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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fttriple:oai:gotriple.eu:sPilojnaWOYo3zjphA2rI 2023-05-15T16:40:51+02:00 On the state dependency of the equilibrium climate sensitivity during the last 5 million years Köhler, P. Boer, B. Heydt, A. S. Stap, L. B. Wal, R. S. W. 2018-09-27 https://doi.org/10.5194/cp-11-1801-2015 https://cp.copernicus.org/articles/11/1801/2015/ en eng Copernicus Publications doi:10.5194/cp-11-1801-2015 10670/1.s5dks3 1814-9324 1814-9332 https://cp.copernicus.org/articles/11/1801/2015/ undefined Geographica Helvetica - geography eISSN: 1814-9332 geo envir Text https://vocabularies.coar-repositories.org/resource_types/c_18cf/ Journal Article https://vocabularies.coar-repositories.org/resource_types/c_6501/ 2018 fttriple https://doi.org/10.5194/cp-11-1801-2015 2023-01-22T17:52:23Z 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 Köhler, P. Boer, B. Heydt, A. S. Stap, L. B. Wal, R. S. W. On the state dependency of the equilibrium climate sensitivity during the last 5 million years |
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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 |
Köhler, P. Boer, B. Heydt, A. S. Stap, L. B. Wal, R. S. W. |
author_facet |
Köhler, P. Boer, B. Heydt, A. S. Stap, L. B. Wal, R. S. W. |
author_sort |
Köhler, P. |
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 |
2018 |
url |
https://doi.org/10.5194/cp-11-1801-2015 https://cp.copernicus.org/articles/11/1801/2015/ |
genre |
Ice Sheet |
genre_facet |
Ice Sheet |
op_source |
Geographica Helvetica - geography eISSN: 1814-9332 |
op_relation |
doi:10.5194/cp-11-1801-2015 10670/1.s5dks3 1814-9324 1814-9332 https://cp.copernicus.org/articles/11/1801/2015/ |
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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1766031267106652160 |