科学家力驳全球暖化怀疑论

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Copenhagen climate summit: scientists rally against climate change sceptics

It’s official. Global warming is continuing, despite attempts by sceptics to show otherwise. That was the message from the world’s leading climate scientists on the second day of the climate summit in Copenhagen.

One after the other, the British Met Office and the World Meteorological Organisation (WMO) went public with their latest measurements, showing that 2009 is shaping up to be the fifth hottest year on record and – more importantly – that the \'noughties’ are set to be much the warmest decade ever.

But just a few miles away from the cavernous Bella Centre, climate sceptics were saying exactly the opposite at an alternative conference. They claim, as a central part of their case, that the world has been getting cooler since 1998. But the scientists will have none of it. “We are in a warming trend. There is no doubt about it,” insisted Michael Jarraud, the Secretary General of the WMO.

His organisation, a UN body, draws its analysis on world temperatures from three separate sets of data. One is processed by the Met Office; until 2002 it ran it with the Climatic Research Unit at East Anglia University, of the hacked e-mail controversy, but now does the job itself. The others come from the US Government’s National Oceanic and Atmospheric Administration and NASA.

All have come to the same conclusion. Depending on what happens in the last three weeks of the year, it could end up as the fourth, fifth or sixth hottest on record, but it will certainly be much warmer than 2008, which was anomalously low thanks to a cooling La Nina in the Pacific. And the jump between average temperatures in the 1990s and the current decade is one of the greatest ever.

Temperatures only appear to have fallen if 1998 - an anomalously hot year - is taken as the starting point. Beginning, for example, with 1997 or 1999 gives a very different picture and independent statistical analysis has concluded that a cooling trend could only be determined by “people coming at the data with preconceived notions”.

But the scientists do not just rely on rising temperatures – which naturally vary from year to year while continuing on a longer term warming track - to judge that the world is still getting hotter. The IPCC, for example, also looks at what is happening to sea levels – since the water in the ocean expands as it heats up - and to snow and ice.

Sea levels, it said yesterday, have risen steadily by about 3.5 millimetres a year since 1993, while the frozen areas of the world have shrunk. The Arctic ice-cap, for example, is only about half as big as it was in 1950, and the IPCC says that the latest measurements show it could disappear altogether in summer as soon as 2030.