scholarly journals Shortwave forcing and feedbacks in Last Glacial Maximum and Mid-Holocene PMIP3 simulations

2015 ◽  
Vol 373 (2054) ◽  
pp. 20140424 ◽  
Author(s):  
Pascale Braconnot ◽  
Masa Kageyama
Keyword(s):  
Last Glacial Maximum ◽  
Land Surface ◽  
Relative Strength ◽  
Glacial Maximum ◽  
Climate Feedbacks ◽  
Vegetation Feedback ◽  
Last Glacial ◽  
Model Biases ◽  
Simulated Climate

Simulations of the climates of the Last Glacial Maximum (LGM), 21 000 years ago, and of the Mid-Holocene (MH), 6000 years ago, allow an analysis of climate feedbacks in climate states that are radically different from today. The analyses of cloud and surface albedo feedbacks show that the shortwave cloud feedback is a major driver of differences between model results. Similar behaviours appear when comparing the LGM and MH simulated changes, highlighting the fingerprint of model physics. Even though the different feedbacks show similarities between the different climate periods, the fact that their relative strength differs from one climate to the other prevents a direct comparison of past and future climate sensitivity. The land-surface feedback also shows large disparities among models even though they all produce positive sea-ice and snow feedbacks. Models have very different sensitivities when considering the vegetation feedback. This feedback has a regional pattern that differs significantly between models and depends on their level of complexity and model biases. Analyses of the MH climate in two versions of the IPSL model provide further indication on the possibilities to assess the role of model biases and model physics on simulated climate changes using past climates for which observations can be used to assess the model results.

scholarly journals Impacts of land surface properties and atmospheric CO<sub>2</sub> on the Last Glacial Maximum climate: a factor separation analysis

2009 ◽  
Vol 5 (1) ◽  
pp. 29-71
Author(s):  
A.-J. Henrot ◽  
L. François ◽  
S. Brewer ◽  
G. Munhoven
Keyword(s):  
Last Glacial Maximum ◽  
Northern Hemisphere ◽  
Land Surface ◽  
Glacial Maximum ◽  
Last Glacial ◽  
Tropical Precipitation ◽  
North East ◽  
Sensitivity Studies ◽  
Simulated Climate ◽  
Orographic Forcing

Abstract. Many sensitivity studies have been carried out, using simplified GCMs to test the climate response to Last Glacial Maximum boundary conditions. Here, instead of adding the forcings successively as in previous studies, we applied the separation method of Stein and Alpert (1993), in order to determine rigourously the different contributions of the boundary condition modifications, and isolate the pure contributions from the interactions among the forcings. We carried out a series of sensitivity experiments with the model of intermediate complexity Planet Simulator, investigating the contributions of the ice sheet expansion and elevation, the lowering of the atmospheric CO2 and of the vegetation cover change on the LGM climate. The results clearly identify the ice cover forcing as the main contributor to the cooling of the Northern Hemisphere, and also to the tropical precipitation disruption, leading to the shouthward shift of the ITCZ, while the orographic forcing mainly contributes to the disruption of the atmospheric circulation in the Northern Hemisphere. The isolated vegetation contribution also induces strong cooling over the continents of the Northern Hemisphere, that is further sufficient to affect the tropical precipitation and reinforce the southwards shift of the ITCZ, when combined with the ice forcing. The combinations of the forcings generate many non linear interactions, that reinforce or weaken the pure contributions, depending on the climatic mechanism involved, but they are generally weaker than the pure contributions. Finally, the comparison between the LGM simulated climate and climatic reconstructions over Eurasia suggests that our results reproduce well the south-west to north-east temperature gradients over Eurasia.

