology and Volcanism), and the Climate History Network.
9. Constraining teleconnection behavior under differing boundary conditions
Co-conveners: Tyler R. Jones (INSTAAR, University of Colorado), William H. G. Roberts (Bristol) and James W. C. White (INSTAAR, University of Colorado)
The response of the climate system to changed boundary conditions, such as those associated with the Last Glacial Maximum or the mid-Holocene, is a fundamental question in climate dynamics. A central focus has been reconstructing tropical Pacific climate, which is important because the tropical Pacific is thought to significantly influence both global mean climate and global climate variability through teleconnections with the El Nino Southern Oscillation (ENSO).
Proxy and model-based evidence of ENSO system behavior suggests that ENSO teleconnection strength is sometimes non-linearly linked to ENSO. Furthermore, in regions known to be highly sensitive to tropical Pacific climate variability, inconsistent spatial teleconnection patterns occurring at ENSO frequencies may result independently of ENSO variations. Therefore, determining trigger mechanisms for shifts in multi-year to decadal climate variability - especially variability commonly assumed to be caused by ENSO teleconnections - is important for understanding regionally unique climate changes that occur on human timescales.
10. Ice-sheet and sea-level variability during late-Cenozoic warm periods: PALSEA2
Co-conveners: Anders Carlson, Andrea Dutton, Antony Long and Glenn Milne
The behavior of ice sheets and their impact on sea level during late Cenozoic warm periods provides important information on the natural variability of ice sheets when they were in a similar configuration as today. As part of the Paleo Constraints on Sea level rise 2 (PALSEA2) PAGES working group, this session aims to consider what the paleo record can say about rates, sources and processes of sea-level change during past warm periods such as the Holocene, the last interglaciation, other interglaciations like Marine Isotope Stage 11, and the Pliocene optimum, as well as transitions into and out of these warm periods.
We seek contributions that draw on evidence from geologic records, and models of climate, ice sheets and glacial isostatic effects. Contributions are encouraged to synthesize results in a broader context, integrate diverse methodologies and data sources, and identify potential paths towards reconciling existing datasets and/or filling gaps in understanding past ice-sheet and sea-level behavior.
11. Climate of Quaternary Interglacials from observations and model simulations
Co-conveners: Aline Govin, Emilie Capron, Nathaelle Bouttes and Maria F. Sanchez Goñi,
Quaternary Interglacials represent excellent case studies to assess current climate changes in the natural climatic context of past warm periods. Various feedback processes amplifying the original insolation changes are necessary to explain the diversity of Quaternary Interglacials in terms of their thermal magnitude, duration and climatic variability. Evaluating the role of these processes during the last 1 Ma represents a major challenge in climate research. Two main obstacles are identified: (a) the scarcity of paleo-data documenting the regional expression of past interglacials, and (b) the imperfect parameterization of current climate models, which do not integrate all oceanic and atmospheric processes involved in ice growth and decay.
This session will offer a multi-disciplinary environment to improve our understanding of climatic forcing and feedbacks shaping the climatic patterns and amplitudes of Quaternary Interglacials, as well as of climatic transitions in and out of past interglacials, from decennial to orbital time scales. We invite communications presenting recent high-resolution records from the marine, terrestrial and ice realms, targeted climate model exercises, new data syntheses and model-data comparisons. This session is supported by the PAGES/PMIP QUIGS working group.
12. Trace elements and their isotopes as geochemical proxies of past ocean conditions
Co-conveners: Catherine Jeandel, Robert Anderson, Susan Little, Thomas Marchitto and Daniel Sigman
Trace elements and their isotopes archived in marine sediments, corals, microfossils, authigenic minerals and other media have been exploited widely to reconstruct past ocean conditions, including, but not limited to: temperature, nutrient concentrations, ocean circulation, biological productivity and export production, dissolved inorganic carbon system parameters, and external sources of material to the ocean, for example as dust or via boundary exchange. Despite this importance, most proxies of necessity have been calibrated in a rather ad hoc way. Most calibrations use samples that do not necessarily represent modern conditions, or they have been calibrated solely in the lab. Calibration is normally empirical and based on only partial understanding of the processes that relate the measurable proxy to the environmental variable that it encodes.
