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Christensen
Latin America and the Caribbean are warming largely in line with the global trend and are likely to continue doing so. Local exceptions to the general tendency will appear, but available models do not give robust results for every part of the region. In particular, many issues related to changes in the Amazonas are still unresolved because important aspects of the interaction between vegetation and climate are still little understood. Different models also tend to behave differently in simulating the present climate within the region, and that limits the ability to take the simulated responses to anthropogenic forcings at their face value for the region. For this reason, the best estimate of climate change and variability in the region comes from assessing the results from many models, as was done by Christensen and others (IPCC 2007). The present analysis tries to go behind some of the statements provided there, by undertaking a comparative assessment of the results of general circulation models (GCMs).
Images of Present Change Temperature As noted above, LAC is projected to continue to warm at a rate little different from that of the world as a whole. Figure A.1 shows the geographical distribution of linear temperature trends for the periods 1901–2005 and 1979–2005, respectively. The long-term trend shows larger geographical variations and noticeable hot spots in southeast Brazil, Uruguay, northeast Argentina, and northwestern Mexico, where the warming has been more than double the global increase. For the more recent period, the warming trend shows less geographical variance.
Precipitation Data are less widely available for precipitation than for temperature, but the information that is available shows that precipitation varies widely within the LAC region. Figure A.2 depicts the geographical distribution of change. The most noticeable large-scale, coherent pattern is a long-term tendency toward drying in the tropics and subtropics (the Caribbean and northern South America), while temperate (southern South America) climates experience more precipitation. For large parts of the region, data are not readily available for analysis. In some countries efforts have been made to rescue and collect observational data, though not necessarily to make them publicly available. Analysis of these data confirms the broad tendencies, but trends may vary quite widely even at the community level (scale of 1–200 km), with quite large positive