Kevin Trenberth has been prominent in all aspects of climate variability and climate change research and is a leader in the Intergovernmental Panel on Climate Change assessments and in the World Climate Research Programme. Trenberth has published on many topics. Trenberth has evaluated many datasets and been the primary promoter of the need to reanalyze global data into fields in ways that meet climate requirements for continuity and consistency. He has determined the mass of the atmosphere as a fundamental physical quantity and how it varies as water vapor varies, and utilized the conservation constraint to evaluate datasets. One area of greatest impact has been in resolving outstanding issues concerning the global heat and energy budget of planet Earth. He has improved estimates of heat, energy and water transports within the atmosphere to a point where, when combined with top-of-atmosphere observed radiation, they now provide estimates of ocean heat transports as a residual that agree well with directly observed values. The work has proven vital for validating coupled atmosphere-ocean climate models and understanding heat flows that is so important in climate change. It has also provided a paradigm for the role of El Niño in the climate system, as heat is redistributed throughout the atmosphere and ocean system during the course of El Niño events. Trenberth recognized the importance of and was involved in El Niño research long before it became popular. Seminal contributions include identification of major decadal changes in El Niño and the 1976-77 "climate shift", and he correctly attributed tropical sea surface temperature changes and the 1988 La Niña as a cause of the 1998 North American drought. He has played a major role in determining the global water cycle and how it changes as climate changes, with particular foci on changes in precipitation frequency, intensity and amount, and thus on how droughts and floods change. He has been a leader of the development of the global climate observing system and the Global Earth Observations initiative.
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