With much the same logic by which the late Oliver J. Flanagan came to the conclusion that there was no sex in Ireland before television, it is easy to believe that the greenhouse effect began around 1980. In fact the greenhouse effect began about three billion years ago and made life possible on Earth. The problem as far as global warming is concerned is an enhanced greenhouse effect, a relatively recent phenomenon brought about by man-made interference, albeit inadvertent, with atmospheric chemistry.
Although the enhanced greenhouse effect does not make headlines every day, it is still with us and is likely to remain so. Current assessments suggest that levels of greenhouse gases in the atmosphere will have roughly doubled by the third quarter of this century and there is now a strong consensus that this has significant implications for the global climate.
As successive reports appear to lay before us the findings of sophisticated climate models, there is increasing agreement on what these implications are. The main difference between reports lies in their assessment of the effects in various regions of the world.
The latest offering in this context is a report from the UK Meteorological Office's Hadley Centre for Climate Prediction and Research. The authors agree with previous estimates that if the atmosphere continues to absorb greenhouse gases at the same rate as at present a rise in average global temperature of about two degrees will occur by about 2080.
This increase in temperature, by means of thermal expansion of the oceans and the melting of glaciers and ice sheets, would result in a rise in sea level of 40 cm and increase the average annual number of people affected by flooding from 13 million to over 90 million. Indeed, the effects of rising sea levels have already become noticeable in the South Pacific with the submergence of two uninhabited islands in recent times. Inhabited islands in countries like Kiribati and Tuvalu are seriously at risk.
According to a separate report, warming of this kind in Alpine regions would result in an upwards shift in the winter snowline, with corresponding losses to the Swiss tourist industry of about 2000 million Swiss francs annually.
This ill wind would blow some good, of course. Cereal yields, according to the Hadley Centre, could be expected to increase in North America, China, Argentina, and over much of Europe. Cereal yields in Africa the Middle East, on the other hand, and particularly in India, may experience a significant decrease.