Analysis: Why the IPCC exaggerates greenhouse warming of the oceans by at least 2.5 times
Why the IPCC exaggerates greenhouse warming of the oceans by at least 2.5 times
A new paper finds the deep oceans have cooled contrary to alarmist claims of deep ocean warming by Trenberth’s “missing heat” from carbon dioxide. Trenberth’s theory, one of at least 14 excuses for the ~18 year ‘pause’ of global warming, now appears to be dead in the water.
Data from the new paper can be used to derive that the world’s oceans have warmed only about 0.008°C over the past 19 years from 1992-2011, and imply that the IPCC exaggerates net greenhouse forcing on the oceans by at least a factor of 2.5 times.
According to the author Dr. Carl Wunsch, one of the world’s most respected oceanographers,
“A total change in [world ocean] heat content, top-to-bottom, is found (discussed below) of approximately 4 × 10^22 Joules in 19 years, for a net heating of 0.2±0.1 W/m2, smaller than some published values (e.g., Hansen et al., 2005, 0.86±0.12 W/m2 ; Lyman et al., 2010, 0.63±0.28 W/m2; or von Schuckmann and Le Traon, 2011, 0.55±0.1 W/m2; but note the differing averaging periods), but indistinguishable from the summary Fig. 14 of Abraham et al. (2013). Perhaps coincidentally, it is similar to the 135-year 700 m depth ocean rate of 0.2±0.1 W/m2 of Roemmich et al. (2012).”
Although the paper does not compare these estimates to those of the IPCC, using the “IPCC formula” for forcing from CO2 [which includes alleged positive feedback from water vapor], we find that over the same 19 year period studied by Dr. Wunsch that greenhouse gas forcing allegedly increased by 0.505 W/m2 given the increase in CO2 levels from 356.38 ppm in 1992 to 391.63 ppm in 2011:
5.35*ln(391.63/356.38) = 0.505 W/m2
However, Dr. Wunsch notes above that over the same period the world oceans warmed by only 0.2 ± 0.1 W/m2, or 2.5 times less than the IPCC alleged forcing from greenhouse gases. Note this is assuming that all ocean warming over that period was from greenhouse gas forcing and none from ocean oscillations, solar amplification mechanisms, clouds, global brightening, natural variability, etc. The actual greenhouse forcing on the oceans after feedbacks and natural variability is thus most likely to be a minimum of 2.5 times less than the IPCC claims.
Dr. Wunsch also finds a forcing of 1 W/m2, if continuously maintained, would change global mean ocean temperature by only about 0.04C.
“Consider, for example, that greenhouse gas warming of the ocean [since ~1850] is widely believed to be of order 1 W/m2 (e.g., Hansen et al., 2005) or less. The volume of the ocean is about 1.3 × 10^18 m3 . Using a mean density of 1038 kg/m3, the total mass is about 1.34 × 10^21 kg, and with a heat capacity of roughly 3.8 × 103 J/kg/◦C, the global heat capacity is approximately 5.4×10^24 J/◦C. A heating rate of 1 W/m2, if maintained for 20 years, produces an energy content change of about 2.2 × 10^23 J for a change in global ocean mean temperature of about 0.04◦C.”
Per the IPCC formula above, the alleged increase in greenhouse forcing over the recent 19 years is 0.505 W/m2, which would thus translate to an ocean warming of only 0.505*.04 = 0.02C. Dr. Wunsch finds the oceans have warmed only 0.2 W/m2 over the 19 years, which would translate to only a very tiny 0.2*0.04 = 0.008C.
The estimated ocean heating rates in Dr. Wunsch’s paper are also much less than prior estimates:
Wunsch: 2.1 x 10^21 Joules/year
Levitus (2012): 4.36 x 10^21 Joules/yr, 2.1 times faster
Silly Skeptical Science Hiroshima bomb calculator: 7.96 x 10^21 Joules/yr, 3.8 times faster
These findings are understandable in the context of the ~18 year pause in surface warming [thus no change in the temperature gradient between the atmosphere and ocean surface] and because longwave infrared radiation from greenhouse gases cannot heat the oceans.
Full paper by Dr. Wunsch available here
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