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The world still has a chance to limit global warming to a maximum of 1.5° C above preindustrial levels, but major, immediate changes will be necessary, according to a report released today (October 8) by the UN Intergovernmental Panel on Climate Change (IPCC). If temperatures increase by more than this amount, the report argues, the risk of extreme weather events such as droughts and floods could dramatically increase, putting millions of people in danger.

“It’s a line in the sand and what it says to our species is that this is the moment and we must act now,” Debra Roberts, cochair of a working group on the impacts of climate change, tells The Guardian. “This is the largest clarion bell from the science community and I hope it mobilises people and dents the mood of complacency.”

Temperatures are currently about 1° C higher than preindustrial levels. At the current rate of warming, the world as a whole will reach the 1.5° mark between 2030 and 2052, the report concludes. (Many regions have already experienced this condition on a short-term basis.)

To curb the trend, governments will have to spearhead “rapid and unprecedented societal transformation,” including major reductions in their carbon emissions. The world currently pumps more than 40 billion tons of CO₂ into the atmosphere each year; the IPCC calls for that number to be cut by more than 1 billion tons per year over the next decade. By 2050, the report says, the burning of coal for fuel should be all but abandoned.

If emissions can’t be cut to a sufficient degree, researchers will need to devise effective methods of removing CO₂ from the air, such as devoting land to growing trees and biofuel crops, Erik Solheim, executive director of the UN Environment Program, tells The Washington Post. “[N]et zero must be the new global mantra.”

The IPCC report underwent an extensive peer-review process that elicited tens of thousands of comments and includes a special “summary for policymakers” that resulted from discussions among scientists and government officials last week in Incheon, South Korea, the Post reports.

“Frankly, we’ve delivered a message to the governments. . . . What we’ve done is said what the world needs to do,” Imperial College London’s Jim Skea, cochair of the IPCC panel, said at a press conference. “It’s now their responsibility . . . to decide whether they can act on it.”