scholarly journals Review of Comparison of observed borehole temperatures in Antarctica with simulations using a forward model driven by climate model outputs covering the past millennium

2020 ◽  
Author(s):  
Anonymous
Keyword(s):  
Climate Model ◽  
Forward Model ◽  
Model Driven ◽  
The Past ◽  
Borehole Temperatures ◽  
Past Millennium

scholarly journals Teleconnections and relationship between the El Niño–Southern Oscillation (ENSO) and the Southern Annular Mode (SAM) in reconstructions and models over the past millennium

2020 ◽  
Vol 16 (2) ◽  
pp. 743-756 ◽  
Author(s):  
Christoph Dätwyler ◽  
Martin Grosjean ◽  
Nathan J. Steiger ◽  
Raphael Neukom
Keyword(s):  
Climate Model ◽  
El Nino ◽  
Southern Oscillation ◽  
Southern Annular Mode ◽  
Last Millennium ◽  
Annular Mode ◽  
Model Simulations ◽  
The Past ◽  
Climate Model Simulations ◽  
Past Millennium

Abstract. The climate of the Southern Hemisphere (SH) is strongly influenced by variations in the El Niño–Southern Oscillation (ENSO) and the Southern Annular Mode (SAM). Because of the limited length of instrumental records in most parts of the SH, very little is known about the relationship between these two key modes of variability over time. Using proxy-based reconstructions and last-millennium climate model simulations, we find that ENSO and SAM indices are mostly negatively correlated over the past millennium. Pseudo-proxy experiments indicate that currently available proxy records are able to reliably capture ENSO–SAM relationships back to at least 1600 CE. Palaeoclimate reconstructions show mostly negative correlations back to about 1400 CE. An ensemble of last-millennium climate model simulations confirms this negative correlation, showing a stable correlation of approximately −0.3. Despite this generally negative relationship we do find intermittent periods of positive ENSO–SAM correlations in individual model simulations and in the palaeoclimate reconstructions. We do not find evidence that these relationship fluctuations are caused by exogenous forcing nor by a consistent climate pattern. However, we do find evidence that strong negative correlations are associated with strong positive (negative) anomalies in the Interdecadal Pacific Oscillation and the Amundsen Sea Low during periods when SAM and ENSO indices are of opposite (equal) sign.

scholarly journals A comparison of model simulations of Asian mega-droughts during the past millennium with proxy reconstructions

2014 ◽  
Vol 10 (3) ◽  
pp. 2685-2716 ◽  
Author(s):  
B. Fallah ◽  
U. Cubasch
Keyword(s):  
Asian Monsoon ◽  
Climate Model ◽  
Severity Index ◽  
Ice Age ◽  
Drought Severity ◽  
Model Simulations ◽  
The Past ◽  
Global Circulation Models ◽  
Proxy Reconstructions ◽  
Past Millennium

Abstract. Two PMIP3/CMIP5 climate model ensemble simulations of the past millennium have been analyzed to identify the occurrence of Asian mega-droughts. The Palmer Drought Severity Index (PDSI) is used as the key metric for the data comparison of hydro-climatological conditions. The model results are compared with the proxy data of the Monsoon Asia Drought Atlas (MADA). Our study shows that Global Circulation Models (GCMs) are capable to capture the majority of historically recorded Asian monsoon failures at the right time and with a comparable spatial distribution. The simulations indicate that ENSO-like events lead in most cases to these droughts. Both, model simulations and proxy reconstructions, point to less monsoon failures during the Little Ice Age. During historic mega-droughts of the past millennium, the monsoon convection tends to assume a preferred regime described as "break" event in Asian monsoon. This particular regime is coincident with a notable weakening in Pacific Trade winds and Somali Jet.

scholarly journals The 15th century Arctic warming in coupled model simulations with data assimilation

2009 ◽  
Vol 5 (3) ◽  
pp. 389-401 ◽  
Author(s):  
E. Crespin ◽  
H. Goosse ◽  
T. Fichefet ◽  
M. E. Mann
Keyword(s):  
Data Assimilation ◽  
Surface Temperature ◽  
Climate Model ◽  
Three Dimensional ◽  
Coupled Model ◽  
Internal Variability ◽  
The Arctic ◽  
Arctic Warming ◽  
The Past ◽  
Past Millennium

