Atmospheric Chemistry and Physics Discussions www.atmos-chem-phys-discuss.net 1680-7367 1680-7375 10 1 2010 10.5194/acpd-10-1939-2010 http://www.atmos-chem-phys-discuss.net/10/1939/2010/ http://www.atmos-chem-phys-discuss.net/10/1939/2010/acpd-10-1939-2010.html http://www.atmos-chem-phys-discuss.net/10/1939/2010/acpd-10-1939-2010.pdf 1939 1956 2010-01-25 Aerosol-induced changes of convective cloud anvils produce strong climate warming I. Koren ilan.koren@weizmann.ac.il L. A. Remer O. Altaratz J. V. Martins A. Davidi Department of Environmental Sciences, Weizmann Institute, Rehovot 76100, Israel Laboratory for Atmospheres, NASA Goddard Space Flight Center, Greenbelt, Maryland, USA Department of Physics and Joint Center for Earth Systems Technology, University of Maryland, Baltimore County, USA The effect of aerosol on clouds poses one of the largest uncertainties in estimating the anthropogenic contribution to climate change. In contrast, even small human-induced perturbations in cloud coverage, lifetime, height or optical properties can change the instantaneous radiative energy flux by hundreds of watts per unit area, and this forcing can be either warming or cooling. Clouds and aerosols form a complex coupled system that, unlike greenhouse gases, have relatively short lifetime (hours to days) and inhomogeneous distribution. This and the inherent complexity of cloud microphysics and dynamics, and the strong coupling with meteorology explain why the estimation of the overall effect of aerosol on climate is so challenging. <br><br> Here we focus on the effect of aerosol on cloud top properties of deep convective clouds over the tropical Atlantic. The tops of these vertically developed clouds consist of mostly ice and can reach high levels of the atmosphere, overshooting the lower stratosphere and reaching altitudes greater than 16 km. 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