Scientists from several institutions, including the U.S. Geological Survey and the University of Washington have found that if humans significantly reduce emissions of greenhouse in the next decade or two, enough ice in the Arctic is probably remains intact during the late summer and early fall bear survive.
"What we have planned in 2007 was based solely on the scenario of greenhouse gases business quo," said Steven Amstrup, a researcher Emeritus with the U.S. Geological Survey and the principal investigator with the Montana conservation organization international polar bears. "This is a pretty disastrous perspective, but he did not consider mitigation of greenhouse gases.
That study provided that only about one-third of 22,000 bears the planet could be left by medium if the dramatic decline in the Arctic ice continues and that finally they may disappear completely. The work resulted in 2008 polar bears as a threatened species listing.
New research, published in the Dec. 16 in nature, is based in part on the model proposed by Cecilia Bitz, a UW Associate Professor of atmospheric sciences. He said, there is no 'tipping point' which would result in an irreversible loss of the summer sea ice when global warming greenhouse gas-based increased above a certain threshold.
"Our research has a very promising, hope, but it is also an incentive to mitigate the greenhouse effect" Bitz said.
Amstrup is the main author of the paper in nature. Addition Bitz, co-authors are Eric DeWeaver from the National Science Foundation, David Douglas and George Durner USGS Alaska Science Center, Bruce Marcot service forest United States in Oregon and David Bailey of the National Center for Atmospheric Research in Colorado.
Because scientists were specifically looking to see if there is a tipping point that seasonal ice in the Arctic could not recover, they used a systemic circulation with a component of particularly sensitive to rising temperatures, with the main parts of it designed by Bitz sea ice model.
"We did not necessarily need to compare with other models, since we have uses a property that is extremely sensitive in the Arctic, which allowed us to make a more conservative statement on the potential to slow the loss of sea ice," she says.
Previous work by Bitz and others have shown that unchecked temperature increases, accompanied by natural environmental volatility, could result in the loss of large areas of ice in the Arctic in less than a decade. It also showed that greenhouse gas emissions business quo that ice does not recover after such rapid loss of ice continues and it has largely disappeared completely in the following decades.
However, the new nature study shows that if greenhouse gas emissions have been reduced considerably in the near future, rapid loss of ice would be followed by substantial remaining ice from this century, as well as a partial recovery of ice disappeared during the rapid loss of ice retention.
Polar bears depend on ice for access to the seal ringed and bearded, their primary food source. During the seasons when they cannot reach the sea ice, especially bears go without food and can lose 2 pounds per day. Periods where they do not have access to ice increased and should continue increases with the current level of greenhouse gas emissions.
In this study, the prospects of potential generated by the model of general circulation, as well as several features in the history of the life of polar bears, sea ice were placed in a model system, which can, for example, consider the relationship between polar bears and their environment. These results indicated that retention increase of greenhouse gas mitigation sea ice habitat can bear survive in many of this century and in several regions of the Arctic, as would happen with any mitigation measures.
Amstrup divided the Arctic in four distinct ecoregions depending on the nature of ice generally found there and the study of 2007 showed a very high probability that polar bears would become missing in two of these regions being given current trends in emissions of greenhouse gases.
"There is still a fairly high probability in each of these regions that polar bears could disappear", said Amstrup. "But with measures to mitigate and aggressive management of hunting and other direct interactions of bears and humans, the probability of extinction is now lower than the probability that polar bear numbers will be simply reduced."
"With mitigation measures, the conditions for the bears could even improve in the other two ecoregions." The advantage of mitigation for bears is substantial. »
Senior research from USGS, with additional funding service forest, the u.s. Department of energy and the National Science Foundation.
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For more information, please contact Amstrup at 406-581-6183 or samstrup@pbears.org, or 206-543-1339 or bitz@atmos.washington.edu Bitz.
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