Nations’ Greenhouse Gas Emissions - Past and Current
The Art
The Science
“CO2 Emitted Long Ago Continues to Contribute to Climate Change Today
“The carbon dioxide not removed from the atmosphere by natural sinks lingers for thousands of years. This means CO2 emitted long ago continues to contribute to climate change today. The long lifetime of atmospheric CO2 is one of the primary reasons why the COVID-19 pandemic–related reduction in greenhouse gas emissions—a decrease of 7% between 2019 and 202033,34,35—had no measurable impact on atmospheric CO2 concentrations and little effect on global temperatures… Because of historical trends, cumulative CO2 emissions from fossil fuels and industry in the US are higher than from any other country (Figure 2.1b).
Carbon dioxide, along with other greenhouse gases like methane and nitrous oxide, is well-mixed in the atmosphere. This means these gases warm the planet regardless of where they were emitted, and all countries that emit them contribute to the warming of the entire globe. For the first half of the 20th century, the vast majority of greenhouse gas emissions came from the United States and Europe, but emissions from the rest of the world, particularly Asia, have been rising rapidly (Figure 2.1a) In 2021, for example, US emissions were 17% lower than 2005 levels and falling. Currently, the country that emits the most CO2 on an annual basis is China.
In order to understand the total contributions of past actions to observed climate change, additional warming from CO2 emissions from land use, land-use change, and forestry, as well as emissions of nitrous oxide and the shorter-lived greenhouse gas methane, should also be taken into account alongside cumulative fossil CO2 emissions. Accounting for all these factors and emissions from 1850–2021, US emissions are estimated to comprise approximately 17% of current global warming, China 12%, European Union 10%, and emissions from the 47 least-developed countries collectively 6%.38 The present is shaped by the past; future global warming depends on decisions made today ….”
USGCRP, 2023: Fifth National Climate Assessment. Crimmins, A.R., C.W. Avery, D.R. Easterling, K.E. Kunkel, B.C. Stewart, and T.K. Maycock, Eds. U.S. Global Change Research Program, Washington, DC, USA. https://doi.org/10.7930/NCA5.2023
