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  • Open Access

Separating Greenhouse-Gas Driven Forcing from Natural Fluctuations in the Time Series for Global Mean Temperatures

Cyrus C. Taylor*

  • *Contact author: cct@case.edu
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Phys. Rev. Lett. 136, 104201 – Published 12 March, 2026

DOI: https://doi.org/10.1103/897x-zrmv

Abstract

The year 2024 was the hottest in the modern era, followed by 2023. Do these temperatures signal unexpected changes in the climate system? Writing the global annual mean temperature as the sum of two terms, greenhouse-gas driven climate change and fluctuations due to internal and external variability, we model the first term by extending the logarithmic dependance of the temperature anomaly to non-equilibrium conditions. We validate the method using the illustrative scenarios considered by the IPCC. Fitting the data, we find that the residuals for 2023 and 2024 are consistent with past fluctuations. We comment on how putative changes in the climate regime will manifest themselves in coming years.

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References (29)

  1. WMO confirms 2024 as warmest year on record at about 1.55 °C above pre-industrial level (2025), https://wmo.int/news/media-centre/wmo-confirms-2024-warmest-year-record-about-155degc-above-pre-industrial-level.

  2. G. A. Schmidt, Z. Hausfather, D. Visioni, and M. Clyne, Cracking the puzzle of the anomalous temperatures in 2023: Observational and modeling studies to identify and understand potential factors and future implications I poster, in AGU24, Session GC23K (AGU, Washington, D.C., 2024), https://agu.confex.com/agu/agu24/meetingapp.cgi/Session/225040.
  3. G. A. Schmidt, Z. Hausfather, D. Visioni, and M. Clyne, Cracking the puzzle of the anomalous temperatures in 2023: Observational and modeling studies to identify and understand potential factors and future implications II oral, in AGU24, Session GC21O (AGU, Washington, D.C., 2024), https://agu.confex.com/agu/agu24/meetingapp.cgi/Session/233589.
  4. G. A. Schmidt and Z. Hausfather, Global mean surface temperature anomalies in 2023/2024, in State of the Global Climate 2024, WMO-No. 1368 (World Meteorological Association (WMO), Geneva, Switzerland, 2025), https://wmo.int/sites/default/files/2025-03/WMO-1368-2024_en.pdf.
  5. G. Hegerl and F. Zwiers, Use of models in detection and attribution of climate change, WIREs Climate Change 2, 570 (2011).
  6. W. S. Broecker, Climatic change: Are we on the brink of a pronounced global warming?, Science 189, 460 (1975).
  7. R. T. Pierrehumbert, Principles of Planetary Climate (Cambridge University Press, Cambridge, England, 2010).
  8. W. Zhong and J. D. Haigh, The greenhouse effect and carbon dioxide, Weather 68, 100 (2013).
  9. M. Etminan, G. Myhre, E. J. Highwood, and K. P. Shine, Radiative forcing of carbon dioxide, methane, and nitrous oxide: A significant revision of the methane radiative forcing, Geophys. Res. Lett. 43, 12614 (2016).
  10. D. M. Romps, J. T. Seeley, and J. P. Edman, Why the forcing from carbon dioxide scales as the logarithm of its concentration, J. Clim. 35, 4027 (2022).
  11. S. Arrhenius, On the influence of carbonic acid in the air upon the temperature of the ground, London, Edinburgh, Dublin Philos. Mag. J. Sci. 41, 237 (1896).
  12. NOAA Global Monitoring Laboratory, The noaa annual greenhouse gas index (aggi), https://gml.noaa.gov/aggi/aggi.html (2025) (accessed: 2026-01-09).
  13. K. von Schuckmann et al., Heat stored in the earth system 1960–2020: Where does the energy go?, Earth Syst. Sci. Data 15, 1675 (2023).
  14. D. Hartmann, Global Physical Climatology, International Geophysics (Elsevier Science, New York, 2015).
