Prof. Zhaohua Wu

Department of Earth, Ocean, and Atmospheric Science, Florida State University

10:15, 28 July, 2014

Room 303, Keyan Building, IAP

Abstract

The globally averaged climate has been experiencing significant warming at an unprecedented pace in the past century. This warming is spatially and temporally non-uniform, and one needs to understand its evolution in order to better evaluate its potential societal and economic impact. In this talk, the evolution of global land surface temperature trend in the last century is diagnosed using the spatial–temporally multidimensional ensemble empirical mode decomposition method. We find that the noticeable warming (>0.5 K) started sporadically over the global land and accelerated until around 1980. Both the warming rate and spatial structure have changed little since. The fastest warming in recent decades (>0.4 K/decade) occurred in northern midlatitudes. From a zonal average perspective, noticeable warming (>0.2 K since 1900) first took place in the subtropical and subpolar regions of the Northern Hemisphere, followed by subtropical warming in the Southern Hemisphere. The two bands of warming in the Northern Hemisphere expanded from 1950 to 1985 and merged to cover the entire Northern Hemisphere. In additional to these evolution characteristics, I will also show that the globally averaged warming has no "hiatus"; rather, it is the downward swing of the multi-decadal variability that shadowed the continuing warming, making the globally averaged temperature more or less flat (or decreasing a little bit) over the last fifteen years.