Earth rapidly is approaching the point where the amount of warming locked in by human pollution exceeds the limits nations set last year at the international climate meeting in Paris, according to government-backed research unveiled Monday.
The planet faces “committed warming” by 2.7 degrees before 2100 if fossil fuels are burned at current rates for another 15 years, the scientists based in Colorado and Germany determined.
Even if people were able instantly to stop all further emissions of heat-trapping greenhouse gases, the temperatures by the end of the century would increase by 2.3 degrees, the scientists said in a peer-reviewed analysis published Monday in the journal Nature Climate Change.
“Our work shows that there isn’t much more room for emissions before making those targets unachievable,” said Robert Pincus, an atmospheric scientist with the Cooperative Institute for Research in Environmental Sciences, a partnership between the University of Colorado and the federal National Oceanic and Atmospheric Administration.
This “committed warming” analysis increasingly is critical because it tells policymakers around the world how long people have, given current rates of pollution, before temperatures reach various thresholds.
The research conducted by Pincus and atmospheric scientist Thorsten Mauritsen of Germany’s Max Planck Institute for Meteorology did not rely on computer model simulations, the basis of earlier climate change research. Instead, the scientists used measurements from the atmosphere and of temperatures to calculate the extent of future warming. They factored in the capacity of oceans to absorb carbon pollution. They incorporated detailed data on the planet’s energy imbalance in which carbon dioxide, methane and other heat-trapping gases build up in the atmosphere.
“Our estimates are based on things that have already happened, things we can observe, and they point to the part of future warming that is already committed to by past emissions,” Mauritsen said. “Future carbon dioxide emissions will then add extra warming on top of that commitment.”
The findings suggest political leaders who hashed out the Paris agreement last year have fallen behind in efforts to address global warming. During those United Nations-backed meetings, leaders of 195 countries, including the U.S., agreed to actions to contain temperature increases this century to less than 3.6 degrees above the average temperatures in 1850. Nations agreed to work at limiting warming to 3 degrees.
Temperatures since 1850 already have increased by about 1.5 degrees, the scientists said. They also noted that, historically, human emissions of greenhouse gases have increased every year. Even if pollution stayed steady until 2053, they calculated, there’s a 50 percent chance of surpassing the Paris agreement target of 3.6 degrees.
The U.S. Department of Energy, National Science Foundation and Max Planck Society funded the research before Americans elected President Donald Trump. Trump is trying to back the U.S. out of its commitments to help combat potentially ruinous global warming. White House officials in June initiated a process to withdraw from the Paris agreement. Trump has said the agreement imposes intolerable financial burdens. But other nations are mobilizing to try to reduce pollution and hold temperature increases to tolerable levels.
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