New research from Duke University has found that current climate models might be overestimating expected warming.
"Based on our analysis, a middle-of-the-road warming scenario is more likely, at least for now," Patrick Brown, a doctoral student at Duke University’s Nicholas School of the Environment, said in a statement. "But this could change."
Natural variability in surface temperatures, the study authors found, can affect warming rates from decade to decade, something the researchers called "climate wiggles."
Climate models, like those used by the International Panel on Climate Control, got the "big picture right," Brown said, but according to the new analysis at Duke, they underestimated the "climate wiggles" that can occur with natural variability.
"Our model shows these wiggles can be big enough that they could have accounted for a reasonable portion of the accelerated warming we experienced from 1975 to 2000, as well as the reduced rate in warming that occurred from 2002 to 2013," Brown explained.
"Statistically, it’s pretty unlikely that an 11-year hiatus in warming, like the one we saw at the start of this century, would occur if the underlying human-caused warming was progressing at a rate as fast as the most severe IPCC projections," Brown said. "Hiatus periods of 11 years or longer are more likely to occur under a middle-of-the-road scenario."
Brown explained that the IPCC's middle-of-the-road scenario "match[ed] up well" with their model that suggested there was a 70 percent likelihood a warming hiatus could last from 1993 and 2050.
The Duke researchers with San Jose State University and the U.S. Department of Agriculture created this new model based on reconstructed records of surface temperatures for the last 1,000 years.
"Our analysis clearly shows that we shouldn’t expect the observed rates of warming to be constant. They can and do change," co-author Wenhong Li said.
Last year, the IPCC released its fourth and final volume of its giant climate assessment, which concluded that emissions, mainly from the burning of fossil fuels needed to drop to zero by the end of this century for the world to have a chance of keeping the temperature rise below a level that many climate scientists consider dangerous.
Failure to do so, which could require deployment of technologies that suck greenhouse gases out of the atmosphere, could lock the world on a trajectory with "irreversible" impacts on people and the environment, the report said. Some impacts already being observed included rising sea levels, a warmer and more acidic ocean, melting glaciers and Arctic sea ice and more frequent and intense heat waves.
"Science has spoken. There is no ambiguity in their message. Leaders must act. Time is not on our side," U.N. Secretary-General Ban Ki-moon said at the report's launch in Copenhagen.
On Earth Day this week, President Barack Obama echoed similar thoughts.
"Climate change can no longer be denied," Obama said. "It can’t be edited out. It can’t be omitted from the conversation. And action can no longer be delayed. That’s why I’ve committed the United States the world in combatting this threat."
The federal agricultural officials announced voluntary programs and initiatives for farmers, ranchers and foresters to combat global warming.
Agriculture Secretary Tom Vilsack unveiled the plans at Michigan State University Thursday, where Obama signed the sweeping farm bill into law last year. The efforts, many of which have their roots in that law, aim to reduce net greenhouse gas emissions, boost carbon capture and storage and come with various enticements, including grants, low-interest loans and technical assistance.
Vilsack said that the agriculture industry accounts for about 9 percent of U.S. emissions, adding that compares favorably with the rest of the globe but can be improved.
"American farmers and ranchers are leaders when it comes to reducing carbon emissions and improving efficiency in their operations," he said in prepared remarks. "We can build on this success in a way that combats climate change and strengthens the American agriculture economy."
The Associated Press contributed to this report.
Front page image via Shutterstock.