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Climate change - Learning from the past climate

Final Report Summary - PAST4FUTURE (Climate change - Learning from the past climate)

Executive Summary:
A. Objectives of Past4Future
Paleo-climatic records contain a wealth of information on the stability and variability of climate and its ability to perform abrupt changes. The challenges for the multi-disciplinary Past4Future team are to better understand the climate system, to improve the prediction of future climate changes and to advance the knowledge on abrupt climate changes in interglacial periods.

The key objective for Past4Future are formulated in the following questions:

• What are the dynamics of the climate over interglacial periods?
• What causes climate changes and abrupt changes over the course of interglacial periods?
• What causes climate changes and abrupt changes over the course of interglacial periods?
• Can we understand the greenhouse gas records of the interglacial periods?
• What can the past tell us about risks for climate changes/threats in the future?

B. Key Questions
To meet the objectives the Past4Future program will address the following challenging key questions:

• What is the risk of abrupt changes in interglacials?
• Can we understand the greenhouse gas records of the interglacial periods?
• What is the risk of rapid collapse of ice sheets?
• Were there significant changes in ocean circulation during previous interglacial periods?

C. Key project results
Past4Future combines past-climate datasets from ice sheets, ocean sediments, cave deposits, Past4Future is a Collaborative Project under the 7th Framework Programme of the European Commission. The Past4Future project investigates the climate and environment of past warm peri-ods (interglacials) to inform on future climate and possible abrupt changes. The overarching motiva-tion for all 22 Past4Future partners working with paleo-science archives (ice sheets, ocean sedi-ments, cave deposits, corals, and pollen) is the ambition to understand the climate system and the importance of predicting future climate changes, using the extended perspective offered by observa-tions and modelling of the climate history over the Quaternary era.

Past4Future has clearly shown how important past interglacials are for improving understanding of climate under conditions similar to or warmer than today (as expected in the next century). This is illustrated by the fact that interglacials are discussed many times in the palaeo-climate chapter of IPCC [IPCC, 2013, Chapter 5], and form a major part of the discussion about ice sheets and sea level in the future.

Comparisons between models and data show that it is possible to understand the climate trends during the present interglacial, the last 11.7 thousand years. The trends are relatively weak, so this is not providing a very strong constraint. On the other hand for the last interglacial, the period from 128 thousand to 115 thousand years before present, where temperatures where higher than the present has great potential to understand the climate trends. Here the limitations are fewer observations with less constrained dating.

Three key results of the Past4Future project have stood out as being of particular importance relative to the future. The first one is that the Past4Future results unambiguously demonstrate that abrupt climate changes are not limited to glacial conditions, but can also occur in a warm world. Changing ocean circulation, increasing greenhouse gas concentrations and instabilities of the remaining polar ice sheets are candidates for causing future abrupt changes.

The second issue concerns sea level and ice sheets. It has become increasingly accepted that sea level was 5-10 m higher than the present in the last interglacial, implying substantial reduction of the Greenland and/or Antarctic ice sheets. Indeed to obtain numbers in the mid and high range both Greenland and West Antarctica would have to be substantially retreated. Substantial progress was made, through the analysis of the NEEM ice core in Greenland and Antarctic ice cores, and through ice sheet modelling advances.

The third issue is the very clear documentation from palaeo-records (especially ice cores) that the greenhouse concentration have not reached levels similar to the present in the past 800.000 years although temperatures have been significantly warmer than the present. If the CO2 trend (and its stable carbon isotopic ratio) over the Holocene can be reasonably reproduced with Earth system models incorporating carbon cycle components, it is not the case for the last interglacial. This means that possibly the representation of terrestrial mechanisms such as the dynamics of peatlands and permafrost soils is not correct in these models.

The strength of the project relied on the interdisciplinary team of experts that was formed, bringing together the paleo-climatic data and modeling communities. Strong emphasis was put on communi-cating the project results to an audience including scientists within and external to the climate science community, as well as policymakers and the public. Two volumes of the Magazine PAGES present the results short and concisely for a broader audience.

Project Context and Objectives:
1. A summary description of project context and objectives
Records from palaeo-archives, such as marine sediments and ice sheets, have demonstrated that, during the last several million years, the most dramatic climate changes were the coming and going of glacial and interglacial periods with temperature changes of 5 - 6 °C globally and up to 25 °C in the High Arctic.

While the cold glacial periods were characterised by abrupt temperature changes of up to 10 - 15 °C over a few decades in the Arctic, the subsequent interglacial warm climates exhibited abrupt regional changes of temperature even if the amplitude of these were substantially smaller. This relative climate stability may be part of the reason for the impressive evolution of human culture and tech-nology in our present interglacial period.

Impacts on the environment, human health and society in Europe demonstrate how grave the still rather modest global warming during the last 100 years is:
• The temperature increase since 1900 has been 0.8 °C globally, but in Europe the increase was 1.0 °C over the same period.
• During the past five decades, Europe has experienced 300 flood events that led to massive loss of lives and damages at the 100 billion € level. A continued rise in temperature over Europe will likely increase the frequency of extreme flood events in this region.
• Annual precipitation trends in Europe in the 20th century show the contrasting picture of 10 - 40% wetter in northern Europe and up to 20% drier in southern Europe.
• Since 1850, glaciers in the European Alps have lost 2/3 of their volume with loss accelerating in the last three decades. In 2050, only 25% of the glaciers in the Swiss Alps will likely still be there.
• The minimum summer sea-ice extent in the Arctic was reduced by 50% in 2007 compared to the minimum extent in the 1950s.
• The length of the growing season for plants in Europe increased by 10 days between 1962 and 1995, and is projected to increase in the future.

A global warming of 0.8 °C is still rather moderate. However, the predicted warming of 1.4 - 4 °C globally, and 1 - 5.5 °C in Europe, by the year 2100, is dramatic and this will violently impact the environment, human health and society in Europe, as well as profoundly affect the increasingly globalized world.

Understanding of the future changes, their risks and the costs connected with the climate-induced changes, is a necessity for maintaining Europe’s quality-of-life and international competitiveness. The required knowledge and insight can be achieved through reliable and sound climate change projections, in particular those with significantly reduced uncertainties on key aspects, processes and mechanisms. This will be especially true for projections dealing with ocean circulation, sea ice, ice sheets, and monsoons in response to changing global climate, as these have not yet been well constrained.

To relieve this situation, it is imperative to understand past climate and impacts. How can we expect good predictions of the future if the predictive tools are not able to model the past? Many of the pro-cesses and modes of variability, that are key to uncertainties about how European climates may evolve, are of a more long-term nature for which the instrumental database is too short-term. The instrument-based observations are registered during times of mixed natural and human influences; therefore, gaining a thorough understanding of the natural aspects of climate change, intercalated with man-made ones, requires data and model simulations of climate states that are similar to the modern, but without significant human influence. Our philosophy is that models used for predictions must demonstrate solid capacity to model the past especially that of recent warm periods. The past offers an opportunity both to improve models, and constrain the range of predictions with longer timescales through observation.

