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 engineering projects; and energy planning - all based on the assumption that past climatic data, without modification, are a reliable guide to the future. This is no longer a good assumption'.

21. They estimated that if present trends continue, the combined concentration of CO2 and other greenhouse gases in the atmosphere would be equivalent to a doubling of CO2 from pre-industrial levels, possibly as early as the 2030s, and could lead to a rise in global mean temperatures 'greater than any in man's history'. Current modelling studies and 'experiments' show a rise in globally averaged surface temperatures, for an effective CO2 doubling, of somewhere between 1.5&deg;C and 4.5&deg;C, with the warming becoming more pronounced at higher latitudes during winter than at the equator.

22. An important concern is that a global temperature rise of 1.5 - 4.5&deg;C, with perhaps a two to three times greater warming at the poles, would lead to a sea level rise of 25-140 centimetres. A rise in the upper part of this range would inundate low-lying coastal cities and agricultural areas, and many countries could expect their economic, social, and political structures to be severely disrupted. It would also slow the 'atmospheric heat-engine' which is driven by the differences between equatorial and polar temperatures, thus influencing rainfall regimes. Experts believe that crop and forest boundaries will move to higher latitudes; the effects of warmer oceans on marine ecosystems or fisheries and food chains are also virtually unknown.

23. There is no way to prove that any of this will happen until it actually occurs. The key question is: How much certainty should governments require before agreeing to take action? If they wait until significant climate change is demonstrated, it may be too late for any countermeasures to be effective against the inertia by then stored in this massive global system. The very long time lags involved in negotiating international agreement on complex issues involving all nations have led some experts to conclude that it is already late. Given the complexities and uncertainties surrounding the urgent that the process start now. A four track strategy is needed, combining:
 * improved monitoring and assessment of the evolving phenomena;
 * increased research to improve knowledge about the origins, mechanisms, and effects of the phenomena;
 * the development of internationally agreed policies for the reduction of the causative gases; and
 * adoption of strategies needed to minimize damage and cope with the climate changes, and rising sea level.

24. No nation has either the political mandate or the economic power to combat climatic change alone. However, the Villach statement recommended such a four track strategy for climate change, to be promoted by governments and the scientific community through WMO, UNEP, and ICSU backed by a global convention if necessary. /…