The anthropogenic emissions of these gases have been increasing rapidly since the beginning of the industrial era and their mean lifetime in the atmosphere is long (about 10 years for CH₄, 100 years for N₂O and much longer for CO₂).
The Copernicus Atmosphere Monitoring Service (CAMS) is recording the net fluxes at the surface (emissions from a source minus uptake from a sink) of these gases. In doing so, one can link the increase of the greenhouse gas concentrations in the atmosphere to the net flux of the sources and sinks of these gases. These sources and sinks are associated with both anthropogenic and natural processes.
Global increase in net fluxes of CO₂, CH₄ and N₂O into the atmosphere
There is significant variability from year to year, but the estimated net fluxes have been increasing during recent decades as shown by the positive trends of their global values, which show the total mass emitted into the atmosphere per year.
The current CO₂ total net flux is about 5 PgC per year, which is equivalent to an increase in atmospheric concentration of about 2.5 ppm per year.
To put this number into context one can consider how much more CO₂ can be released into the atmosphere before the 1.5°C temperature target is exceeded. Using the sensitivity studies of the IPCC 5thAssessment Report, a rough estimate is that in order to stay below the 1.5°C temperature target, the future cumulative net flux of CO₂ into the atmosphere should not exceed 150-400 GtC. If one assumes the same flux as derived from the recent measurements, this would mean another 30 to 80 years before we can observe that the 1.5°C target is exceeded.
Anthropogenic emissions of CO₂ partly compensated by a natural flux into oceans and vegetation
Anthropogenic emissions of CO₂ come from the combustion of fossil fuels and from industrial processes as well as deforestation. They have been partly compensated by a natural flux (sink) into oceans and vegetation. This implies that the observed CO₂ growth in the atmosphere does not only depend on anthropogenic emissions, but also on natural processes that have the potential to capture or release CO₂ into or from the ocean and land reservoirs of carbon. Vegetation can act as both a source and a sink for carbon, through uptake of carbon via photosynthesis and release of carbon through respiration. The land sink associated with vegetation growth has a strong inter-annual variability because it responds rapidly to climate anomalies such as droughts.
Large regional variations in sinks and sources
For Europe specifically, it is estimated that the CO₂ flux from land vegetation contributes to reduce the global net flux associated with atmospheric growth of CO₂, but the relative magnitude of this sink has been decreasing since the 1990s (from capturing 40% of the global growth previously, to about 20% now), likely further to changes in the atmospheric transport of heat and humidity over Europe. More generally, regional variations of temperature and precipitation modify the fluxes from year to year, for instance during El Niño events. On a decadal scale, the relative contribution of the fluxes to the total global flux is stable in several regions, like Australia or tropical Asia, but increasing land sinks are noticed in Boreal and Temperate Eurasia and in Tropical South America.
The net flux of CH₄ is linked to a combination of anthropogenic emissions (e.g., from agriculture, fossil fuel and waste), natural emissions from wetlands and wildfire, together with a net chemical sink in the atmosphere. For CH₄, the different regions also show different net fluxes, with tropical South America and temperate Eurasia having the highest contributions of around 12 and 15 percent of the global net flux respectively during the last decade, while Europe’s contribution is around 8 percent.
Emissions of N₂O are largely due to the microbial processes of nitrification and denitrification, which occur naturally in soils, freshwater systems and in the ocean. However, human activities, namely the use of fertilizers in agriculture, have greatly increased the emissions. Further emissions arise from industrial processes, waste water, as well as the combustion of fossil fuels and biomass. The growth rate of atmospheric N₂O is the balance of the emissions and the atmospheric sink. Trends in N₂O emissions are region-dependent, with the largest increasing trend in temperate Asia owing to more nitrogen fertilizer usage there. Temperate Asia contributed 14% to the global emission compared to 6% in Europe during the past decade.
The “About the data” section explains more about the production and reliability of the values presented here.