“Limiting warming to 1.5 degrees Celsius is not impossible, but will require unprecedented transitions in all aspects of society,” warned Hoesung Lee, chair of the Intergovernmental Panel on Climate Change (IPCC), upon the release of the panel’s report in October 2018. The IPCC says global net human-caused carbon-dioxide emissions must be reduced to zero by 2050 to keep global warming below 1.5°C. In the absence of such action, the IPCC predicts that the Earth’s temperature will increase to over double this, to 3.2°C above pre-industrial levels by 2100, with catastrophic consequences.