This is the difference in the atmospheric CO2 of a given year compared to the previous year. We call this an ‘increase’ rather than a ‘change’ because in recent history, every year has had more CO2 in the atmosphere than the previous year. However, in the past there was sometimes a decrease, for example in the 1850s, which is why those values are negative. The yearly CO2 increase depends on the processes that emit CO2 into the atmosphere and absorb CO2 out of the atmosphere. The average lifetime of CO2 in the atmosphere is just over 400 years.
The Yearly Atmospheric CO2 Increase is critical because as long as it increases, the warming effect due to CO2 is also increasing.
The primary unit here is parts per million (ppm), which describes the increase in the concentration of atmospheric CO2 per year. The secondary unit here is gigatonnes, which describes the weight of the increase in atmospheric CO2 per year. We show this to be able to relate to emissions, which are commonly expressed in gigatonnes.Wikipedia: Parts-per notation
Not only is atmospheric CO2 increasing every year, the rate is also growing. There are large yearly fluctuations that are mostly due to the changes in CO2 absorbed by the Earth’s land mass. You can read about in the Yearly Absorption of Human CO2 Emissions.Yearly Absorption of Human CO2 Emissions
In the chart you can see a smooth line before the late 1950s and a fluctuating line thereafter. In reality, there were fluctuations before the 1950s too, but there are not enough measurements to confidently calculate the yearly fluctuations and that is why there is a smooth line highlighting the trend. In 1958 the direct continuous measurements of atmospheric CO2 started at Mauna Loa under Charles Keeling, after whom the Keeling Curve is named.Wikipedia: Mauna Loa Observatory
The data since 1958 is from NOAA’s Global Monitoring Laboratory, which has a global network of air sampling sites to measure CO2. The atmospheric CO2 increase is calculated by taking the difference between consecutive deseasonalized December-January averages. For recent years where only parts of the months are available, the increase is calculated as the difference between the average of the available months compared to that same period of the previous year. If monthly data is not yet available, the daily estimate data is used to compare the available days with the same days of the previous year.
The values from 1850 to 1957 are taken from the Global Carbon Budget 2022.
Globally averaged marine surface annual mean growth rates dataCredits: Ed Dlugokencky and Pieter Tans, NOAA/GML (gml.noaa.gov/ccgg/trends/)Update cycle: monthlyDelay: ~ 3 months
Globally averaged marine surface monthly mean dataCredits: Ed Dlugokencky and Pieter Tans, NOAA/GML (gml.noaa.gov/ccgg/trends/)Update cycle: dailyDelay: ~ 2 days
Global Carbon Budget 2022Credits: Friedlingstein et al (2022) - full reference below **Update cycle: yearlyDelay: ~9 months after end of yearReference: ** Global Carbon Budget 2022, by Pierre Friedlingstein, Michael O'Sullivan, Matthew W. Jones, Robbie M. Andrew, Luke Gregor, Judith Hauck, Corinne Le Quéré, Ingrid T. Luijkx, Are Olsen, Glen P. Peters, Wouter Peters, Julia Pongratz, Clemens Schwingshackl, Stephen Sitch, Josep G. Canadell, Philippe Ciais, Robert B. Jackson, Simone R. Alin, Ramdane Alkama, Almut Arneth, Vivek K. Arora, Nicholas R. Bates, Meike Becker, Nicolas Bellouin, Henry C. Bittig, Laurent Bopp, Frédéric Chevallier, Louise P. Chini, Margot Cronin, Wiley Evans, Stefanie Falk, Richard A. Feely, Thomas Gasser, Marion Gehlen, Thanos Gkritzalis, Lucas Gloege, Giacomo Grassi, Nicolas Gruber, Özgür Gürses, Ian Harris, Matthew Hefner, Richard A. Houghton, George C. Hurtt, Yosuke Iida, Tatiana Ilyina, Atul K. Jain, Annika Jersild, Koji Kadono, Etsushi Kato, Daniel Kennedy, Kees Klein Goldewijk, Jürgen Knauer, Jan Ivar Korsbakken, Peter Landschützer, Nathalie Lefèvre, Keith Lindsay, Junjie Liu, Zhu Liu, Gregg Marland, Nicolas Mayot, Matthew J. McGrath, Nicolas Metzl, Natalie M. Monacci, David R. Munro, Shin-Ichiro Nakaoka, Yosuke Niwa, Kevin O'Brien, Tsuneo Ono, Paul I. Palmer, Naiqing Pan, Denis Pierrot, Katie Pocock, Benjamin Poulter, Laure Resplandy, Eddy Robertson, Christian Rödenbeck, Carmen Rodriguez, Thais M. Rosan, Jörg Schwinger, Roland Séférian, Jamie D. Shutler, Ingunn Skjelvan, Tobias Steinhoff, Qing Sun, Adrienne J. Sutton, Colm Sweeney, Shintaro Takao, Toste Tanhua, Pieter P. Tans, Xiangjun Tian, Hanqin Tian, Bronte Tilbrook, Hiroyuki Tsujino, Francesco Tubiello, Guido R. van der Werf, Anthony P. Walker, Rik Wanninkhof, Chris Whitehead, Anna Willstrand Wranne, Rebecca Wright,Wenping Yuan, Chao Yue, Xu Yue, Sönke Zaehle, Jiye Zeng, and Bo Zheng (2022), Earth System Science Data, 14, 4811–4900, 2022, DOI: 10.5194/essd-14-4811-2022.