Imma Perfetto
Cosmos science journalist
In a stark update on the current state of global climate change, a report by the World Meteorological Organisation (WMO) has found that atmospheric levels of the three main greenhouse gasses all reached record highs in 2021.
In 2021, global average carbon dioxide concentrations were 415.7 parts per million (ppm), methane at 1908 parts per billion (ppb) and nitrous oxide at 334.5 ppb.
The well respected WMO report says researchers detected the largest year-on-year jump in methane concentrations since systematic measurements began nearly 40 years ago.
The increase in average carbon dioxide levels between 2020 to 2021 (2.5 ppm) was greater than the annual growth rate over the past decade (2.46 ppm/year).
The causes behind these exceptional increases in greenhouse gases are still being investigated.
“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 Professor 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.
Greenhouse gases: carbon dioxide, methane, and nitrous oxide
WMO doesn’t measure greenhouse gas emissions, instead it measures the concentrations of greenhouse gasses that remain in the atmosphere after being absorbed by sinks like the ocean and the biosphere.
Carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) are three of the main greenhouse gasses contributing to the warming effect on our climate – known as radiative forcing.
Nitrous oxide is the third most important individual contributor to this, and is emitted into the atmosphere from both natural sources (approximately 57%) – including oceans and soils – and human sources (approximately 43%) including burning biomass, fertiliser, and industrial processes.
The report found that the increase in N2O from 2020 to 2021 (1.3 ppb) was slightly higher than the average annual increase over the past 10 years (1.01 ppb/year).
Atmospheric methane is the second largest contributor. According to the report, global averages have been increasing since 2007 and the rate of increase is accelerating.
“There are cost-effective strategies available to tackle methane emissions, especially from the fossil fuel sector, and we should implement these without delay. However, methane has a relatively short lifetime of less than 10 years and so its impact on climate is reversible,” explains Taalas.
While implementing all efforts to reduce methane emissions is essential, it isn’t a substitute for reducing carbon dioxide emissions – since the accumulation of CO2 in the atmosphere is irreversible on human timescales.
“As the top and most urgent priority, we have to slash carbon dioxide emissions which are the main driver of climate change and associated extreme weather, and which will affect climate for thousands of years through polar ice loss, ocean warming and sea level rise,” says Taalas.
Current carbon dioxide levels are primarily caused by emissions from the combustion of fossil fuels and cement production.
“We need to transform our industrial, energy and transport systems and whole way of life.The needed changes are economically affordable and technically possible. Time is running out,” Talaas urges.