Houghton Lecture/PAOCQ – Using Observations to Understand the Pattern Effect and its Contribution to Climate Sensitivity

Featuring David Thompson, Colorado State University

Abstract:
The “pattern effect” refers to the dependence of climate sensitivity on the spatial structure of temperature change. Evidence for the pattern effect and its role in climate change is derived almost entirely from numerical experiments. In this talk, I will explore the structure and role of the pattern effect in climate change using a range of observational data sets. The results provide an observational estimate of the role of the pattern effect in climate variability on monthly timescales. Consistent with numerical simulations, the observations indicate large negative climate feedbacks over the western Pacific. However, unlike the results of such experiments, they also indicate equally large positive feedbacks over the stratocumulus decks of the subtropical Pacific and large negative feedbacks over land. Land areas are not considered in current numerical simulations of the pattern effect, but the observations indicate that they account for roughly 80% of the global-mean negative internal feedback on monthly timescales. The talk will conclude with a discussion of the differences between observed and simulated estimates of the pattern effect across a range of model configurations, the reasons for these differences, and their implications for simulations of climate change.

About this year’s Houghton Lecturer:
David Thompson is a professor in the Department of Atmospheric Science at Colorado State University and in the School of Environmental Sciences at the University of East Anglia, UK. His research focuses on the physical processes that govern large-scale climate variability and change, with an emphasis on analyzing and diagnosing the observed climate system. His work has examined the dynamics of extratropical climate variability, the role of the atmospheric circulation in climate change, the imprint of stratospheric ozone depletion on surface climate, the role of the stratosphere in climate variability, and atmosphere–ocean coupling.

Houghton Lecture Series

Supported by the Houghton Fund, Houghton Lecturers are distinguished visitors from outside MIT, invited by the EAPS Program in Atmospheres, Oceans and Climate (PAOC) to spend a period of time, ranging from a week to several months, as scientists-in-residence.

Contact: kbauer@mit.edu