Climate change made the last eight years the hottest on record

The last eight years were the hottest in global records that date to 1880, with 2021 ranking as the sixth-hottest year, according to analyses of global weather station and ocean measurements released Thursday by NASA’s Goddard Institute for Space Studies and the US National Oceanic and Atmospheric Administration.

Last year’s global average temperature was a bit more than 1° Celsius higher than the 1880-1900 average.

Berkeley Earth, a non-profit that looks at stations and ocean data, found last year to be virtually tied with 2015 and 2018 for the fifth-hottest year.

NASA, NOAA and Berkeley Earth are three of the five major research groups that conduct temperature analyses. The EU Copernicus Climate Change Service, which published its results last week, evaluates satellites, surface records, weather balloons and other measurements and estimates the global figure from them. This analysis placed 2021 as the fifth-hottest year since 1979.

Scientists tabulate these rankings every year. Another research centre, the UK Met Office, is expected to report its data soon. Researchers are quick to point out that annual results reflect natural, statistical noise in the climate system. For example, 2021 was cooler than several previous years in part because a cooling La Niña phase of the equatorial Pacific Ocean tamped temperatures down. The 2010s were by far the hottest decade on record. Every decade has averaged hotter than the prior one since the 1960s.

Scientists have become more direct with policymakers and the public in recent years. Guidance that nations should zero-out the impact of emissions by 2050 — and halve emissions by 2030 — has become a rallying point for global policy in the last three years.

The UK Met Office this week released an estimate that the world has to slow its carbon dioxide pollution by 20 per cent in just the next five years to have a reasonable chance of limiting warming to 1.5°C. Emissions last year rose by 4.9 per cent, almost to 2019 levels, after a significant pandemic-related drop in 2020.

Extraordinary climate events continued to pile up in 2021, including what may be the most dramatic heatwave ever observed, historic flooding in central Europe and deadly cyclones and flooding in India. Munich Re calculated costs from 2021 climate disasters to be $280bn globally.