BY JIM GREEN
The human impact on climate change is more certain than ever before and the Earth's main surface temperature is predicted to rise further than previous estimates, according to the Intergovernmental Panel on Climate Change (IPCC).
The IPCC, which operates under the auspices of the World Meteorological Organisation and the United Nations Environment Program, comprises about 2500 scientists. A draft summary of the IPCC's latest report, known as the IPCC Third Assessment Report, was leaked to the New York Times in late October, and the broad thrust of the scientists' latest findings was spelt out by IPCC chairperson Dr Robert Watson in his opening address to the November 13-24 greenhouse conference at the Hague.
Watson said: "The Earth's surface temperature this century is clearly warmer than any other century during the last thousand years... The Earth has warmed by between 0.4 and 0.8 degree centigrade over the last century, with land areas warming more than the oceans, and with the last two decades being the hottest this century. Indeed, the three warmest years during the last one hundred years have all occurred in the 1990s and the twelve warmest years during the last one hundred years have all occurred since 1983.
"In addition, there is evidence that precipitation patterns are changing, that sea level is increasing, that glaciers are retreating world-wide, that Arctic sea ice is thinning, and that the incidence of extreme weather events is increasing in some parts of the world...
"The atmospheric concentrations of greenhouse gases have increased because of human activities, primarily due to the combustion of fossil fuels — coal, oil and gas — deforestation and agricultural practices.
The IPCC is now projecting global mean surface temperatures will rise 1.5-6oC between 1990 and 2100, up from its 1995 forecast of 1-3.5oC.
Emissions of greenhouse gases would have to be reduced by vastly more than Kyoto protocol targets in order to stabilise atmospheric concentrations. The CSIRO's Dr. Graeme Pearman says that current carbon dioxide emission levels would have to be cut by more than 60% just to stabilise levels in the atmosphere.