WASHINGTON — New evidence shows man-made pollution has "contributed substantially" to global warming and the earth is likely to get a lot hotter than previously predicted, a United Nations-sponsored panel of hundreds of scientists finds.
The conclusions by the Intergovernmental Panel on Climate Change, the most authoritative scientific voice on the issue, is expected to widely influence climate debate over the next decade.
The report’s summary was being distributed to government officials worldwide this week.
It is the first full-scale review and update of the state of climate science since 1995, when the same panel concluded there is "a discernible human influence" on the earth’s climate because of the so-called greenhouse effect caused by the buildup of heat-trapping chemicals in the atmosphere.
Today, the panel says in its new assessment that there is stronger evidence yet on the human influence on climate and that it is likely that man-made greenhouse gases already have contributed substantially to the observed warming over the last 50 years.
The scientists, in revised estimates, conclude that if greenhouse emissions are not curtailed, the earth’s average surface temperatures could increase from 2.7 to nearly 11 degrees Fahrenheit by the end of this century, substantially more than estimated in its report five years ago.
It attributes the increase mainly to a reduced influence from sulfate releases from industry and power plants. Such releases, which tend to have a cooling influence, will likely dramatically decline in industrial countries because of other environmental concerns, the scientists maintain.
"What this report is clearly saying is that global warming is a real problem and it is with us and we are gong to have to take this into account in our future planning," said Kevin Trenberth, head of climate analysis section at the National Center for Atmospheric Research.
Three years ago, industrial nations tentatively agreed to curtail the release of greenhouse gases — mainly carbon dioxide from burning fossil fuels — to below 1990 levels as a first step to address global warming.
But none of the major industrial countries has yet ratified the agreement, crafted in Kyoto, Japan, in 1997. Skeptics argue that the science has yet to be conclusive and that computer models used to predict future climate are not reliable enough to warrant a dramatic and expensive shift in energy use to curtail carbon emissions into the atmosphere.
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