2. The following key questions succinctly summarise the key objectives of Past4Future:
What are the dynamics of the climate over interglacial periods?
At the global scale, the interglacial climate variability is small compared to the changes during glacial periods. Nonetheless, it has caused significant changes in the Earth system and at regional scale. The difference between the warmest period of the last interglacial and the typical climate of the present interglacial is comparable to the change in temperature expected by year 2100. These dynamics are responding to 1) changing external forcing factors, such as orbital forcing, changing solar irradiance, and volcanic eruptions, and to 2) the reaction of internal factors, such as large-scale ocean circulation and shifts of the Inter Tropical Convergence Zone. Past4Future-generated palaeo-data, in unprecedented resolution, allow studying the inter-annual climate-change variability representing an essential ground-truthing of climate models.

What causes climate changes and abrupt changes over the course of interglacial periods?
Reconstructing the past climate clearly demonstrates its ability to change abruptly and at a rate fast enough to impact ecosystems and societies. We know that these abrupt changes (also known as regime shifts or large-scale ecosystem transitions) have occurred during both our current interglacial and the previous one, the latter being a period with many climate features similar to those projected for our future. Yet, the underlying causes of these changes, their thresholds for activation, the rate at which they occur, and even the full extent of the impacted regions, have been poorly understood. In order to improve our understanding of the likelihood and possible impacts of such transitions and climate changes in our future, Past4Future critically assesses their past occurrences and underlying mechanisms using an innovative and combined data-model approach.

Can we understand the greenhouse gas records of the interglacial periods?
Prior to the anthropogenic period, greenhouse gases mirrored the climate changes with lower con-centrations in cold periods and higher concentrations in warmer periods. Some differences between climate changes and greenhouse gas concentrations have been puzzling: Why do the greenhouse gases overshoot at the onset of interglacial periods and why do the gas records in the present inter-glacial dip 5000 years BP? – Understanding the dynamics of biogeochemical cycles in the past is crucial for predicting the future.

What can the past tell us about risks for climate changes/threats in the future?
In its Fourth Assessment Report, the IPCC made estimates of climate changes and their impacts, focused on those expected in the next century. However, some predictions with high societal rele-vance were highly uncertain, mainly because of uncertainties in greenhouse gas emission scenarios, non-linear behavior, and a limited understanding of some processes. The study of past warmer periods, for which increasingly detailed datasets are now available, offers the possibility to test and limit the range of such predictions. Indeed, looking back at the past is the only way to observe pro-cesses, such as ice sheet dynamics, that have timescales far longer than the observational record. The last interglacial period represents a particular value in this regard because, during millennia, the temperature, especially in the Arctic and Antarctic, was at levels similar to those expected towards year 2100. That interglacial period can, therefore, be used as a test-case of the effects of a warm climate, and to test whether events currently considered to have low probability actually did occur. In IPCC’s Fifth Assessment Report, published in the final Past4Future year, the modelling of selected past periods are explicitly included. In relation to this IPCC assessment, Past4Future is timing the publication of key results in order to deliver data benchmarking the models, to coordinate the European modelling efforts, and to implement new methods for data-model comparison.

