Increase in atmospheric methane set another record during 2021

For the second year in a row, NOAA scientists observed a record annual increase in atmospheric levels of methane, a powerful, heat-trapping greenhouse gas that’s the second biggest contributor to human-caused global warming after carbon dioxide.

NOAA’s preliminary analysis showed the annual increase in atmospheric methane during 2021 was 17 parts per billion (ppb), the largest annual increase recorded since systematic measurements began in 1983. The increase during 2020 was 15.3 ppb. Atmospheric methane levels averaged 1,895.7 ppb during 2021, or around 162% greater than pre-industrial levels. From NOAA’s observations, scientists estimate global methane emissions in 2021 are 15% higher than the 1984-2006 period. 

Globally averaged, monthly mean atmospheric methane amounts in parts per billion, based on observations from ocean surface sites since 1983. Values for the last year are preliminary. Image by NOAA Climate.gov, based on data from NOAA Global Monitoring Laboratory.

Meanwhile, levels of carbon dioxide also continue to increase at historically high rates. The global surface average for carbon dioxide during 2021 was 414.7 parts per million (ppm), which is an increase of 2.66 ppm over the 2020 average. This marks the 10th consecutive year that carbon dioxide increased by more than 2 parts per million, which represents the fastest sustained rate of increase in the 63 years since monitoring began.

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