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The IPCC exaggerate: Monckton calculates how much

Following on from blackbody discussions, here is Christopher Monckton’s simple account of how we know the IPCC is exaggerating climate sensitivity. This comes from page 12 of Moncktons: Regulation without reason  (on the Canadian coal regulations.)

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Guest Post: Christopher Monckton

Are the IPCC’s global-warming projections proving accurate?

IPCC (2007, scenario A2) expects 3.4 C° manmade global warming to 2100. The calculations so far in this paper have assumed that the IPCC is right. Environment Canada does not ask any questions about the IPCC’s global-warming projections. Officials should have made some allowance for IPCC overshoot.

Since 1750, whence IPCC dates our influence on climate, a recent study (Blasing, 2011) shows 3 W m–2 of forcing from our greenhouse-gas emissions, less –1 W m–2 from non-GHG influences (IPCC, 2007). Global temperature had risen by 0.5 C° from 1750-1983 (Hansen, 1984), with a further 0.3 C° since (HadCRUt3, 2011). Of this 0.8 C° warming, 50 to 100% may be manmade. Thus, the 261-year transient climate sensitivity parameter is (0.4 to 0.8)/(3 – 1) = 0.2 to 0.4 C° W–1 m2. Multiplying by the forcing at CO2 doubling, i.e. 5.35 ln 2 (Myhre et al., 2001, cited by IPCC, 2001, 2007), gives transient sensitivity of 0.75 to 1.5 C° by 2100, when CO2 concentration will have doubled. Dividing this value by 0.7, the fraction of all forcings attributable to CO2, allows for non-CO2 forcings. Expected warming would thus be 1.1 to 2.1 C° to 2100, 32 to 62% of IPCC’s central estimate.

Since 1850, the year when the first global-temperature record was kept, the most rapid rate of warming sustained for more than a decade was 0.17 C°/decade (HadCRUt3, 2011). Assume that, after no warming in the 2000s, this maximum supra-decadal warming rate were to become the average rate for the next nine decades. Warming would be 1.5 C° by 2100, 44% of IPCC’s central estimate.

Since 1950, when Man first began emitting enough CO2 to influence the climate, 0.72 C° of warming has occurred (HadCRUt3, 2011). This rate, extrapolated from the past 61 years to the next 90, gives 1.1 C° of warming by 2100. Assuming 20 to 40% acceleration in the warming rate to allow for rising CO2 concentrations net of the logarithmic diminution in the CO2 forcing gives 1.3 to 1.5 C° warming to 2100.

Averaging the results obtained from data over three recent periods by distinct methods gives 1.3 to 1.7 C° warming by 2100 – 40 to 50% of the IPCC’s estimate.

A theoretical checksum: In Kiehl & Trenberth (1997), total forcing from H2O, CO2, CH4, O3, and N2O is given as 125 W m–2 in clear skies and 86 in cloud, or ~101 W m–2 overall. Holding insolation and albedo constant, the difference between surface temperatures with and without these GHGs is 288 – 255 = 33 C°. Ignoring minor forcings, climate sensitivity of the whole atmosphere is (5.35 ln 2)(33/101) = 1.2 C°, which, divided by 0.7 to allow for non-CO2 forcings, gives total warming at CO2 doubling by 2100 of 1.7 C°, or 50% of IPCC’s central estimate, more than halving the cost-effectiveness of the regulations.

 

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 Disclaimer: Views expressed in a guest post are those of the author.

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