I don’t want to discuss this in too much detail as Sou over at HotWhopper has already done quite a thorough job. Basically, however, there is a recent Watts Up With That (WUWT) post called by land and by sea. It includes the figure below and in the text says
In addition, the land temperature rises much more rapidly than the SST.
The implication seems to be that they seem to be the same in the 60s and 70s, but for some reason the land temperature has risen faster, in recent times, than the ocean temperature. Isn’t it fairly obvious that this is precisely what one would expect.
Down to a depth of 700m, the oceans have a mass of about 2.5 x 1020kg. Sea water has a specific heat capacity of 4000 J kg-1 K-1 and so to increase the ocean temperature by 1 K would take require an energy input of 1024 J. The atmosphere has a mass of 5 x 1018 kg. Estimating the land mass involved is more difficult, but unless the energy can penetrate deeply it is less than 1018 kg. Let’s say the total mass of land and atmosphere is 1019 kg. The specific heat capacity is about 1000 J kg-1 K-1, so it would take 1022 J to increase the temperature of the land and atmosphere by 1 K. I appreciate that this is simple, but it is showing that to change the ocean temperature by some amount would require 100 times as much energy as changing the land and atmosphere temperature by the same amount.
Additionally, observations suggest that 90% of the excess energy in the last few decades has gone into the ocean. This would suggest that the change in ocean temperature should be about 10 times smaller than the change in land and atmosphere temperature. This is not quite what is seen in the figure above, but that’s because I’ve ignored any gradients in the energy distribution and so one might not expect the ocean temperature (or atmospheric temperature) to increase by the same amount at all levels.
The simple point, however, is that the ocean temperature rising more slowly than the land temperature is not a surprise. It would be much more of a surprise if they did rise at the same rate. Why are the temperature anomalies similar in the 60s and 70s? Well, these are anomalies, not absolute temperatures. It’s the difference between some long-term mean and the current average temperature. The long-term mean is typically based on the period 1950-1980 (or 1960-1990) and so one would expect the anomaly to be close to zero during that period. That’s the only reason they’re the same in the 60s and 70s. As shown over at HotWhopper, if you extend it to earlier times, they start to diverge again, as expected.
I’ve been trying to not be too unpleasantly critical of what is said on WUWT in the hope that it might be possible to discuss climate change in a manner that isn’t so antagonistic. It’s posts like this, where they seem to show a complete lack of understanding of basic science, that makes me wonder if it is indeed possible to engage with those who typically post on WUWT.
Addendum – 9 May 2013
In the comments below, caerbannog666 explains where to get a python script (credit to Kevin C at Skeptical Science) that will produce temperature anomalies from the raw data. I downloaded this about 15 minutes ago, followed the instructions and indeed have produced a figure (below) of the temperature anomaly data (solid line). I haven’t been through the code in detail, but it does indeed appear to do exactly as described. The dashed line is the NASA temperature anomalies and indeed appears remarkably similar to that determined very quickly with a python script that is about a page long.