There is therefore an urgent need for more thorough assessment of geochemical proxies to fully understand the uses and limitation of present proxies, and to develop and reliably calibrate new proxies for environmental variables that are presently difficult to reconstruct. The wealth of new and high-resolution trace element and isotope data generated by GEOTRACES as well as by contemporary initiatives offers an unprecedented opportunity to assess our understanding of geochemical proxies. This session invites presentations that exploit modern ocean observations of trace elements and their isotopes to critically examine and improve the application of geochemical proxies of past ocean conditions.
13. Pliocene climate variability over glacial-interglacial timescales (PlioVAR)
Co-conveners: Erin McClymont, Aisling Dolan, Alan Haywood and Ulrich Salzmann
The Pliocene epoch (~2.6-5.3 million years ago) is arguably the best-resolved example of a climate state in long-term equilibrium with current or predicted near-future atmospheric CO2 concentrations. At a global scale, the Pliocene is characterized by a warmer climate, reduced continental ice volume, and reduced ocean/atmosphere circulation intensity. Emerging datasets and recent modeling work has demonstrated that variability on orbital timescales (and regional non-synchronicity) should be expected in the Pliocene, and could valuable insights into important regions or processes within a warmer world than present. As part of the PAGES PlioVAR working group, this session welcomes submissions which reconstruct and/or model late Pliocene climates and environmental responses. Contributions investigating marine and terrestrial environmental change, ice-sheet behavior, biotic responses and/or biogeochemical cycling are encouraged, so as to better understand climate forcings and feedbacks through both data analysis and data-model integration.
14. Hydroclimate variability through the ages: Data, models, mechanisms
Co-conveners: Matthias Prange, Nick Scroxton, Mahyar Mohtadi, Stephan Steinke and Heidi Roop
Predicting changes in terrestrial hydroclimate is vital in our efforts to adapt and mitigate the worst effects of climate change. Reliable paleoclimate archives of the hydrological response to changing climate are indispensable to assess the sensitivity of precipitation systems to a range of different forcings on multiple time scales, and to evaluate climate model skills in projecting future climate. Projections of future rainfall are often explained in the common maxim “The wet get wetter and the dry get drier”. To what extent does the paleoclimate record provide evidence to either back up this claim, or challenge it? How did the hydroclimate respond to past changes in global climate? Which mechanisms drive hydroclimatic changes and to which extent do different regions respond similarly to the same forcing? And can we begin to separate out knowledge about the mean state of terrestrial rainfall from changes to interannual variability and the frequency of extreme events? For this session we seek the latest research that helps answer these and similar questions.
We invite contributions from both paleoclimate reconstructions and climate modeling to provide new insight into past hydroclimate variability in both the tropics and extratropics. Although the focus will be on hydroclimatic variations during the Quaternary, contributions regarding earlier periods are also welcome. Multi-proxy and multi-site approaches, which broaden our understanding of the spatial variability of past rainfall, as well as studies that shed light onto forcing mechanisms of past rainfall variability (e.g. combining proxy studies with climate modeling) are particularly welcome.
15. The Holocene – its climate variability and rapid transitions
Co-conveners: Raymond S. Bradley and Heinz Wanner
The Holocene is the closest analog for today’s climate state. Future global warming will be superimposed on natural climate variability that can be better understood by examining the Holocene.
Several scientific questions are of interest:
- To what extent was Holocene climate variability determined by natural forcings or stochastic variability?
- What was the role of meltwater from ice sheets during the early Holocene?
- How did the Atlantic Meridional Overturning Circulation (AMOC) vary in the Holocene, and how did this affect climate across the globe?
- How did Holocene climate vary within the Tropics, and what changes occurred in monsoon circulation systems?
- How did regional temperatures evolve (in terms of timing and magnitude of changes) after the Holocene Thermal Maximum?
