Warming, if it resumes again after the 18-26 year "pause" in global surface temperatures, tending to decrease the temperature differences or gradients between the equator and the poles, and it is temperature differences [not absolute temperatures] that lead to extreme weather including cyclones and hurricanes, explaining why the models predict fewer hurricanes in a warmer climate.
Bulletin of the American Meteorological Society 2014 ; e-View
Hurricanes and climate: the U.S. CLIVAR working group on hurricanes
Kevin J.E. Walsh
, Suzana J. Camargo , Gabriel A. Vecchi , Anne Sophie Daloz , James Elsner , Kerry Emanuel ,Michael Horn , Young-Kwon Lim , Malcolm Roberts , Christina Patricola , Enrico Scoccimarro , Adam H. Sobel ,Sarah Strazzo , Gabriele Villarini , Michael Wehner , Ming Zhao , James P. Kossin , Tim LaRow , Kazuyoshi Oouchi , Siegfried Schubert , Hui Wang , Julio Bacmeister , Ping Chang , Fabrice Chauvin , Christiane Jablonowski , Arun Kumar , Hiroyuki Murakami , Tomoaki Ose , Kevin A. Reed , R. Saravanan , Y. Yamada ,Colin M. Zarzycki , Pier Luigi Vidale , Jeffrey A. Jonas and Naomi Henderson
While a quantitative climate theory of tropical cyclone formation remains elusive, considerable progress has been made recently in our ability to simulate tropical cyclone climatologies and understand the relationship between climate and tropical cyclone formation. Climate models are now able to simulate a realistic rate of global tropical cyclone formation, although simulation of the Atlantic tropical cyclone climatology remains challenging unless horizontal resolutions finer than 50 km are employed. This article summarizes published research from the idealized experiments of the Hurricane Working Group of U.S. CLIVAR (CLImate VARiability and predictability of the ocean-atmosphere system). This work, combined with results from other model simulations, has strengthened relationships between tropical cyclone formation rates and climate variables such as mid-tropospheric vertical velocity, with decreased climatological vertical velocities leading to decreased tropical cyclone formation. Systematic differences are shown between experiments in which only sea surface temperature is increased versus experiments where only atmospheric carbon dioxide is increased, with the carbon dioxide experiments more likely to demonstrate the decrease in tropical cyclone numbers previously shown to be a common response of climate models in a warmer climate. Experiments where the two effects are combined also show decreases in numbers, but these tend to be less for models that demonstrate a strong tropical cyclone response to increased sea surface temperatures. Further experiments are proposed that may improve our understanding of the relationship between climate and tropical cyclone formation, including experiments with two-way interaction between the ocean and the atmosphere and variations in atmospheric aerosols.
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