A new paper has appeared (thanks to Timo Hämeranta for alerting us to it!) [also to Marcel Crok to alerting me to the typo in the original posting]. Urban, Nathan M., and Klaus Keller, 2009. Complementary observational constraints on climate sensitivity. Geophys. Res. Lett., 36, L04708, doi:10.1029/2008GL036457, February 25, 2009. in press, which provides further discussion of this question.

The abstract of this paper reads:

“A persistent feature of empirical climate sensitivity estimates is their heavy tailed probability distribution indicating a sizeable probability of high sensitivities. Previous studies make general claims that this upper heavy tail is an unavoidable feature of (i) the Earth system, or of (ii) limitations in our observational capabilities. Here we show that reducing the uncertainty about (i) oceanic heat uptake and (ii) aerosol climate forcing can - in principle - cut off this heavy upper tail of climate sensitivity estimates. Observations of oceanic heat uptake result in a negatively correlated joint likelihood function of climate sensitivity and ocean vertical diffusivity. This correlation is opposite to the positive correlation resulting from observations of surface air temperatures. As a result, the two observational constraints can rule out complementary regions in the climate sensitivity-vertical diffusivity space, and cut off the heavy upper tail of the marginal climate sensitivity estimate”.

A key statement in the text of their paper reads:

“Surface temperature observations permit high climate sensitivities if there is substantial unrealized “warming in the pipeline” from the oceans. However, complementary ocean heat observations can be used to test this and can potentially rule out large ocean warming. Ocean heat observations are compatible with high sensitivities if there is substantial surface warming which is penetrating poorly into the oceans. Again, complementary surface temperature observations can test this, and can potentially rule out large surface warming.”

By “unrealized warming in the pipeline”, they mean heat that is being stored within the ocean, which can subsequently be released into the ocean atmosphere. It is erroneous to consider this heat as “unrealized warming”, if the Joules of heat are actually being stored in the ocean. The heat is “realized”; it would just not be entering the atmosphere yet. As discussed in the Physics Today paper Pielke Sr., R.A., 2008: A broader view of the role of humans in the climate system. Physics Today, 61, Vol. 11, 54-55, there has been no heating of the upper ocean since mid-2003. Moreover, there has been no heating within the troposphere (e.g. see Figure 7 of the RSS MSU data).

Thus, there is no “warming in the pipeline” using the author’s terminology, nor any heating within the atmosphere! Perhaps the heating that was observed prior to 2003 will begin again, however, it is scientifically incorrect to report that there is any heat that has not yet been realized within the climate system.
The answer to the question posted in this weblog “Is There Climate Heating In “The Pipeline”? is NO. Read more here.