Project Results:
• Dating sediment cores from Atlantic and Indian Southern Oceans documented the climate during the past 30,000 years as well as the onset of the Last Interglacial period.
• Database with records from ice cores, speleothems, pollen, loess, and marine sediment cores.
• Simulations impacted by coral reef reconstructions and terrestrial fluxes over the past 18,000 years to hindcast atmospheric CO2 since the end of the last ice age.
• Increase in CO2 contents did occur in two steps: A slow and gradual increase over 12,000 years followed by a rapid jump within 300 years.
• Compiled data for sea surface temperatures and sea ice since end of last ice age.
• Sampled planktonic Mg/Ca records in the East Atlantic for the past 3200 years.
• Applied the Bern3D dynamical ocean/energy-balance atmosphere model in 800,000-year simula-tions with orbital, greenhouse gas, and ice sheet forcings.
• Analysed pollen contents of North Atlantic and Greenland Sea cores from both the Last Interglacial and the Present Interglacial periods.
• Coupling the LOVECLIM atmosphere/ocean/vegetation model to the GRISLI dynamic ice sheet model resulting in the first preliminary simulations of Termination 1.
• Documented Terminations 1 and 2 in Pleistocene sediment cores from the Polar Frontal and sub-Antarctic zones of the Pacific Ocean.
• Reconstructed and modelled biomass fire intensity, compared and extended by analysis of regional trends during the Holocene.
• Performed time-slice simulations to investigate the sensitivity of atmospheric dynamics with respect to various ice sheet configurations during the early Holocene.
• Determined sea surface conditions for 39 stations of North Atlantic and adjacent basins from Younger Dryas to 6000 BP.
• LOVECLIM experiments analysing climate sensitivity in the Last Interglacial to melting of the Greenland Ice Sheet.
• Completed EMIC LOVECLIM simulations for the last 1150 years, using the PMIP3 protocol for solar and volcanic forcings.
• Documented the rapid ending of the Last Interglacial associated with a 3 °C warming in Greenland.
• Achieved high-resolution records of 28 bioactive trace elements from the NEEM ice core, incl. low-resolution profiles from the Holocene and high-resolution profiles from Dansgaard-Oeschger events.
• Investigated the influence of early agricultural activities with the LPJ dynamic global vegetation model.
• Forced the CH4 model with climate output from GCM freshwater experiments to mimic the reduc-tion in the Atlantic Meridional Overturning Circulation at the 8.2 ka event.
• Determined that the Greenland Ice Sheet contributed at least 0.8 m to sea level rise during the Last Interglacial; and very unlikely more than 2 m of the observed 4-8 m Eemian sea level rise. Therefore, Antarctica must have contributed significantly by melting during Last Interglacial (i.e. the Eemian interglacial).
• Reconstructed sea ice concentrations in Atlantic and Pacific marine sectors revealing that map-ping the distribution of sea-ice-related diatom species allows for qualitative estimates of winter sea ice extent in the past.
• Revealed that Atlantic Meridional Overturning Circulation transported heat and moisture to the northern high latitudes thereby acting as a strong positive feedback to fuel the ice sheet growth during the Last Interglacial.
• Data assimilation simulation of the last millennium showed sub-polar gyres weakening and a southward shift of the western boundary currents in the North Atlantic and the North Pacific be-tween the Medieval Climate Anomaly (950-1250 AD) and the Little Ice Age (1400-1700 AD).
• Established an updated overview of meta-information of data used in Past4Future, incl. description, location, timescale, data acquisition, data curator and data manager.
• Completed analysis and assessment of opinions, comments and attitudes expressed by the stakeholders on how best to communicate and disseminate, to the stakeholders and to the Euro-pean citizens, the results and conclusions reached by Past4Future.
• Processed FAMOUS transient sensitivity simulations of the Last Interglacial and Present Inter-glacial and they conformed to INTERDYNAMIC standard.
• Analysed simulations covering the past 1500 years using data assimilation, focusing on the high latitudes of the Northern Hemisphere, Europe and Antarctica.
• Assessed the observed link between accumulation records and large-scale atmospheric circulation patterns during the early Holocene.
• Performed model/data comparison over the last millennium over Antarctica. All analysed models displayed a cooling trend during the pre-industrial period, consistent with proxy-based recon-structions.
• During Younger Dryas, the role of Arctic sea ice in the Atlantic Meridional Overturning Circulation reduction showed an enhanced export from the Arctic; and the radiogenic isotope signature sug-gested a Canadian source.
• Transient simulations covering the last millennium evaluated the sensitivity of the Arctic sea ice in the Present Interglacial to volcanic and solar forcing
• High-resolution CO2 and δ13CO2 records from Antarctica showed that, at the very end of Last In-terglacial, carbon isotopes supported a release of carbon from the terrestrial biosphere. This ex-plains the constant CO2 concentrations for 3000 years at the end of the interglacial despite signif-icant climate cooling.
• The JSBACH model simulated CH4 emissions from boreal wetlands during six time slices over the last 6000 years. The model results suggested that CH4 emissions from boreal wetlands increased slightly during the Holocene.
• Analysis techniques applied to soluble iron and aluminium in a section of Greenland ice core dated to 1729-1733 AD indicated that volcanism is a source of highly soluble aluminium and iron.
• Based on an orbital forcing, the CLIMBER-JSBACH model calculated an enhanced African Mon-soon System leading to a higher vegetation fraction in the Sahel and the Sahara.
• Compiled a sea level record over the last deglaciation, based on reef cores from Tahiti.
• Quantified the importance of ablation-related processes for ice sheet feedbacks in the evolution of past Northern Hemisphere ice sheets throughout the last glacial-interglacial cycle.
• Obtained data from a high-resolution IP25 record from Arctic Ocean’s Lomonosov Ridge about Arctic sea ice formation and its relationship to the Younger Dryas Cooling Event.
• Carried out simulations covering the past millennium for both hemispheres, revealing a general increase in the ice extent over the pre-industrial period, in broad agreement with available proxies in polar regions.
• Finalised a multi-proxy deep water study of the Gardar Drift over the Holocene (i.e. Present In-terglacial).
• Completed studies of ice sheet response and surface water conditions spanning MIS5e (Last In-terglacial) at the Eirik sediment drift.
• Established a new diatom record from the western Pacific sector of the Southern Ocean providing transfer-function-based information on sea surface summer temperature changes for the past 150,000 years.
• Completed palynological analyses and quantitative reconstructions of central North Atlantic sea surface conditions during the Last Interglacial.
• Finished quantitative reconstructions of climate in Atlantic Canada during the Last Interglacial.
• Determined that, during MIS5e, the East Greenland / East Iceland Current system was weaker and allowed pronounced inflow of warm Atlantic waters to the southwestern Nordic seas, creating warmer conditions there than in the Holocene and contributing to the Greenland Ice Sheet retreat.
• Showed that, during the last deglaciation and until 15,000 years ago, the bottom waters in the South Indian Ocean remained isolated from the better-ventilated deep waters of northern origin.
• Established that South Atlantic deep waters were significantly better ventilated during MIS5 than during Holocene, whereas bottom water ventilation in the South Atlantic and the South Indian Ocean was similar during Last Interglacial and Present Interglacial.
• Performed simulations with data assimilation to illustrate the potential role of freshwater discharge from Antarctica in the cooling observed over land and in ocean 10,000 - 8000 years ago.
• Reconstructed a standardised volcanic forcing (SO4) dataset covering the entire Holocene.
• Completed the construction of a standardised Total Solar Irradiance dataset covering the last 9000 years.
• Results from a suite of Last Interglacial reconstructions (Mg/Ca, isotopes, foraminifera and Ice-Rafted Debris counts) in the central and western North Atlantic revealed rapid changes in North Atlantic hydrography during late Last Interglacial, similar to those identified in early Last Intergla-cial.
• Compared Last Interglacial snapshot (at 129 ka, 125 ka, 121 ka and 115 ka BP) to Present Inter-glacial snapshots (at 12 ka, 8 ka, 5 ka and 3 ka BP), using available high-resolution palaeo-archives to illustrate how climate occasionally flips to contrasting states.
• Present Interglacial and Last Interglacial temperature dynamics, based on the PIG2LIG-4FUTURE database and from more than 800 sites, were found suitable for setting a reference framework and guidelines for model / data comparison purposes.
• Used the coupled carbon-climate model CLIMBER-JSBACH in a transient mode to simulate the carbon dynamics within the last 8000 years.
• The interglacial CH4 isotope records showed a similar temporal evolution during Present Intergla-cial and Last Interglacial, likely related to the development of peatlands and their evolution from minerotrophic fens to ombrotrophic bogs in the course of warm periods.
• Determined levoglucosan concentrations in the NEEM ice core for the past two millennia, revealing past biomass burning.
• Completed a detailed review of ice core proxies for sea ice as well as analyses of Greenland shallow ice cores, leading to conclude a rather weak dependence of sea salt on sea ice.
• Planktic foraminiferal assemblage and stable isotope analyses for the Holocene and MIS5e from cores in the NW Atlantic revealed a strikingly different surface water circulation in W Labrador Sea during MIS5e as compared to the Holocene.
• Applied the BERN3D coupled three-dimensional dynamical ocean/energy balance atmosphere model in several 800,000 year simulations with prescribed orbital, greenhouse gas, and ice sheet forcings.
• Completed analyses of Holocene palynology for sediment cores from Davis Strait, Fram Strait, Labrador Sea, Chukchi Sea, and Greenland Sea.
• Completed palynological analyses of Last Interglacial sediment cores from the North Atlantic and the Greenland Sea.
• Transient FAMOUS simulations for the interglacials have been completed with fixed CMIP5 pre-industrial greenhouse gases.
• LOVECLIM transient simulations have allowed analysis of the impacts of different forcings on the spatio-temporal variability of the Holocene Thermal Maximum.
• Deglacial climate evolution and the response to melting of major ice sheets have been studied through experiments with the MIT-EMIC model.
• Documented Termination 1 and Termination 2 in several late Pleistocene sediment cores from the sub-Antarctic and Polar Frontal zones of the Pacific sector.
• The Last Interglacial and Present Interglacial FAMOUS transient sensitivity simulations were pro-cessed and conformed to INTERDYNAMIC standard.
