Scientists: Future Climate Change Could Be Sudden

Photos Reuters Photo Audio/Video Japan Vows To Change U.S. Opinion On Kyoto - (Reuters)

By Matt Daily

AMSTERDAM (Reuters) - Future changes in the earth's climate may happen suddenly, triggered by man-made factors such as smokestacks and exhaust pipes, scientists said on Thursday.

Although there is a high degree of uncertainty in forecasting, the panel of climate scientists said there would more likely be dramatic shifts, rather than the steady, progressive change previously predicted by other scientists.

``We are heading into uncharted waters and it is difficult to predict what lies ahead,'' Tom Pedersen of University of British Columbia told reporters in Amsterdam, which is currently hosting a conference called ``Challenges of a changing earth.''

The United Nations (news - web sites) will resume talks in Bonn next week on the implementation of the 1997 Kyoto Protocol (news - web sites), which calls on industrialized states to reduce carbon dioxide emissions by an average of 5.2 percent from 1990 levels by 2010.

But the future of that treaty remains in doubt following the United States' rejection of the pact earlier this year.

Evidence of past changes in climate gathered in Greenland shows dramatic shifts occurred in periods of less than 10 years, according to Stefan Rahmstorf of the Potsdam Institute for Climate Change in Germany.

Those shifts typically occurred when a critical ecological ''threshold'' was breached. They could be triggered in future by heat-trapping gases accumulating in the earth's atmosphere, he told the conference.

``SHELTERED PERIOD'' MAY NOT LAST

Pedersen said rapid changes in the amounts of carbon dioxide, methane and nitrous oxide in the atmosphere have coincided with temperature change.

``What many people don't realize is that we are currently living within a sheltered period of only about 10,000 years in which conditions have been comparatively stable,'' he said.

Rahmstorf listed several ``low probability, high impact'' scenarios that could cause sharp changes in the earth's climate, including the melting of the West Antarctic ice sheet, the death of tropical forests, shifts in monsoon circulation and changes in ocean currents.

``Nobody believes these things are highly probable,'' he said. ''But we do need to be conscious of them when making climate policy. We need to take into account the risks of accidents or surprises.''

Paul Crutzen, who won the Nobel Prize for chemistry in 1995, said an abrupt change in climate could have occurred in the 1970s if a slightly different combination of ozone-depleting chemicals had been used.

``Had industry used bromine instead of chlorine in the chemicals used in spray cans and as solvents and refrigerants, we would have had a catastrophic ozone hole everywhere and at all seasons by the mid-1970s,'' he said.

``Consequences for life on the surface of the planet would have been severe,'' said Crutzen. ``We avoided such a fundamental change in the Earth's chemical mode of operation by luck rather than planning and foresight.''

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