PARIS | The global emissions of methane, a greenhouse gas much more potent than CO2, increased by 9 % between 2006 and 2017, with the main source sectors of energy and agriculture, according to a study published on Wednesday.
If these emissions are for 40 % of natural origin (emissions from wetlands in particular), about 60% are due to human activities, according to the study conducted by more than 100 international researchers under the aegis of the Global Carbon Project.
Methane is the second greenhouse gas of anthropogenic origin after carbon dioxide (CO2), but its warming effect is 28 times higher per kilogram than that of CO2 on a 100-year time horizon. Its concentrations in the atmosphere have more than doubled since the beginning of the industrial era, up to 23 % of the global warming produced by the greenhouse gases.
The increase calculated by the researchers (from producing activities observed and atmospheric measurements) corresponds to scenarios a climate of strong warming between +3 and 4 degrees by 2100.
Is well beyond the objectives of the Paris agreement of 2015, to maintain the global elevation of the temperature ” well below 2°C relative to pre-industrial levels, in keeping with the action taken to limit the temperature rise to 1.5°C “. To take this last goal, the greenhouse gas emissions are expected to fall 7.6 % annually, according to the UN.
“If we want to respond to the Paris agreement, it is not enough to limit the emissions of carbon dioxide, it is necessary to reduce, as well as those of methane,” warns Marielle Saunois, of the Laboratory of Climate Sciences and the Environment (CEA/CNRS/university of Versailles Saint-Quentin, france), who coordinated this study.
The researcher argues for a quantification more regular (this is only the second kind of study) of the methane emissions, similar to what is done for CO2, ” because the reduction of emissions can be quickly beneficial for the climate “, in particular because of its shorter lifetime in the atmosphere than CO2.
Over the period studied, agriculture is according to researchers at the origin of the majority of anthropogenic (related to human activity) methane, with 30 % derived from herds of livestock (fermentation digestive and manures) and 8 % for the cultivation of rice.
Beside fossil fuels, the exploitation of oil and gas accounts for 22% of anthropogenic emissions, and coal mining 11 %.
The management of solid and liquid wastes account for 18 % of emissions, and the fires of biomass and biofuel 8 %, the rest of the emissions are related to transport and industry.
Regionally, the tropical regions are the most issuers (64% of the total, in particular because of the many wetlands). The regions with the highest emissions are the South America, Africa, South East Asia and China. The emissions increase in all regions of the world, with the exception of Europe.
The researchers are concerned that emissions do not increase abruptly from areas of permafrost (permanently frozen ground) under the effect of global warming, but note that there is ” still no signal going in this direction “.