- What were the triggers behind the rapid climate transitions during the mid-Holocene around 4200 years BP and how did different societies react?
- Which dynamical processes determined the changes between warmer and cooler, or wetter and drier periods during the Neoglacial period?
16. Multidisciplinary reconstruction of paleofloods
Co-conveners: Lothar Schulte, Daniel Schillereff, Gerardo Benito, Bruno Wilhelm, Juan Carlos Peña, Juan Ignacio Santisteban, Carles Balasch, Blas Valero-Garcés and Markus Stoffel
Climate variability and surface hydrological conditions determine the pattern of river systems and flood hazard, that may affect significantly environmental and socioeconomic systems. In the context of global warming and related societal demand, the transfer of long flood series to relevant public agencies is crucial for an accurate evaluation of the most recent severe-catastrophic floods. The session is devoted to multidisciplinary approaches that contribute to the generation of series of paleofloods (from multidecadal to millennia) in catchments of different sizes and record also low-frequency extreme events.
The session, co-sponsored by the PAGES Floods Working Group (http://www.pastglobalchanges.org/ini/wg/floods/intro), invites contributions that will focus on the following topics:
- Methodological progress in the field of multidisciplinary paleoflood reconstruction (geomorphology, geochronology, sedimentology, bio-indicators, speleothems, historical sources, hydraulic and climate modeling, etc.).
- Accuracy, uncertainties and possibility of calibration of different paleoflood records.
- The control mechanisms and forcings (orbital, solar, climate, volcanic, land use, etc.) involved in paleofloods of basins with diverse features and size.
- Synchronous or asynchronous response of basins due to differences of catchment geomorphology, hydrology and connectivity.
- The impact of land-use changes (agricultural practices, mining, river management, etc.) on paleoflood magnitude and frequency.
- Attribution of paleofloods to warm or cool climate periods, higher or lower humidity, and to regional-scale synoptic situations.
- Analysis of atmospheric circulation modes that have produced periods of higher paleoflood frequency.
- Reconstruction of extreme flows of paleofloods by hydraulic modeling.
17. Abrupt climate change: Challenges for Earth system understanding
Co-conveners: Gerrit Lohman, Ruza Ivanovic, Lauren Gregoire, Gregor Knorr, Stephen Barker and Andrea Burke
Understanding the dynamics of past periods in which abrupt changes have occurred remains a major challenge in climate research. For example, during the last deglaciation (21 thousand years ago until present) several large and abrupt environmental changes took place that have been linked with collapsing ice sheets and rapid reorganisations of ocean circulation. Reaching a better knowledge of how and why these abrupt changes took place, as well as their effect on the wider environment, is key to achieving a fully process-based understanding of the climate system.
The fundamental questions remain: How can progressive climate trends trigger such rapid events? Are they stochastic responses in a variable Earth System? What are the ice-ocean-atmosphere interactions that lead to these events? What was their impact on environmental systems? For this session, we invite contributions covering data acquisition and high-resolution records, new model concepts and mechanistic studies, as well as combined data-model analyses that provide a basis for an enhanced understanding of abrupt environmental change.
18. Human impact on global aquatic systems
Co-conveners: Nathalie Dubois, Peter Gell and Keely Mills
Lake ecosystems have responded to climate change over multiple cycles. Additionally, they have been subjected to anthropogenic pressures for millennia. There remains a challenge in distinguishing a human cause of change from that driven by climate and so often identifying the point of first human impact is challenging. With the adoption worldwide of industrial technology the impact of people on lakes over recent centuries is clear. While in some regions change was gradual, in many instances changes were abrupt. Ongoing pressure on lake ecosystems have shifted the character of many outside their historical range. These changes may be maintained by ongoing human pressure whereby the management of that pressure may result in a recovery of the wetland to a previous condition. Alternatively, the pressure may result in the weakening of stabilizing mechanisms and the establishment of feedbacks that entrench the lake in a new state.
