Earth hottest now in last 400 years
(AP)
Updated: 2006-06-23 09:39
The Earth is running a slight fever from greenhouse gases, after enjoying
relatively stable temperatures for 2,000 years. The US National Academy of
Sciences, after reconstructing global average surface temperatures for the past
two millennia, said Thursday the data are "additional supporting evidence ...
that human activities are responsible for much of the recent warming."
Other new research showed that global warming produced about half of the
extra hurricane-fueled warmth in the North Atlantic in 2005, and natural cycles
were a minor factor, according to Kevin Trenberth and Dennis Shea of the
National Center for Atmospheric Research, a research lab sponsored by the US
National Science Foundation and universities.
![This satellite image released by NASA shows the minimum concentration of Arctic sea ice in 2005. On September 21, 2005, the sea ice extent dropped to 2.05 million square miles. The National Academy of Sciences said the Earth is running a slight fever from greenhouse gases. [AP/file]](xin_080603230947056297093.jpg)
This satellite image released by
NASA shows the minimum concentration of Arctic sea ice in 2005. On
September 21, 2005, the sea ice extent dropped to 2.05 million square
miles. The National Academy of Sciences said the Earth is running a slight
fever from greenhouse gases. [AP/file] |
The academy had been asked to report to US Congress on how researchers drew
conclusions about the Earth's climate going back thousands of years, before data
was available from modern scientific instruments. The academy convened a panel
of 12 climate experts, chaired by Gerald North, a geosciences professor at Texas
A&M University, to look at the "proxy" evidence before then, such as tree
rings, corals, marine and lake sediments, ice cores, boreholes and glaciers.
Combining that information gave the panel "a high level of confidence that
the last few decades of the 20th century were warmer than any comparable period
in the last 400 years," the panel wrote. It said the "recent warmth is
unprecedented for at least the last 400 years and potentially the last several
millennia," though it was relatively warm around the year 1000 followed by a
"Little Ice Age" from about 1500 to 1850.
Their conclusions were meant to address, and they lent credibility to, a
well-known graphic among climate researchers ¡ª a "hockey-stick" chart that
climate scientists Michael Mann, Raymond Bradley and Malcolm Hughes created in
the late 1990s to show the Northern Hemisphere was the warmest it has been in
2,000 years.
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