The threat of global warming can be significantly lessened if nations cut emissions of heat-trapping greenhouse gases by 70 percent this century, according to a new study. This would help reduce the most dangerous aspects of climate change including massive losses of Arctic sea ice and permafrost and significant sea level rise, although global temperatures will still rise.
The study, led by scientists at the National Center for Atmospheric Research (NCAR), will be published in Geophysical Research Letters. It was funded by the Department of Energy and the National Science Foundation, NCAR’s sponsor.
“This research indicates that we can no longer avoid significant warming during this century,” said NCAR scientist Warren Washington, the lead author for the study. However, a catastrophe can be avoided if the world implements the recommended emission cuts of 70 percent, he said.
The Obama Administration’s proposed cap-and-trade program would bring U.S. emissions 20 percent below 2005 levels by 2020 and 83 percent by 2050. But the program is still under debate. The Obama Administration has sent strong signals that it would take a leading role in setting global policy.
Most recently, the White House Office of Management and Budget approved the U.S. Environmental Protection Agency’s finding that greenhouse gas emissions threaten the public. This means the EPA may soon announce an “endangerment finding” that will enable the agency to write regulations under the Clean Air Act that limit emissions.
Earlier this year, scientists in the United Kingdom said that a government plan to reduce carbon emissions by one-third by 2020 is not enough to prevent changes to the climate. Scientists from the Tyndall Centre of Climate Change said in order to prevent temperatures from rising above a level that causes extreme weather events, droughts and food shortage, emissions cuts will have to run much deeper. The UK’s goal is to cut carbon emissions 80 percent by 2050.
The European Union agreed in December 2008 to cut greenhouse emissions by 20 percent and to ensure that 20 percent of its energy needs come from renewable sources by 2020. They could increase cuts to 30 percent if nations such as the United States, Russia and China followed suit.
According to the NCAR study, average global temperatures have warmed by close to 1 degree Celsius (almost 1.8 degrees Fahrenheit) since the pre-industrial era, primarily due to human-produced emissions of greenhouse gases. This heat-trapping gas has increased from a pre-industrial level of about 284 parts per million (ppm) in the atmosphere to more than 380 ppm today. An additional warming of about 1 degree C may be the threshold for dangerous climate change, according to the study.
Key finding: If carbon dioxide were held to 450 ppm, global temperatures would increase by 0.6 degrees C (about 1 degree F) above current readings by the end of the century, however, if emissions continue on their present course temperatures would rise by almost four times that amount, to 2.2 degrees C (4 degrees F) above current readings.