Carbon dioxide levels now higher than at any time in past 3.6 million years

Smokestacks spewing smoke against an orange sky.
Industrial pollution. Image via UK Met Office.

Levels of climate-warming carbon dioxide (CO2) and methane in the atmosphere continued to rise in 2020, with CO2 levels reaching their highest point in 3.6 million years, according to NOAA research, despite the economic slowdown caused by the coronavirus pandemic response.

According to the NOAA report, released April 7, 2021, the global average for CO2 in the atmosphere in 2020 was 412.5 parts per million (ppm) in 2020, rising by 2.6 ppm during the year. That rate of increase was the fifth-highest in NOAA’s 63-year record.

The rise happened despite an estimated 7% reduction in global carbon emissions due to the pandemic. Without the economic slowdown, the 2020 increase would have been the highest on record, said Pieter Tans, senior scientist at NOAA’s Global Monitoring Laboratory.

Scripps Institution of Oceanography released similar findings, also on April 7, saying that atmospheric CO2 concentrations at the Mauna Loa Observatory monitoring station in Hawaii are now at record levels. Their measurements show that the average for March 2021 was 417.14 ppm, which is 50% higher than the average for the years 1750-1800, just prior to the Industrial Revolution.

Graphs with jagged lines running inexorably from lower left to upper right.
These graphs depict the mean global atmospheric burden of carbon dioxide as analyzed from measurements collected by NOAA’s Global Greenhouse Gas Reference Network. Image via NOAA Global Monitoring Laboratory.

According to the NOAA report:

The atmospheric burden of CO2 is now comparable to where it was during the Mid-Pliocene Warm Period around 3.6 million years ago, when concentrations of CO2 in the atmosphere ranged from about 380 to 450 parts per million. During that time sea level was about 78 feet higher than today, the average temperature was 7 degrees F (3.9 degrees C) higher than in pre-industrial times, and studies indicate large forests occupied areas of the Arctic that are now tundra.

The NOAA’s sample analysis for 2020 also showed a significant jump in the atmospheric burden of methane. While methane is less abundant than CO2, it’s 28 times more potent at trapping heat in the atmosphere. Atmospheric methane’s annual increase for 2020 was 14.7 parts per billion, which is the largest annual increase since systematic measurements began in 1983.

Methane in the atmosphere is generated by many different sources, such as fossil fuel development and use, decay of organic matter in wetlands, and as a byproduct of livestock farming. Determining which specific sources are responsible for variations in methane annual increase is difficult. Ed Dlugokencky, research chemist at NOAA’s Global Monitoring Lab, said:

Although increased fossil emissions may not be fully responsible for the recent growth in methane levels, reducing fossil methane emissions are an important step toward mitigating climate change.

Colm Sweeney, assistant deputy director of the Global Monitoring Lab, said in a statement:

Human activity is driving climate change. If we want to mitigate the worst impacts, it’s going to take a deliberate focus on reducing fossil fuels emissions to near zero, and even then we’ll need to look for ways to further remove greenhouse gasses from the atmosphere.

Every year in early April, the Global Monitoring Laboratory releases a preliminary estimate of the global annual atmospheric increase for greenhouse gases from January 1 in one year to January 1 in the next year. This preliminary estimate is based on measurements from weekly air samples collected at about 40 sites around the world. While the preliminary estimates are typically a little higher than the final calculation, which incorporates additional measurements, the 2020 increase is likely to remain one of the largest in the entire record.

Bottom line: Levels of atmospheric carbon dioxide (CO2) and methane continued to rise in 2020, said NOAA, despite the economic slowdown caused by the coronavirus pandemic response.


April 14, 2021

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