Heat waves

Abstract

Thermal comfort is felt individually. Heat generally means thermal discomfort activating the thermoregulatory system of the body. Heat conditions are weatherdetermined and if lasting for several days or longer are called heat wave. Quantification of heat needs the total energy budget of the human body. This energy budget is influenced by air temperature, humidity, ventilation, radiation, bodily activity, clothing, mass and shape of the body, health state, age, and also by individual predisposition. In the case of overheating the body’s thermoregulatory system failed to keep the temperature in the tolerable range of temperature in the core parts of the body. Indicators are in use allowing a simplified description of the energy budget of the human body, so capturing effects of heat as well. These indicators classify the environmental conditions by either recommending the type of feasible bodily activity, or by requiring the cooling of the human body, both in order to avoid health damage due to overheating. The climatic conditions show a global distribution of heat stress. In some parts of the tropics, heat stress occurs on more than 300 days per year, and in the mid-latitudes, heat stress occurs on about 20–100 days. Indigenous and non-indigenous populations do acclimate to endemic or periodical heat conditions, helping to better cope with these. Heat waves can develop more frequently, when on average there are more such heat days. In recent years, the number of days with heat stress, and of days occurring in heat waves, increased in the mid-latitudes. The forecast climate change points to further increase of heat stress in many parts of the world.