Thursday, 13 January 2005: 2:15 PM
Solar dimming/brightening and consequences for the water cycle
Incoming shortwave irradiance at the surface is directly modified by cloud and aerosol changes and represents one crucial part of the cloud feedback loop in the climate system. Observations show that solar irradiance has recently been decreasing in stations worldwide by about 4% from 1961 to 1990 due to changed cloud optical thickness, cloud distribution and aerosol concentrations. This has been described as "global dimming" effect. Current research (including satellite observations, earthshine data and surface measurements) also show a reversal of this effect during the 1990s. We will present observational evidence of solar dimming and brightning and will discuss what consequences this effect has on modifying the water cycle (changing evaporation and precipitation rates). The analysis is based on climate simulation studies with general circulation models.