Why the IPCC’s report on global warming matters

FOR decades scientists have warned that rising atmospheric concentrations of greenhouse gases from the burning of fossil fuels risk adversely affecting the climate, increasing ocean acidity, the frequency of freak weather and other symptoms of planetary ill-health. But it seemed that keeping the temperature within 2°C of pre-industrial levels, although disruptive, would probably leave Earth in a chronic but stable condition.A report unveiled this week from the Intergovernmental Panel on Climate Change (IPCC), a UN-backed body that musters the science needed to inform policy, shows how optimistic that was. The survey was commissioned in 2015 by the then 195 signatories of the Paris climate agreement—which commits them to keep warming “well below” 2°C and to “pursue efforts towards 1.5°C”. The effects and technical feasibility of keeping warming within this tighter limit were the report’s focus (see ). How it was put together, the message it contains and the reaction it elicited all matter.