Model-based changes in global annual mean surface temperature change (Delta T_g) and radiative forcing due to land ice albedo changes (Delta R_[LI]) over the last 5 Myr, supplementary material ...

• Main Authors: Köhler, Peter, de Boer, Bas, von der Heydt, Anna S, Stap, Lennert Bastiaan, van de Wal, Roderik S W
• Format: Dataset
• Language: English
• Published: PANGAEA 2015
• Subjects: Ice Sheet
• Online Access: https://dx.doi.org/10.1594/pangaea.855449; https://doi.pangaea.de/10.1594/PANGAEA.855449

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 ... : With an inverse climate model setup, that include 3D-ice sheet models, the benthic d18O global stack LR04 of the last 5 Myr (Lisiecki and Raymo, 2005, doi:10.1029/2004PA001071) was in a previous study (de Boer et al., 2014, doi:10.1038/ncomms3999) deconvolved into a temperature component and a sea level (ice sheet) component. The calculated changes in land ice area (as function of time and latitude) combined with incoming solar radiation (Laskar et al., 2004, doi:10.1051/0004-6361:20041335) and a simplified energy balance scheme (Köhler et al., 2010, doi:10.1016/j.quascirev.2009.09.026) are used to calculate changes in radiative forcing due to land ice albedo changes (Delta R_[LI]) over the last 5 Myr (changes normalized to global changes in radiative forcing, units: W/m^2). Three different assumptions on polar amplification are then used to calculate out of the model-based changes in temperature over the northern hemispheric land ice sheets (related to deep ocean temperature and derived from the ...