• Transient simulations of the last four climatic cycles (420 to 0 ka BP), incl. Eem and Holocene, using the CLIMBER (atmosphere-ocean-vegetation) model forced by orbital and CO2 variations.
• Performed INTERDYNAMIC and snapshot simulations for Eem (Last Interglacial) and the prein-dustrial period (i.e. 130, 128, 125 and 0 ka) with versions of CLIMBER.
• Documented Holocene ocean circulation based on marine sediment cores from (sub)polar to tropical regions of the Atlantic Ocean.
• Identified an in-phase relationship between the North Atlantic climate and the California Current strength, incl. evidence of the establishment of atmospheric-oceanic teleconnections between the North Atlantic and the North Pacific, allowing transference of the Greenland signal into the Cali-fornian Margin.
• Synthesised decadal ice core chemical data in the Antarctic EDML and EDC ice cores, incl. time series derived from ion chromatography and continuous-flow analysis for sea salt aerosol, mineral dust, biogenic and volcanic sulfur as well as nitrogen compounds.
• Procured records of Mg/Ca-based temperature, δ18O and δ13C using planktonic foraminifera from East Pacific cores.
• Levoglucosan-based reconstruction and modelling of forest fire intensity compared and extended by analysis of regional trends during the Holocene.
• Early Holocene time-slice simulations to investigate the sensitivity of atmospheric dynamics with respect to different ice sheet configurations.
• Coupled the LOVECLIM atmosphere-ocean-vegetation model to the GRISLI dynamic ice sheet model and the first preliminary simulations for Termination 1.
• Developed a coupling scheme between climate model CLIMBER and 3D ice sheet model GRISLI, incl. simulations of the Last Interglacial.
• Data from Black Sea sediments revealed interplay between the deglaciation warming and the decay of eastern part of the Fennoscandian ice sheet.
• Established the chronology of reef cores from Tahiti based on U-Th-14C comparison ages.
• Documented the latest part of the deglacial history, covering the period 9000-7000 years BP off SW and W Greenland, based on sedimentological, magnetic and foraminiferal data from marine cores.
• Multicentennial-scale records of planktic foraminiferal stable oxygen isotope and Mg/Ca records from the Indian Ocean – Atlantic Ocean corridor south of Africa, documented surface hydrographic changes during MIS8-MIS5, and inferred dynamics of Indian-Atlantic water transport on a millennial timescale and linkage with changes in the Atlantic Meridional Overturning Circulation.
• Analyses of the relative contribution of changes in atmospheric circulation and of reduced sea surface temperatures in the Southern Ocean, due to impact on ocean circulation of increased West Antarctic melting rate, revealed that they both contributed to the observed cooling.
• Compiled sea surface summer temperature and winter sea ice reconstructions for the last two Terminations based on transfer functions of diatom records from marine sediment cores.
• Transient simulations showed that data assimilation induces long-term shifts in the model state characterised by persistent circulation anomalies.
• Reconstructed and modelled forest fire intensity in West Africa and the Americas was compared and extended by analysis of regional trends during the Holocene.
• The main modes of Northern Hemisphere atmospheric variability, e.g. the North Atlantic Oscillation, the Arctic Oscillation and the Pacific - North America Pattern, compare very well to spatial patterns and percentage of total variability.
• Weather patterns derived by cluster analysis for the North Atlantic / European and the Arctic region showed little change due to both orbital forcing and implementation of different ice sheet dis-tribution, confirming the stability of atmospheric circulation on a regional scale.
• Established that the 126,000 years BP measurements in Greenland ice cores were driven by a Last Interglacial reduction in Arctic sea ice and an associated high-latitude sea surface warming; this finding improved air temperature estimates from Greenland ice core isotope data.
• In model-data comparisons over the last millennium for Antarctica, models tended to over¬estimate the recent warming compared to observations.
• The Max-Planck Earth System model simulated runoffs in North Africa, confirming three different viable pathways for human migration during the Last Interglacial from Sahara to the Mediterranean coast.
• Analyses of simulations with data assimilation indicated that Antarctic freshwater discharge po-tentially contributed to the cooling effect observed over land and ocean 10,000-8000 years ago.
• Reconstructed a standardised volcanic forcing (SO4) dataset covering the entire Holocene.
• Completed simulations for the last millennium to assess sensitivity of Arctic sea ice in the Present Interglacial to volcanic and solar forcing.
• Resolved the dating of the EDML ice core and synchronised it to Greenland ice core records.
• Documented high-resolution multi-proxy reconstructions of surface hydrographic changes near Eirik and Gardar Drifts during the Last Interglacial.
• Proxy-based Last Interglacial reconstructions in the North Atlantic revealed rapid hydrographical changes in early and late Last Interglacial.
• New time series using available high-resolution paleo-archives depicted the spatial and tempo-ral characters of climate variability across key transitions and events.
• Completed high-resolution climate reconstructions from Alboran Basin and Sicily Strait, Mediter-ranean region.
• Simulated and reconstructed temperature time series for the Present Interglacial and the Last In-terglacial combined with their respective deglaciations.
• Identified causes of model-data differences, providing a global picture of the Present Interglacial-to-Last Interglacial surface temperature evolution, responses to orbital forcing, and climate feedbacks effecting short-term and long-term changes.
• Extended the δ13CO2 records over the last 24,000 years, i.e. incl. the Last Glacial Maximum, the glacial/interglacial transition and the pre-boreal period into the Holocene.
• Obtained high-resolution CO2 and δ13CO2 records from EPICA Dome C and Talos Dome ice cores for MIS5.5 the preceding deglaciation and the glacial inception.
• Identified a similar sequence of carbon cycle events during the penultimate and the last glacial termination: at the very end of the last interglacial, carbon isotopes supported a release of carbon from the terrestrial biosphere.
• New carbon cycle data explained the long-standing riddle of constant CO2 concentrations for 3000 years at the end of the interglacial, despite significant climate cooling.
• Applying the flow-injection analysis technique on Greenland ice core samples indicated that vol-canism was a source of highly soluble aluminium and iron.
• Simulations of northern peat development and areal extent showed that carbon stocks in modern peatland soils increased very significantly after the Last Glacial Maximum, suggesting a persistent carbon sequestration rate in peatlands under current climate conditions.
• For the Holocene, radiocarbon production, solar activity, solar-induced climate change and total solar irradiance have been reconstructed and the latter also predicted for the next centuries.
• Periods of high solar activity were quite common throughout the Holocene; during 28% of the pe-riod, the solar activity was higher than the modern average.
• Procured high-resolution data of CH4 for the Holocene from the NEEM ice core in Greenland.
• Related CH4 isotope records during Last Interglacial and Present Interglacial to the development of peatlands and their evolution from minerotrophic fens to ombrotrophic bogs in the course of warm periods.
• Documented the annual variability imprinted in the CH4 signal, most probably related with in situ production.
• Using the JSBACH model to simulate CH4 emissions from boreal wetlands over the last 6000 years, has suggested that CH4 emissions from boreal wetlands increased slightly over the course of the Holocene.
• Model evaluation of atmospheric impacts and ice core imprints of methane bursts into the atmos-phere from clathrate degassing included C and H isotopic signature, and high-resolution ice core data provided the best signature of a clathrate degassing event.
• Produced a high-resolution, Krypton-corrected, record of carbon isotopes in methane over the last 160,000 years.
• Revealed sub-millennial structures in the atmospheric CH4 variability and obtained depth markers for chronological comparison of the NEEM ice core records with speleothems.
• Mediated CO2, CH4 and N2O by terrestrial biosphere processes sensitive to climate and CO2 leading to feedbacks between climate and land; this contributed to the sharp rise of CO2, CH4 and N2O in the atmosphere since pre-industrial times.
• The JSBACH model simulated the boreal methane emissions and the catotelm and acrotelm ac-cumulation during Present Interglacial and Last Interglacial to be very similar in magnitude.
• Pre-industrial CH4 emissions from boreal wetlands increased slightly during the Holocene.
• A probability distribution of the Greenland ice sheet contribution to sea level rise during the Last Interglacial indicated that the ice, very likely, contributed at least 0.8 m but not more than 3.6 m.
• Model simulations of the last glacial-interglacial cycle included calibrating parameters on the last deglaciation to fit age-depth relationship in the various ice cores and present topography.
• Completed the work considering implications of glacial - isostatic adjustment for ice sheet elevation during the Last Interglacial.
• Quantified the importance of ablation-related processes with respect to ice sheet feedbacks in the evolution of past Northern Hemisphere ice sheets during the last glacial-interglacial cycle.
• Provided the best estimates of Greenland and Antarctic ice sheet topography and volume during the Present Interglacial.
• New estimates for amplitude and timing of Melt Water Pulse 1A, incl. possible ice sheet sources (Laurentide vs Antarctica) and their impact on the oceanic circulation.
• Sea ice cover in the western Labrador Sea proved to be strongly related to glacier meltwater re-lease with the most extensive sea ice during periods of more meltwater.
• Completed a diatom sea ice dataset from West Greenland and Iceland waters, incl. diatom data from surface sediments and monthly mean sea ice index data over 30 years.
• Finished the development of a diatom-based transfer function for the quantitative reconstruction of past circum-Antarctic sea ice concentrations and probabilities.
• Applied the reconstruction of sea ice concentrations to existing records from the Atlantic and Pa-cific marine sectors, revealing that mapping the distribution of sea ice related diatom species, preserved in surface sediments, allowed for qualitative estimates of past winter sea ice extent.
• Completed a 3000-year quantitative data series of sea surface temperature and annual sea ice duration off the sub-Antarctic Kerguelen Islands.
• Determined East Greenland glacial melting rates and sea ice variability based on radiographs and sedimentary parameters.
• Constructed sea ice records for the last deglaciation and middle-late Holocene off Newfoundland.
• Developed a diatom-based transfer function approach to estimate the pre-industrial Antarctic sea ice extent.
• Completed and analysed simulations, for both hemispheres, with and without data assimilation covering the past millennium.
