Not so innocent as it looks, a pertinent question is asked by Judith Curry on Twitter:<\/p>\n\n\n\n
How much of a change in cloudiness would it take to account for the 0.53 W\/m2<\/sup> increase in TOA radiative forcing since 2003?<\/em><\/p><\/blockquote>\n\n\n\n
https:\/\/twitter.com\/curryja\/status\/1375144537522204672<\/em><\/a><\/p>\n\n\n\n
She asks it in relation with a recent article accepted for publication on Observational evidence of increasing global radiative forcing<\/em> (Kramer et al., 2021).<\/p>\n\n\n\n
This question touches a central point of climate science because it cannot be an experimental science in which one can play with parameters in isolation from each other. Only a few limited ongoing instrumental observations and Palaeolithic reconstructions may serve to try to distinguish natural from anthropogenic processes, in particular radiative forcing processes. However, most of this job, if not all of it, takes place in silico<\/em>.<\/p>\n\n\n\n
The question can also be formulated in a more general way:<\/p>\n\n\n\n
Is it at all possible, at global scope and by instrumental observations, to distinguish the causes of radiative forcing difference of 0.53 W\u00b7m-2<\/sup> over a time period of 15 years?<\/em> <\/p><\/blockquote>\n\n\n\n
To the cloudiness suggestion:<\/p>\n\n\n\n
- From a simple, two-layers energy balance budget<\/a> it can be estimated that, all other things remaining constant, a 1% increase in cloudiness (which amounts to approx. 66% overall) may induce a temperature increase of 0.54 \u00b0C at the Earth surface and of 0.45 \u00b0C at the top of atmosphere (TOA).<\/li>
- Without consideration for any system feedback, a radiative forcing of 0.53 W\u00b7m-2<\/sup> would induce a temperature rise of 0.11 \u00b0C at the surface, and 0.18 \u00b0C at TOA.<\/li>
- To obtain a same temperature increase, thus to respond to a forcing of 0.53 W\u00b7m-\u20112<\/sup>, it would take a change in cloudiness by 0.27 % for the surface, or by 0.4 % for the TOA.<\/li>
- Is cloudiness, or change of cloudiness, measurable with such accuracy and precision at the aggregated global scope? What was it in 2003, and in 2018?<\/li><\/ul>\n\n\n\n
From an overall energy balance perspective:<\/p>\n\n\n\n
- In general, and to simplify, modelers estimate all in- and outgoing heat fluxes, and let any remaining quantity warm or cool the oceans, thus reporting a so-called accumulated ocean heat or \u201cheat content anomaly\u201d.
According to NASA<\/a>, over the 1993\u20132019 period, a heat flux anomaly of 0.36 to 0.41 W\u00b7m-2<\/sup> for the first 700 m of depth would have accumulated. Over time, other heat release periods should also occur so that the imbalance does not let us boil or freeze for ever (it never did).<\/li>- Over this time period of 26 years, this heat flux would have implied a temperature change to a well homogenized 700-meter water column of 0.10 to 0.11 \u00b0C, a hard to measure change.<\/li>
- A question, similar to the previous one, arises regarding instrumental observation: is it at all possible to measure such heat accumulation precisely, accurately, and at the aggregated global scope (by localized temperature monitoring or any other valid method)?<\/li><\/ul>\n\n\n\n
In all these evaluations, errors will have to be taken into account; those arising from instrumental imprecisions and inaccuracies, those that are embedded in the data massaging process (averaging over time and locations), and systemic ones deriving from incomplete and imperfect model designs, their parametrization and simplifications.<\/p>\n\n\n\n
Said differently: the resulting balance sheet of any model should entail an account for garbage; but it appears that it is at the same time the energy accumulating in oceans. The NASA-Goddard simplified representations<\/a> does not show any, others (Trenberth, Fasullo, & Kiehl, 2009) show an \u201cnet absorbed\u201d of 0.9 W\u00b7m-2<\/sup> or the U.S. Global Change Research Program (USGCRP)<\/a> indicates a \u201cSurface imbalance\u201d of 0,6 \u00b10.17 W\u00b7m-2<\/sup> (one appreciates the margin precision). However, taking into account all potential errors, the true range of validity of this imbalance may well be of the order of hundreds of percent, thus challenging the narrative of a ticking time bomb accumulated in the ocean depths.<\/p>\n\n\n\n
One final question must be addressed to the climate science community:
will the heat accumulated in the oceans ever be trashed?<\/p>\n\n\n\n
\n\n\n\nKramer, R. J., He, H., Soden, B. J., Oreopoulos, L., Myhre, G., Forster, P. M., & Smith, C. J. (2021). Observational evidence of increasing global radiative forcing. Geophysical Research Letters, 48(e2020GL091585). https:\/\/doi.org\/10.1029\/2020GL091585<\/p>\n\n\n\n
Trenberth, K. E., Fasullo, J. T., & Kiehl, J. (2009). Earth\u2019s global energy budget.
Bulletin of the American Meteorological Society, 90(3), 311\u2013323. https:\/\/doi.org\/10.1175\/2008BAMS2634.1<\/p>\n\n\n\n
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