Tropical deforestation: Modeling local‐ to regional‐scale climate change

Abstract

A tropical deforestation experiment has been conducted in which the tropical moist forest throughout the Amazon Basin and SE Asia has been replaced by scrub grassland in a version of the National Center for Atmospheric Research Community Climate Model (Version 1), which also incorporates a mixed layer ocean and the Biosphere‐Atmosphere Transfer Scheme. In both regions we find a smaller temperature increase than did all other previous experiments except that of Henderson‐Sellers and Gornitz (1984); indeed, temperatures decrease in some months. On the other hand, we find larger runoff decreases and a larger difference between the changes in evaporation and precipitation than all earlier experiments indicating a basin‐wide decrease in moisture convergence. Disturbances in South America extend beyond the region of land‐surface change causing temperature reductions and precipitation increases to the south of the deforested Amazon. Changes to the surface climate in the deforested area take between 1 to 2 years to become fully established although the root zone soil moisture is still decreasing in year 3 and the variability of soil moisture and total cloud amount continue increasing throughout the 6‐year integration. Besides temperature and precipitation, other fields show statistically significant alterations, especially evaporation and net surface radiation (both decreased).