The Pliocene Model Intercomparison Project Phase 2: large-scale climate features and climate sensitivity


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Christian.Stepanek [ at ] awi.de

Abstract

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 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 1.7 and 5.2 °C relative to the pre-industrial era with a multi-model mean value of 3.2 °C. Annual mean total precipitation rates increase by 7 % (range: 2 %–13 %). On average, surface air temperature (SAT) increases by 4.3 °C over land and 2.8 °C over the oceans. 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 2.3. In the Atlantic and Pacific oceans, meridional temperature gradients are reduced, while tropical zonal gradients remain largely unchanged. 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 a doubling of CO2 (including ice sheet feedbacks) is 67 % greater than ECS; this is larger than the increase of 47 % obtained from the PlioMIP1 ensemble. Proxy-derived estimates of Pliocene sea surface temperatures are used to assess model estimates of ECS and give an ECS range of 2.6–4.8°C. This result is in general accord with the ECS range presented by previous Intergovernmental Panel on Climate Change (IPCC) Assessment Reports.



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Article
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Helmholtz Program: Cooperations Across Research Fields (2021-2027): CARF
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ISI/Scopus peer-reviewed
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Published
Eprint ID
53211
DOI 10.5194/cp-16-2095-2020

Cite as
Haywood, A. M. , Tindall, J. C. , Dowsett, H. J. , Dolan, A. M. , Foley, K. M. , Hunter, S. J. , Hill, D. J. , Chan, W. L. , Abe-Ouchi, A. , Stepanek, C. , Lohmann, G. , Chandan, D. , Peltier, W. R. , Tan, N. , Contoux, C. , Ramstein, G. , Li, X. , Zhang, Z. , Guo, C. , Nisancioglu, K. H. , Zhang, Q. , Li, Q. , Kamae, Y. , Chandler, M. A. , Sohl, L. E. , Otto-Bliesner, B. L. , Feng, R. , Brady, E. C. , von der Heydt, A. S. , Baatsen, M. L. J. and Lunt, D. J. (2020): The Pliocene Model Intercomparison Project Phase 2: large-scale climate features and climate sensitivity , Climate of the Past, 16 (6), pp. 2095-2123 . doi: 10.5194/cp-16-2095-2020


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