Climate Change and Climatic Variability in Latin America and the Caribbean
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Temperature The balance of evidence assessed by the IPCC leads to the following statement: All of Central and South America is very likely to warm during this century. The annual mean warming is likely to be similar to the global mean warming in southern South America but larger than the global mean warming in the rest of the area (IPCC 2007). This implies that temperatures in all seasons will continue to rise during the 21st century. Some aspects of temperature-related events are also expected to change. Unless the temperature increase is a result of entirely new circulation patterns, changes in heat wave frequency and intensity are expected. Likewise, there is an enhanced risk of changes in the seasonality of some severe events because a higher temperature level in general will tend to favor a longer warm season with possible related extreme events. A clear example is the hurricane season (Box A.3).
Box A.3
Hurricanes An important driver for tropical cyclones and hence hurricanes is the sea surface temperature. A threshold of about 26째C determines whether a hurricane can be formed. In a warmer world with everything else being equal, the hurricane season is likely to be prolonged and the area prone to hurricane development may expand. However, a zone free of such systems will always remain near the equator, where atmospheric motions cannot support the development of intensive storms. March 2004 saw the first hurricane ever identified in the southern Atlantic. This hurricane severely affected the coastal zone of northeast Brazil. Such systems could become more frequent because of higher sea surface temperatures in the region. In the tropics, particularly when the sun is close to its zenith, outgoing longwave radiative cooling from the surface to space is not effective in the optically thick environment caused by the high water vapors over the oceans. Links to higher latitudes are weakest at this time, and transport of energy by the atmosphere, such as occurs when the sun is less strong, is not an effective cooling (continued)