Understanding the timing, nature and trajectory of these changes is critical for the effective management of aquatic systems. These paleolimnological approaches have direct relevance to many national and international protocols including understanding the natural ecological character of wetlands of international significance under the Ramsar convention. This session brings together researchers of the impact of people on lakes and wetlands, and their catchments and is an activity of the PAGES Aquatic Transitions (http://pastglobalchanges.org/ini/wg/aquatic-transitions/intro) working group.
19. Do species move, adapt or die? Exploring past biodiversity, ecological change and community dynamics in the fossil record
Co-conveners: Nicki Whitehouse, Helen Roe, Donatella Magri, Althea Davies and M. Jane Bunting
The remains of many species are well-preserved in Quaternary palaeoecological deposits and offer the opportunity to explore the formation, development and dynamics of biological communities over long temporal periods and address a range of key ecological and conservation questions. These include issues such as how species and communities differ in their responses to changing environmental conditions and whether these differ over time-scales. Do species primarily move, adapt or die? Are responses essentially the same over time or is there evidence for adaptation or niche evolution? What can the fossil record tell us about the vulnerability of particular communities and species – are some more vulnerable to extinction or declining populations compared with others?
For some groups, taxonomic issues also present significant challenges to understanding long-term community changes, although for others, new approaches to taxonomy, analytical advances (e.g. aDNA analysis) and novel modeling methods offer the potential to enhance and indeed revolutionize ecological interpretations and our understanding of species responses to future climate change. We solicit papers that address these themes, dealing with all types of biological proxy records from paleoecological and paleolimnological contexts, using standard paleoecological methods, species distribution models, novel modeling methods, aDNA approaches and phylogeography. We particularly encourage papers that seek to explore species and community spatio-temporal dynamics and interactions, spread, extinction and niche evolution, over the different time-scales that apply to Quaternary studies.
20. From early human impacts to the Great Acceleration: A paleoscience perspective on the climate-landscape-human multiple connections
Co-convenors: Nathalie Dubois, Pierre Francus, Andrea Zerboni, Stefano Biagetti, Jérémy Jacob, Carla Lancelotti, Marco Madella and Debora Zurro
Impacts of human activities on natural systems have been plentiful, variable, and sometimes abrupt, especially since the “Great Acceleration”, i.e. the second half the 20th century. The growing awareness of these impacts on our planet raises questions about the sustainability of natural resources and the viability of our planet for future generations. Yet, early human communities had to face climatic and environmental changes, cope with them and employ innovative adaptive strategies to survive with altered natural resources. The archaeological record worldwide preserves evidence of an impressively diversified number of human responses to climatic changes, demonstrating an extraordinary ability of early societies to respond and adapt to harsh environmental conditions.
Paleoscience places the Great Acceleration into a longer time-frame by identifying anthropogenic fingerprints of early and past human impacts and their spatial and temporal evolution. This session aims at gathering contributions dealing with the study of human responses to climate change and human impacts on natural environments, from earlier times through the Great Acceleration. This includes the roles of demographic and technological evolution as well as adaptation to climatic fluctuations. Altogether, this should lead to deciphering of the exact timing and extent of changes, and the relations of cause and effect behind them. We aim to bring together different research communities, in particular but not exclusively: geoarcheologists, paleolimnologists, paleoecologists, archeobotanists, climate modelers, and geomorphologists. Therefore studies using a multidisciplinary approach are particularly welcome, as well as those presenting novel tracers of early human impact (such as biomarkers or fossil DNA), and the study of annually resolved records. This session contributes mostly to the theme "Humans" within the new PAGES scientific scope, in particular, the GloSS, Aquatic Transition, LandCover6K, Regional Integration and Varves working groups.
21. Sediment flux: Past peaks and troughs
Co-conveners: Bernd Zolitschka, Peter Gell and Fabien Arnaud
Variations of sediment fluxes from land surfaces (sources) to lakes or oceans (sinks) reflect changes in soil erosion due to variations in climate and human impact. These variations influence processes at local, regional and global spatial scales, and from short to long timescales. Sediment flux variations affect lakes, rivers, floodplains, deltas, and coastal environments. Conversely, recording both the amount and the nature of eroded materials in so-called "sinks" gives a unique opportunity to understand environmental trajectories within their source area.
