Climate Change: Atmospheric levels of 3 greenhouse gases reach record high

WMO’s Greenhouse Gas Bulletin reports biggest year-on-year jump in methane concentrations in 2021

Staff Correspondent
October 27

The atmospheric levels of the three main greenhouse gases – Carbon Dioxide, Methane, and Nitrous Oxide all reached new record highs in 2021, according to a new report from the World Meteorological Organization (WMO).
The increase in the levels of these gases is being viewed as yet another ominous climate change warning. 
WMO’s Greenhouse Gas Bulletin reported the biggest year-on-year jump in methane concentrations in 2021 since systematic measurements began nearly 40 years ago.
The reason for this exceptional increase is not clear, but seems to be a result of both biological and human-induced processes, reads a statement from WMO. 
‘The increase in carbon dioxide levels from 2020 to 2021 was larger than the average annual growth rate over the last decade”, the report says. 
Measurements from WMO’s Global Atmosphere Watch network stations show that these levels continue to rise in 2022 over the whole globe.
“Between 1990 and 2021, the warming effect on our climate (known as radiative forcing) by long-lived greenhouse gases rose by nearly 50%, with carbon dioxide accounting for about 80% of this increase”, it says. 
Carbon dioxide concentrations in 2021 were 415.7 parts per million (ppm), methane at 1908 parts per billion (ppb), and nitrous oxide at 334.5 ppb, the report notes, adding that these values constitute, respectively, 149%, 262%, and 124% of pre-industrial levels before human activities started disrupting the natural equilibrium of these gases in the atmosphere.
“WMO’s Greenhouse Gas Bulletin has underlined, once again, the enormous challenge – and the vital necessity – of urgent action to cut greenhouse gas emissions and prevent global temperatures rising even further in the future,” said WMO Secretary-General Prof. Petteri Taalas
The continuing rise in concentrations of the main heat-trapping gases, including the record acceleration in methane levels, shows that we are heading in the wrong direction,” he said. 
WMO UN Climate Change conference, COP27, in Egypt from 7-18 November.
 On the eve of the conference in Sharm-el-Sheikh it will present its provisional State of the Global Climate 2022 report, which will show how greenhouse gases continue to drive climate change and extreme weather.  The years from 2015 to 2021 were the seven warmest on record.
The WMO reports seek to galvanize COP27 negotiators into more ambitious action decision-makers to achieve the Paris Agreement goal to limit global warming to well below 2, preferably to 1.5 degrees Celsius, compared to pre-industrial levels, the statement said, adding that the average global temperature is now more than 1.1°C above the 1850–1900 pre-industrial average.
WMO measures atmospheric concentrations of greenhouse gases – what remains in the atmosphere after gases are absorbed by sinks like the ocean and biosphere. This is not the same as emissions.

“As long as emissions continue, global temperature will continue to rise.  Given the long life of CO2, the temperature level already observed will persist for decades even if emissions are rapidly reduced to net zero”, it adds. 

Highlights of the report 

Carbon dioxide (CO2)
-Atmospheric carbon dioxide reached 149% of the pre-industrial level in 2021, primarily because of emissions from the combustion of fossil fuels and cement production. 
-Global emissions have rebounded since the COVID-related lockdowns in 2020.

  • Of the total emissions from human activities during the 2011–2020 period, about 48% accumulated in the atmosphere, 26% in the ocean and 29% on land.
    -There is concern that the ability of land ecosystems and oceans to act as “sinks” may become less effective in future, thus reducing their ability to absorb carbon dioxide and act as a buffer against larger temperature increase, the report says. 
    -In some parts of the world the transition of the land sink into CO2 source is already happening, it adds. 
    Methane (CH4)
    -Atmospheric methane is the second largest contributor to climate change and consists of a diverse mix of overlapping sources and sinks, so it is difficult to quantify emissions by source type.
    -Since 2007, globally-averaged atmospheric methane concentration has been increasing at an accelerating rate.
    -The annual increases in 2020 and 2021 (15 and 18 ppb respectively) are the largest since systematic record began in 1983.
    -Causes are still being investigated by the global greenhouse gas science community. Analysis indicates that the largest contribution to the renewed increase in methane since 2007 comes from biogenic sources, such as wetlands or rice paddies, it says. 
    -It is not yet possible to say if the extreme increases in 2020 an 2021 represent a climate feedback – if it gets warmer, the organic material decomposes faster, the report says.
    -If it decomposes in the water (without oxygen) this leads to methane emissions. Thus, if tropical wetlands become wetter and warmer, more emissions are possible, it adds. 

-The dramatic increase might also be because of natural interannual variability. The years 2020 and 2021 saw La Niña events which are associated with increased precipitation in the tropics.
Nitrous oxide (N2O)
-Nitrous oxide is the third most important greenhouse gas.
-It is emitted into the atmosphere from both natural sources (approximately 57%) and anthropogenic sources (approximately 43%), including oceans, soils, biomass burning, fertilizer use, and various industrial processes.

  • The increase from 2020 to 2021 was slightly higher than that observed from 2019 to 2020 and higher than the average annual growth rate over the past 10 years, the report notes. 

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