Last week more than 150 nations signed the Paris Agreement, pledging to hold the increase in the global average temperature to well below 2 degrees Celsius above pre-industrial levels and to pursue efforts to limit the temperature increase to 1.5 degrees Celsius. Now, the first comprehensive analysis of the impacts of that half centigrade difference has been published in the journal Earth System Dynamics. The scientists found the additional 0.5 degrees Celsius would lead to longer heatwaves--"the difference between events at the upper limit of present-day natural variability and a new climate regime"--as well as more severe droughts and, in the tropics, decreased crop yield and the potential demise of all coral reefs. The extra 0.5 degrees Celsius could also mean that global sea levels rise 10 centimeters more by 2100.
"We found significant differences for all the impacts we considered," says the study's lead author Carl Schleussner, a scientific advisor at Climate Analytics in Germany.
The researchers analyzed climate models used in the Intergovernmental Panel on Climate Change Fifth Assessment Report, which focused on the projected regional impacts of 1.5 degrees Celsius and 2 degrees Celsius of warming, and considered 11 indicators, including extreme weather events, water availability, crop yields, coral reef degradation and sea-level rise.
They found that projected climate impacts at a 2 degrees Celsius increase are significantly more severe than at a 1.5 degrees Celsius increase in some regions. In the Mediterranean, for example, fresh-water availability by 2100 would be some 10 percent lower in a 1.5 degrees Celsius world and 17 percent lower in a 2 degrees Celsius world. In Central America and West Africa, the half-degree difference could reduce maize and wheat yields by twice as much. Tropical regions would bear the brunt of the impacts of an additional half degree of warming, experiencing heat waves at about twice the global rate. Those events could last up to three months at 2 degrees Celsius, compared with two months at 1.5 degrees Celsius, the researchers say.
Tropical coral reefs are particularly sensitive to the half degree increase. By 2100, some reefs might adapt to 1.5 degrees Celsius of warming, but the larger increase would put nearly all of them at risk of severe degradation from coral bleaching.
EPA Moves Forward with Clean Energy Incentives Program
The U.S. Environmental Protection Agency (EPA) has sent a proposal on the Clean Energy Incentive Program (CEIP), an optional program included in the Clean Power Plan that rewards states for early investment in certain renewable energy or energy efficiency projects in 2020 and 2021, to the Office of Management and Budget for review. The move is the final step before the CEIP can be formally proposed to the public (subscription).
The EPA released details on the draft CEIP as part of the final Clean Power Plan--the Obama administration's rule to limit greenhouse gas emissions from the existing fleet of fossil fuel-fired power plants--in August. But, earlier this year, the Supreme Court issued a stay of the Clean Power Plan.
"Many states and tribes have indicated that they plan to move forward voluntarily to work to cut carbon pollution from power plants and have asked the agency to continue providing support and developing tools that may support those efforts, including the CEIP," the EPA said. "Sending this proposal to OMB for review is a routine step and it is consistent with the Supreme Court stay of the Clean Power Plan."
Pleasant Weather Affecting Americans' View of Climate Change
A new study in the journal Nature finds that 80 percent of Americans live in counties where the weather is more pleasant than four decades ago. This mild temperature trend, the study says, is increasingly preferred, lessening many Americans' concern about climate change.
"Rising temperatures are ominous symptoms of global climate change, but Americans are experiencing them at times of the year when warmer days are welcomed," said study co-author Patrick J. Egan, an associate professor at New York University's Wilf Family Department of Politics. He adds that "whereas weather patterns in recent decades have served as a poor source of motivation for Americans to demand a policy response to climate change, public concern may rise once people's everyday experiences of climate change effects start to become less pleasant."
Conducted by New York and Duke universities, the study examined each county in every U.S. state from 1974 to 2013--assessing the mildness of winters, rainfall averages, and humidity and heat intensity during summer months. It found that 99 percent of Americans live in places where the average January temperature increased.
"Here in the U.S., when we're experiencing ice storms, the idea of a 1.5 or 2 degree rise might sound like good news," said Megan Mullin, associate professor of environmental politics at Duke University. As a result, she said, scientists need to reconsider their messages.
The Climate Post offers a rundown of the week in climate and energy news. It is produced each Thursday by Duke University's Nicholas Institute for Environmental Policy Solutions.