  15. IPCC, Summary for Policymakers, 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, edited by V. Masson-Delmotte, P. Zhai, A. Pirani, S. Connors, C. Péan, S. Berger, N. Caud, Y. Chen, L. Goldfarb, M. Gomis, M. Huang, K. Leitzell, E. Lonnoy, J. Matthews, T. Maycock, T. Waterfield, O. Yelekçi, R. Yu, and B. Zhou (Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA, 2021), 10.1017/9781009157896.001.
  16. C. D. Jones, C. Koven, Z. Nicholls, S. Liddicoat, M. Meinshausen, and J. Lewis, Technical Summary of the Working Group I contribution to the IPCC sixth assessment report—input data for box TS.5, figure 1 (v20220817) (2023) NERC EDS Centre for Environmental Data Analysis, 10.5285/d6a301f3429b44e7924296f840f68fe6.
  17. C. D. Jones, C. Koven, Z. Nicholls, S. Liddicoat, M. Meinshausen, and J. Lewis, Summary for Policymakers of the Working Group i Contribution to the IPCC Sixth Assessment Report—data for figure SPM.8 (v20210809) (2023) NERC EDS Centre for Environmental Data Analysis, 10.5285/98af2184e13e4b91893ab72f301790db.
  18. Data retrieved from https://gml.noaa.gov/ccgg/trends/data.html. Data Source: Dr. Xin Lan, NOAA/GML (http://gml.noaa.gov/ccgg/trends/) and Dr. Ralph Keeling, Scripps Institution of Oceanography (http://scrippsco2.ucsd.edu/).
  19. N. J. L. Lenssen, G. A. Schmidt, J. E. Hansen, M. J. Menne, A. Persin, R. Ruedy, and D. Zyss, Improvements in the GISTEMP uncertainty model, J. Geophys. Res. 124, 6307 (2019).
  20. B. Huang, X. Yin, M. J. Menne, R. Vose, and H.-M. Zhang, Improvements to the land surface air temperature reconstruction in NOAAGlobalTemp: An artificial neural network approach, Artif. Intell. Earth Syst. 1, e220032 (2022).
  21. R. A. Rohde and Z. Hausfather, The berkeley earth land/ocean temperature record, Earth Syst. Sci. Data 12, 3469 (2020).
  22. C. P. Morice, J. J. Kennedy, N. A. Rayner, J. P. Winn, E. Hogan, R. E. Killick, R. J. H. Dunn, T. J. Osborn, P. D. Jones, and I. R. Simpson, An updated assessment of near-surface temperature change from 1850: The HadCRUT5 data set, J. Geophys. Res. 126, e2019JD032361 (2021).
  23. H. Hersbach et al., The ERA5 global reanalysis, Q. J. R. Meteorol. Soc. 146, 1999 (2020).
  24. UK Met Office Climate dashboard: Get the data, https://climate.metoffice.cloud/temperature.html takes you to the climate dashboard data compilation.
  25. IPCC, Summary for policymakers, 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, edited by V. Masson-Delmotte, P. Zhai, A. Pirani, S. Connors, C. Péan, S. Berger, N. Caud, Y. Chen, L. Goldfarb, M. Gomis, M. Huang, K. Leitzell, E. Lonnoy, J. Matthews, T. Maycock, T. Waterfield, O. Yelekçi, R. Yu, and B. Zhou (Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA, 2021), pp. 3–32, 10.1017/9781009157896.001.
  26. R. von Mises, Chapter ix—analysis of statistical data, in Mathematical Theory of Probability and Statistics, edited by R. von Mises (Academic Press, New York, 1964), pp. 431–493.
  27. J. Durbin and G. Watson, Testing for serial correlation in least squares regression. III, Biometrika 58, 1 (1971).
  28. C. Smith, B. Hall, F. Dentener, J. Ahn, W. Collins, C. Jones, M. Meinshausen, E. Dlugokencky, R. Keeling, P. Krummel, J. Mühle, Z. Nicholls, and I. Simpson, IPCC Working Group 1 (WG1) Sixth Assessment Report (AR6) Annex III Extended Data, 10.5281/zenodo.5705391 (2021).
  29. P. Friedlingstein et al., Global carbon budget 2024, Earth Syst. Sci. Data 17, 965 (2025).

Outline

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Phys. Rev. Lett. 136, 104201– Published 12 March, 2026
  • Received 9 April 2025
  • Revised 2 October 2025
  • Accepted 9 February 2026
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Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.

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