Global Carbon Budget 2021

The "Balance Sheet" for the Global Carbon Budget

The 2021 global carbon budget[1] is out and is undergoing peer review. The budget contains emission estimates for 2020 and preliminary estimates for 2021. I’m reporting these in GtC; to convert these figures to GtCO2, you can multiply these numbers by 3.67. In 2020, fossil fuel and industry emissions totaled 9.5 GtC and land use change totaled 0.88 GtC. In 2021, preliminary estimates are that fossil fuel and industry emissions totaled 9.92 GtC while land use change totaled 0.8 GtC. In terms of cumulative emissions, this means that from 1750, anthropogenic emissions have totaled 691 GtC through 2020 and about 702 GtC through 2021.

Meanwhile, CO2 concentrations have increased from about 277.6 ppm in 1750 to 414.24 ppm in 2020 and 416.45 ppm in 2021.[2] That’s a 49% increase in CO2 concentrations. If we convert the 136.6 ppm increase from 1750 to 2020, that means that there is 291 GtC more carbon in the atmosphere now than there was in 1750.



From the estimates in the paper, about 42% of our emissions remain in the atmosphere (the rest gets taken up by land and oceans). So of the 691 GtC we emitted from 1750 to 2020, about 290 GtC is still in the atmosphere. In other words, virtually all the increase in CO2 concentrations is due to human emissions. The paper resolved the total carbon budget to ~10 GtC from 1750-2020.

The global carbon budget 2021 report, with analysis of uncertainties in these estimates, can be found here.[3] There is a lot more information here than what I’m reporting above. It’s extremely fascinating for those interested in empirical data.

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