CH4, better known as methane, is the second gas responsible for the greenhouse effect, and although its emissions are much weaker than those of CO2, they are in fact much more dangerous.
Today, its concentration in the atmosphere has reached the highest peaks.
Methane emissions made an "unprecedented jump" in 2021, reaching a record level, revealed the World Meteorological Organization (WMO) in a report published on Wednesday, October 26.
Figures which, according to its Secretary General Petteri Taalas, underline "once again the enormous challenge - and the vital need - for urgent action to reduce greenhouse gas emissions and prevent temperatures from rising further. more in the future globally".
An increase in methane emissions is indeed not a good omen when this super polluting gas is, on its own, responsible for 30% of global warming.
Even if CO2 represents nearly two thirds of global greenhouse gas emissions, the methane problem is "at least as important as that of CO2" insists Euan Nisbet, researcher at Royal Holloway of the University of London and one of the leading specialists in the climate impact of methane.
Indeed, this gas has a much higher warming power than carbon dioxide.
"Compared to CO2, molecule for molecule, methane is much more harmful to the climate", warns this expert, because a particle of this gas traps about 80 times more heat than carbon dioxide over twenty years.
For the WMO, the reason for this exceptional increase compared to 2020 in the level of methane "is not clear, but seems to be the result of both biological and human-induced processes".
For Euan Nisbet, "the extreme and unexpected increase in atmospheric methane over the past two years is particularly worrying" and scientists are "not sure why this is happening".
"The question is very complex", continues the British researcher.
"We believe this is mainly caused by biological causes, such as the emission of methane in wetlands or by livestock."
In search of solutions, sometimes unusual
Some countries are groping to find solutions to reduce these emissions of methane of biological origin.
In New Zealand, the gas, naturally emitted in the form of farts and burps by the archipelago's 6.2 million cows and 26 million sheep, is among the country's biggest environmental problems.
Prime Minister Jacinda Ardern has therefore decided to legislate, presenting, on Tuesday, October 11, a plan aimed at setting up a tax to tax methane emissions from livestock and provoking the ire of New Zealand farmers.
A week later, convoys of agricultural machinery converged in major New Zealand cities as protesters called on the government to drop its plan now dubbed the "fart tax" ("taxe sur les pets", in French) which , if applied, would be a world first.
But according to researcher Euan Nisbet, simpler measures could be put in place to significantly reduce methane emissions around the world.
"What we can do quickly and cheaply would be, for example, to stop burning crop waste or to reduce methane emissions from landfills by covering them with soil."
Landfills can be a major source of methane, which then results from decomposition.
Although approximately 40% of the methane released into the atmosphere is of natural origin (livestock, wetlands, etc.), the role of humans in the emission of this gas has long been largely underestimated, and the energy sector fossils would also play a significant role.
50 "super-emitters"
About fifty sites called "super-emitters" of methane have been discovered by a NASA mission.
A major and fortuitous discovery, which the American space agency welcomed on Tuesday.
These sites, mostly linked to the fossil fuel sector, are among the most polluting in the world in terms of methane.
Thanks to the EMIT mission, installed on the International Space Station, and its imaging spectrograph
Next-generation Earth-observing device, NASA was able to detect methane leaks "among the largest ever seen," NASA's Andrew Thorpe said in a statement.
"What we have found in such a short time is already beyond what one could imagine."
In Turkmenistan, for example, the instrument has identified twelve "plumes" of methane from gas and oil infrastructure east of the port city of Hazar, some stretching over 32 kilometers that NASA says would release 50,400 kilos of methane per hour.
In New Mexico, United States, EMIT detected another plume about three kilometers long, coming from one of the largest oil fields in the world which would produce 18,300 kilos of methane per hour.
Satellite image of methane plumes from gas and oil infrastructure detected east of Hazar, Turkmenistan provided by the US space agency, October 25, 2022. © AFP
By locating the largest methane leaks in the world, this discovery could drastically reduce emissions of this gas.
"NASA's discovery is extremely useful," said researcher Euan Nisbet.
"Satellite is proving essential to finding methane leaks in coal mines and gas fields. Leaks that cost money to those 'super-emitters' who I'm sure would like to know in order to put an end to it. Reducing such leaks would also make it possible to tackle the CO2 they contain", he adds.
Crucial issue of the Paris agreement
Methane is a gas that remains much shorter than CO2 in the atmosphere.
“Where carbon dioxide lingers for centuries, methane stays in the atmosphere for about a decade,” says Euan Nisbet, for whom “getting rid of methane could slow global warming in the short term. one of the gases that we can reduce the fastest".
The researcher says that if put in place, "measures to reduce human-made emissions would have a rapid impact".
A reduction in methane emissions would even be crucial to meet the objectives of the Paris climate agreement signed in 2015.
Problem, the first two countries the most emitters of methane in the world have not yet kept any commitment to reduce methane.
China is by far the biggest emitter in the world with, according to the figures quoted by the expert Euan Nisbet, around 89 million tonnes per year, coming in particular from its coal industry.
India rejects approximately 32 million tonnes annually, due in particular to cattle farming, the coal industry and poor waste management.
The United States and Russia follow with respectively 31 and 35 tonnes of methane released into the atmosphere each year.
If the United States has already committed to reducing its emissions of this greenhouse gas at COP26, "China and India, the biggest emitters, can do much more", according to Euan Nisbet.
To read: COP26: more than 80 countries commit to reducing methane emissions by 30% by 2030
Commitments are therefore expected in this field, especially since 10 days before COP27, the UN warned on Wednesday that the world is still "very far" from the objectives of the Paris agreement which limit global warming. climate at 1.5°C.
According to the organization, current international commitments leave the Earth on track for a warming of 2.6°C.
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