Studies Point to Human Role in Global Warming

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Studies Point to Human Role in Global Warming

By USHA LEE MCFARLING, LA Times Science Writer

Two new studies that focus on rising ocean temperatures provide some of the strongest evidence yet that humans are to blame for global warming. The two independent studies, being published today in the journal Science, each used computer models and a new set of global temperature readings from across the world's seas to test if natural climate swings could be responsible for the 0.11 degree warming seen in the upper two miles of the oceans since 1955. Though the increase sounds small, spread over the world's oceans it is a huge amount. It is enough heat, scientists estimated, to satisfy California's energy demands for the next 200,000 years. The studies found that computer simulations of the Earth's climate could not produce the extensive warming seen today without factoring in the presence of man-made pollutants such as greenhouse gases and sulfate aerosol, which act to warm the Earth by trapping heat near the surface. When the pollutants were added to models, the temperature readings generated closely simulated the actual temperature records. "The curves were so good, the data looked faked," said Tim Barnett, an oceanographer and climatologist at the Scripps Institution of Oceanography in La Jolla, and lead author of one of the studies. "You just don't get it this good the first time around. But there it was." The new findings come as the Bush administration is facing heavy criticism from environmentalists and some foreign governments for repudiating the Kyoto Protocol, a global accord that attempts to reduce the emission of greenhouse gases. The new studies mirror others that provide hints of global warming, including those showing a 1.08 degree warming in air temperatures at the Earth's surface in the last century, a thinning of polar sea ice and a retreat of the world's high-latitude glaciers. The oceans are the biggest factor in the planet's climate regulation. They cover 72% of the planet's surface and have a huge capacity to absorb and store heat for hundreds of thousands of years. They are not easily warmed. "The oceans are the memory of the climate system," said Sydney Levitus, the lead author of one of the studies and a researcher at the National Oceanographic and Atmospheric Administration. The studies also suggest that even if the emission of greenhouse gases were stopped immediately, pollutants already in the atmosphere would double the warming seen in the oceans within two to four decades. "We're at the very bottom of a sharply accelerating curve," Barnett said. The issue of climate change has been a topic of intense scientific and political debate for the past decade. Today, there is agreement that the Earth's air and oceans are warming, but disagreement over whether that warming is the result of natural cycles, such as those that regulate the planet's periodic ice ages, or caused by industrial pollutants from automobiles and smokestacks. Last year a blue-ribbon panel at the National Research Council, puzzling over discrepancies between temperatures taken near the surface of the Earth and those high in its atmosphere, concluded that global warming was indeed "real." But the panel did not reach a conclusion on the cause.

'Circumstantial Evidence' Cited This week, several leading climate theorists said the new studies--on the heels of years of increasing global air temperatures--leaves little question over what is to blame. "It's another piece of evidence we now have that humans are at fault for this increase in global heat content," said Jeff Kiehl, a senior scientist in the climate modeling section of the National Center for Atmospheric Research in Boulder, Colo., who was not involved in the studies. "It's going to be harder for the critics to say we aren't changing the climate." Tom Crowley, a veteran climate researcher at Texas A&M, added, "People get convicted all the time on the weight of circumstantial evidence. To me, it's a massive weight of evidence indicating this is not natural variation or anything like it." The computer climate models did include natural variability, but the effect of natural cycles on climate was swamped by the addition of man-made pollutants, Barnett said. Although how the process works is not fully understood, long-term changes in ocean temperature could vastly change weather on land by altering ocean currents and the formation and progression of storms, just as El Niņo patterns do. Up to now, few climate models had used reliable global ocean temperatures. This was in large part because good temperature data on the world's oceans were not readily available. Though millions of readings had been taken from ships since the 1940s, the data were not compiled. They were spread around the globe, much of them hidden in military archives on dusty 3x5 index cards. Levitus and his group at the United Nations-sponsored Global Oceanographic Data Archeology and Rescue Project have spent a decade collecting and compiling about 2.3 million ocean temperature readings. In a study published in Science last year, he and colleagues used the data to report for the first time the extent of warming: 0.11 degrees in the world's oceans. A year ago, Levitus was reluctant to conclude that greenhouse gases were the main cause of the ocean warming. The new studies have convinced him. "I think it's the strongest evidence to date," he said. "There's little question we're seeing the effect." Climate modelers are always hungry for new data on which to test their models, which are theoretical and only as good as the assumptions about climate that go into making them. When the new ocean temperatures became available, scientists scrambled to test their computer models against the new data. Today's reports are the first of those efforts to use the models and new data to assess the factors causing excess warming. As the models improve, scientists hope to use them to make more reliable predictions of how the climate will change in the future. "This gives one a sense of reliability," Kiehl said of the new results. "It's certainly good news for the modeling community." "I'm a fan of [these studies]," said George Boer, a senior research scientist at the Canadian Centre for Climate Modeling and Analysis. Boer said he was particularly impressed that the models had not just predicted broad warming over the entire ocean, but performed the more difficult task of discerning the temperature variations in different ocean basins. The North Atlantic, for instance, contained warmer waters at deeper levels in the models and in actual temperature readings because of extensive mixing of waters there. Computer climate models have come under fire from critics for being "tuned" so they are in agreement with observed temperature readings and for being unable to predict regional phenomena like El Niņo events. That criticism does not affect these studies because the models used were built before the ocean temperature readings became available. Still, there are other criticisms of the new studies. Kevin Trenberth, who heads the climate analysis section of the National Center for Atmospheric Research and has written on the "use and abuse" of climate models, said he was concerned that the results could be inaccurate because the ocean temperature readings are sparse in some parts of the globe, particularly the southern polar oceans. He added that the two models use different variables. The model used by Barnett, known as the Parallel Climate Model, is not fully accurate, Trenberth said, because it does not include changes in energy from the sun and the impact of volcanoes, both of which have a cooling effect. The model used by Levitus, known as the Geophysical Fluid Dynamics Laboratory model, may be a bit too warm. Though Trenberth believes the results do suggest that global warming is detectable and can be attributed to a rise in greenhouse gases, he said modelers still have work to do. "Neither result is quite as good as claimed and neither model can be acclaimed as the model that can be used for definitive predictions of the future," he said. Throughout the debate over climate change, other critics have been even more skeptical of studies based on computer modeling, which they say does not fully represent the real climate system. Trenberth agreed with the predictions of both models that ocean warming would continue. Nonetheless, it is difficult for climate scientists to accurately predict the long-term consequences of global ocean warming and almost impossible to say how various regions, such as Southern California, could be specifically affected. Local changes in fish populations and the migrations of sea lions in the region are not necessarily due to global climate change. These shifts can be attributed to smaller-scale climate events, like El Niņos or a decades-long shift in ocean temperatures off the coast known as the Pacific Decadal Oscillation. The causes of these natural climate cycles are still not fully understood, and add to the difficult business of prediction. "To me the question of whether global warming is happening is receding as the central question," said Crowley at Texas A&M. "In my view, it's already here--and I didn't believe that two years ago. Now the question is: How will it affect us?"



-- Repubs are Killers (GOP@murders.com), April 13, 2001

Answers

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All greenies now turn in your car keys!

Alternatively, the left-wing wackos could hold their breath for 12 hours out of the day to reduce the carbon dioxide levels!!!

-- libs are idiots (moreinterpretation@ugly.com), April 13, 2001.


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