New report presents strongest evidence yet of human link to global warming, Duke expert saysFebruary 02, 2007DURHAM, N.C. — Evidence presented in the first phase of the Intergovernmental Panel on Climate Change's 4th Assessment Report, released today in Paris, paints the clearest picture yet that human-derived greenhouse gases are playing a significant role in observed global warming, says a Duke University scientist who co-authored one of the report's main chapters. "We are now seeing, not merely predicting, effects of greenhouse warming on a scale and in ways that were not observable before," said Gabriele Hegerl, associate research professor at Duke's Nicholas School of the Environment and Earth Sciences, who also co-authored a summary of the report for policymakers. "When you look at the changes in temperature, circulation, ocean warming, arctic sea ice reduction and glacial retreat together, it paints a much clearer picture that external drivers, particularly greenhouse gases, are playing a key role," she said. "As a result, we can be much more confident that 20th century climate changes were not just linked to natural variability." Hegerl was a coordinating lead author of the IPCC report's chapter on "Understanding and Attributing Climate Change." Francis Zwiers of the Canadian Centre of Climate Modeling and Analysis was also a coordinating lead author of the chapter. IPCC assessment reports are issued every five to six years to provide a comprehensive review of the current state of knowledge on climate change. The 2007 report will be issued in four phases during the year. The first phase, released today in Paris, focuses on the physical evidence of global change. THE IPCC operates under the auspices of the United Nations Environmental Programme and the World Meteorological Organization and draws on the expertise of about 2,500 scientists worldwide. Hegerl and her chapter's team of co-authors were charged with reviewing the evidence of changes observed so far and assessing which changes can be attributed to greenhouse gas increases and other external influences on climate. In the chapter, they look at the actual measurements of climate and weather changes and compare them with predictions made for the 20th century by sophisticated computer models. "We've studied improved observations from land, sea and space, as well as better temperature reconstructions covering the last 1,000 years," Hegerl said. By comparing observation against modeled projections, she says scientists are gaining a better sense of which external climate influences have been important. "Understanding the observations is really what this all is about. For instance, looking at the patterns of change in 20th-century temperatures, we can now distinguish between changes caused by greenhouse gases, man-made aerosols, variability in solar radiation and major volcanic eruptions," Hegerl said. "We can also better understand which changes in the more distant past were caused by external influences of climate, such as volcanic eruptions, and how strong the variability of the climate system is. "One of the most fascinating things is that we see that changes have already happened or are happening now in more climate variables than just temperature," Hegerl added. "For instance, there have been observed changes in ocean temperatures, global rainfall and in circulation of the atmosphere. We now are beginning to understand that these changes occur at least partly in response to anthropogenic influences on climate. This allows us to better evaluate model simulations, which do simulate aspects of these changes, although not as successfully as they simulate changes in temperature," she said. "There are still things, like ice-sheet melting, that the models don't do very well yet. But overall, the predictions and uncertainty ranges of future climate change are becoming much better understood and much more credible," Hegerl said. The IPCC report "hits the nail squarely on the head," she said. "It gives a very balanced view of the evidence for climate change, predictions of future change, and the remaining uncertainties, and it draws input from very large number of scientists worldwide." The report went through several phases of review, giving individual experts and governments opportunity to comment. "There were many steps that ensure that the report is both scientifically rigorous and balanced," Hegerl said. "The information in the report will be very important to develop effective policies to address global climate change and to prepare for the change that is coming our way,\\\ Duke University |
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| Related Global Warming Current Events and Global Warming News Articles Is global warming unstoppable? In a provocative new study, a University of Utah scientist argues that rising carbon dioxide emissions - the major cause of global warming - cannot be stabilized unless the world's economy collapses or society builds the equivalent of one new nuclear power plant each day. Oceans' uptake of manmade carbon may be slowing The oceans play a key role in regulating climate, absorbing more than a quarter of the carbon dioxide that humans put into the air. Research challenges for understanding landscape changes identified Nine research challenges and four research initiatives that are poised to advance the study of how Earth's landscapes change were unveiled today in a new report by the National Research Council. Study: Sea stars bulk up to beat the heat A new study finds that a species of sea star stays cool using a strategy never before seen in the animal kingdom. The sea stars soak up cold sea water into their bodies during high tide as buffer against potentially damaging temperatures brought about by direct sunlight at low tide. Drug industry, nonprofits join forces to fight world's neglected diseases Drug companies and nonprofit organizations are joining forces to develop new drugs and vaccines to target so-called "neglected" diseases that claim millions of lives in the developing world each year. Health care accounts for 8 percent of US carbon footprint The American health care sector accounts for nearly a tenth of the country's carbon dioxide emissions, according to a first-of-its-kind calculation of health care's carbon footprint. Cave Study Links Climate Change to California Droughts California experienced centuries-long droughts in the past 20,000 years that coincided with the thawing of ice caps in the Arctic. Reducing greenhouse gases may not be enough to slow climate change Because land use changes are responsible for 50 percent of warming in the US, policymakers need to address the influence of global deforestation and urbanization on climate change, in addition to greenhouse gas emissions. Past climate of the northern Antarctic Peninsular informs global warming debate The seriousness of current global warming is underlined by a reconstruction of climate at Maxwell Bay in the South Shetland Islands of the Antarctic Peninsula over approximately the last 14,000 years, which appears to show that the current warming and widespread loss of glacial ice are unprecedented. Climate variability impacts the deep sea Deep-sea ecosystems occupying 60% of the Earth's surface could be vulnerable to the effects of global warming warn scientists writing in the Proceedings of the National Academy of Sciences. More Global Warming Current Events and Global Warming News Articles |
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