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Methane and Global Warming

June 6, 2022

Many years ago, I was writing an article about synthetic gems, so I accessed the Wikipedia page for jewelry. I was surprised to see that I had been redirected to a page for jewellery. I had never heard this term, which is the British English word for jewelry. Wikipedia's style manual allows articles to be submitted in either American English or British English for general topics, and jewelry/jewellery would fall into that category. A Google Search for jewelry gives 3,840,000,000 results, and a Google search for jewellery gives 2,940,000,000; so, the usage is about evenly split.

That incident reminded me of my undergraduate chemistry course, which was taught by a British chemist. His classroom of American teenagers found humor in his pronunciation of the chemical compound, methane. He pronounced it meee-thane, using a long vowel e rather than the short vowel e with which we were familiar. In the decades that have passed since that time in the 1960s, methane has become much more serious as one cause of global warming.

One glance at the infrared spectrum of carbon dioxide, the principal cause of global warming, and that of methane shows the source of the problem. In each case, the infrared radiation that the Earth seeks to radiate after being heated by sunlight is not transmitted back into space. This is the greenhouse effect, well known to even elementary school students.

General features of the infrared transmittance of carbon dioxide and methane.

General features of the infrared transmittance of carbon dioxide and methane, as derived from various Internet sources and rendered using Inkscape. Higher resolution spectra can be found at refs. 1-2.[1-2]

Now, with all 2021 data analyzed, it's been found that the concentration of atmospheric methane set another record during 2021, as carbon dioxide levels also recorded a huge rise.[3-5] These data were from the National Oceanic and Atmospheric_ dministration (NOAA) Mauna Loa observatory in Hawaii.[3] Atmospheric methane increased by 17 parts per billion (ppb) in 2021, and this was the largest annual increase since 1983 when data were first collected.[3]

This follows the 15.3 ppb increase in 2020.[3] The total atmospheric methane now stands at 1,895.7 ppb, which is about 162% greater than that of pre-industrial levels.[3] Carbon dioxide at the end of 2021 stands at 414.7 parts per million (ppm), marking the tenth consecutive year that carbon dioxide increased by more than 2 parts per million.[3] NOAA also tabulates the annual global average levels of nitrous oxide and sulfur hexafluoride, two other greenhouse gases.[3]

Global Annual Increase in Methane (CH4)
(Source: NOAA.[4])
Year Annual
Increase (ppb)
Year Annual
Increase (ppb)
1984 12.82±0.84 2003 4.80±0.57
1985 12.31±0.91 2004 -4.89±0.42
1986 12.90±0.65 2005 0.38±0.41
1987 11.40±0.72 2006 1.94±0.56
1988 10.79±0.55 2007 7.79±0.57
1989 11.08±0.59 2008 6.53±0.44
1990 8.75±0.47 2009 4.70±0.41
1991 14.06±0.55 2010 5.19±0.71
1992 2.36±0.51 2011 4.83±0.58
1993 3.83±0.59 2012 5.01±0.51
1994 7.21±0.61 2013 5.70±0.58
1995 3.96±0.56 2014 12.77±0.50
1996 2.50±0.48 2015 10.02±0.70
1997 6.27±0.69 2016 7.09±0.67
1998 12.15±0.70 2017 6.85±0.79
1999 2.43±0.65 2018 8.67±0.52
2000 -1.52±0.54 2019 9.89±0.64
2001 -0.73±0.56 2020 15.27±0.38
2002 3.27±0.56 2021 16.99±0.38

Global annual increase in atmospheric methane.

Global annual increase in atmospheric methane, graphed using Gnumeric from the table data above. (Click for larger image.)

Says NOAA administrator, Richard W. Spinrad,
"Our data show that global emissions continue to move in the wrong direction at a rapid pace... The evidence is consistent, alarming and undeniable. We need to build a Climate Ready Nation to adapt for what's already here and prepare for what's to come. At the same time, we can no longer afford to delay urgent and effective action needed to address the cause of the problem - greenhouse gas pollution."[3]

Last year, humans emitted about 36 billion tons of carbon dioxide, and 640 million tons of methane were emitted into the atmosphere. Methane is about 25 times more powerful a global warming agent than carbon dioxide; but, fortunately, the atmospheric residence time of methane is approximately nine years, while the affect of carbon dioxide is considerably longer.[3] It's estimated that about 40% of the Ford Model T emissions from 1911 are still in our atmosphere.[3] Today's atmospheric carbon dioxide level is about that of the mid-Pliocene, 4.3 million years ago, when the average temperature was 7 degrees Fahrenheit higher than that in pre-industrial times, and sea level was about 75 feet higher.[3]

Since the residence time of atmospheric methane is so short, reducing its emission will have a beneficial short-term impact on global warming. The largest methane source is biological, coming from from microbial emission in wet, anaerobic environments such as swamps and other wetland ecosystems.[5] Methane in smaller amounts is emitted from enteric fermentation in termites and wild animals.[5] Food production is a problem, also, since methane is a byproduct of digestion in cows and other ruminant animals.[5] Animal waste and landfills emit methane, also.[5] Fossil fuel (both coal and oil) contributes about 30% of the total methane emission.[3] These methane sources are easy to pinpoint and control.[3] Methane also contributes to ozone formation at ground-level, and this causes about 500,000 premature deaths globally each year.[3]

Through use of carbon isotopic analysis, the NOAA found that biological sources of methane were a primary driver of methane increase after 2006, and this might indicate that a feedback loop may have developed in which more rain leads to increased methane release in tropical wetlands.[3] Furthermore, melting of frozen soils and permafrost in the Arctic leads to increases in both atmospheric carbon dioxide and methane.[5] There are two NOAA websites, CarbonTracker-CO2 and CarbonTracker-CH4, that provide updates on these atmospheric gases.[5-6]

Gloabl methane, July-August, 2007

CarbonTracker-CH4 column average CH4 for July-August, 2007. Warm colors show high concentrations, while cool colors show low concentrations. There are relatively large emissions from wetlands in Western Siberia and emissions from anthropogenic and natural sources in India and Asia, and the methane is moved by weather systems to form the patterns in this animation. (NOAA image.)


  1. NIST Chemistry WebBook-Methane.
  2. NIST Chemistry WebBook-Carbon Dioxide.
  3. Increase in atmospheric methane set another record during 2021, National Oceanic and Atmospheric Administration, U.S. Department of Commerce, Press Release, April 7, 2022.
  4. Trends in Atmospheric Methane, Global CH4 Monthly Means, NOAA.
  5. CarbonTracker-CH4.
  6. CarbonTracker-CO2.

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