On the state dependency of the equilibrium climate sensitivity during the last 5 million years
It is still an open question how equilibrium warming in response to increasing radiative forcing – the specific equilibrium climate sensitivity S – depends on background climate. We here present palaeodata-based evidence on the state dependency of S, by using CO2 proxy data together with a 3-D ice-s...
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Copernicus Publications
2015
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Online Access: | https://doi.org/10.5194/cp-11-1801-2015 http://www.clim-past.net/11/1801/2015/cp-11-1801-2015.pdf https://doaj.org/article/dd0bbc8ef1c343fbaf2eb6ecd579ecd9 |
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fttriple:oai:gotriple.eu:oai:doaj.org/article:dd0bbc8ef1c343fbaf2eb6ecd579ecd9 2023-05-15T16:40:51+02:00 On the state dependency of the equilibrium climate sensitivity during the last 5 million years P. Köhler B. de Boer A. S. von der Heydt L. B. Stap R. S. W. van de Wal 2015-12-01 https://doi.org/10.5194/cp-11-1801-2015 http://www.clim-past.net/11/1801/2015/cp-11-1801-2015.pdf https://doaj.org/article/dd0bbc8ef1c343fbaf2eb6ecd579ecd9 en eng Copernicus Publications 1814-9324 1814-9332 doi:10.5194/cp-11-1801-2015 http://www.clim-past.net/11/1801/2015/cp-11-1801-2015.pdf https://doaj.org/article/dd0bbc8ef1c343fbaf2eb6ecd579ecd9 undefined Climate of the Past, Vol 11, Iss 12, Pp 1801-1823 (2015) geo envir Journal Article https://vocabularies.coar-repositories.org/resource_types/c_6501/ 2015 fttriple https://doi.org/10.5194/cp-11-1801-2015 2023-01-22T19:19:14Z It is still an open question how equilibrium warming in response to increasing radiative forcing – the specific equilibrium climate sensitivity S – depends on background climate. We here present palaeodata-based evidence on the state dependency of S, by using CO2 proxy data together with a 3-D ice-sheet-model-based reconstruction of land ice albedo over the last 5 million years (Myr). We find that the land ice albedo forcing depends non-linearly on the background climate, while any non-linearity of CO2 radiative forcing depends on the CO2 data set used. This non-linearity has not, so far, been accounted for in similar approaches due to previously more simplistic approximations, in which land ice albedo radiative forcing was a linear function of sea level change. The latitudinal dependency of ice-sheet area changes is important for the non-linearity between land ice albedo and sea level. In our set-up, in which the radiative forcing of CO2 and of the land ice albedo (LI) is combined, we find a state dependence in the calculated specific equilibrium climate sensitivity, S[CO2,LI], for most of the Pleistocene (last 2.1 Myr). During Pleistocene intermediate glaciated climates and interglacial periods, S[CO2,LI] is on average ~ 45 % larger than during Pleistocene full glacial conditions. In the Pliocene part of our analysis (2.6–5 Myr BP) the CO2 data uncertainties prevent a well-supported calculation for S[CO2,LI], but our analysis suggests that during times without a large land ice area in the Northern Hemisphere (e.g. before 2.82 Myr BP), the specific equilibrium climate sensitivity, S[CO2,LI], was smaller than during interglacials of the Pleistocene. We thus find support for a previously proposed state change in the climate system with the widespread appearance of northern hemispheric ice sheets. This study points for the first time to a so far overlooked non-linearity in the land ice albedo radiative forcing, which is important for similar palaeodata-based approaches to calculate climate sensitivity. However, ... Article in Journal/Newspaper Ice Sheet Unknown Climate of the Past 11 12 1801 1823 |
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geo envir |
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geo envir P. Köhler B. de Boer A. S. von der Heydt L. B. Stap R. S. W. van de Wal On the state dependency of the equilibrium climate sensitivity during the last 5 million years |
topic_facet |
geo envir |
description |
It is still an open question how equilibrium warming in response to increasing radiative forcing – the specific equilibrium climate sensitivity S – depends on background climate. We here present palaeodata-based evidence on the state dependency of S, by using CO2 proxy data together with a 3-D ice-sheet-model-based reconstruction of land ice albedo over the last 5 million years (Myr). We find that the land ice albedo forcing depends non-linearly on the background climate, while any non-linearity of CO2 radiative forcing depends on the CO2 data set used. This non-linearity has not, so far, been accounted for in similar approaches due to previously more simplistic approximations, in which land ice albedo radiative forcing was a linear function of sea level change. The latitudinal dependency of ice-sheet area changes is important for the non-linearity between land ice albedo and sea level. In our set-up, in which the radiative forcing of CO2 and of the land ice albedo (LI) is combined, we find a state dependence in the calculated specific equilibrium climate sensitivity, S[CO2,LI], for most of the Pleistocene (last 2.1 Myr). During Pleistocene intermediate glaciated climates and interglacial periods, S[CO2,LI] is on average ~ 45 % larger than during Pleistocene full glacial conditions. In the Pliocene part of our analysis (2.6–5 Myr BP) the CO2 data uncertainties prevent a well-supported calculation for S[CO2,LI], but our analysis suggests that during times without a large land ice area in the Northern Hemisphere (e.g. before 2.82 Myr BP), the specific equilibrium climate sensitivity, S[CO2,LI], was smaller than during interglacials of the Pleistocene. We thus find support for a previously proposed state change in the climate system with the widespread appearance of northern hemispheric ice sheets. This study points for the first time to a so far overlooked non-linearity in the land ice albedo radiative forcing, which is important for similar palaeodata-based approaches to calculate climate sensitivity. However, ... |
format |
Article in Journal/Newspaper |
author |
P. Köhler B. de Boer A. S. von der Heydt L. B. Stap R. S. W. van de Wal |
author_facet |
P. Köhler B. de Boer A. S. von der Heydt L. B. Stap R. S. W. van de Wal |
author_sort |
P. Köhler |
title |
On the state dependency of the equilibrium climate sensitivity during the last 5 million years |
title_short |
On the state dependency of the equilibrium climate sensitivity during the last 5 million years |
title_full |
On the state dependency of the equilibrium climate sensitivity during the last 5 million years |
title_fullStr |
On the state dependency of the equilibrium climate sensitivity during the last 5 million years |
title_full_unstemmed |
On the state dependency of the equilibrium climate sensitivity during the last 5 million years |
title_sort |
on the state dependency of the equilibrium climate sensitivity during the last 5 million years |
publisher |
Copernicus Publications |
publishDate |
2015 |
url |
https://doi.org/10.5194/cp-11-1801-2015 http://www.clim-past.net/11/1801/2015/cp-11-1801-2015.pdf https://doaj.org/article/dd0bbc8ef1c343fbaf2eb6ecd579ecd9 |
genre |
Ice Sheet |
genre_facet |
Ice Sheet |
op_source |
Climate of the Past, Vol 11, Iss 12, Pp 1801-1823 (2015) |
op_relation |
1814-9324 1814-9332 doi:10.5194/cp-11-1801-2015 http://www.clim-past.net/11/1801/2015/cp-11-1801-2015.pdf https://doaj.org/article/dd0bbc8ef1c343fbaf2eb6ecd579ecd9 |
op_rights |
undefined |
op_doi |
https://doi.org/10.5194/cp-11-1801-2015 |
container_title |
Climate of the Past |
container_volume |
11 |
container_issue |
12 |
container_start_page |
1801 |
op_container_end_page |
1823 |
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