• Finished palynological analyses of sediment cores from the northern North Atlantic for the Last Interglacial.
• Provided compelling evidence from the 231Pa/230Th records that the Atlantic Meridional Overturning Circulation rate, above 2000 m depth, was enhanced during the Last Glacial Inception.
• Showed that Atlantic Meridional Overturning Circulation transported heat and moisture to the northern high latitudes and acted as a strong positive feedback to fuel ice sheet growth during the glacial inception.
• Completed multi-proxy analyses of sediment cores from the North Atlantic to document sea surface conditions and the structure of water masses during the Present Interglacial and Last Interglacial.
• Simulation with data assimilation over the last millennium showed a weakening of the sub-polar gyres and a southward shift of the western boundary currents in the North Atlantic and the North Pacific between the so-called Medieval Climate Anomaly (ca. 950-1250 AD) and the Little Ice Age (ca. 1400-1700 AD).
• Bottom waters in the South Indian Ocean remained isolated from better-ventilated deep waters of northern origin until ~15,000 years ago.
• Identified an in-phase relationship between North Atlantic climate and California Current strength: The California Current weakened during the North Atlantic - dominated millennial events, Younger Dryas and Heinrich Stadial 1.
• Evidenced the establishment of atmosphere-ocean teleconnections between the North Atlantic and the North Pacific, involving the Intertropical Convergence Zone, the North Pacific High and the Aleutian Low; allowing the transference of the Greenland signal into the Californian Margin.
• New, high-resolution records of the surface ocean hydrography from the Indian Ocean / Atlantic Ocean gateway, south of Africa, documented recurrent and high-amplitude salinity oscillations in the Agulhas Leakage area during the penultimate climatic cycle.
• Carried out sea surface summer temperature reconstructions for Last Interglacial and the Holocene based on transfer functions of diatom records from marine sediment cores from the Atlantic Ocean and the Pacific Ocean.
• Water mass structures during the Last Interglacial revealed a strikingly different surface water circulation in the West Labrador Sea during MIS5e compared to the Holocene, with a more strongly developed or displaced gyre system close to the mid-Atlantic.
• A multi-proxy comparison of the Present Interglacial and Last Interglacial in a Nordic Seas core revealed a predominantly zonal surface circulation and an overall increased presence of Atlantic water masses in the Nordic Seas during the Last Interglacial compared to the Present Interglacial.
• Publication of papers that focused on climate variability in Holocene paleoceanography with data from Greenland, Newfoundland, Caribbean and W Africa.
• Published the analysis of a marine sediment core off East Africa for the influence on monsoonal shifts on paleoceanography for the last 25,000 years.
• Published the work on the impacts of Mayan land use on a lacustrine watershed in Yucatan Pen-insula, Mexico, as seen through clay and ostracode analyses.
• Completed the study of marine laminated records from the tropical southeast Pacific and recon-structed the history of humidity, ventilation and biological production over the last 10,000 years in relation to El Niño Southern Oscillation and the Intertropical Convergence Zone mean position.
• Finalised the study of changes in the East Asian monsoon and its impact on oceanic circulation in the South China Sea.
• Completed and published a comparison of Atlantic Meridional Overturning Circulation sensitivity to Greenland meltwater forcing in Last Interglacial and Present Interglacial simulations with that of future warming scenarios.
• Simulated the Allerød-Younger Dryas transition, using the LOVECLIM model.
• Evaluated several forcing scenarios, incl. the impact of meltwater, radiative forcing and shifts in atmospheric circulation.
• Applied data assimilation to constrain the LOVECLIM model using proxy-based temperature re-constructions.
• Published results on the impact of meltwater fluxes during the penultimate deglaciation, as mod-elled with iLOVECLIM and as reconstructed with δ13C records from marine sediment cores.
• Obtained initial climatic state and ice sheet topography at 21,000 and 140,000 years BP through simulation of the last glacial period and glacial-interglacial cycle.
• Perturbations of Fresh Water Forcing produced a strong decrease in the strength of the Atlantic Meridional Overturning Circulation.
• A 5 °C cooling over Greenland and a 1.5 °C cooling over the Northern Hemisphere followed after the Termination 1 decrease in the Atlantic Meridional Overturning Circulation.
• Determined timing and speed of the glacial ice retreat and the onset of the Atlantic sub-Polar Gyre off west Greenland.
• Characterised the variability of the Labrador Current off NE Newfoundland.
• Established the simulation ensemble needed in the particle filter approach to get a wider ensemble spread in the deep ocean.
• Completed and published simulations with assimilation of surface temperature data for selected Last Interglacial and Present Interglacial periods.
• Finalised the Holocene and Eemian CCSM4 simulation analyses.
• Publication of a paper on the relationship of Greenland snow accumulation and atmospheric cir-culation variability.
• Published the Eemian simulations for sensitivity of Greenland's surface climate to changes in the ice sheet topography.
• Quantified, based on Eemian simulations, the impact by a smaller Greenland ice sheet on the moisture transport to selected ice core locations.
• Published an investigation of the stability of the N Atlantic eddy-driven jet during Last Interglacial and Present Interglacial as well as past glacial winter climates.
• Publication of a paper on the comparison between data and multi‐model simulations of the tran-sient Present Interglacial and Last Interglacial climates, with a focus on surface temperatures.
• Completed and published the results of Last Interglacial simulations with NorESM.
• Effectuated Last Interglacial and Present Interglacial freshwater hosing experiments with FAMOUS and published an inter-model comparison of the basic diagnostic variables.
• Performed Last Interglacial and Present Interglacial simulations using the CLIMBER model to test the impact of freshwater forcing scenarios.
• Compared the baseline experiment results and analysed the impact of Fresh Water Forcing sce-narios on Atlantic Meridional Overturning Circulation strength, surface air temperature and annual precipitation.
• Finalised Present Interglacial and Last Interglacial freshwater hosing experiments using the LOVECLIM model.
• Extreme freshwater hosing experiments tested the sensitivity of Present Interglacial and Last In-terglacial climates to freshwater forcing.
• Applying the LOVECLIM EMIC model, the climate sensitivity to freshwater forcing was compared for Present Interglacial, Last Interglacial and future warming scenarios.
• Using the IPSL model, with and without interactive melting from Greenland, simulations were completed for 9500 years and 6000 years BP.
• Tested the sensitivity of simulated interglacial climates to solar forcing and added a constant solar irradiance reduction for a 200-year period based on available solar reconstructions.
• Performed a similar sensitivity experiment for the volcanic forcing, using the derived radiative forcing from the historical 1258 AD eruption as a perturbation for the two interglacial time slice simulations.
• An ensemble of simulations over the Holocene, driven by the new reconstruction of volcanic forc-ing, was accomplished and analysed.
• Completed volcanic-solar experiments for Present Interglacial and Last Interglacial, using the LOVECLIM model.
• Tested the sensitivity of Present Interglacial and Last Interglacial climates to radiative forcing through experiments with extreme forcing.
• Studied the impact of solar forcing on Greenland’s ice sheet during Holocene using iLOVECLIM model simulations.
• Performed experiments, using the IPSL model, to better understand the impact of volcanic erup-tions on the present-day conditions.
• Completed high-resolution reconstructions of Ice-Rafted Debris as well as sea surface salinity and sea surface temperature during the Last Interglacial in the South Atlantic Ocean.
• Characterised ice rafting, surface ocean hydrography, and deep-ocean flow during the Last In-terglacial.
• High-resolution reconstruction of surface ocean changes associated with the large transient re-ductions in North Atlantic Deep Water, defined for the Last Interglacial.
• Obtained evidence that reduced surface buoyancy was driving the deep circulation changes as-sociated with rapid ice sheet melt and freshwater fluxes.
• Completed reconstructions of changes in deep-water, climate, and surface ocean hydrography in the North Atlantic showed a coupled surface/deep-water variability at short timescales during the Last Interglacial.
• Established high-resolution reference alkenone records as a proxy for sea-surface temperature.
• Delineated past abrupt climate changes and their dynamics in the Mediterranean Sea and in the Atlantic Ocean.
• Improved the description of the climate over the last centuries as a basis for determining if palaeo-reconstructions were comparable with observational / instrumental data.
• Identified highly non-linear transitions in the Present Interglacial and the Last Interglacial intervals and deglaciations, using high-resolution archives representing diverse aspects of the Earth’s sys-tem.
• The Holocene (i.e. Present Interglacial) and the previous interglacial period (i.e. Last Interglacial) share three similar abrupt structures: (i) deglaciation warming interrupted by rapid cold reversals, (ii) temperature maxima, followed by (iii) progressively cooler climate conditions punctuated by warm events.
• The Little Ice Age is the most recent and significant expression of the fine-scaled oscillations im-posed on the robust global cooling trend observed during the pre-industrial era.
• Rapid climate changes seem to be largely unpredictable in rate of change and intensity, and this could pose a significant challenge to quantifying their impact.
• The cooling trend during the Last Interglacial was persistent in the North Atlantic whereas a Last Interglacial warming progression was evident at tropical locations.
• The comparison of Present Interglacial and Last Interglacial temperature dynamics resulted in the PIG2LIG4FUTURE database.
• The Last Interglacial-relative-to-Present Interglacial anomalies at mid-latitudes were up to 6 °C and those in the tropics were less than 2 °C. The amplitude of variation during the Present Interglacial was no more than 2 °C.
• The difference in magnitude of the simulated changes, larger in the Last Interglacial than in the Present Interglacial, was the most significant feature in the comparison of simulated temperature.
• The main Present Interglacial temperature trends were the warmest-month-cooling-trend over the Northern Hemisphere continents and the coldest-month-warming-trend over North Africa and South Asia.
• During the Present Interglacial, nearly all trends in annual temperature proxies were significantly similar to the model results.
