Mearns is an expert in regional climate change and its impacts. She draws on computer simulations to develop scenarios for decision makers who are preparing for the societal and environmental impacts of climate change. Mearns also investigates the effects of climate change on agriculture and on human health, particularly in relationship to the frequency of extreme weather events such as heat waves. She has served as lead or co-convening lead author on several Intergovernmental Panel on Climate Change reports and shared in the 2007 Nobel Peace prize. Mearns is director of the Weather and Climate Impacts Assessment Science Program and a senior scientist in NCAR’s Institute for Mathematics Applied to Geosciences.