Climate Dynamics

, Volume 42, Issue 9–10, pp 2339–2351 | Cite as

Scaling fluctuation analysis and statistical hypothesis testing of anthropogenic warming

  • S. LovejoyEmail author


Although current global warming may have a large anthropogenic component, its quantification relies primarily on complex General Circulation Models (GCM’s) assumptions and codes; it is desirable to complement this with empirically based methodologies. Previous attempts to use the recent climate record have concentrated on “fingerprinting” or otherwise comparing the record with GCM outputs. By using CO2 radiative forcings as a linear surrogate for all anthropogenic effects we estimate the total anthropogenic warming and (effective) climate sensitivity finding: ΔT anth  = 0.87 ± 0.11 K, \(\uplambda_{{2{\text{x}}{\text{CO}}_{2} ,{\text{eff}}}} = 3.08 \pm 0.58\,{\text{K}}\). These are close the IPPC AR5 values ΔT anth  = 0.85 ± 0.20 K and \(\uplambda_{{2{\text{x}}{\text{CO}}_{2} }} = 1.5\!-\!4.5\,{\text{K}}\) (equilibrium) climate sensitivity and are independent of GCM models, radiative transfer calculations and emission histories. We statistically formulate the hypothesis of warming through natural variability by using centennial scale probabilities of natural fluctuations estimated using scaling, fluctuation analysis on multiproxy data. We take into account two nonclassical statistical features—long range statistical dependencies and “fat tailed” probability distributions (both of which greatly amplify the probability of extremes). Even in the most unfavourable cases, we may reject the natural variability hypothesis at confidence levels >99 %.


Anthropogenic warming Scaling Natural climate variability Statistical testing 



P. Dubé, the president of the Quebec Skeptical Society, is thanked for helping to motivate this work. An anonymous reviewer of an earlier version of this paper is thanked for the opinion that a GCM free approach to anthropogenic warming cannot work, concluding: “go get your own GCM”.This work was unfunded, there were no conflicts of interest.


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Copyright information

© Springer-Verlag Berlin Heidelberg 2014

Authors and Affiliations

  1. 1.PhysicsMcGill UniversityMontrealCanada

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