• Holocene deep-water proxy-data revealed a transition from haline to thermal sensitivity of over-turning during the Holocene.
• Created a reliable CO2 dataset from the Greenland ice sheet and published the results.
• Synthesis of the vegetational development in central and northern Europe during the Last Inter-glacial.
• Completed high-resolution CO2 and δ13CO2 records for the entire last glacial cycle and published the results.
• Developed a new ice core weathering proxy that showed a clear increase in weathering rates at the MBE, about 430,000 years ago.
• Collected, measured and analysed ice core samples for 42 chemical elements, using the ICP-SFMS analytical technique.
• Developed, applied and published a method to include shifting cultivation and wood harvest in static land-use reconstructions.
• Simulated carbon emissions from gross land-use transitions in the nitrogen-enabled LPX-Bern 1.0 Dynamic Global Vegetation Model.
• Analysed the contribution of land turnover and wood harvest to emissions from land use change and addressed these effects in all four greenhouse gas concentration trajectories adopted by IPCC for the 5th Assessment Report.
• Determined that the shifting cultivation and wood harvest within the remaining forests now con-tribute 19% of the mean annual land-use emissions of Carbon.
• Identified and analysed two distinct modes of solar variability based radiocarbon simulation results of the Present Interglacial, providing important constraints for both dynamo models of sun-like stars and investigations of possible solar influence on Earth’s climate.
• Completed transient simulations for the Holocene with cGENIE and transient Eemian simulations with CLIMBER-JSBACH.
• Integrated a new permafrost module in the CLIMBER-2 EMIC model and conducted simulations for the Terminations and the glacial-interglacial cycles.
• Determined that no upward revision of conventional land-use emission estimates is needed to reconcile the simulated terrestrial carbon balance versus the balance diagnosed from the ice core records.
• Comparing charcoal reconstruction results for the Holocene elucidated the role of fire as an im-portant component of the Earth System.
• Published a paper on modelling fire dynamics in the Holocene.
• Obtained high-resolution records of iron and other bioactive trace elements from ice cores in the Northern Hemisphere during the Last Interglacial and the Present Interglacial.
• An innovative method, based on a flow-injection-analysis technique, was optimised for simulta-neous determination of soluble Fe and Al in Polar ice cores.
• Examined the climatic conditions during MIS19 using high-resolution stable-isotope records of foraminifera from North Atlantic sediment samples, in order to assess the stability and duration of the Last Interglacial and evaluate the climate system's response to known, orbitally-induced, in-solation changes.
• Analysed CLIMBER-LPJ simulation results on peat accumulation through the last 21,000 years.
• Published the model description and first results of dynamically simulating the evolution of peat-land area and wetland areas worldwide.
• Simulated the evolution of N2O emissions from the terrestrial biosphere using the LPX model.
• Tested the sensitivity to a large-scale organisation of ocean circulation and climate by completing the first simulations of atmospheric N2O with a coupled ocean-atmosphere-land model.
• Compared LPX transient simulations to ice core results for N2O, CH4 and N-isotopes.
• Identified a CH4 emission peak at the onset of Present Interglacial, a decline in emissions until 5000 years ago and then a rise until the last millennium.
• Proved that the decline in total N2O emissions during the early Present Interglacial was predomi-nantly of oceanic origin and that land emissions of N2O remained rather constant in the Present Interglacial.
• Revealed the important role of temperature and precipitation changes in forcing N2O emission changes.
• Completed simulations of CH4 emissions from boreal wetlands during the Present Interglacial and the Last Interglacial as well as equilibrium runs of CH4 hydrates.
• Procured a high-resolution reference record of biomass burning during the last 2000 years, based on carbon monoxide changes in Antarctic ice cores.
• Secured bipolar high-precision, high-resolution CH4, δ13CH4 and δD(CH4) records from Arctic and Antarctic ice cores during the Last Interglacial and the Present Interglacial.
• Established an unprecedented data basis for a source de-convolution of Holocene CH4 cycle changes, essential for assessing the influence of early human land-use changes on CH4 emissions during the last 4000 years.
• Extended the records of δ15N2O and δ18O(N2O) over the Holocene.
• Identified an increase in N2O emissions from land and ocean over the glacial termination and a roughly constant emission from land over the Holocene.
• Demonstrated that sea level rise during the Last Interglacial was substantially greater than could be accounted for by a collapse of the Greenland ice sheet.
• Determined that the low post-glacial rebound rates in the Weddell Sea during late Present Inter-glacial were due to ice sheet re-advance.
• Modified the existing Holocene ice load history to reflect evidence that the Weddell Sea grounding line, 4000 years ago, retreated to behind the present limit before it re-advanced.
• A suite of modified loading histories with a glacial isostatic adjustment model provided almost uniform improvements to predictions of present-day bedrock uplift rates, thereby reducing the data-model mismatch compared with the unmodified retreat model.
• GPS uplift rates in the Weddell Sea region were similar to those from the model variants and re-vealed an improved fit in models characterised by early retreat behind the present-day grounding line, a relatively long stillstand and a short re-advance that continued to present-day.
• Applied the results of the Greenland ice sheet modelling and the Last Interglacial sea level data to estimate the upper bounds to possible contributions to sea level from the Antarctic ice sheet in the Last Interglacial.
• Refined the use of a perturbed-physics ensemble of ice sheet models to produce a range of Last Interglacial sea level predictions from Greenland.
• Completed and published the work considering implications of glacial-isostatic adjustment for ice sheet elevation during the Eemian.
• Determined the impact of positive degree-days on the surface mass balance of the ice sheet and quantified the importance of ablation-related processes with respect to ice sheet feedbacks in the evolution of Northern Hemisphere ice sheets throughout the last glacial-interglacial cycle.
• Established the northern limit of Antarctic sea ice during the Holocene and published the sea ice and climate conditions during Holocene in the Antarctic Peninsula and, for the last 2000 years, off Adélie Land.
• Compiled sea ice reconstructions for the Present Interglacial and the Last Interglacial.
• Obtained sea ice records for the last deglaciation and middle-to-late Holocene off Newfoundland, based on the IP25 proxy.
• Reconstructed Pleistocene Antarctic sea ice extent and Southern Ocean winter sea ice for the Last Interglacial and the Present Interglacial, based on diatom transfer functions.
• Mapped the distribution of sea ice biomarkers in the central Arctic Ocean surface sediments and established the first sea ice biomarker records from MIS6 / MIS5.
• Reconstructed the late-winter sea ice concentration of the past 7000 years, using a diatom-based transfer function.
• Compiled and published the Holocene dinoflagellate cyst records from the Nordic Seas.
• Achieved a comprehensive overview of Holocene fluctuations in sea surface temperature, salinity and sea ice cover in the Nordic seas as well as a first estimate of a calibration curve for sea salt / sea ice in Antarctica.
• Synthesised sea ice proxies and analysed simulations driven by sea ice reconstructions, based on dinoflagellate cyst records.
• Established a database for sea ice reconstructions in the Southern Ocean during the Last Inter-glacial.
• Substantiated that a long-lasting perennial sea ice coverage in the Fram Strait did persist only at the very end of the Last Glacial Maximum.
• Demonstrated that perennial sea ice coverage in the Fram Strait was abruptly reduced at the onset of Heinrich Event 1 and that maximum sea ice conditions in the strait prevailed during the Younger Dryas cooling event.
• Completed and published the Mg/Ca Sea Surface Temperature reconstructions the Last Intergla-cial results from the North Atlantic Eirik and Gardar sediment drifts.
• Compared Last Interglacial geochemical precipitation proxies, in sediment cores at W African margin and South American margin, to benthic carbon isotopes as a Thermo-Haline Circulation proxy in the Atlantic.
• Reconstructed Pleistocene Antarctic sea surface summer temperatures and compiled Southern Ocean reconstructions of sea surface summer temperatures for the Last Interglacial and the Pre-sent Interglacial, based on diatom transfer functions.
• Established a Northern Hemisphere database on diatom distribution as reference data for sea surface summer temperatures transfer functions.
• Published results comparing reconstructed proxy data from the Atlantic Multidecadal Oscillation inflow region to instrumental time series and Atlantic Multidecadal Oscillation model results com-pared to proxy reconstructions covering the last millennium.
• Tested and published the possible link between Atlantic Multidecadal Oscillation and external (i.e. solar and volcanic) forcing over the last 500 years.
• Quantified the effects of ocean circulation and orbital insolation on tropical precipitation, based on a 130-115 ka transient simulation using an ocean-atmosphere general circulation model.
• Conducted final sortable silt analyses and stable isotope measurements, spanning MIS5e at the Gardar drift.
• Created an extension of the database for temperature field reconstructions of the Southern Ocean during the Last Interglacial
• Continued the archiving of Past4Future data in the PANGAEA database, an Open Access library aimed at archiving, publishing and distributing geo-referenced data from Earth system re-search, while guaranteeing long-term availability of its contents through a commitment of the operating institutions; the database now holds 458 Past4Future datasets.
• Submitted the synthesising white paper “Sensitivity of ice sheets" to the Geological Society in London.
• Submitted the synthesis paper “Comparison of carbon cycle dynamics during past and present interglacials" to Quaternary Science Reviews.
• In the context of EGU Annual Assemblies in 2010-2014, 172 presentations were authored and given by Past4Future scientists at Past4Future-dedicated sessions.
• During the entire project period, 238 peer-reviewed Past4Future publications have been published; all include a specific acknowledgement of Past4Future and its EU FP7 grant.
• In the Past4Future period, January 2010 – December 2014, project foreground has been disse-minated in 616 outreach products and of these 26% targetted a non-scientific, broader audience.
• At least 106,000 persons all over Europe have been reached through the disseminating activities by Past4Future making wider parts of the society aware of the present climate context in relation to aspects of the past climate, and the pertinent projections for our future climate.

