Scientists warned Thursday that the Earth has already missed time windows that would allow humans to reverse global warming and could be quickly approaching several others.
According to the study, published in the journal Science, an economically feasible plan to cut emissions in time to prevent a 1.5 degree C global temperature increase has already passed. By 2027, it may be impossible to prevent a 2 degree increase, says Thomas Stocker, of the Oeschger Centre for Climate Change in Bern, Switzerland.
"We propose the rather obvious fact that certain climate targets have or will disappear in the near future," he says. "If you judge by the world's emissions, we are certainly not on the correct path. [This year] was again a record year for emissions. With continuing emissions, climate targets become more and more difficult to achieve. Some targets have disappeared and some are fast approaching."
According to Stocker, the world's carbon emissions would have to decrease about 3.2 percent per year starting in 2020 in order to avoid an increase of 2 degrees C by the end of the century; if emission reductions started in 2032, they'd have to be cut by more than 6 percent annually to reach that target.
Though some scientists have proposed that climate change could be reversed by injecting gasses into the atmosphere to "turn down" the sun, Stocker says the most obvious solution is to get serious about carbon emissions.
"There's always room for dreaming, but if you really look at it, the sheer scale of the problem is such that there are very few options here other than coming back to the root problem of emissions," he says. "I don't think we have the luxury to wait for decades. We first knew about this problem two decades ago. If we brought down our emissions then, these targets would be much easier to achieve."
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Jason Koebler is a science and technology reporter for U.S. News & World Report. You can follow him on Twitter or reach him at firstname.lastname@example.org.