Reconciling modeled and observed temperature trends over Antarctica

Abstract

Over the last three decades, ozone depletion over Antarctica has affected temperature and winds in the lower stratosphere, and even in the troposphere and at the surface. The second Chemistry Climate Model Validation activity (CCMVal2) concluded that chemistry-climate models simulate stratospheric cooling that is too large compared to observations, even though the modeled and observed ozone trends are similar. However, these comparisons were based only on radiosonde data available for 1969-1998. Here, we investigate trends in the Southern Hemisphere polar cap in the latest version of the Community Earth System Model (CESM1) with its high-top atmospheric component, WACCM4, fully coupled to an ocean model. We compare model trends with observations for different periods and with other modeling studies to show much better agreement with more recent data, and conclude that the discrepancy between observed trends and those calculated by high-top models may not be as large as previously reported.