(Bloomberg) -- Meeting the Paris accord’s temperature targets will take massive cuts to greenhouse gas emissions within 15 years, but won’t require them to be reduced to zero, according to a new study published Monday in the journal Nature Climate Change.
If those targets—between 1.5 to 2 degrees Celsius (2.7 to 3.6 Fahrenheit)—are overshot, the consequences would likely require both drastic cuts to emissions and geoengineering efforts to remove carbon from the atmosphere, according to the paper by Katsumasa Tanaka at the National Institute for Environmental Studies in Japan and Brian O’Neill at the U.S. National Center for Atmospheric Research.
"If we overshoot the temperature target, we do have to reduce emissions to zero. But that won’t be enough," Tanaka said in a statement. "We’ll have to go further and make emissions significantly negative to bring temperatures back down to the target by the end of the century."
Tanaka’s team began looking at both the accord’s temperature goals and requirement that countries “achieve net-zero greenhouse gas emissions in the second half of this century,” according to the statement.
The scientists created scenarios that would achieve both the temperature goals and emissions guidelines. The group concluded to do so would necessitate cutting emissions 80 percent by 2033 to meet the 1.5 degree target or about 66 percent by 2060 to meet the 2 degree mark. “In both these cases, emissions could then flatten out without ever falling to zero,” according to the statement.
However, there is growing doubt the targets in the Paris accords will be met, especially since President Donald Trump has pledged the U.S. will pull out of the international agreement. The United Nation’s Intergovernmental Panel on Climate Change is working on a report which is expected to conclude that geoengineering will be needed to meet the 1.5 degree goal.
Recognizing this difficulty, Tanaka and O’Neill looked at the possibility the targets would be missed.
If the 1.5-degree mark is missed, emissions would have to fall to zero by 2070 and then be negative for the rest of the century. In the 2-degree scenario emissions would have to drop to zero by 2085 and then stay negative for a shorter period of time to get back below 2 degrees.
Both scenarios would require removing carbon from that atmosphere. The researchers also looked at scenarios reducing emissions to zero by 2060 and 2100. In the first case, the temperature rose 2 degrees before declining. In the second instance, it rose above that mark by 2043 and stayed there for 100 years or more.
"The timing of when emissions are reduced really matters," O’Neill said. "We could meet the goal set out in the Paris Agreement of reducing emissions to zero in the second half of the century and still wildly miss the temperature targets in the same agreement if we wait to take action."
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