Carbon dioxide levels are now higher than at any time in the past 3.6 million years
The atmospheric burden of CO₂ is now comparable to the level it was at during the Mid-Pliocene warm period around 3.6 million years ago, when concentrations of carbon dioxide ranged from about 380 to 450 parts per million, reports NOAA. During that period the sea level was about 24 metres higher than today, the average temperature was around 4ºC higher than in pre-industrial times, and studies indicate that large forests occupied areas of the Arctic that are now tundra.
Levels of the two most important anthropogenic greenhouse gases, carbon dioxide and methane, continued their unrelenting rise in 2020 despite the economic slowdown caused by the coronavirus pandemic response, NOAA has announced.
The global surface average for carbon dioxide (CO₂), calculated from measurements collected at NOAA’s remote sampling locations, was 412.5 parts per million (ppm) in 2020, rising by 2.6 ppm during the year. The global rate of increase was the fifth-highest in NOAA’s 63-year record, following 1987, 1998, 2015 and 2016. The annual mean at NOAA’s Mauna Loa Observatory in Hawaii was 414.4 ppm during 2020.
Analysis of samples from 2020 also showed a significant jump in the atmospheric burden of methane, which is far less abundant but 28 times more potent than CO₂ at trapping heat over a 100-year time frame. NOAA’s preliminary analysis showed the annual increase in atmospheric methane for 2020 was 14.7 parts per billion (ppb), which is the largest annual increase recorded since systematic measurements began in 1983.
Compiled by Reinhold Pape