Spatial pattern and temporal evolution of glacial terminations of the last 800 ka

The second QUIGS workshop brought together 28 delegates to assess current knowledge and research needs on the spatio-temporal patterns of climate forcing, responses and feedbacks that characterize glacial terminations, i.e. transitions between glacial and interglacial periods

Evaluation of biospheric components in earth system models using modern and palaeo-observations: The state-of-the-art

PublishedJournal ArticleEarth system models (ESMs) are increasing in complexity by incorporating more processes than their predecessors, making them potentially important tools for studying the evolution of climate and associated biogeochemical cycles. However, their coupled behaviour has only recently been examined in any detail, and has yielded a very wide range of outcomes. For example, coupled climate-carbon cycle models that represent land-use change simulate total land carbon stores at 2100 that vary by as much as 600 Pg C, given the same emissions scenario. This large uncertainty is associated with differences in how key processes are simulated in different models, and illustrates the necessity of determining which models are most realistic using rigorous methods of model evaluation. Here we assess the state-of-the-art in evaluation of ESMs, with a particular emphasis on the simulation of the carbon cycle and associated biospheric processes. We examine some of the new advances and remaining uncertainties relating to (i) modern and palaeodata and (ii) metrics for evaluation. We note that the practice of averaging results from many models is unreliable and no substitute for proper evaluation of individual models. We discuss a range of strategies, such as the inclusion of pre-calibration, combined process-and system-level evaluation, and the use of emergent constraints, that can contribute to the development of more robust evaluation schemes. An increasingly data-rich environment offers more opportunities for model evaluation, but also presents a challenge. Improved knowledge of data uncertainties is still necessary to move the field of ESM evaluation away from a "beauty contest" towards the development of useful constraints on model outcomes. © 2013 Author(s).This paper emerged from the GREENCYCLESII mini-conference “Evaluation of Earth system models using modern and palaeo-observations” held at Clare College, Cambridge, UK, in September 2012. We would like to thank the Marie Curie FP7 Research and Training Network GREENCYCLESII for providing funding which made this meeting possible. Research leading to these results has received funding from the European Community’s Seventh Framework Programme (FP7 2007–2013) under grant agreement no. 238366. The work of C. D. Jones was supported by the Joint DECC/Defra Met Office Hadley Centre Climate Programme (GA01101). N. R. Edwards acknowledges support from FP7 grant no. 265170 (ERMITAGE). N. Vázquez Riveiros acknowledges support from the AXA Research Fund and the Newton Trust

Constraints on the evolution of climate during marine isotope stage 11

International audienceMarine Isotope Stage 11 (MIS11) is the interglacial period dated around 400 kyr ago. It has been the subject of great attention as a possible "analogue" to the Holocene due to its orbital configuration, close to that of the present period. In this study, we will present data on MIS11 and the last 30 kyr from marine sediment cores from different basins, in order to be able to have a global view of these periods and to compare timing of different climatic records in different hemispheres. The work presented here is based on new data from core MD07-3077 and MD07-3076 that were collected in the Atlantic sector of the Southern Ocean (44°09'S, 14°13'W, 3770 m water depth), and its comparison with cores ODP 980 (55°29'N, 14°42'W, 2179 m water depth) and NA87-22 (55°30'N, 14°42'W, 2161 m water depth) from the North Atlantic (Oppo et al., 1998; Waelbroeck et al., 2001). A new chronology for MIS11 will be presented, based on correlation with the age scale of EPICA Dome C ice core age scale (EDC3). This chronology is common for all cores, which allows the comparison of the phasing of events between the two hemispheres. The benthic isotopic records from these cores reveal a different timing of circulation changes in the North Atlantic than in the South Atlantic site, as well as a general increase in the benthic carbon isotopic ratio during MIS11 with respect to the Holocene. Periods of increased ventilation of deep waters in the South Atlantic are interpreted as augmentations in the strength of North Atlantic Deep Water (NADW) production. The sequence of events during Termination V shows a lead of the changes in water mass properties at the North Atlantic site with respect to the South Atlantic site. We interpret this lead as reflecting an inflow of brine-generated waters from the Nordic Seas, similarly to what is observed over the last deglaciation. Conversely, circulation changes during the glacial inception towards MIS10 first occur in the Southern Ocean, as previously observed during MIS5-4 transition (Govin et al., 2008) and could likewise be explained by progressive cooling and expansion of sea ice around Antarctica

Unprecedented coring performance with the upgraded Research Vessel Marion Dufresne

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Evaluation of biospheric components in Earth system models using modern and palaeo-observations: the state-of-the-art

International audienceEarth system models (ESMs) are increasing in complexity by incorporating more processes than their predecessors, making them potentially important tools for studying the evolution of climate and associated biogeochemical cycles. However, their coupled behaviour has only recently been examined in any detail, and has yielded a very wide range of outcomes. For example, coupled climate–carbon cycle models that represent land-use change simulate total land carbon stores at 2100 that vary by as much as 600 Pg C, given the same emissions scenario. This large uncertainty is associated with differences in how key processes are simulated in different models, and illustrates the necessity of determining which models are most realistic using rigorous methods of model evaluation. Here we assess the state-of-the-art in evaluation of ESMs, with a particular emphasis on the simulation of the carbon cycle and associated biospheric processes. We examine some of the new advances and remaining uncertainties relating to (i) modern and palaeodata and (ii) metrics for evaluation. We note that the practice of averaging results from many models is unreliable and no substitute for proper evaluation of individual models. We discuss a range of strategies, such as the inclusion of pre-calibration, combined process- and system-level evaluation, and the use of emergent constraints, that can contribute to the development of more robust evaluation schemes. An increasingly data-rich environment offers more opportunities for model evaluation, but also presents a challenge. Improved knowledge of data uncertainties is still necessary to move the field of ESM evaluation away from a "beauty contest" towards the development of useful constraints on model outcomes

Evaluation of biospheric components in earth system models using modern and palaeo-observations: The state-of-the-art

Earth system models (ESMs) are increasing in complexity by incorporating more processes than their predecessors, making them potentially important tools for studying the evolution of climate and associated biogeochemical cycles. However, their coupled behaviour has only recently been examined in any detail, and has yielded a very wide range of outcomes. For example, coupled climate–carbon cycle models that represent land-use change simulate total land carbon stores at 2100 that vary by as much as 600 Pg C, given the same emissions scenario. This large uncertainty is associated with differences in how key processes are simulated in different models, and illustrates the necessity of determining which models are most realistic using rigorous methods of model evaluation. Here we assess the state-of-the-art in evaluation of ESMs, with a particular emphasis on the simulation of the carbon cycle and associated biospheric processes. We examine some of the new advances and remaining uncertainties relating to (i) modern and palaeodata and (ii) metrics for evaluation. We note that the practice of averaging results from many models is unreliable and no substitute for proper evaluation of individual models. We discuss a range of strategies, such as the inclusion of pre-calibration, combined process- and system-level evaluation, and the use of emergent constraints, that can contribute to the development of more robust evaluation schemes. An increasingly data-rich environment offers more opportunities for model evaluation, but also presents a challenge. Improved knowledge of data uncertainties is still necessary to move the field of ESM evaluation away from a "beauty contest" towards the development of useful constraints on model outcomes

Climate and the Evolution of the Ocean: The Paleoceanographic Data

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