This session aims to gather a multidisciplinary audience of geomorphologists, paleoecologists, limnogeologists and sedimentologists studying past changes in sediment fluxes at all time scales and in any natural environment. Multidisciplinary studies are particularly welcome, as well as those presenting quantified reconstructions of flux changes using high-resolution records in order to put the current acceleration in a longer temporal perspective. This session contributes to the themes of the GloSS, Aquatic Transitions, Regional Integration and Varves working groups.
22. Understanding past variations in atmospheric greenhouse gases to constrain future feedbacks in the Earth system
Co-conveners: Thomas Bauska, Peter Hopcroft, Beni Stocker and Zicheng Yu
Reconstructed concentrations of atmospheric greenhouse gases – including carbon dioxide (CO2) methane (CH4) and nitrous oxide (N2O) – show that they vary on different timescales and appear to be sensitive to climate. For example, atmospheric CO2 variability is likely dominated by long-term changes in deep- ocean and terrestrial carbon reservoirs, CH4 is highly sensitive to tropospheric temperature and humidity, and terrestrial precipitation, while N2O variability largely reflects changes in the oxygen content of the intermediate ocean and climate-driven emissions from soils. Greenhouse gas variations therefore result from multiple feedbacks which can be simulated by Earth-system models. However, available observations are often not sufficient to constrain these model predictions.
Since large and fast climatic changes occurred already in the past, the palaeo-perspective is particularly instructive in this context. Reconstructed greenhouse gas variations may provide useful insights into mechanisms and the strength of Earth-system feedbacks that are operating also today. This session invites contributions from diverse disciplines aimed at quantifying and understanding how CO2, CH4, and N2O have varied in the past. Contributions that include new observational constraints, that combine modelling with observations or that evaluate new processes are invited, and research aimed at identifying past to future constraints are particularly welcome. The scope is relatively open and may cover pre-Quaternary climates, glacial-interglacial change, millennial-scale events, volcanic eruptions or more recent centennial-decadal variability.
23. Regional syntheses of human-climate-environment interactions
Co-conveners: Fabien Arnaud, Marie-Jose Gaillard-Lemdahl, Peter Gell, Thomas Hoffman and Veerle Vanacker
During the past decades, detailed paleo-environmental reconstructions for specific case-studies have allowed us to get new insights in the dynamics of human-landscape interactions. They have shown that geomorphic thresholds, temporal lags and non-linear behavior are important elements to be considered when analyzing human-climate-environment interactions. Synthesizing the complex interplay between humans, climate and the environment at the regional scale is still a major asset. Integrated proxy analyses from lake and fluvial sediments, and peat bogs are particularly useful, as they have the potential to record regional change.
In this session, we welcome regional assessments of human-climate-environment interactions, as well as methodological studies that tackle the complexity of analyzing coupled human-landscape interactions in a synthetic way as they could inspire regional analyses. This session is a joint initiative by the PAGES GloSS, LandCover6K, Aquatic Transitions and the Regional Integration working groups.
24. Regional versus global in past monsoon dynamic: disentangling wind and precipitation proxies
Co-conveners: Catherine Kissel, Franck Bassinot, Zhimin Jian and Bruno Malaizé
If the "Global Monsoon" concept is now widely accepted, inter-regional differences and potential diachronisms between paleo-records are still debated. Separating at different time scales and in different regions the atmospheric circulation aspects (i.e. wind intensity and direction) from the hydrological aspects (i.e. source of evaporation, transport, precipitation intensity and location) is now critical to reconcile paleo-records and assess properly the mechanisms of past monsoonal changes.
This session is dedicated to data and/or model results that (i) bring information about past changes in monsoonal regimes with a special emphasis on regional-global relationships, and (ii) make it possible to disentangle circulation from hydrological aspects in order to get a more comprehensive understanding of mechanisms involved.