Abstract. An ensemble of simulations of the climate of the past millennium conducted with a three-dimensional climate model of intermediate complexity are constrained to follow temperature histories obtained from a recent compilation of well-calibrated surface temperature proxies using a simple data assimilation technique. Those simulations provide a reconstruction of the climate of the Arctic that is compatible with the model physics, the forcing applied and the proxy records. Available observational data, proxy-based reconstructions and our model results suggest that the Arctic climate is characterized by substantial variations in surface temperature over the past millennium. Though the most recent decades are likely to be the warmest of the past millennium, we find evidence for substantial past warming episodes in the Arctic. In particular, our model reconstructions show a prominent warm event during the period 1470–1520. This warm period is likely related to the internal variability of the climate system, that is the variability present in the absence of any change in external forcing. We examine the roles of competing mechanisms that could potentially produce this anomaly. This study leads us to conclude that changes in atmospheric circulation, through enhanced southwesterly winds towards northern Europe, Siberia and Canada, are likely the main cause of the late 15th/early 16th century Arctic warming.

scholarly journals Testing the consistency between changes in simulated climate and Alpine glacier length over the past millennium

2018 ◽  
Author(s):  
Hugues Goosse ◽  
Pierre-Yves Barriat ◽  
Quentin Dalaiden ◽  
François Klein ◽  
Ben Marzeion ◽  
...  
Keyword(s):  
20Th Century ◽  
Climate Models ◽  
Climate Model ◽  
Global Climate ◽  
Global Climate Models ◽  
Late 20Th Century ◽  
The Past ◽  
Simulated Climate ◽  
Glacier Length ◽  
Past Millennium

Abstract. It is standard to compare climate model results covering the past millennium and reconstructions based on various archives in order to test the ability of models to reproduce the observed climate variability. Up to now, glacier length fluctuations have not been used systematically in this framework even though they offer information on multi-decadal to centennial variations complementary to other records. One reason is that glacier length depends on several complex factors and so cannot be directly linked to the simulated climate. However, climate model skill can be measured by comparing the glacier length computed by a glacier model driven by simulated temperature and precipitation to observed glacier length variations. This is done here using the version 1.0 of Open Global Glacier Model (OGGM) forced by fields derived from a range of simulations performed with global climate models over the past millennium. The glacier model is applied to a set of Alpine glaciers for which observations cover at least the 20th century. The observed glacier length fluctuations are generally well within the range of the simulations driven by the various climate model results, showing a general consistency with this ensemble of simulations. Sensitivity experiments indicate that the results are much more sensitive to the simulated climate than to OGGM parameters. This confirms that the simulations of glacier length can be used to evaluate the climate model performance, in particular the summer temperatures that largely control the glacier changes in our region of interest. Simulated glacier length is strongly influenced by the internal variability of the system, putting limitations on the model-data comparison for some variables like the trends over the 20th century in the Alps. Nevertheless, comparison of glacier length fluctuations on longer timescales, for instance between the 18th century and the late 20th century, appear less influenced by the natural variability and indicate clear differences in the behaviour of the various climate models.

scholarly journals Rates of global temperature change during the past millennium

2011 ◽  
Vol 7 (4) ◽  
pp. 2341-2354
Author(s):  
C. Shen ◽  
W.-C. Wang ◽  
G. Zeng ◽  
Y. Peng ◽  
Y. Xu
Keyword(s):  
Greenhouse Gases ◽  
Surface Temperature ◽  
Temperature Change ◽  
20Th Century ◽  
Time Scale ◽  
Climate Model ◽  
Global Climate Model ◽  
Surface Temperature Change ◽  
The Past ◽  
Past Millennium

Abstract. We examine the characteristics (amplitude and phase) of the temporal variation in the rates of global-mean surface temperature change during the past millennium. The study was conducted by applying 20-, 30-, and 50-yr sliding windows to the observations of recent century and reconstructions of earlier times. The analysis focuses on the characteristics of the 20th century within the context of the millennium as well as their sensitivity to the low frequency variability of sea surface temperature (SST) and time scales. On 20-yr time scale, comparable rates to that of the 20th century in both amplitude and phase occur in earlier nine centuries. The peak in the amplitude of rates in the 20th century on 30-yr time scale, although is not the largest during the past millennium, but is the most persistent. On 50-yr time scale, the 20th century warming rates are the highest and the most persistent during the past millennium. The results also indicate that although the SST variability does not affect much the amplitude of the rates, but the phases is quite different, thus highlighting the importance of the role of oceans in affecting the rates. We also analyzed the characteristics from global climate model (1000–1999 AD) simulations with different climate (solar, volcanic, and greenhouse gases) forcing. Except for the one driven by the solar forcing, other forcing simulates similar amplitudes as the observed ones. However, only greenhouse gases (GHG) forcing can reproduce the persistent high warming rates of the 20th century.

scholarly journals A comparison of model simulations of Asian mega-droughts during the past millennium with proxy reconstructions

2015 ◽  
Vol 11 (2) ◽  
pp. 253-263 ◽  
Author(s):  
B. Fallah ◽  
U. Cubasch
Keyword(s):  
Asian Monsoon ◽  
Climate Model ◽  
Severity Index ◽  
Ice Age ◽  
Drought Severity ◽  
Model Simulations ◽  
The Past ◽  
Global Circulation Models ◽  
Proxy Reconstructions ◽  
Past Millennium

