A CLIMATE-CHANGE SCENARIO FOR THE TROPICS

This paper describes the construction of a climate change scenario for a region representing the 'extended' Tropics - 30 degrees N to 30 deg rees S - using a methodology that combines results from a simple clima te model and a Global Climate Model (GCM) transient climate change exp eriment. The estimated date by which this climate change scenario migh t be realized ranges from as early as the end of the 2030s to as late as well into the 22nd century. The central estimate is for this scenar io to describe the climate of the 2060s, which would represent a globa l warming rate of about 0.2 degrees C per decade, with associated atmo spheric CO2 concentrations estimated to be about 560 ppmv, 55% higher than 1990 levels. The role of anthropogenic aerosols in offsetting par t of this future global warming and altering the regional character of the changes has not been considered. The paper presents changes in me an temperature; mean rainfall; rainfall seasonality, variability, freq uency, and intensity and soil moisture. These patterns of change deriv e from only one GCM climate change experiment; different experiments w ould yield different patterns for the same global warming. There is al so some discussion about possible changes in tropical cyclone (TC) act ivity, although since TCs remain poorly modelled in GCMs, the full ran ge of possibilities (from reduced activity, through no change, to incr eased activity) should be considered in any impact assessment.