11.6.4 Extremes

Little research is available on extremes of temperature and precipitation for this region. Table 11.1 provides estimates on how frequently the seasonal temperature and precipitation extremes as simulated in 1980 to 1999 are exceeded in model projections using the A1B scenario. Essentially all seasons and regions are extremely warm by this criterion by the end of the century. In Central America, the projected time mean precipitation decrease is accompanied by more frequent dry extremes in all seasons. In AMZ, models project extremely wet seasons in about 27% (18%) of all DJF (MAM) seasons in the period 2080 to 2099. Significant changes are not projected in the frequency of extremely wet or dry seasons over SSA.

On the daily time scale, Hegerl et al. (2004) analyse an ensemble of simulations from two AOGCMs and find that both models simulate a temperature increase in the warmest night of the year larger than the mean response over the Amazon Basin but smaller than the mean response over parts of SSA. Concerning extreme precipitation, both models project more intense wet days per year over large parts of south-eastern South America and central Amazonia and weaker precipitation extremes over the coasts of northeast Brazil. Intensification of the rainfall amounts are consistent, given the agreement between the MMD model simulations over parts of south-eastern South America and most of AMZ but with longer periods between rainfall events, except in north-western South America, where the models project that it will rain more frequently (Meehl et al., 2005; Tebaldi et al., 2006).