Wednesday, February 5, 2014
Environmental Science and Engineering Seminar
Coupled ocean-atmosphere dynamics of global warming
Shang-Ping Xie, Professor, Department of Climate, Atmospheric Science & Physical Oceanography, UC San Diego
Global surface air temperature has increased by less than 1oC over the past century, a change due to anthropogenic emission of greenhouse gases. Atmospheric concentration of CO2 exceeded 400 ppm at Mauna Loa in 2013 for the first time, yet global temperature has remained flat for the past 15 years. Our model results show that this apparent deviation from the anthropogenic climate warming is largely due to a decadal cooling of the tropical Pacific Ocean. This result is supported by seasonal and regional variations of climate anomalies over the past decade. This pause of global warming is temporary, illustrating the importance of natural variability in interpreting decadal climate trends.
The current California drought is in the third year. How precipitation will change in the face of global warming is an important question but difficult to answer. The challenge has to do with the characteristics of precipitation change. While surface temperature is expected to rise everywhere in response to the greenhouse gas forcing, precipitation change is to first order spatially variable, positive in some regions and negative in some others. Spatial pattern of ocean warming has emerged as an important factor for tropical rainfall change. The talk will discuss recent research in coupled ocean-atmosphere interactions pertinent to regional climate change.