Carbon budget

For the assessment of the biogeochemical cycle by which carbon is exchanged at the global level between sources and sinks in the biosphere, pedosphere, geosphere, hydrosphere, and atmosphere, also referred to as the Global Carbon Budget, see Carbon cycle.
Carbon budget and emission reduction scenarios needed to reach the two-degree target agreed to in the Paris Agreement (without net negative emissions, based on peak emissions)[1]

A carbon budget is a concept used in climate policy to help set emissions reduction targets in a fair and effective way. It examines the "maximum amount of cumulative net global anthropogenic carbon dioxide (CO2) emissions that would result in limiting global warming to a given level".[2]: 2220  It can be expressed relative to the pre-industrial period (the year 1750). In this case, it is the total carbon budget. Or it can be expressed from a recent specified date onwards. In that case it is the remaining carbon budget.[2]: 2220 

A carbon budget that will keep global warming below a specified temperature limit is also called an emissions budget or quota, or allowable emissions.[3][4][5] Apart from limiting the global temperature increase, another objective of such an emissions budget can be to limit sea level rise.[6]

Scientists combine estimates of various contributing factors to calculate the carbon budget. The estimates take into account the available scientific evidence as well as value judgments or choices.[7][8][9]

Global carbon budgets can be further sub-divided into national emissions budgets. This can help countries set their own emission goals. Emissions budgets indicate a finite amount of carbon dioxide that can be emitted over time, before resulting in dangerous levels of global warming. The change in global temperature is independent of the source of these emissions, and is largely independent of the timing of these emissions.[10][11]

To translate global carbon budgets to the country level, a set of value judgments have to be made on how to distribute the remaining carbon budget over all the different countries. This should take into account aspects of equity and fairness between countries[8] as well as other methodological choices.[12] There are many differences between nations, such as population size, level of industrialisation, historic emissions, and mitigation capabilities. For this reason, scientists are attempting to allocate global carbon budgets among countries using various principles of equity.[13]

  1. ^ Christiana Figueres; Hans Joachim Schellnhuber; Gail Whiteman; Johan Rockström (2017-06-29). "Three years to safeguard our climate". Nature. Vol. 546, no. 7660. pp. 593–595. doi:10.1038/546593a. ISSN 0028-0836. Retrieved 2022-05-01.
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  3. ^ Meinshausen, Malte; Meinshausen, Nicolai; Hare, William; Raper, Sarah C. B.; Frieler, Katja; Knutti, Reto; Frame, David J.; Allen, Myles R. (April 2009). "Greenhouse-gas emission targets for limiting global warming to 2 °C". Nature. 458 (7242): 1158–1162. Bibcode:2009Natur.458.1158M. CiteSeerX 10.1.1.337.3632. doi:10.1038/nature08017. PMID 19407799. S2CID 4342402.
  4. ^ Matthews, H Damon; Zickfeld, Kirsten; Knutti, Reto; Allen, Myles R (1 January 2018). "Focus on cumulative emissions, global carbon budgets and the implications for climate mitigation targets". Environmental Research Letters. 13 (1): 010201. Bibcode:2018ERL....13a0201D. doi:10.1088/1748-9326/aa98c9.
  5. ^ Raupach, Michael R.; Davis, Steven J.; Peters, Glen P.; Andrew, Robbie M.; Canadell, Josep G.; Ciais, Philippe; Friedlingstein, Pierre; Jotzo, Frank; van Vuuren, Detlef P.; Le Quéré, Corinne (21 September 2014). "Sharing a quota on cumulative carbon emissions". Nature Climate Change. 4 (10): 873–879. Bibcode:2014NatCC...4..873R. doi:10.1038/nclimate2384. hdl:11250/2484054.
  6. ^ Clark, Peter U.; Mix, Alan C.; Eby, Michael; Levermann, Anders; Rogelj, Joeri; Nauels, Alexander; Wrathall, David J. (2018). "Sea-level commitment as a gauge for climate policy". Nature Climate Change. 8 (8): 653–655. Bibcode:2018NatCC...8..653C. doi:10.1038/s41558-018-0226-6. hdl:10044/1/63152. ISSN 1758-678X. S2CID 91593244.
  7. ^ Rogelj, Joeri; Forster, Piers M.; Kriegler, Elmar; Smith, Christopher J.; Séférian, Roland (2019-07-18). "Estimating and tracking the remaining carbon budget for stringent climate targets". Nature. 571 (7765): 335–342. Bibcode:2019Natur.571..335R. doi:10.1038/s41586-019-1368-z. hdl:10044/1/78011. ISSN 0028-0836. PMID 31316194. S2CID 197542084.
  8. ^ a b Matthews, H. Damon; Tokarska, Katarzyna B.; Nicholls, Zebedee R. J.; Rogelj, Joeri; Canadell, Josep G.; Friedlingstein, Pierre; Frölicher, Thomas L.; Forster, Piers M.; Gillett, Nathan P.; Ilyina, Tatiana; Jackson, Robert B. (2020). "Opportunities and challenges in using remaining carbon budgets to guide climate policy". Nature Geoscience. 13 (12): 769–779. Bibcode:2020NatGe..13..769M. doi:10.1038/s41561-020-00663-3. hdl:20.500.11850/454127. ISSN 1752-0894. S2CID 227236155.
  9. ^ Canadell, J.G., P.M.S. Monteiro, M.H. Costa, L. Cotrim da Cunha, P.M. Cox, A.V. Eliseev, S. Henson, M. Ishii, S. Jaccard, C. Koven, A. Lohila, P.K. Patra, S. Piao, J. Rogelj, S. Syampungani, S. Zaehle, and K. Zickfeld, 2021: Chapter 5: Global Carbon and other Biogeochemical Cycles and Feedbacks. In Climate Change 2021: The Physical Science Basis. Contribution of Working Group I to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change [Masson-Delmotte, V., P. Zhai, A. Pirani, S.L. Connors, C. Péan, S. Berger, N. Caud, Y. Chen, L. Goldfarb, M.I. Gomis, M. Huang, K. Leitzell, E. Lonnoy, J.B.R. Matthews, T.K. Maycock, T. Waterfield, O. Yelekçi, R. Yu, and B. Zhou (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA, pp. 673–816, doi:10.1017/9781009157896.007.
  10. ^ Zickfeld, K.; Arora, V. K.; Gillett, N. P. (March 2012). "Is the climate response to CO emissions path dependent?". Geophysical Research Letters. 39 (5): n/a. Bibcode:2012GeoRL..39.5703Z. doi:10.1029/2011gl050205.
  11. ^ Cite error: The named reference pmid19516338 was invoked but never defined (see the help page).
  12. ^ Cite error: The named reference :5 was invoked but never defined (see the help page).
  13. ^ Cite error: The named reference :9 was invoked but never defined (see the help page).