Earth's Temperature Warmest in 400 Years

[Menydh]

Expert Panel Concludes Earth's Temperature Warmest in 400 Years

Environment News Service
June 22, 2006

The Earth is hotter today than it has been in four centuries and likely warmer than it has been in the past 1,000 years, according to a review of surface temperature research released Thursday by the U.S. National Academies of Science.

The 155 page report provides additional evidence that "human activities are responsible for much of the warming," the authors said.

The study, written by a panel of 12 climate experts, assesses the state of scientific efforts to reconstruct surface temperature records for the Earth over approximately the last 2,000 years.

Widespread reliable instrument records of global temperatures are available only for the last 150 years, leaving scientists to estimate past climatic conditions by analyzing proxy evidence from sources such as tree rings, corals, ocean and lake sediments, cave deposits, ice cores, boreholes, and glaciers.

Committee chair Gerald North said the panel’s review of instrument and proxy data affords "a high level of confidence that global mean surface temperature was higher during the last few decades of the 20th century than during any comparable period during the preceding four centuries."

"This statement is justified by the consistency of the evidence from a wide variety of geographically diverse proxies," said North, a geosciences professor at the University of Texas A&M.

The committee said average surface temperatures in the Northern Hemisphere rose about one degree Fahrenheit (0.6 degrees Celsius) during the 20th century.

The report was requested last year by House Science Committee Chairman Sherwood Boehlert, a New York Republican, in a bid to silence global warming skeptics critical of a surface temperature reconstruction widely known as the "hockey stick" study.

Published in 1998 by climate scientists Michael Mann, Raymond Bradley and Malcolm Hughes, the study suggested average surface temperatures in the Northern Hemisphere during the late 20th century were higher than at any time in the past 1,000 years.

The upward curve of a graph illustrating the research indicates that temperatures were relatively flat from A.D. 1000 to 1900 before sharply rising after 1900 – the chart resembles a hockey stick.

The graph appeared in the 2001 report by the United Nations Intergovernmental Panel on Climate Change and emerged as oft-cited evidence that human greenhouse gas emissions are driving an increase in global temperatures.

Some scientists questioned the statistical methods used by the researchers and the findings of the study. Climate skeptics have latched onto this criticism and repeatedly attacked the study as flawed in a bid to cast doubt on humanity’s contribution to climate change.

Last June, House Energy and Commerce Committee Chairman Joe Barton, a Texas Republican, attempted to launch a probe into the background of the authors – a move that drew sharp criticism from Boehlert and several scientific organizations worldwide.

The controversy prompted Congressman Bohlert to ask the National Academies, an independent organization chartered by Congress to advise the government on scientific matters, to review the study as well as other research on surface temperatures.

North said the panel largely endorsed the findings of the hockey stick study.

The conclusions of the study have "subsequently been supported by an array of evidence," including large-scale surface temperature reconstructions and pronounced changes in proxy indicators, North said.

Some of these changes, such as melting on icecaps and the retreat of glaciers around the world, "appear to be unprecedented during at least the last 2,000 years," North told reporters at a briefing in Washington, DC.

The panel said it had less confidence that warming was unprecedented over the last thousand years because of a lack of precisely dated proxy evidence for temperatures prior to 1600, in particular in the Southern Hemisphere.

"The picture is much murkier before 1600 and considerably murkier when you go further back in time," said committee member Kurt Cuffey, a geography professor at the University of California, Berkeley. "We start losing sources of information … and start relying more and more on data from fewer and fewer geographic locations."

The study by Mann and his colleagues also concluded that the 1990s were the warmest decade, and 1998 the warmest year in 1,000 years – the panel said larger uncertainties in temperature reconstructions for decades and individual years precluded it from outright support of those conclusions.

Questions about the statistical methods used by the authors of the hockey stick study should not cast doubt on its primary conclusions, said committee member Peter Bloomfield, a statistics professor at North Carolina State University.

"All of the statistical choices made were reasonable at the time," Bloomfield said. "I saw nothing that spoke to me of any manipulation … it was an honest attempt to construct a data analysis."

The panel said its review of other research gave it "very little confidence" in statements about average global surface temperatures prior to A.D. 900 because the proxy data for that time frame are sparse.

The panel stressed that global temperature records are only one piece of the global climate picture and not the primary evidence of climate change.

"Human activities are increasing the concentrations of certain greenhouse gases and these gases inevitably cause warming," Cuffey said. "That is not up for debate."

Boehlert praised the work of the committee and said it "shows the value of Congress handling scientific disputes by asking scientists to give us guidance."

Scientists need to do more work to develop a better sense of what global temperatures were prior to 1600, Boehlert said, and "Congress ought to let them go about that work without political interference."


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[Menydh]

Earth Hottest It's Been in 2,000 Years

Environmental News Network
June 23, 2006

The Earth is running a slight fever from greenhouse gases, after enjoying relatively stable temperatures for 2,000 years. The 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 National Science Foundation and universities.

The academy had been asked to report to 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 "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.

