A landmark report by the UN Intergovernmental Panel on Climate Change released Monday spelled out a grim planetary future in no uncertain terms. If greenhouse gases warm the atmosphere by as much as 1.5 degrees Celsius, the most dire effects of climate change will be unleashed. Coastlines will be submerged, droughts and wildfires exacerbated, coral reefs exterminated, severe food shortages and poverty deepened. And humanity has only a fast-closing 12-year window to make the changes necessary to avoid this fate.
Previously, the IPCC’s work had focused on the effects of 2 degrees Celsius of warming, which scientists once considered the threshold for these nightmarish effects. But that half-degree would quite literally make a world of difference. Climate change will be much worse than the leading authorities thought. Mitigating the worst impacts will take unprecedented, coordinated global action—shutting down coal plants, passing a substantial carbon tax, restoring forests, and sharply cutting transportation emissions.