The PMIP3 Simulated Climate Changes over Arid Central Asia during the Mid‐Holocene and Last Glacial Maximum

2020 ◽  
Vol 94 (3) ◽  
pp. 725-742
Author(s):  
Hongna XU ◽  
Tao WANG ◽  
Huijun WANG ◽  
Jiapeng MIAO ◽  
Jianhui CHEN ◽  
...  
Keyword(s):  
Central Asia ◽  
Last Glacial Maximum ◽  
Climate Changes ◽  
Glacial Maximum ◽  
Arid Central Asia ◽  
Last Glacial ◽  
Simulated Climate

scholarly journals Influence of dynamic vegetation on climate change and terrestrial carbon storage in the Last Glacial Maximum

2013 ◽  
Vol 9 (4) ◽  
pp. 1571-1587 ◽  
Author(s):  
R. O'ishi ◽  
A. Abe-Ouchi
Keyword(s):  
Carbon Storage ◽  
Last Glacial Maximum ◽  
Glacial Maximum ◽  
Atmospheric Co2 ◽  
Terrestrial Carbon ◽  
Dynamic Global Vegetation Model ◽  
Vegetation Feedback ◽  
Last Glacial ◽  
The Last Glacial Maximum ◽  
The Last Glacial

Abstract. When the climate is reconstructed from paleoevidence, it shows that the Last Glacial Maximum (LGM, ca. 21 000 yr ago) is cold and dry compared to the present-day. Reconstruction also shows that compared to today, the vegetation of the LGM is less active and the distribution of vegetation was drastically different, due to cold temperature, dryness, and a lower level of atmospheric CO2 concentration (185 ppm compared to a preindustrial level of 285 ppm). In the present paper, we investigate the influence of vegetation change on the climate of the LGM by using a coupled atmosphere-ocean-vegetation general circulation model (AOVGCM, the MIROC-LPJ). The MIROC-LPJ is different from earlier studies in the introduction of a bias correction method in individual running GCM experiments. We examined four GCM experiments (LGM and preindustrial, with and without vegetation feedback) and quantified the strength of the vegetation feedback during the LGM. The result shows that global-averaged cooling during the LGM is amplified by +13.5 % due to the introduction of vegetation feedback. This is mainly caused by the increase of land surface albedo due to the expansion of tundra in northern high latitudes and the desertification in northern middle latitudes around 30° N to 60° N. We also investigated how this change in climate affected the total terrestrial carbon storage by using offline Lund-Potsdam-Jena dynamic global vegetation model (LPJ-DGVM). Our result shows that the total terrestrial carbon storage was reduced by 597 PgC during the LGM, which corresponds to the emission of 282 ppm atmospheric CO2. In the LGM experiments, the global carbon distribution is generally the same whether the vegetation feedback to the atmosphere is included or not. However, the inclusion of vegetation feedback causes substantial terrestrial carbon storage change, especially in explaining the lowering of atmospheric CO2 during the LGM.

Carbon storage and continental land surface change since the last glacial maximum

1996 ◽  
Vol 15 (8-9) ◽  
pp. 843-849 ◽  
Author(s):  
H. Faure ◽  
J.M. Adams ◽  
J.P. Debenay ◽  
L. Faure-Denard ◽  
D.R. Grants ◽  
...  
Keyword(s):  
Carbon Storage ◽  
Last Glacial Maximum ◽  
Land Surface ◽  
Glacial Maximum ◽  
Surface Change ◽  
Last Glacial ◽  
The Last Glacial Maximum ◽  
The Last Glacial

Seasonal variation of westerly jet over Asia in Last Glacial Maximum: Role of the Tibetan Plateau heating

2021 ◽  
pp. 1
Author(s):  
Jing Lei ◽  
Zhengguo Shi ◽  
Xiaoning Xie ◽  
Yingying Sha ◽  
Xinzhou Li ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Central Asia ◽  
Last Glacial Maximum ◽  
General Circulation ◽  
Heat Budget ◽  
Glacial Maximum ◽  
The Tibetan Plateau ◽  
Last Glacial ◽  
Westerly Jet

