evidence: The accumulation of carbon dioxide in the atmosphere, caused primarily by the burning of fossil fuels, had been worrying scientists since the 1970s. The discovery of the "ozone hole" above Antarctica had given atmospheric scientists enormous credibility and clout among the public, and an international treaty banning chlorofluorocarbons, the chemicals causing the problem, was swiftly signed. [...] Thanks to COVID-19, the next IPCC assessment report probably won’t be delivered before the delayed conference in Glasgow at the end of 2021. There probably won’t be anything in it that tells us more than what we already know – CO₂ levels are rising, the consequences are piling up, and campaigns for delaying meaningful action have been spectacularly successful for the last 30 years. Some scientists, including Columbia University professor James Hansen, argue that the agonising efforts of scientists to avoid provoking accusations of alarmism have led to an innate optimism bias. The official science reported by the IPCC may in some cases be a cautious underestimate. It’s likely worse – much worse – than we think.