Potential Impact:
Past4Future has delivered essential foreground on the sensitivity and dynamics of the climate system under conditions very different from the most recent period of the present interglacial. These results have led to a better understanding of natural variability and its relationship to climate forcing. In particular, the final results of Past4Future’s research have impacted these areas:
• Increased the capability of climate models to produce, under natural conditions, the range and variability of climates observed during warm millennia.
• Improved our understanding of the operation and stability under different boundary conditions within warm periods, incl. those warmer than today.
• Resolved how feedbacks, especially CO2 sinks and permafrozen sources of greenhouse-gases, have varied under warmer conditions in different parts of the globe, and used this to improve pa-rameters for biogeochemical feedbacks in Earth system models.
• Ascertained whether low-probability events, such as large-scale changes in ocean circulation, ac-tually did occur during the last two interglacials.
• Determined the fate of the Antarctic and Greenland ice sheets and the associated global sea level, particularly during the Last Interglacial, when polar temperatures were comparable to those expected in year 2100
• Applied the new knowledge in ice-model physics as a constraint on the wide range of estimates for global sea level in the future.

Furthermore, the work and foreground of Past4Future have influenced these aspects:
• Knowledge gained from detailed studies of the Last Interglacial and the Present Interglacial has significantly increased the scientific understanding of the dynamics of the Earth system, the op-eration of feedbacks, and the occurrence of abrupt changes under conditions warmer than today.
• The strong integration of European researchers in palaeo-climate reconstruction, incl. a platform for more robust synergies between past-climate and future-climate modelling. This will have a lasting impact by strengthening the European climate research.
• The role of Europe as a participant and a stakeholder in palaeo-climate data synthesis and the modelling work, implemented in assessment reports, notably by the IPCC.
• Information required by policy-makers to assess and select the measures necessary to avoid hazardous climate change, in particular by providing an evidence base for the likely operation of the Earth system under the warmer climate expected in the coming century.

