Summary
Every time the U.N. Intergovernmental Panel on Climate Change (IPCC) issues a new report surveying the science of global warming, the alarm sounds louder. Now, 8 years after its last report, the message of IPCC’s latest assessment, released this week, is urgent and unequivocal: The window for mitigating the worst projected impacts of global climate change is closing. Average global temperatures are now 1.1°C above preindustrial records, and under every scenario for future greenhouse gas emissions that the panel examined, average warming of 1.5°C—a target set by the 2015 Paris climate accord—will very likely be reached within the next 20 years.