Abstract. Two PMIP3/CMIP5 climate model ensemble simulations of the past millennium have been analysed to identify the occurrence of Asian mega-droughts. The Palmer drought severity index (PDSI) is used as the key metric for the data comparison of hydro-climatological conditions. The model results are compared with the proxy data of the Monsoon Asia Drought Atlas (MADA). Our study shows that global circulation models (GCMs) are capable of capturing the majority of historically recorded Asian monsoon failures at the right time and with a comparable spatial distribution. The simulations indicate that El Niño-like events lead, in most cases, to these droughts. Both model simulations and proxy reconstructions point to fewer monsoon failures during the Little Ice Age. The results suggest an influential impact of volcanic forcing on the atmosphere–ocean interactions throughout the past millennium. During historic mega-droughts of the past millennium, the monsoon convection tends to assume a preferred regime described as a "break" event in Asian monsoon. This particular regime is coincident with a notable weakening in the Pacific trade winds and Somali Jet.

scholarly journals Testing the consistency between changes in simulated climate and Alpine glacier length over the past millennium

2018 ◽  
Vol 14 (8) ◽  
pp. 1119-1133 ◽  
Author(s):  
Hugues Goosse ◽  
Pierre-Yves Barriat ◽  
Quentin Dalaiden ◽  
François Klein ◽  
Ben Marzeion ◽  
...  
Keyword(s):  
20Th Century ◽  
Climate Models ◽  
Climate Model ◽  
Global Climate ◽  
Global Climate Models ◽  
Late 20Th Century ◽  
The Past ◽  
Simulated Climate ◽  
Glacier Length ◽  
Past Millennium

Abstract. It is standard to compare climate model results covering the past millennium and reconstructions based on various archives in order to test the ability of models to reproduce the observed climate variability. Up to now, glacier length fluctuations have not been used systematically in this framework even though they offer information on multi-decadal to centennial variations complementary to other records. One reason is that glacier length depends on several complex factors and so cannot be directly linked to the simulated climate. However, climate model skill can be measured by comparing the glacier length computed by a glacier model driven by simulated temperature and precipitation to observed glacier length variations. This is done here using the version 1.0 of the Open Global Glacier Model (OGGM) forced by fields derived from a range of simulations performed with global climate models over the past millennium. The glacier model is applied to a set of Alpine glaciers for which observations cover at least the 20th century. The observed glacier length fluctuations are generally well within the range of the simulations driven by the various climate model results, showing a general consistency with this ensemble of simulations. Sensitivity experiments indicate that the results are much more sensitive to the simulated climate than to OGGM parameters. This confirms that the simulations of glacier length can be used to evaluate the climate model performance, in particular the simulated summer temperatures that largely control the glacier changes in our region of interest. Simulated glacier length is strongly influenced by the internal variability in the system, putting limitations on the model–data comparison for some variables like the trends over the 20th century in the Alps. Nevertheless, comparison of glacier length fluctuations on longer timescales, for instance between the 18th century and the late 20th century, appear less influenced by the natural variability and indicate clear differences in the behaviour of the various climate models.

scholarly journals Potential causes of 15th century Arctic warming using coupled model simulations with data assimilation

2009 ◽  
Vol 5 (1) ◽  
pp. 1-27 ◽  
Author(s):  
E. Crespin ◽  
H. Goosse ◽  
T. Fichefet ◽  
M. E. Mann
Keyword(s):  
Data Assimilation ◽  
Surface Temperature ◽  
Climate Model ◽  
Coupled Model ◽  
Internal Variability ◽  
The Arctic ◽  
Arctic Warming ◽  
The Past ◽  
15Th Century ◽  
Past Millennium

Abstract. An ensemble of simulations of the climate of the past millennium using a three-dimensional climate model of intermediate complexity are constrained to follow temperature histories obtained from a recent compilation of well-calibrated surface temperature proxies using a simple data assimilation technique. Those simulations provide a reconstruction of the climate of the Arctic that is compatible with model physics, the forcing applied and the proxy records. Available observational data, proxy-based reconstructions and our model results suggest that the Arctic climate is characterized by substantial variations in surface temperature over the past millennium. Though the most recent decades are likely to be the warmest of the past millennium, we find evidence for substantial past warming episodes in the Arctic. In particular, our model reconstructions show a particularly warm period at the end of the 15th century. This warm event is likely related to the internal variability of the climate system. We examine the roles of competing mechanisms that could potentially produce this anomaly. These examinations lead us to conclude that changes in atmospheric circulation, through enhanced southwesterly winds towards northern Europe, Siberia and Canada, are likely the main cause of the Arctic warming during the late 15th century.

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