Guest essay by Dr Doug Hoyt

In the past few years, three articles have come out that, taken together, lead one to conclude that climate sensitivity is very low, being less than 1 C for a CO2 doubling compared to the 3 C figure favored by the IPCC.

The first article is by Levitus et al (2005). They conclude that the oceans warmed by 0.06 C between 1948 and 1998. It represented an increase in heat content of 2 x 10^23 joules.

In 2006, Lyman et al. showed that the oceans cooled between 2003 and 2005 with a net loss of energy of 0.32 x 10^23 joules. Climate models do not predict or allow for such cooling of the oceans.

In 2007, Gouretski and Koltermann showed that the early heat content measurements were incorrect because they did not take into account changes in instrumentation. They concluded that between 1955 and 1996 that the oceans only gained 1.28 x 10^23 joules with an uncertainty of 0.8 x 10^23 joules. Essentially the earlier Levitus paper was wrong.

Combining the Lyman and Gouretski papers, the net ocean heat content between 1955 and 2005 seems to be only 0.98 x 10^23 joules with an error of (0.8 + 0.11) x 10^23 joules or 0.91 x 10^23 joules, adding the error terms of the two papers. The net heat content change is therefore essentially statistically indistinguishable from zero. The net warming of the ocean from 1948 to the present seems to be only 0.03 +/- 0.03 C.

The corresponding net radiative imbalance is about 0.1 W/m^2, well below the model predictions which equal 0.85 W/m^2 for 1993 to 2003 (Hansen et al., 2005). Instead of a climate sensitivity of 3 C for a CO2 doubling, the climate sensitivity is only about 0.4 C. There is little or no energy “in the pipeline” and thus a good reason to believe that all the observed warming of the atmosphere has already occurred.
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