AbstractThe westerly jet (WJ) is an important component of atmospheric circulation, which is characterized by prominent seasonal variations in intensity and position. However, the response of WJ over Asia during the Last Glacial Maximum (LGM) is still not clear. Using general circulation model experiments, the seasonal behaviors of WJ over Central Asia and Japan are analyzed in this paper. The results show that, compared to present day (PD), the WJ presents a complicated response during the LGM, both in intensity and position. Over Central Asia, it becomes weaker in both summer and winter. But over Japan, it is enhanced in summer but becomes diminished in winter. In terms of position, the WJ over Central Asia shifts southwards in both summer and winter, while the WJ over Japan moves southwards in summer but does not change obviously relative to PD in winter. Such WJ changes are well explained by meridional temperature gradients in high troposphere, which is closely linked to seasonal thermal anomalies over the Tibetan Plateau (TP). Despite of cooler LGM condition, the anomalous warming center over TP becomes stronger in summer. Derived from the heat budget equation, the stronger heating center is mainly caused by the weaker adiabatic cooling generated from ascending motion over south of TP. In winter, the cooling over TP is also strengthened and mostly owes to the subsidence-induced weaker adiabatic heating. Due to the importance of WJ, the potential role of TP thermal effect should be focused when explaining the East Asian climate change during the LGM.

scholarly journals The PMIP4 contribution to CMIP6 – Part 4: Scientific objectives and experimental design of the PMIP4-CMIP6 Last Glacial Maximum experiments and PMIP4 sensitivity experiments

2017 ◽  
Author(s):  
Masa Kageyama ◽  
Samuel Albani ◽  
Pascale Braconnot ◽  
Sandy P. Harrison ◽  
Peter O. Hopcroft ◽  
...  
Keyword(s):  
Last Glacial Maximum ◽  
Land Surface ◽  
Climate Model ◽  
Model Performance ◽  
Coupled Model ◽  
Glacial Maximum ◽  
Current Phase ◽  
Last Glacial ◽  
Sensitivity Experiments ◽  
Intercomparison Project

Abstract. The Last Glacial Maximum (LGM, 21,000 years ago) is one of the suite of paleoclimate simulations included in the current phase of the Coupled Model Intercomparison Project (CMIP6). It is an interval when insolation was similar to present, but global ice volume was at a maximum, eustatic sea level was at or close to a minimum, greenhouse gas concentrations were lower, atmospheric aerosol loadings were higher than today, and vegetation and land-surface characteristics were different from today. The LGM has been a focus for the Paleoclimate Modelling Intercomparison Project (PMIP) since its inception, and thus many of the problems that might be associated with simulating such a radically different climate are well documented. The LGM state provides an ideal case study for evaluating climate model performance because the changes in forcing and temperature between the LGM and pre-industrial are of the same order of magnitude as those projected for the end of the 21st century. Thus, the CMIP6 LGM experiment could provide additional information that can be used to constrain estimates of climate sensitivity. The design of the Tier 1 LGM experiment (lgm) includes an assessment of uncertainties in boundary conditions, in particular through the use of different reconstructions of the ice sheets and of the change in dust forcing. Additional sensitivity experiments have been designed to quantify feedbacks associated with land-surface changes and aerosol loadings, and to isolate the role of individual forcings. Model analysis and evaluation will capitalise on the relative abundance of palaeoenvironmental observations and quantitative climate reconstructions already available for the LGM.

The role of dust in climate changes today, at the last glacial maximum and in the future

2001 ◽  
Vol 54 (1-3) ◽  
pp. 43-80 ◽  
Author(s):  
Sandy P. Harrison ◽  
Karen E. Kohfeld ◽  
Caroline Roelandt ◽  
Tanguy Claquin
Keyword(s):  
Last Glacial Maximum ◽  
Climate Changes ◽  
Glacial Maximum ◽  
Last Glacial ◽  
The Future ◽  
The Last Glacial Maximum ◽  
The Last Glacial
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