CIESIN Thematic Guides

How and Where Climatic Parameters Are Expected to Vary due to Global Warming

Emissions of "greenhouse gases" into the atmosphere at the current level will lead to an unprecedented increase in mean global temperature over the next few decades. To predict potential increases in mortality due to global warming, the quality, magnitude, frequency, and location of the climatic changes associated with global warming must be known. A World Health Organization Task Group (1990a) admits in the report Potential Health Effects of Climatic Change, however, that the extent and distribution of these changes are not well understood at the present.

In the chapter "Human Health" of Characterization of Information Requirements for Studies of CO2 Effects, White and Hertz-Piccioto (1985) say there are "no firm predictions regarding seasonal temperature changes in specific regions or regarding changes in other meteorologic variables such as humidity and precipitation." The authors maintain that how global warming might change the variability of climate also is not known. Given these uncertainties, White and Hertz-Piccioto conclude that it is impossible to predict today what the impacts of CO2-induced climate change will be on human health in the future.

Attempts have been made to develop plausible scenarios of the extent and distribution of climate change due to global warming based on current knowledge. Working Group II of the Intergovernmental Panel on Climate Change (IPCC) (1990) derives scenarios from both General Circulation Models and Soviet palaeoanalog techniques and describes them in Potential Impacts of Climate Change. Although these scenarios are used to assess the potential impacts of climate change, the working group voices little confidence in the regional estimates of key climatic factors that it developed. The group does, however, make some assessments of potential impacts of climate change by predicting the response of sensitive natural and biological systems to "significant variations."

The IPCC models estimate the average global temperature will rise by as much as 2° to 5° Celsius by the middle of the 21st century. In "The Greenhouse Effect," Schneider (1989) predicts that, as a result of this increase in temperature, an array of environmental changes, such as sea-level rise, flooding, drought, and increased frequency and intensity of some weather extremes, may occur. The potential for direct and indirect health effects from global warming will depend upon how, where, and when such weather events take place.