PREDICTIONS OFF CLIMATE CHANGES CAUSED BY MAN-MADE EMISSIONS OF GREENHOUSE GASES - A CRITICAL-ASSESSMENT

Predictions ofthe most advanced computer models ofthe changes in the g lobal climate that may result from man-made emissions of greenhouse ga ses are described and assessed in the light of the uncertainties in fu ture emissions and atmospheric concentrations of these gases, and of t he limitations of the models Predictions of the globally averaged temp erature rise, produced by the doubling of atmospheric carbon dioxide o ver 70 years, range from 1.3 to 2.6 degrees C, on average about 0.3 de grees C decade (-1). The scattering of solar radiation by atmospheric aerosols is calculated to reduce this global warming to about 1.0 degr ees C or 0.2 degrees C decade(-1). Warming is predicted to occur every where but to be most marked in high latitudes ofthe Northern Hemispher e. Globally averaged precipitation is predicted to rise by a few per c ent but with large geographical variations and areas of both increase and decrease. The largest increases are expected to occur in intertrop ical convergence zone, and in middle and high latitudes, especially in winter. Decreases are predicted in the subtropics. The best current e stimate of the rise in sea level resulting from an annual increase of 1% p.a. of carbon dioxide is 4 cm decade (-1).