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Cutting greenhouse gases now would save world from worst global warming scenarios

If nations worked together to produce large cuts in greenhouse gases, the world would be saved from global warming’s worst-case-scenarios, according to a new study from the National Center for Atmospheric Research (NCAR).

The study found that, although temperatures are set to rise this century, cutting greenhouse gases by 70 percent the globe could avoid the most dangerous aspects of climate change, including a drastic rise in sea level, melting of the Arctic sea ice, and large-scale changes in precipitation. In addition such cuts would eventually allow the climate to stabilize by the end of the century rather than a continuous rise in temperatures.

Lamplugh glacier in Alaska. Photo by: Rhett A. Butler.

“This research indicates that we can no longer avoid significant warming during this century,”
says Warren Washington, a scientist with NCAR and lead author of the study. “But, if the world were to implement this level of emission cuts, we could stabilize the threat of climate change and avoid catastrophe.”

Using supercomputer studies with the NCAR-based Community Climate System Model, the researchers assumed that carbon dioxide levels could be maintained at 450 parts per million. The U.S. Climate Change Science Program has stated that 450 ppm is a reasonable target if nations quickly tackle climate change.

Holding carbon dioxide levels at 450 ppm would lead to global temperatures increasing another 0.6. degree Celsius (about 1 degree Fahrenheit); currently global temperatures have already risen 1 degree Celsius (nearly 1.8 degrees Fahrenheit). However, if business continues as usual, carbon dioxide levels are estimated to reach 750 ppm by the end of the century, leading to what many climatologists consider a catastrophic rise of 2.2 degrees Celsius (4 degrees Fahrenheit)—with no end in sight.

The models found that checking carbon dioxide levels at 450 ppm would keep sea levels from rising above 14 centimeters (5.5 inches) due to the thermal expansion of a warming ocean, though the model didn’t factor in the amount of sea level rise that may occur due to melting glaciers. If carbon dioxide levels increase unchecked, sea level is expected to go up 22 centimeters (8.7 inches)—again not taking into account glacier melt.

Furthermore, arctic ice in the summer would continue to melt about 25 percent, but stabilize by the end of the century if emissions are checked. Whereas, if not, the ice will shrink by three-quarters and continue disappearing. Under such a scenario some studies have predicted a complete loss of Arctic ice. In addition, cuts now will allow the Arctic ecosystem to survive largely intact, preserving birds, mammals, and fish, including saving an important fisheries industry.

Changes in precipitation, including drought in America’s Southwest and increased precipitation in Canada, would be halved if emissions are cut as opposed to business as usual scenarios.

“Our goal is to provide policymakers with appropriate research so they can make informed decisions,” Washington says. “This study provides some hope that we can avoid the worst impacts of climate change—if society can cut emissions substantially over the next several decades and continue major cuts through the century.”

Nations will be meeting in Copenhagen in December of this year to decide on a new global framework for combating climate change.

The study will be published in Geophysical Reseach Letters on April 21st.

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