Earth hottest in 400 years

The Herald Sun
AP 23 Jun 2006

THE Earth is the hottest it has been in at least 400 years and perhaps thousands of years, US scientists say.

The US National Academy of Sciences reached that conclusion in a broad review of scientific work requested by the US Congress. In a report released yesterday it found the "recent warmth is unprecedented for at least the last 400 years and potentially the last several millennia".

A panel of top climate scientists told lawmakers Earth was running a fever and "human activities are responsible for much of the recent warming".

Their 155-page report said average global surface temperatures in the Northern Hemisphere rose about half a degree Celsius during the 20th century.

The report was requested in November by chairman of the House Science Committee Congressman Sherwood Boehlert, a Republican, to address those who questioned whether global warming was a major threat.

Climate scientists Michael Mann, Raymond Bradley and Malcolm Hughes had concluded the Northern Hemisphere was the warmest it has been in 2000 years.

Their research was known as the "hockey-stick" graphic because it compared the sharp curve of the hockey blade with the recent uptick in temperatures and the stick's long shaft to centuries of previous climate stability.

The scientists confirmed that research from the late 1990s was "likely" to be true, said John "Mike" Wallace, an atmospheric sciences professor at the University of Washington and a panel member.

The report's conclusions "are very close to being right" and are supported by even more recent data, Prof Wallace said.

Overall, the panel agreed that the warming in the last few decades of the 20th century was unprecedented over the last 1000 years, though relatively warm conditions persisted around the year 1000, followed by a "Little Ice Age" from about 1500 to 1850.