This is the average amount of CO2 that is in the atmosphere in a given year. The yearly average highlights the long-term trends of atmospheric CO2 and allows us to see modern day levels compared to pre-industrial levels, even as far back as the last 800,000 years. This is critical because the amount of CO2 in the atmosphere is directly related to the warming of the Earth. The warming impact due to atmospheric CO2 can be seen in the Monthly Greenhouse Gases Impact on Energy Balance.Monthly Greenhouse Gases Impact on Energy Balance
The primary unit here is parts per million (ppm), which describes the concentration of atmospheric CO2 per year. The secondary unit here is gigatonnes, which describes the weight of atmospheric CO2 per year. We show this to be able to relate to emissions, which are commonly expressed in gigatonnes.Wikipedia: Parts-per notation
In 60 years the CO2 concentration has steadily risen from just over 300 ppm to more than 400 ppm. To get a feeling for the natural concentrations of CO2, we can compare this to historical values.
When we look at the last 1,000 years, we can clearly see that the CO2 level started rising at the end of the 18th century, coinciding with the industrial revolution.
Throughout the last glacial period, roughly 100,000 to 12,000 years ago, we can see a drastic variation in CO2 levels. This was also a drastic period! Ice sheets reached the northern parts of the US, the UK, Germany and Northeast Siberia. There were sea-level changes up to 120 meters. However, the changes in CO2 levels were smaller and much slower compared to what we have been experiencing over the last 200 years.
The last 800,000 years offer some perspective on the CO2 levels during the recurring glacial periods and the unusually high CO2 level of our time. The current level of over 400 ppm was unheard of in the past, which saw values between 180 ppm and 300 ppm.Wikipedia: Carbon Dioxide in Earth's Atmosphere
The data are from the Global Carbon Budget 2022 and two subgroups of NOAA, the Global Monitoring Laboratory for recent data and the National Centers for Environmental Information for paleoclimatology data.
The Global Monitoring Laboratory has a global network of air sampling sites where they measure CO2. They have an annual mean dataset starting in 1980. For the years between 1959 and today that are unavailable, the atmospheric increase values are used to calculate an estimate for the annual means.
The Global Carbon Budget 2022 provides yearly atmospheric increase values going back to 1750, which are used to estimate the yearly atmospheric CO2 between 1750 and 1959.
National Centers for Environmental Information holds datasets that contain reconstructions of historic CO2 levels going back 800,000 years based on Antarctic ice cores.
Globally averaged marine surface annual mean rates dataCredits: Ed Dlugokencky and Pieter Tans, NOAA/GML (gml.noaa.gov/ccgg/trends/)Update cycle: yearlyDelay: ~ 3 months
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: monthlyDelay: ~ 3 months
Estimated Global Trend daily valuesCredits: Ed Dlugokencky and Pieter Tans, NOAA/GML (gml.noaa.gov/ccgg/trends/)Update cycle: dailyDelay: ~ 2 days
Antarctic Ice Core Revised Composite and Individual Core CO2 DataCredits: Bernhard Bereiter, Sarah Eggleston, Jochen Schmitt, Christoph Nehrbass-Ahles, Thomas F. Stocker, Hubertus Fischer, Sepp Kipfstuhl and Jerome Chappellaz. 2015. Revision of the EPICA Dome C CO2 record from 800 to 600 kyr before present. Geophysical Research Letters. . doi: 10.1002/2014GL061957
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.