In 2019, the growth in global greenhouse gas (GHG) emissions (excluding those from land-use change) slowed down to 0.6%, reaching 51.7 gigatonnes of CO2 equivalent (GtCO2 eq. This revised growth rate is half of last year’s estimate of 1.1% and less than half of the average annual growth rate of 1.5% since 2005. However, in 2020, the year in which the world economy and society was fully affected by the COVID-19 pandemic, global total GHG emissions are estimated to have declined by about 4% to 49.8 GtCO2 eq. This is the only report that provides estimations of all recent global greenhouse gas emissions (not only CO2).
Revised growth of 0.6% in global greenhouse gas emissions in 2019
The 0.6% increase was mainly due to a 0.5% increase in global CO2 emissions from fossil-fuel combustion and industrial non-combustion processes, including cement production. CO2 emissions contributed by about three quarters to the total GHG emissions in 2019, whereas global emissions of methane (CH4), nitrous oxide N2O) and fluorinated gases (F-gases) had shares of 18%, 6% and 2.5%, respectively. Collectively, these other greenhouse gas emissions increased by 0.9% in 2019: emissions of CH4, N2O and F-gases changed in 2019 by a respective 1.0%, -7% and 3.9%.
Decrease of more than 3.7% in global emissions in 2020 due to COVID-19 pandemic recession
The more than 3.7% decrease in global GHG emissions in 2020 was mainly due to a 5.1% decrease in global CO2 emissions from fossil-fuel combustion and industrial non-combustion processes, which is very close to CO2 estimates published by other organisations. The global change in emissions in 2020 of CH4, N2O and F-gases estimated with the Fast-Track method was +0.1%, -0.4% and +4.6%, resulting in a total GHG decrease of 3.7% in 2020.
However, the figures for the non-CO2 gases due not include all recession effects not included in the extrapolation method. Including them leads to a total decline in global GHG emissions in 2020, including COVID-19 recession impacts, of about -4.0% (or 49.7 GgCO2 eq rounded).
The Fast-Track estimates of total GHG emissions in 2020 for the top-5 countries and the European Union showed that all declined except for China that saw an increase of 1.5%. The others saw all declining GHG emissions in 2020: United States (-8.5%), European Union (EU-27) (-8.4%), India (-3.9%), Russian Federation (-4.9%), and Japan (-6.3%).
For CH4, N2O and the F-gases, the report uses the Global Warming Potential (GWP) metric from the Fourth Assessment Report (AR4) of the IPCC with a the time horizon of 100 years. In the AR4 the GWPs of CH4 and N2O are 25 and 298, respectively.