Greenhouse gas pollution and warming slowed down slightly. The ozone hole expanded to normal size.
Atmospheric CO2 continued to increase rapidly by 2.3 ppm, 7% slower than the previous year but 5% faster than the average 2000–2019 rate. This was likely partly due to reduced energy use during the COVID-19 pandemic. Average CO2 concentration reached 414 ppm; a 31% increase from 1960.
Global air temperature increased by 0.03°C in 2020, reaching 0.85°C above the 1961-1990 mean. This is the second highest in the historical record, only 0.01°C short of 2016.
The ozone hole returned to normal size (1% greater than the 2000-2019 average) after being very small the previous year due to an unusual polar air circulation pattern.
Sea ice extent continued to decline. Ice extent on both hemispheres was the lowest since 1978. Their combined extent was 7% lower than the 2000–2018 average.