Atmospheric circulations and climate change

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Atmospheric circulations play a fundamental role in determining the climate of Earth. Under climate change scenarios, the atmospheric circulation mediates surface temperature and radiation changes. As a result, knowledge of the response of these circulations to changes in greenhouse gases and other radiative forcing agents is central to confident predictions of Earth's future climate. The atmospheric circulation is, in turn, affected by changes in temperature and radiation. The goal of this proposed research program is, therefore, to expose both the effects of climate change on the atmospheric circulation and the effects of changes in the atmospheric circulation on the other aspects of the climate. Specifically, this research program will address (i) the physical mechanisms underlying the sensitivity of the mean tropical atmospheric circulation to the radiative forcing of carbon dioxide, (ii) the interactions between the mean tropical circulation, atmospheric humidity and clouds, and the radiative heating that drives the circulation, and (iii) the effect of these mean circulation changes on extreme weather such as hurricanes. This research will use a hierarchy of climate models that explicitly simulate the fluid motion of the atmosphere and have representations of the hydrological cycle and radiation that range from simplified ones to those of comprehensive climate models. This approach of reducing the complexity of Earth's climate through simplifying the representations of processes within climate models allows the essential physical processes responsible for the changes in climate to be revealed. The physical mechanisms elucidated in the hierarchy of climate models will be validated by comparison to observations of Earth and will be used to analyze and interpret the projections of future climate prepared for the United Nations Intergovernmental Panel on Climate Change. Thus, the research results will have implications for climate change mitigation and adaptation strategies.