Similar spatial patterns of climate responses to aerosol and greenhouse gas changes

Spatial variations in ocean warming have been linked to regional changes in tropical cyclones(1), precipitation(2,3) and monsoons(4). But development of reliable regional climate projections for climate change mitigation and adaptation remains challenging(5). The presence of anthropogenic aerosols, which are highly variable in space and time, is thought to induce spatial patterns of climate response that are distinct from those of well-mixed greenhouse gases(4,6-9) Using CMIP5 climate simulations that consider aerosols and greenhouse gases separately, we show that regional responses to changes in greenhouse gases and aerosols are similar over the ocean, as reflected in similar spatial patterns of ocean temperature and precipitation. This similarity suggests that the climate response to radiative changes is relatively insensitive to the spatial distribution of these changes. Although anthropogenic aerosols are largely confined to the Northern Hemisphere, simulations that include aerosol forcing predict decreases in temperature and westerly wind speed that reach the pristine Southern Hemisphere oceans. Over land, the climate response to aerosol forcing is more localized, but larger scale spatial patterns are also evident. We suggest that the climate responses induced by greenhouse gases and aerosols share key ocean-atmosphere feedbacks, leading to a qualitative resemblance in spatial distribution.