It had compared the sharp curve of the hockey blade to the recent uptick in temperatures -- a 1 degree rise in global average surface temperatures in the Northern Hemisphere during the 20th century -- and the stick's long shaft to centuries of previous climate stability.

That research is "likely" true and is supported by more recent data, said John "Mike" Wallace, an atmospheric sciences professor at the University of Washington and a panel member.

Rep. Sherwood Boehlert, R-N.Y., chairman of the House Science Committee, had asked the academy for the report last year after the House Energy and Commerce Committee chairman, Rep. Joe Barton, R-Texas, launched an investigation of the three climate scientists.

The Bush administration has maintained that the threat from global warming is not severe enough to warrant new pollution controls that the White House says would have cost 5 million Americans their jobs.

"This report shows the value of Congress handling scientific disputes by asking scientists to give us guidance," Boehlert said Thursday. "There is nothing in this report that should raise any doubts about the broad scientific consensus on global climate change."

The academy panel said it had less confidence in the evidence of temperatures before 1600.

But it considered the evidence reliable enough to conclude there were sharp spikes in carbon dioxide and methane, the two major "greenhouse" gases blamed for trapping heat in the atmosphere, beginning in the 20th century, after remaining fairly level for 12,000 years.

Between 1 A.D. and 1850, volcanic eruptions and solar fluctuations had the biggest effects on climate. But those temperature changes "were much less pronounced than the warming due to greenhouse gas" levels by pollution since the mid-19th century, the panel said.

The National Academy of Sciences is a private organization chartered by Congress to advise the government of scientific matters.


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[Savage]

And the water is rising...

[Savage]

Arctic people `will need to adapt` due to rapid climate change in the region

REYKJAVIK, Iceland -
The four million inhabitants of the Arctic will have to change their way of life if warming trends in the region continue apace, leaders have warned. A scientific assesment says the climate changes present serious challenges to the health and food security of some indigenous peoples, challenging the survival of some cultures. "We are asking first for action to slow climate change, but realise that we will be forced to make adapations," said Geir Tommy Pedersen, President of the Saami Council.


A four-year scientific assessment of climate change in the Arctichas been published, and says the area is warming at nearly twice the global average.
The Arctic Climate Impact Assessment (ACIA) will be used by rim nations and indigenous groups to inform policy.

Circumpolar representatives say local people will have to adapt to survive.

"We are asking first for action to slow climate change," said Geir Tommy Pedersen, President of the Saami Council.

"However, we realise that we will be forced to make some adaptations, as we are already seeing the effects of climate change in our communities. We need to be given the resources to deal with these challenges."

An information campaign highlighting the results of the assessment has already been started by the Arctic indigenous peoples.

"We need to tell our own people about what is in this report," said Rodion Sulyandziga, of the Russian Association of Indigenous Peoples of the North.

"They are already facing many challenges, but we must prepare them for this challenge also. More than this, we need to tell the rest of the world about the necessity of taking action on climate change, and taking it now."

The assessment was prepared by about 300 scientists for the Arctic Council, the intergovernmental forum for the eight countries which have territories in the region and six indigenous groups.

It is a review of all that is known about climate change currently in the region.

Its main findings are:

a.. Average winter temperatures have increased by as much as 3-4C (4-7F) in the past 50 years in Alaska, Western Canada, and Eastern Russia. Computer models project a rise of 4-7C (7-13F) over the next 100 years.
b.. Current recorded and observational data show Arcticsea ice is thinning fast. Computer models project at least 50% of summer sea ice to be gone by 2100, with some simulations even showing complete disappearance by the end of the century.
c.. Should the Arctic Ocean become ice-free in summer, it is likely that polar bears and some seal species would be driven toward extinction.
d.. This would also present huge difficulties for local people who hunt food on and around the ice.
e.. At the same time, reduced sea ice extent is likely to increase marine access to some of the region`s resources, including its oil and gas reserves.
f.. Agriculture will become easier in some areas as the permafrost retreats; warmer waters are likely to make some fisheries more productive.
g.. Warming over Greenlandwill lead to substantial melting of the Greenland Ice Sheet, contributing to global sea-level rise at increasing rates.
h.. Arctic climate changes present serious challenges to the health and food security of some indigenous peoples, challenging the survival of some cultures.
i.. Over the next 100 years, climate change is expected to accelerate, contributing to major physical, ecological, social, and economic changes, and the assessment has documented that many of these changes have already begun.
The assessment`s findings and projections are being presented in detail at a scientific symposium in Reykjavik, Iceland, from Tuesday.
Its authors say its projections are based on a moderate estimate of future emissions of carbon dioxide and other greenhouse gases, and incorporate results from five major global climate models used by the Intergovernmental Panel on Climate Change.


Further warming will expand crop production in the region
"The impacts of global warming are affecting people now in the Arctic," says Robert Corell, chair of the ACIA.

"The Arcticis experiencing some of the most rapid and severe climate change on earth. The impacts of climate change on the region and the globe are projected to increase substantially in the years to come."

Once the researchers have discussed the report, political representatives from the Arctic nations - Canada, Denmark, Finland, Iceland, Norway, Russia, Sweden, and the US - and the indigenous groups will also gather to mull its findings.

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