What Is the Current Level of Global Net GHG Emissions?
Global net greenhouse gas (GHG) emissions can be measured in two ways: first, by summing up the emissions and removals at man-made sources and sinks, and second, by measuring changes in atmospheric concentrations, which include the effects of both human and natural processes. Both measures show that the world is currently a long way off from net zero.
The PIK dataset on the Climate Watch website shows that man-made global emissions of carbon dioxide (CO2) in 2022 were 37.1 gigatonnes (Gt) and man-made global emissions from other GHGs — methane, nitrous oxide, and fluorinated gases — were the equivalent of an additional 12.2 Gt of CO2. The 2023 “State of Carbon Dioxide Removal” report estimates that the current CO2 removal rate from human efforts is 2 Gt per year. Thus, a bottom-up estimate of net GHG emissions from human activity is the equivalent of approximately 49 Gt of CO2 per year. An estimated current annual rate of GHG emissions and removals is shown in Figure 1.
Figure 1. Estimated Annual Rate of GHG Emissions and Removals in 2022
Source: Based on data from the 2022 PIK dataset and the 2023 “State of Carbon Dioxide Removal” report.
Data from the Global Monitoring Laboratory of the National Oceanic and Atmospheric Administration (NOAA) tell a similar story. The NOAA data in Figure 2 show an average annual increase in atmospheric CO2 concentration of 2.15 parts per million (ppm) for the period 2020–2022. A 1 ppm increase in concentration is equal to 7.82 Gt of CO2. Thus, the net rate of human and natural emissions of CO2 can be calculated to be approximately 17 Gt. This is less than the bottom-up estimate above, implying that the land and oceans are currently acting as a carbon sink. Natural emission and removal rates of carbon dioxide can change significantly and rapidly, and it cannot be assumed that the current natural rate of absorption will continue.
Figure 2. Annual Mean Growth Rate for Mauna Loa, Hawaii
Source: Global Monitoring Laboratory of NOAA. Image provided by NOAA Global Monitoring Laboratory, Boulder, Colorado, USA.