Rising levels of greenhouse gases are pushing up world temperatures which may hit record high, say experts
GLOBAL temperatures this year could beat the record set in 1998, when El Nino - a disturbance of Pacific Ocean currents that warms the earth's atmosphere - was at its strongest.
Climate experts say a new and persistent underlying warming trend is brewing in the Pacific and this will push temperatures to record highs.
Natural climate variation explains some of the global warming but the heat-trapping properties of rising levels of carbon dioxide and other greenhouse gases will also have contributed to the effect.
The Hadley Centre for Climate Prediction and Research in Britain put the odds at 50-50 that this year could match or exceed the temperature record of 1998. The director for space studies at America's National Aeronautics and Space Administration (Nasa) put the odds even higher.
A decade without any big volcanic eruptions and a peak in solar intensity can account for only part of the overall warming, says Dr James Hansen. 'Clearly, it's primarily due to human forcing.'
The global average temperature reached 14.4 deg C in 1998, while last year's was 14.3 deg C - as against an average of 13.8 deg C between 1880 to 2001.
Areas like Alaska have experienced more intensive warming, in patterns that largely match computer projections of the climatic effect of rising greenhouse gases.
Satellite tracking of surface conditions on Greenland's vast ice sheet saw more melting last summer than at any time in the 24-year satellite record, the National Oceanic and Atmospheric Administration has reported.
And the Arctic sea ice was found to have retreated more than it had done before during the 24-year span.
Polar experts point out that it is exceedingly difficult to ascribe regional changes to human actions, rather than natural cycles in ocean and weather circulation around the Northern Hemisphere.
But scientists also add that it is getting harder to link the continuing global climb in temperatures mainly to natural climate fluctuations.
Even if this year sets no record, it is almost certain to follow the trend of temperature rises that has led to shifts in the planet's drought and storm patterns, continuing retreats of terrestrial ice - and a resulting rise in sea levels in coming decades.
American and British climate teams and the World Meteorological Organisation have reported that last year would nudge out 2001 as the second-warmest year since the late 1800s.
Some scientists still doubt that the human influence will alter the climate beyond the range of natural variability.
'We don't really know enough about the climate to say with any confidence how much of this warming is natural and how much is caused by human activities,' said Dr John Christy, the director of the Earth System Science Center at the University of Alabama in Huntsville.
But fewer and fewer climate experts now agree with this view. In 1990, Dr Christy and a team that included Nasa satellite experts pioneered a method for measuring the average temperature of the atmosphere above the earth's surface, using instruments on weather satellites.
And after examining three decades of satellite data, they reported cooling or only slight warming of the earth's upper atmosphere - a finding pounced upon by sceptics of the greenhouse theory.
But new analyses of the same data by an independent team of scientists have suggested that much more warming is going on in the upper atmosphere - more than three times as much as Dr Christy estimated.
These analyses are also more in line with surface trends and estimates produced by computer models.
While the debate about the amount of atmospheric warming continues, there is little disagreement about the extent of warming on the earth's surface.
The shifts around the Arctic, whether natural or human-induced, are profound, says Dr Waleed Abdalati, Nasa's director of polar programmes.
This year, he co-authored a study showing that the surface melting in Greenland, for example, was unexpectedly accelerating the seaward crawl of the ice sheet.
And if the Greenland ice-melt keeps accelerating, scientists may have to change their projections of how much a little warming can raise sea levels. --New York Times
The Straits Times Interactive, 13. januar 2003
