Guest Post by Willis Eschenbach
According to the current climate paradigm, if the forcing (total downwelling energy) increases, a combination of two things happens. Some of the additional incoming energy (forcing) goes into heating the surface, and some goes into heating the ocean. Lately there’s been much furor about what the Levitus ocean data says about how much energy has gone into heating the ocean, from the surface down to 2000 metres depth. I discussed some of these issues in The Layers of Meaning in Levitus.
I find this furor somewhat curious, in that the trends and variations in the heat content of the global 0-2000 metre layer of the ocean are so small. The size is disguised by the use of units of 10^22 joules of energy … not an easy one to wrap my head around. So what I’ve done is I’ve looked at the annual change in heat content of the upper ocean (0-2000m). Then I’ve calculated the global forcing (in watts per square metre, written here as “W/m2”) that would be necessary to move that much heat into or out of the ocean. Figure 1 gives the results, where heat going into the ocean is shown as a positive forcing, and heat coming out as a negative forcing.
I found several things to be interesting about the energy that’s gone into or come out of the ocean on an annual basis.
The first one is how small the average value of the forcing actually is. On average, little energy is going into the ocean, only two-tenths of a watt per square metre. In a world where the 24/7 average downwelling energy is about half a kilowatt per square metre, that’s tiny, lost in the noise. Nor does it portend much heating “in the pipeline”, whatever that may mean.
The second is that neither the average forcing, nor the trend in that forcing, are significantly different from zero. It’s somewhat of a surprise.
The third is that in addition to the mean not being significantly different from zero, only a few of the individual years have a forcing that is distinguishable from zero.
Those were a surprise because with all of the hollering about Trenberth’s missing heat and the Levitus ocean data, I’d expected to find that we could tell something from the Levitus’s numbers.
But unfortunately, there’s still way too much uncertainty to even tell if either the mean or the trend of the energy going into the ocean are different from zero … kinda limits our options when it comes to drawing conclusions.