While 40% of emissions are of natural origin (emissions from wetlands in particular), around 60% are due to human activities, according to the study carried out 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 greater per kilogram than that of CO2 over a 100-year horizon. Its concentrations in the atmosphere have more than doubled since the start of the industrial era, to represent 23% of the global warming produced by greenhouse gases.
The increase calculated by the researchers, based on the productive activities observed and atmospheric measurements, corresponds to climatological scenarios of strong warming, between +3 and 4 degrees Celsius in 2100.
“If we want to respond to the Paris agreement, we must not be content with limiting carbon dioxide emissions, we must reduce them as well as those of methane,” warned Marielle Saunois, of the science laboratory. climate and environment (CEA / CNRS / University of Versailles Saint-Quentin), which coordinated this study.
The Paris agreement, signed in 2015, aims to keep the overall temperature rise below 2 degrees compared to pre-industrial levels. To meet this target, greenhouse gas emissions should drop by 7.6% annually, according to the UN.
If we want to respond to the Paris Agreement, we should not be content with limiting carbon dioxide emissions, we must reduce them as well as those of methane.
Marielle Saunois, laboratory of climate and environmental sciences of the University of Versailles
Over the period studied, agriculture is, according to researchers, responsible for the majority of anthropogenic emissions (linked to human activity) of methane, with 30% coming from livestock herds (digestive fermentation and manure) and 8 % for rice cultivation. In terms of fossil fuels, the exploitation of oil and gas represents 22% of anthropogenic emissions and the extraction of coal 11%.
Solid and liquid waste management accounts for 18% of emissions and biomass and biofuel fires 8%, the rest of the emissions being linked to transport and industry.
Regionally, the tropical regions are the most emitting (64% of the total, in particular due to the numerous wetlands). The regions with the highest emissions are South America, Africa, South East Asia and China. Emissions are increasing in all regions of the world except Europe.