Coping with extreme heat: current exposure and implications for the future

A preview of how effective behavioral, biological, and technological responses might be in the future, when outdoor conditions will be at least 2oC hotter than current levels, is available today from studies of individuals already living in extreme heat These studies indicate that people commonly experience heat conditions that are substantially different from those recorded outdoors at fixed weather stations. In areas where high temperatures are common – particularly those in the hot and humid tropics – several studies report that indoor temperatures in low-income housing can be significantly hotter than those outdoors. A case study indicates that daily indoor heat indexes in almost all the 123 slum dwellings monitored in Kolkata during a summer were above 41oC (106oF) for at least an hour. Economic constraints make it unlikely that technological fixes, such as air conditioners, will remedy conditions like these – now or in the future. People without access to air conditioning will have to rely on behavioral adjustments and/or biological/physiological acclimatization. One important unknown is whether individuals who have lived their entire lives in hot environments without air conditioning possess natural levels of acclimatization greater than those indicated by controlled laboratory studies. Answering questions about the future will require more studies of individual experienced heat conditions, more information on indoor versus outdoor heat conditions, and a greater understanding of the behavioral and biological adjustments made by people living today in extremely hot conditions.