The North Atlantic Climate Response to Stratospheric Sulfate Geoengineering

Climate change is upon us and the natural and human systems we rely on are increasingly vulnerable to its cascading impacts. Yet, global efforts to reduce carbon dioxide emissions are falling short of what is necessary to avoid the worst impacts of climate change. It is within this backdrop that the concept of geoengineering the climate is being considered. Before embarking on this path, it is imperative that potential regional impacts be understood and documented. In this paper, we explore the impacts of stratospheric aerosol geoengineering over the North Atlantic sector, including changes to dominant weather and climate regimes such as the North Atlantic Oscillation, as well as impacts on sea ice, ocean and land, including terrestrial ecosystems. The North Atlantic is of particular interest, not only because of its importance as a major driver of weather and climate across much of the Northern Hemisphere, but also because it is sensitive to the stratospheric temperature and circulation changes that result from an enhanced stratospheric aerosol burden. To quantify these impacts within the presence of internal climate variability, we use a large ensemble of 21^st century experiments with the Community Earth System Model (the Geoengineering Large Ensemble project), in which future global warming is offset using stratospheric sulfur dioxide injections.