Brussels, 02 Sep 2003
The authors of the most comprehensive study of climatic history ever undertaken have concluded that the Earth is hotter now than at any point during the last 2,000 years.
Professor Philip Jones from the University of East Anglia's climatic research unit in the UK co-wrote the research, and believes that the results lend weight to the argument that human activity is responsible for the increase in temperatures.
'You can't explain it in any other way. It's a response to a build up of greenhouse gases in the atmosphere,' Professor Jones said.
In order to make such a claim with any confidence, it was necessary for Professor Jones and his colleague Professor Michael Mann form the University of Virginia in the US to draw up an accurate picture of the Earth's climate over the last two millennia.
They analysed temperature data stretching back to 1,000 years ago, but in order to get an idea of the Earth's climate before then, they had to look for clues contained within ice cores and vegetation that have survived to the present day.
They looked at the trunks of ancient trees from different parts of the world, and by measuring the thickness of their annual growth rings, which are determined by the climate, were able to glean an accurate picture of temperature and conditions throughout history.
Further vital evidence was provided by pockets of air trapped deep within ice formations in Greenland and Antarctica, all of which pointed to the same conclusion.
'What we found was that at no point during those two millennia had it been any warmer than it is now. From 1980 onwards is clearly the warmest period of the last 2,000 years,' Professor Jones revealed.
The scientists also saw evidence that in the past, the Earth's temperature was likely to fluctuate by around 0.2 degrees centigrade every century. Since 1980, however, researchers have recorded a rise in the Earth's temperature of at least that amount.
Finally, Professors Jones and Mann sought to counter claims that the world used to be much hotter in the past, based on anecdotal evidence that vineyards used to flourish in northern Britain 1,000 years ago and that the Vikings left Iceland for Greenland in search of warmer climes.
There are currently many more productive vineyards in Britain than at any time in the past, said the authors, and Vikings left Iceland in search of land, not warmer weather. The debate over the causes of global warming may still be ongoing, but the evidence in support of global warming itself is now compelling.