Climate change scenarios and potential impacts on water availability in northern Mexico

Abstract

ABSTRACT: The climate predictability tool (CPT) is often used to statistically downscale the Intergovernmental Panel on Climate Change scenarios presented in the Fourth Assessment Report. The CPT reduces systematic errors and interpolates to a higher spatial resolution grid. Monthly means of surface temperature and precipitation from around 20 climate models for 4 greenhouse gas emission scenarios were downscaled for Mexico. Transfer functions are constructed using the 1900−1970 period and evaluated for the 1971−1999 period, examining the CPT ability to reproduce the observed climatology and trends in temperature and precipitation. The CPT-downscaled ensembles of climate change projections are considered adequate since, after correcting systematic biases in climate models, the observed climatology and trends in temperature and precipitation for the 1971−1999 period compare well with the observed data from the Climate Research Unit at 50 × 50 km resolution. The ensemble of downscaled climate change scenarios for the 2000−2099 period is then used to estimate some potential impacts of global warming over Mexico, mostly in water-related sectors. Results show that increases in temperature may be larger in the northwestern than in the northeastern part of the country. Precipitation scenarios project large probabilities of decreases in rainfall over northwestern Mexico, with potential reductions as large as 30%, which correspond to a standard precipitation index of around −1, i.e. a moderate drought. Drought of this magnitude may also bring the vegetation into a state of severe water stress and make it prone to forest fires. The combined effect of increased temperature and precipitation reductions could lead to reduced water availability over northwestern Mexico, especially along the USA−Mexico border region after the 2050s.