25. Paleoenvironments of Africa: Pliocene to present
Co-conveners: Andrew S. Carr, Brian M. Chase, Janna Just and Margit H. Simon
This session examines the evidence for, and implications of, environmental change across Africa on multi-decadal to multi-millennial timescales. Spanning the equator and encompassing tropical, sub-tropical and temperate climate systems of both hemispheres, Africa provides a unique opportunity to study not only local and regional climate dynamics but also inter- and intra-hemispheric linkages in the global climate system. However, in comparison with much of the rest of the world, there is relatively little known about how African climates have changed in the past and why, and the patterns and mechanisms of climate variability remain the subject of intense debate.
This inter-disciplinary session seeks to make connections between researchers working in Africa and highlight new records, proxies and syntheses that address existing knowledge gaps at both regional and continental scales. In this context, we also encourage contributions that: 1) combine the consideration of proxy records with general circulation model simulations to explore the mechanisms and dynamics underlying the observed phenomena; and 2) address the impact that environmental change has had on the evolution and dispersion of early hominins.
26. Data Stewardship for paleoscience
Co-conveners: Julien Emile-Geay and Michal Kucera
Paleoscience is a highly collaborative scientific endeavor, increasingly reliant on online databases for data sharing and scientific workflows. Until recently there was no universal way to describe, store and share paleogeoscientific data, but this landscape is evolving rapidly through the integrating efforts of Future Earth/PAGES, LinkedEarth, NEOTOMA, and other initiatives. This session will highlight recent data stewardship efforts, their outcomes in terms of enhanced scientific analyses and insights, challenges and opportunities on the horizon. Of particular interest are contributions that showcase paleoscience that would not have been possible without innovative data stewardship.
27. The climate record of the past 5 million years: from the seasonal cycle to Ice Ages
Co-conveners: George Philander, Natalie Burls, Alexey Fedorov, Peter deMenocal and Christina Ravelo
The seasonal cycle of today, a centerpiece of climate studies, has the limitation that its short timescale of a year precludes the testing of theories for phenomena with long timescales, the oceanic circulation for example. However, the seasonal cycle of today is but one realization from a broad range of possibilities because the two reasons for the seasons, obliquity of the axis of rotation and the eccentricity of the Earth’s orbit, change continuously on geological timescales. Hence certain aspects of the remarkable amplification of climate fluctuations over the past 5 million years, which involve fluctuations in global ice volume, tropical sea surface temperatures, atmospheric CO2 levels, and Antarctic temperatures, can shed light on the climate of today and vice versa.
How and why did the response to Milankovitch forcing change around 3 and 1 Ma ago? What accounts for the spatial variability of climate responses to Milankovitch forcing at a given time? What are the implications of having, as the dominant signal over the past several hundred thousand years, precession over tropical, continental landmasses, but the saw-tooth in sea surface temperatures records from the eastern tropical Pacific?
Contributions on a broad variety of topics covering changes both in the tropics (e.g. the Pliocene problem, ENSO, monsoons, the ITCZ) and high latitudes (e.g. continental glacials, sea ice, the AMOC) are welcome. We hope this session will help bridge the divide between two groups that study climate from two very different perspectives: theoreticians and modelers who adopt a reductionist, idealized approach and paleoclimatologists who adopt a holistic approach that attempts to integrate information from diverse sources.
28. Climate variability signals in groundwater (and unsaturated zone) archives
Co-conveners: Abi Stone, Jason J Gurdak, Koen Beerten and Martine van der Ploeg
Large aquifers across the globe record natural climatic changes in the form of changes to the storage and flux of water, both beneath the water table and in the unsaturated (or vadose) zone. Unraveling past changes in sub-surface water flux and storage in response to past climate change and land use change is a key research area in hydrogeology and paleoclimatology. The groundwater (including the unsaturated zone) archive stores climatic information acquired during recharge and discharge, integrating climate signals such as recharge temperature, origin of precipitation, and dissolved constituents.
