Top climate scientists blame mankind more clearly for global warming

Top climate scientists blame mankind more clearly for global warming

PanARMENIAN.Net - Top climate scientists blamed mankind more clearly than ever as the main cause of global warming in a report on Friday, Sept 27, meant to guide governments in dealing with rising temperatures, delegates said, according to Reuters.

"It's been accepted," Jonathan Lynn, spokesman for the Intergovernmental Panel on Climate Change, told reporters.

Delegates said the report raised the probability that most global warming was manmade to 95 percent, from 90 percent in its previous report in 2007. The report also says that a recent slowdown in warming is unlikely to last.

The report is a synthesis of climate research written by more than 800 scientists. It is expected to say a human influence on the global climate is "extremely likely," language that corresponds to odds of 95 percent. That's up from the "very likely" language used in the 2007 assessment, which corresponds to 90 percent odds, NBC News says.

This is the fifth assessment from the group, issued about once every five years. The degree of confidence that human activity is the main driver of the changing climate has risen with each report.

"Another five years of observation and further research just strengthens the conclusion" that human activity is causing the climate to change, John Reilly, the co-director of the MIT Joint Program on the Science and Policy of Global Change in Cambridge, Mass., said. None of this, he added, will come as a surprise.

Nevertheless, the report is coming out in a different climate context than six years ago, noted Alden Meyer, director of strategy and policy for the Union of Concerned Scientists in Washington, D.C. In the U.S., he noted, more people are linking climate change to extreme weather events such as last year's Hurricane Sandy and the recent flooding in Boulder, Colo., which puts the issue "on a more visceral level," he told NBC News.

Other anticipated highlights from the report include a projection that sea levels could rise nearly three feet by the end of the century if greenhouse gas emissions remain unchecked, which would pose significant adaptation challenges for some of the world's major cities, including New York, New Orleans, Miami, London and Shanghai.

That's an aggressive upward revision of the 2007 assessment, which put the sea level rise between 7 and 23 inches by the end of the century. Several scientists criticized that previous projection as too conservative given the pace of melting in Greenland and other parts of the globe.

Another widely anticipated change to the report reflects increased uncertainty on how much the Earth's surface will warm if concentrations of carbon dioxide in the atmosphere double. Five years ago, the climate panel put the best guess range between 3.2 and 7.1 degrees Fahrenheit. The leaked draft suggested that the final figures this time around could represent a much wider range: a lower possible low, a higher possible high.

This possible downward revision in the rise of Earth's surface temperature, along with what's termed a "hiatus" in surface warming since the unusually strong El Nino year of 1998, have been pounced upon as reason to doubt the alarm over global climate change. The climate panel is expected to dismiss these claims, explaining the slow-down in surface warming as a blip in the long-term warming trend.

The most compelling explanation for the so-called hiatus, in fact, is that the oceans have been warming at a faster clip over the past 15 years, according to MIT's Reilly. "Greenhouse gases are still trapping heat but instead of staying in the atmosphere" — where it would be measured in a rise in surface temperature — "it has been mixed into the ocean," he explained.

"The hiatus, if anything, may just fool us because while the ocean is taking up more heat this past decade sometime in the future it may take up relatively less heat, and then we'll see the atmosphere warming just that much more," Reilly said.

Though there has been speculation that the temperature adjustments and discussion of hiatus show that the panel is getting more conservative in its approach, in order to convince a skeptical world of the issue, Meyer dismisses that as nonsense. "It has always been conservative," he said, explaining that the summary document most people will read is subjected to a line-by-line approval by everyone in the room.

This time around, the panel certainly has given the process more rigor, however, in order to avoid errors such as a high-profile gaffe in the 2007 report suggesting that the Himalayan glaciers would melt by the year 2035. "But I think to say that before this time around they were wild-eyed and radical would be totally wrong. They've always been cautious and conservative," Meyer said.

The report — as well as subsequent assessments on expected climate impacts and how to manage climate change that are slated for release next year — may help inform ongoing negotiations for an agreement to combat global climate change to be adopted at a summit in Paris in late 2015, Meyer noted.

Global warming is the rise in the average temperature of Earth's atmosphere and oceans since the late 19th century and its projected continuation. Since the early 20th century, Earth's mean surface temperature has increased by about0.8 °C (1.4 °F), with about two-thirds of the increase occurring since 1980.

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