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. Recently his primary research has focused on the global energy and water cycles and how they are changing.
"The environment in which all storms form has changed owing to human activities"
Kevin Trenberth, 2011 on attribution of extremes to climate change
His work mainly involves empirical studies and quantitative diagnostic calculations. Trenberth is a primary advocate for the need to develop a climate information system that is an imperative for adaptation to climate change. However, Trenberth has published on many topics and is highly cited. He 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.
Research topics include:
- Interannual variability of climate and El Niño
- Climate change and global warming
- The heat and energy cycles
- The water cycle and atmospheric moisture budget
- The mass of the atmosphere
- Datasets and reanalysis
- The global climate observing system
- Hurricanes and climate change
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 type, frequency, intensity and amount, and thus on how droughts and floods change. In addition, with Aiguo Dai he has improved global estimates of runoff, streamflow, river discharge and the entire hydrological cycle, and how they change over time. He has been a leader of the development of the global climate observing system and the Global Earth Observations initiative.
He has dabbled in paleoclimate. Recently he has been to the fore in raising issues about how hurricanes change as the climate changes: in better determining the relation of hurricane to environmental variables, where the moisture that feeds the heavy rainfalls comes from, and the role of hurricanes in moving energy around.