The Pliocene Model Intercomparison Project Phase 2: large-scale climate features and climate sensitivity
Haywood, Alan M.; Tindall, Julia C.; Dowsett, Harry J.; Dolan, Aisling M.; Foley, Kevin M.; Hunter, Stephen J.; Hill, Daniel J.; Chan, Wing-Le; Abe-Ouchi, Ayako; Stepanek, Christian; Lohmann, Gerrit; Chandan, Deepak; Peltier, Richard W.; Tan, Ning; Contoux, Camille; Ramstein, Gilles; Li, Xiangyu; Zhang, Zhongshi; Guo, Chuncheng; Nisancioglu, Kerim Hestnes; Zhang, Qiong; Li, Qiang; Kamae, Youichi; Chandler, Mark A.; Sohl, Linda E.; Otto-Bliesner, Bette L.; Feng, Ran; Brady, Esther C.; von der Heydt, Anna S.; Baatsen, Michiel L. J.; Lunt, Daniel J
Peer reviewed, Journal article
Published version
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https://hdl.handle.net/11250/2723625Utgivelsesdato
2020Metadata
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Originalversjon
10.5194/cp-16-2095-2020Sammendrag
The Pliocene epoch has great potential to improve our understanding of the long-term climatic and environmental consequences of an atmospheric CO2 concentration near ~ 400 parts per million by volume. Here we present the large-scale features of Pliocene climate as simulated by a new ensemble of climate models of varying complexity and spatial resolution and based on new reconstructions of boundary conditions (the Pliocene Model Intercomparison Project Phase 2; PlioMIP2). As a global annual average, modelled surface air temperatures increase by between 1.4 and 4.7 °C relative to pre-industrial with a multi-model mean value of 2.8 °C. Annual mean total precipitation rates increase by 6 % (range: 2 %–13 %). On average, surface air temperature (SAT) increases are 1.3 °C greater over the land than over the oceans, and there is a clear pattern of polar amplification with warming polewards of 60° N and 60° S exceeding the global mean warming by a factor of 2.4. In the Atlantic and Pacific Oceans, meridional temperature gradients are reduced, while tropical zonal gradients remain largely unchanged. Although there are some modelling constraints, there is a statistically significant relationship between a model's climate response associated with a doubling in CO2 (Equilibrium Climate Sensitivity; ECS) and its simulated Pliocene surface temperature response. The mean ensemble earth system response to doubling of CO2 (including ice sheet feedbacks) is approximately 50 % greater than ECS, consistent with results from the PlioMIP1 ensemble. Proxy-derived estimates of Pliocene sea-surface temperatures are used to assess model estimates of ECS and indicate a range in ECS from 2.5 to 4.3 °C. This result is in general accord with the range in ECS presented by previous IPCC Assessment Reports.