The scientific impact of Past4Future has been achieved through two levels of operation: 1) It has provided a stepwise change in our knowledge of climate dynamics and feedbacks that occurred during the present and the last interglacial periods, thereby substantially advancing our understanding of these important periods. 2) The new insight has been used in a number of ways to inform the scientific communities and the general public about the future.

Past4Future has produced an unprecedented synthesis of 450+ datasets from various archives and different geographical regions; many of the datasets are of an unmatched high resolution (e.g. the IPY international deep ice core drilling project NEEM on the Greenland Ice Sheet). The geographical distribution of the datasets and the excellent time resolution rendered it feasible to use the datasets and the models over a longer time period than ever before, encompassing a much wider range of conditions.

The results of Past4Future have made it possible to find consistent patterns in the slow variations and the rapid changes during the present interglacial period. By implementing carefully synchronised high-resolution proxy-data in sophisticated data assimilation techniques and advanced modelling, Past4Future’s scientists have been able to characterise, much better, the responses of climate to external as well as internal processes. Similarly, the project has identified the full power spectrum of climate variability and the occurrence of abrupt changes associated with interglacial periods.

Past4Future had enough critical mass of data, models and experts to perform and complete the demanding analyses of non-linear responses in the atmosphere, ocean, cryosphere and global bio-geochemical cycles. An obvious impact of this research is a significant strengthening of the under-standing and quantification of climate dynamics and feedback processes occurring in warm periods, and this knowledge can then be applied to improve climate predictions for the coming centuries.

Past4Future has delivered essential foreground on the sensitivity and dynamics of the climate system under conditions very different from the most recent period of the present interglacial. These results have led to a better understanding of natural variability and its relationship to climate forcing. In particular, the final results of Past4Future’s research include:
• Increasing the capability of climate models to produce, under natural conditions, the range and variability of climates observed during warm millennia.
• Improving our understanding of the operation and stability under different boundary conditions within warm periods, incl. those warmer than today.
• Determining how feedbacks, especially CO2 sinks and permafrozen sources of greenhouse-gases, have varied under warmer conditions in different parts of the globe, and using this to improve parameters for biogeochemical feedbacks in Earth system models.
• Ascertaining whether low-probability events, such as large-scale changes in ocean circulation, actually did occur during the last two interglacials.
• Determining the fate of the Antarctic and Greenland ice sheets and the associated global sea level, particularly during the last interglacial (Last Interglacial), when, for millennia, polar temperatures were comparable to those expected in year 2100; and using this new knowledge in ice-model physics as a constraint on the wide range of estimates for global sea level in the future.

Past4Future has achieved maximum impact for the project foreground by adhering to the following principles:
• Strict monitoring and close adherence to the schedule for milestones and deliverables (especially with respect to IPCC AR5), ensuring a close collaboration with the AR5 authors in order to secure the inclusion of Past4Future results.
• Making certain that Past4Future scientists are challenged to synthesise their findings to the highest level, and interacting with scientists, involved in climate predictions, to apply project foreground in such studies.
• Identifying stakeholder needs, and the optimal mode, language and form of foreground dissemination.

List of Websites:

The project website: www.past4future.eu

Beneficiaries

Principal investigators and their coordinates

Beneficiary no. 1 and Project Coordinator
Dorthe Dahl-Jensen, Centre for Ice and Climate, Niels Bohr Institute, University of Copenhagen, Denmark.
ddj@nbi.ku.dk

Beneficiary no. 2
Eystein Jansen, Bjerknes Centre for Climate Research, Unifob A/S, Bergen, Norway.
eystein.jansen@uni.no

Beneficiary no. 3
Jérôme Chappellaz, Centre National de la Recherche Scientifique, Grenoble, France.
jerome@lgge.obs.ujf-grenoble.fr

Beneficiary no. 4
Marit-Solveig Seidenkrantz, Department of Earth Sciences, Aarhus University, Denmark.
mss@geo.au.dk

Beneficiary no. 5
Hubertus Fischer, Oeschger Centre for Climate Change Research, Division of Climate and Envi-ronmental Physics, University of Bern, Switzerland.
hfischer@climate.unibe.ch

Beneficiary no. 6
Joan Grimalt, Department of Environmental Chemistry, Institute of Environmental Assessment and Water Research, Spanish Council for Scientific Research, Barcelona, Spain.
joan.grimalt@idaea.csic.es

Beneficiary no. 7
Rainer Zahn, Institute of Environmental Science and Technology, Universitat Autònoma de Barcelona, Spain.
rainer.zahn@uab.es

Beneficiary no. 8
Eric W. Wolff, British Antarctic Survey, Natural Environment Research Council, United Kingdom.
ew428@cam.ac.uk

Beneficiary no. 9
Dan Lunt, School of Geographical Sciences, University of Bristol, United Kingdom.
d.j.lunt@bristol.ac.uk

Beneficiary no. 10
Hugues Goosse, Institut d’Astronomie et de Géophysique Georges Lemaître, Université Catholique de Louvain, Belgium.
hugues.goosse@uclouvain.be

Beneficiary no. 11
Michael Schulz, Center for Marine Environmental Sciences, Faculty of Geosciences, University of Bremen, Germany.
mschulz@marum.de


Beneficiary no. 12
Victor Brovkin, Max Planck Institute for Meteorology, Hamburg, Germany.
victor.brovkin@mpimet.mpg.de

Beneficiary no. 13
Hans Renssen, Stichting VU-VUmc, Institute for Environmental Studies, VU University Amsterdam, The Netherlands.
hans.renssen@falw.vu.nl

Beneficiary no. 14
Valérie Masson-Delmotte, Laboratoire des Sciences du Climat et de l’Environnement, Commissariat à l’Energie Atomique, Gif-sur-Yvette, France.
valerie.masson@cea.fr

Beneficiary no. 15
Chronis Tzedakis, Department of Geography, University College London, United Kingdom.
p.c.tzedakis@ucl.ac.uk

Beneficiary no. 16
Carlo Barbante, Institute for the Dynamics of Environmental Processes, University of Venice, Italy.
barbante@unive.it

Beneficiary no. 17
Rainer Gersonde, Alfred Wegener Institute for Polar and Marine Research, Bremerhaven, Germany.
rainer.gersonde@awi.de

Beneficiary no. 18
Luke C. Skinner, Department of Earth Sciences, University of Cambridge, United Kingdom.
luke00@esc.cam.ac.uk

Beneficiary no. 19
Thorsten Kiefer, Past Global Changes, PAGES International Project Office, Bern, Switzerland.
kiefer@pages.unibe.ch

Beneficiary no. 20 never acceded to the contract.

Beneficiary no. 21
Hui Jiang, School of Resources & Environmental Sciences, Institute of Estuarine and Coastal Re-search, East China Normal University, China.
hjiang@geo.ecnu.edu.cn

Beneficiary no. 22
Glenn A. Milne, Department of Earth Sciences, University of Ottawa, Canada.
gamilne@uottawa.ca

Beneficiary no. 23
Anne de Vernal, Geochemistry and Geodynamics Research Center, Université du Québec à Montréal, Canada.
devernal.anne@uqam.ca