This information can be used to estimate paleo-recharge temperatures, paleo-atmospheric dynamics, and residence time of groundwater, which is needed to develop management plans in response to global groundwater crisis and future climate change. In addition, other components of the critical zone, such as the pedosphere, the biosphere and the landscape, are (dis)continuous records of palaeo-groundwater level. Extending the time series of past groundwater table variations would allow to enlarge the calibration and validation window for hydro(geo)logical and hydroclimatical models.
This session welcomes studies of global groundwater response to natural climate variability on all time scales using hydrogeochemical, isotopic, pedogeomorphological and modelling approaches. Major themes of this session include:
- Methodologies used to investigate groundwater response to environmental change at different spatial and temporal scales.
- Reconstruction of recharge histories in the saturated and unsaturated zones of groundwater.
- Connections between the hydrological cycle and biogeochemical cycling beneath the surface.
29. Palaeoecological perspectives on the role of animals in community dynamics and trophic interactions
Co-conveners: Althea Davies, Nicki Whitehouse and M. Jane Bunting
Ecosystems are complex, multi-layered and highly interconnected. Changes at higher trophic levels have cascading effects on community composition, vegetation structure and ecosystem function, which put them centre-stage in ecological and societal debates on rewilding and ecosystem services. Research on the mechanisms and ecological consequences of changes at higher trophic levels, particularly changes in animal populations, is dominated by shorter-term ecological data, which may overlook slow or cumulative impacts of trophic shifts on ecosystem variability and function. Conversely, most long-term efforts via paleoecology focus on lower trophic levels, especially on autotrophs (plants, via pollen and diatoms). Higher trophic levels often enter the picture at a relatively late stage as explanatory mechanisms for disturbances, through comparison with cultural and faunal data from archaeological sites and cave systems, or via insect records used to understand past climate. The growing literature on the consequences of megafaunal extinctions and shifting baselines in marine systems shows the potential for a more integrated approach to the study of trophic systems over longer timescales, and provides an opportunity for paleoecology to enrich interdisciplinary and applied debates on the significance of animals in ecosystem function.
In this session, we propose to bring together a diverse range of scientists studying the paleoecological expression of short and long term ecosystem shifts and interactions between trophic levels, with the aims of:
- showcasing the wide range of methodologies for reconstructing the presence and abundance of vertebrates in the past, especially those from higher trophic levels, and linking these records with more familiar vegetation distribution and climate reconstruction studies;
- developing a stronger evidence-base on the role of animals in community dynamics, ecosystem function and trophic interactions over long timescales, to better inform critical scientific, political and public debates on issues such as rewilding; and
- stimulating discussion of future research directions and collaborations on trophic interactions over long timescales.
We invite speakers working on this theme from single and multi-proxy paleoecological perspectives, using fossil, experimental and modelling approaches, to submit abstracts.
*Abstracts submitted to this session have been moved to other sessions*
30. Changing island ecosystems
Co-conveners: Sandra Nogué, Mary Edwards, Peter Langdon, Lea de Nascimento and José María Fernández Palacios
There are over 100,000 islands on Earth, which support 20% of global biodiversity. The characteristics of size, shape and degree of isolation make many of these islands ecologically unique. As well as ecological value, the terrestrial, freshwater and marine ecosystems of islands provide important natural resources necessary for the economies and cultures of many island communities. Paleoecological and paleoclimatological studies on islands worldwide have shown that for example human impacts are nothing new and that in most cases the effects of human settlement are noticeable even at early stages and for long periods. Also, many climate-change scenarios predict an increase in the frequency and magnitude of extreme climatic events and sea-level rise that might have special negative effects on small island ecosystems.
In this session we will address the following question: How can palaeo-data contribute to knowledge of changing island ecosystems over time? Using all types of biological proxy records from paleoecological and paleolimnological contexts, we specifically will discuss: 1) Human impacts and biodiversity baselines: we aim to explore novel proxies such as the application of Lipid biomarkers to identify signals of anthropogenic impact. 2) Climate change adaptation and mitigation: we aim to discuss the effects of climate change (e.g.) sea level shifts on species distribution, dispersal, and resilience. This session will allow us to discuss about paleoecological and paleoeclimatic proxies to better understand the long-term history of biodiversity change in order to identify patterns that have shaped current island ecosystems.
