Human activity is changing the climate in unprecedented and sometimes irreversible ways. The landmark study (6th IPCC Report 2021) warns of increasingly extreme heatwaves, droughts and flooding, and a key temperature limit being broken in just over a decade. The report “is a code red for humanity”, says the UN chief. But scientists say this catastrophe can be avoided if the world acts fast. It is hoped that deep cuts in emissions of greenhouse gases could stabilise rising temperatures.
The report, prepared by 234 scientists from 66 countries, highlights that human influence has warmed the climate at a rate that is unprecedented in at least the last 2,000 years.
In 2019, atmospheric CO2 concentrations were higher than at any time in at least 2 million years, and concentrations of methane and nitrous oxide were higher than at any time in the last 800,000 years.
Global surface temperature has increased faster since 1970 than in any other 50-year period over at least the last 2,000 years. For example, temperatures during the most recent decade (2011–2020) exceed those of the most recent multi-century warm period, around 6,500 years ago, the report indicates.
Meanwhile, global mean sea level has risen faster since 1900, than over any preceding century in at least the last 3,000 years.
The document shows that emissions of greenhouse gases from human activities are responsible for approximately 1.1°C of warming between 1850-1900, and finds that averaged over the next 20 years, global temperature is expected to reach or exceed 1.5°C of heating.
Experts will debate and discuss the impacts of unprecedented climate change and mitigation and adaptation measures to cope with anthropogenic climate change.