The global temperature of Planet Earth is rising due to anthropogenic changes in

the chemical composition of the atmosphere. During the last century the global

surface temperature warmed by about one degree centigrade. This trend is

projected to continue into the future, with a rate that will reflect the level of

mitigation efforts pursued by the global society during the coming decades.

The rising temperature will increase the level of heat stress experienced by

people around the world. The space-time distribution of future heat stress will

depend on the current distribution of surface temperature, as well as the rate by

which the temperature is projected to change. This current distribution of

temperature reflects to a large degree the geography of low-lying areas (valleys),

proximity to water bodies, prevailing wind directions, and land use (e.g.

irrigation). While most discussion of heat stress tends to focus on dry-bulb

temperature, which is the regular temperature as measured by thermometers and

sensed by satellite radiometers. However, humans react to variation in their skin

temperature. The latter reflects not only the regular temperature, but also the level

of humidity. The wet-bulb temperature, measured by wet-bulb thermometers, is

the best approximation of the human skin temperature under well-ventilated

condition. Hence, in this book we choose to focus on the wet-bulb temperature as

a measure of heat stress.