Biological and Environmental Research - Earth and Environmental System Sciences
Earth and Environmental System Modeling
10 June 2020

Drivers of Intermodel Differences in Clear-Sky Climate Feedbacks

The spatial warming pattern drives model differences in the lapse rate and water vapor feedbacks.

Atmospheric warming pattern associated with regional surface warming.
Science

Scientists at Lawrence Livermore National Laboratory in collaboration with colleagues at the University of Washington have found simple diagnostics that can represent complex climate feedback processes, which act to amplify global surface temperature change. Scrutiny of model simulations demonstrates that the current distribution of Antarctic sea ice is a key driver model differences in climate feedback processes. 

Impact

Model representation of the current climate can influence future climate projections via clear-sky climate feedback processes, underscoring the need for accurate model simulations of the current climate.  

Summary

Projections of global temperature change exhibit substantial spread across different climate model simulations. This uncertainty arises from varied climate feedback processes that act to amplify or dampen global surface temperature changes. Here we investigate drivers of intermodel differences in clear-sky (i.e., non-cloud) climate feedbacks. These feedbacks relate to atmospheric temperature (lapse rate feedback) and humidity (water vapor feedback) changes. Clear-sky climate feedbacks across different climate models closely scale with the ratio of tropical and extratropical surface warming. The change in southern extratropical surface warming is closely related to the climatological extent of Antarctic sea ice. As a result, a substantial fraction of model differences in the lapse rate and water vapor feedback can be ascribed to model representation of Antarctic sea ice.  

Contact
Benjamin Santer
Lawrence Livermore National Laboratory (LLNL)
Publications
Po-Chedley, S, K Armour, C Bitz, M Zelinka, B Santer, and Q Fu.  2018.  "Sources of Intermodel Spread in the Lapse Rate and Water Vapor Feedbacks."  Journal of Climate 31(8): 3187-3206.  https://doi.org/10.1175/jcli-d-17-0674.1.