The worst of the global-warming effects can still be reversed, if proper steps are taken fairly quickly to reduce greenhouse gas emissions, according to an analysis by the National Center for Atmospheric Research.
A team led by Warren Washington, a senior scientist at NCAR's Climate and Global Dynamics Division, ran various climate-predicting scenarios with a Community Climate System Model run through a global supercomputer. Most notable is the simulation of what would happen in a world continuing on a path of unchecked human-made emissions of greenhouse gases versus one in which emissions are cut globally by 70 percent.
The results by the year 2100 are a difference between the global temperature rising an average of 1 degree versus 4 degrees Fahrenheit; the sea level rising 5.5 inches versus 8.7 inches; and Arctic ice stabilizing versus having its thin seasonal layer melt away completely.
"The threat of global warming can still be greatly diminished, if nations cut emissions of heat-trapping greenhouse gases by 70 percent this century, according to a new analysis," according to an NCAR statement. "While global temperatures would rise, the most dangerous potential aspects of climate change, including massive losses of Arctic sea ice and permafrost and significant sea level rise, could be partially avoided."
The levels of greenhouse gas in the atmosphere have already risen from 284 parts per million (ppm) before the industrial revolution to more than 380 ppm this year, according to NCAR.
The computer simulation showed that if greenhouse gas emissions can be held at 450ppm--the target labeled as reasonably achievable by the U.S. Climate Change Science Program, if the world reduces emissions by 70 percent--the global temperature would rise by about .6 degrees Celsius (about 1 degree Fahrenheit) by the year 2100. If human-made emissions are left unchecked, the model predicted that greenhouse gas levels would rise to 750ppm by 2100, causing a global temperature increase of 2.2 Celsius (about 4 degrees Fahrenheit).
In the unchecked world, the model found that increasingly warm water temperatures would lead to a greater rise in sea levels, which, in turn, would lead to a negative impact on fisheries, sea bird populations, and mammals living in areas such as the northern Bering Sea. The simulation showed Asia, Australia, Europe, and North America as the areas that would see the greatest increase in average temperature.
It also simulated the U.S. climate specifically. In the world with 70 percent reduced emissions, for example, the U.S. Southwest would see double the amount of annual precipitation by the year 2100.
NCAR, which is funded by the Department of Energy and the National Science Foundation, will publish a full report on its findings next week in the journal Geophysical Research Letters. NCAR's report comes just as the U.S. Congress is about to debate the proposed American Clean Energy and Security Act of 2009, an energy and climate bill that would (among other things) impose a cap-and-trade system for carbon emissions permits and mandate increased use of renewable-energy resources for utilities.
"Our goal is to provide policymakers with appropriate research so they can make informed decisions," NCAR's Washington said in a statement. "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."