Can aerosols spin down the water cycle in a warmer and moister world?

[1] Surface observations show puzzling evidence of reduced solar warming and concurrent increasing temperature during the last four decades. Based on climate simulations with the general circulation model of the Max Planck Institute in Hamburg we suggest that the interactions of greenhouse gas forcing plus direct, semi-direct and indirect aerosol effects on clouds explain this paradox. We argue that reductions in surface solar radiation due to clouds and aerosols are only partly offset by enhanced down-welling longwave radiation from the warmer and moister atmosphere. We conclude that the radiative imbalance at the surface leads to weaker latent and sensible heat fluxes and hence to reductions in evaporation and precipitation despite global warming.

[1]  Lennart Bengtsson,et al.  Transient Climate Change Simulations with a Coupled Atmosphere–Ocean GCM Including the Tropospheric Sulfur Cycle , 1999 .

[2]  Walter A. Robinson,et al.  General circulation model simulations of recent cooling in the east‐central United States , 2002 .

[3]  C. Timmreck,et al.  Monthly Averages of Aerosol Properties: A Global Comparison Among Models, Satellite Data, and AERONET Ground Data , 2003 .

[4]  F. Chauvin,et al.  Sensitivity of the hydrological cycle to increasing amounts of greenhouse gases and aerosols , 2002 .

[5]  H. Paeth,et al.  Greenhouse-gas versus aerosol forcing and African climate response , 2006 .

[6]  B. Liepert,et al.  Observed reductions of surface solar radiation at sites in the United States and worldwide from 1961 to 1990 , 2002 .

[7]  C. Rosenzweig,et al.  Modelling the hydrological cycle in assessments of climate change , 1992, Nature.

[8]  Martin Wild,et al.  Means and Trends of Shortwave Irradiance at the Surface Estimated from Global Energy Balance Archive Data. , 1998 .

[9]  U. Lohmann,et al.  Nonlinear Aspects of the Climate Response to Greenhouse Gas and Aerosol Forcing , 2004 .

[10]  G. Boer.  Climate change and the regulation of the surface moisture and energy budgets , 1993 .

[11]  E. Feigelson,et al.  Evaluation of Long-Term Changes in Radiation, Cloudiness, and Surface Temperature on the Territory of the Former Soviet Union , 1996 .

[12]  M. Claussen,et al.  The atmospheric general circulation model ECHAM-4: Model description and simulation of present-day climate , 1996 .

[13]  Ulrike Lohmann,et al.  Can the direct and semi‐direct aerosol effect compete with the indirect effect on a global scale? , 2001 .

[14]  Ina Tegen,et al.  Multidecadal solar radiation trends in the United States and Germany and direct tropospheric aerosol forcing , 2002 .

[15]  D. Easterling,et al.  Observed climate variability and change of relevance to the biosphere , 2000 .

[16]  A. Robock,et al.  The Global Soil Moisture Data Bank , 2000 .

[17]  Gerald Stanhill,et al.  Global dimming: a review of the evidence for a widespread and significant reduction in global radiation with discussion of its probable causes and possible agricultural consequences , 2001 .

[18]  Glen Lesins,et al.  Stronger Constraints on the Anthropogenic Indirect Aerosol Effect , 2002, Science.

[19]  Joyce E. Penner,et al.  Indirect effect of sulfate and carbonaceous aerosols: A mechanistic treatment , 2000 .

[20]  Ulrike Lohmann,et al.  Erratum: ``Prediction of the number of cloud droplets in the ECHAM GCM'' , 1999 .

[21]  M. Roderick,et al.  The cause of decreased pan evaporation over the past 50 years. , 2002, Science.

[22]  V. Ramanathan,et al.  Aerosols, Climate, and the Hydrological Cycle , 2001, Science.

[23]  Makiko Sato,et al.  A closer look at United States and global surface temperature change , 2001 .

[24]  Syukuro Manabe,et al.  Simulation of hydrologic changes associated with global warming , 2002 .