*Abstracts submitted to this session have been moved to other sessions*
31. Global Dust Deposition in Past, Present, and Future Climates
Co-conveners: Francois De Vleeschouwer, Gisela Winckler, Natalie Mahowald and Fabrice Lambert
Mineral dust aerosols influence global climate by changing Earth’s radiative balance, influencing cloud formations, and by providing micronutrients to marine and terrestrial ecosystems. Recent studies focusing on the current climate have highlighted the importance of the chemistry, mineralogy and size distribution of the dust particles for quantifying the impact of dust onto climate and biogeochemistry. Although much progress has been made in global dust modeling, significant differences persist among various models and between model output and observations.
In this session we want to discuss ways to improve our global knowledge on dust characteristics, simulations and impact on the Earth, including radiative forcing, atmospheric chemistry, and biogeochemistry. We invite contributions focusing on dust reconstructions from climate archives as well as modern observations and model simulations, echoing the goals of the PAGES working group DICE (Dust Impacts on Climate and Environment). We particularly welcome talks that address how to transfer knowledge from the observational community to the model community and vice-versa.
32. Large-scale hydroclimate variability and change of the Common Era: Patterns, Impacts, and Processes
Co-conveners: Edward Cook and Jason Smerdon
Hydroclimate is an increasing focus of the paleoclimate community and the last several years have seen important data products developed to study hydroclimate variability and change during the Common Era. A growing collection of proxy records have been selected and discussed by the PAGES 2K regional working groups and hydroclimate has been targeted by PAGES 2K as the next key variable of study. Independent efforts to assemble continental-scale gridded hydroclimate reconstructions with annual resolutions are also now widely available and close to providing global coverage over land. At the same time, an explosion in the number of last-millennium simulations using fully-coupled climate models has occurred over the last several years.
These collective developments make the time ripe for exploring large-scale hydroclimate variability over the Common Era and the underlying forced and internal variability that causes it. Open and compelling geophysical questions can now be addressed with the paleoclimate and modeling tools that are available, the answers to which can also be connected to historical and documentary knowledge about the impact of past hydroclimate variability on past and present societies.
This session will aim to leverage the important and timely developments described above, to foster a high-profile and dynamic discussion about large-scale hydroclimate variability and change and its impacts on past, present and future societies. In addition to engaging the paleoclimate community, we welcome historians in relevant areas to build an interdisciplinary discussion on this critical topic.
33. Ancient DNA for understanding past biodiversity, human history, and drivers of ecosystem changes: achievements, limits and perspectives
Co-conveners: Charline Giguet-Covex (University of York), Laura Epp (Alfred Wegener Institute), Isabelle Domaizon (Institut National de la Recherche Agronomique) and Inger Greve Alsos (Tromsø University Museum)
Use of ancient DNA (aDNA) has made a major contribution to our understanding of past ecosystems and human history. Recent studies have for instance addressed ecosystem and population changes both in relation to climatic and anthropogenic factors, as well as the history of agro-pastoral activities. However, compared with other proxies, it is still in its infancy in particular for its application to continuous sedimentary records. Hence, whereas, in theory, it can offer to directly identify organisms living in the surrounding of the archive down to species level, and even capture intraspecific or morphologically cryptic variants, we still know little about to what extend the biota is actually represented in the DNA records. Especially, biases or imprecisions related to both taphonomic processes and analytical procedures are not yet fully understood.
In this session, we will bring together specialists using aDNA applied to sediments and bones to study the history of ecosystems and populations in different contexts (e.g. ecology, genetics, archaeology). In particular, we welcome contributions showcasing methodological developments of aDNA analyses, to understand and account for taphonomic processes and biases. Contributions integrating different kinds of data and considering the different spatial and/or temporal scales of these analyses are also highly appreciated.