Only Phil Jones knows which of these Oxford definitions he had in mind when, in an email 10 years ago, he used the word to describe his treatment of a set of temperature data.

Professor Jones' 1999 email is at the centre of a scandal that has lit up the internet with claims by climate sceptics that it is evidence of a "global warming conspiracy".

In one of thousands of emails and documents stolen from the British University of East Anglia last week, Professor Jones tells colleagues he has completed the "trick of adding in the real temps" for the last 20 years "to hide the decline".

In another, US National Centre for Atmospheric Research climatologist Kevin Trenberth says it is a "travesty" that climate scientists cannot account for the "lack of warming at the moment".

The emails contain derisive comments about sceptics, including Professor Jones being "cheered" by the death in 2004 of Australian sceptic John L. Daly.

The scientists say they have been quoted selectively and misunderstood.

Dr Trenberth said the "travesty" he referred to was the lack of quality data to explain anomalies in sea temperature records.

Professor Jones, director of the university's world-renowned Climatic Research Unit, said he meant trick "as in a clever thing to do".

His use of "decline" is understood to refer to a divergence between temperature data from tree ring records and actual temperatures after 1960.

The tree ring data is commonly removed, or "hidden", during analysis.

Dr Trenberth linked the timing of the leaks to next month's Copenhagen climate summit aimed at reducing greenhouse gas emissions.

William Kininmonth, a former head of the National Climate Centre and prominent sceptic, challenged Professor Jones' explanation. "When people talk about a trick to make the data appear to be getting warmer, that is a pretty poor scientific attitude."

But Mr Kininmonth said he believed the overwhelming majority of climate research was authentic.

His problem was with the "slant" put on it by the UN's Intergovernmental Panel on Climate Change. "My feeling is that 99 per cent of the published science is legitimate," he said.

IPCC lead author David Karoly, of Melbourne University, said the leaked material did not change the comprehensive evidence of climate change.