Greenhouse gas pollution caused by human activities trapped 49% more heat in the atmosphere in 2021 than they did in 1990, according to NOAA scientists.
NOAA’s Annual Greenhouse Gas Index, known as the AGGI, tracks increases in the warming influence of human emissions of heat-trapping gases, including carbon dioxide, methane, nitrous oxide, chlorofluorocarbons, and 16 other chemicals. The AGGI converts the complex scientific computations of how much extra heat these gases capture into a single number that can easily be compared to previous years and tracks the rate of change.
Carbon dioxide, or CO2, is by far the most abundant human-emitted greenhouse gas. Roughly 36 billion metric tons of CO2 are emitted each year by transportation, electrical generation, cement manufacturing, deforestation, agriculture, and many other practices. A substantial fraction of CO2 emitted today will persist in the atmosphere for more than 1,000 years. Not surprisingly, it is also the largest contributor to the AGGI in terms of both amount and rate of increase.
NOAA measurements showed the global average concentration of CO2 in 2021 was 414.7 parts per million (ppm). The annual increase was 2.6 ppm during this year, about the average annual increase for the previous decade, and much higher than the increase measured during 2000-2009. CO2 levels have risen by 61 ppm since 1990, accounting for 80% of the increased heat tracked by the AGGI since that year.
“CO2 is the main player because it stays in the atmosphere and oceans for thousands of years and it is by far the largest contributor to global warming,” said GML Senior Scientist Pieter Tans. “Eliminating CO2 pollution has to be front and center in any efforts to deal with climate change.”