The CO2 concentration has reached unprecedented value for more than two million years, according to the World Meteorological Organization. Methane concentrations, second greenhouse gas, have experienced an “exceptional” increase.
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This is one more echo, if necessary, that the lights are red in terms of climate crisis. The concentrations of greenhouse gas in the atmosphere reached record levels in 2021, according to the annual bulletin published by the World Meteorological Organization (OMM) , Wednesday October 26. This additional greenhouse effect leads to an increase in global temperature (+ 1.2 ° C from the pre -industrial era), the multiplication of extreme events or the elevation of the level of the seas.
In 2021, the concentration of the atmosphere in carbon dioxide (co 2 ) amounted to 416 parts per million (ppm), that of methane at 1,908 parts per billion (PPB ) and that of nitrogen oxide at 335 ppb, an increase of 149 %, 262 %and 124 %, respectively, compared to the pre -industrial era, when human activities did not yet disturb the natural balance of these gases in the atmosphere.
The concentration of co 2 , the main greenhouse gas, today has reached unprecedented value for more than two million years. The 2021 record is not a surprise, however, since concentrations arise from greenhouse gas emissions, which continue to increase year after year under the effect of human activities, in particular the exploitation of fossil fuels (coal, oil and gas) and deforestation. After the exceptional decline in 2020, with the COVVI-19 crisis, carbon discharges thus widely left in 2021, and should experience a slight increase in 2022 .
Only the achievement of carbon neutrality, that is to say the principle according to which emissions must not exceed the absorption capacity of natural wells (forests, oceans, etc.), “will allow the Concentration in co 2 to stabilize and then lower slowly in the atmosphere, “recalls the climatologist Pierre Friedlingtein, research director at the CNRS, at the École Normale Supérieure and at the University of Exeter (United Kingdom).
“There is an emergency”
Methane concentrations , the second greenhouse gas in terms of abundance, have experienced an “exceptional” increase in 2020 and 2021, indicates the OMM. With an increase of 15 and 18 PPB, respectively, these are the highest increases since the start of the measures, almost forty years ago. The cause is not clearly established but several hypotheses are on the table, which fall under both biological and anthropic processes.
The increase in temperature in tropical wetlands could have increased the decomposition of organic matter and therefore the emission of methane – into a vicious circle form -, as well as the rise in precipitation in these regions, Under the effect of the La Niña climate phenomenon. Another track: a decrease in the concentration of the radical OH (hydroxyl), which degrades methane in the atmosphere, due to the drop in air pollution, in 2020, at the time of confinements.
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