Changes in the water budget in the Baltic Sea drainage basin in future warmer climates as simulated by the regional climate model RCA3

In this study we investigate three different regional climate change scenarios with respect to changes in the water budget over the Baltic Sea drainage basin. The scenarios are transient climate change scenarios in which the regional climate model RCA3 has been used to downscale results from two general circulation models, with three different emissions scenarios, for the years 1961-2100. First we show that the control climate in the late 20th century is too wet as compared with observations. This wet bias in the simulations is partly attributable to biases in the forcing global models but is also amplified in the regional climate model. The future climate change signal shows a gradually warmer and wetter climate during the 21st century with increased moisture transport into the region via the atmosphere. This leads to an intensification of the hydrological cycle with more precipitation and evaporation. The net precipitation increases in all scenarios in the entire region. The changes are of the order 15%-20% for annual and areal mean fluxes.