A new report from the Intergovernmental Panel on Climate Change (IPCC) states that global warming of 1.5°C (2.7 °F) is essentially inevitable in coming decades. The question now is whether the world can prevent further, more destructive warming of 2°C (3.6°F), or, even worse, 3°C (5.4°F), which is what current policies put us on a trajectory to experience. Our economies can only put another 420 gigatons of greenhouse gas emissions into the atmosphere if we want a good chance of keeping a temperature increase to 1.5°C instead of 2°C. At our current pace, the world’s carbon budget will be used up before 2030. We need to phase out fossil-fuel use, build thousands of new clean power plants — and swiftly move to power our homes, offices, schools, and transportation systems with clean energy.