Watt about Trenberth’s “missing heat”?

There’s been this ongoing controversy about what is referred to as Trenberth’s “missing heat”. Essentially models have been – in an average sense – over predicting the rise in global surface temperatures, when compared to what is observed. My understanding is that climate skeptics have interpreted this “missing heat” as referring to the “fact” that the models have more heat (i.e., higher temperature anomalies) than what is observed. As far as I’m aware, this interpretation is wrong and that it is actually, in some sense, the other way around.

We have measurements of the Earth’s energy budget that allow us to estimate the energy imbalance and hence how much excess energy the Earth is receiving. My understanding is that climate models actually do quite a good job of matching this measured energy imbalance. However, when these models calculate what this excess energy does they predict faster rises in global surface temperatures than is observed. The “missing energy” is therefore not missing energy in the models, but missing energy in the observations. We know how much energy is coming into the climate system but when we calculate how much energy is used in heating the land and atmosphere, heating the oceans, and melting polar ice, there is still some missing. Where is it? This is why scientists have become interested in determining how much energy has been going into the deep oceans (below 700m) because this is difficult to determine and may explain where this energy is going. Recent observations appear to support this possibility.

There’s a recent Watts Up With That (WUWT) post called even more about Trenberth’s missing heat – an eye-opening comment by Roger Pielke Sr. Roger Pielke Sr is a meteorologist with an interest in “climate change and climate variability”. The WUWT post highlights something that he said in a recent article :

About 90 percent of this extra energy goes into the oceans. But meteorologist Roger Pielke Sr. of the University of Colorado in Boulder says he would like to understand why more heat is going into the deep ocean. “Until we understand how this fundamental shift in the climate system occurred,” says Pielke, “and if this change in vertical heat transfer really happened, and is not just due to the different areal coverage and data quality in the earlier years, we have a large gap in our understanding of the climate system.”

These large changes in ocean content reveal that the Earth’s surface is not a great place to look for a planetary energy imbalance. “This means this heat is not being sampled by the global average surface temperature trend,” he says. “Since that metric is being used as the icon to report to policymakers on climate change, it illustrates a defect in using the two-dimensional field of surface temperature to diagnose global warming.”

The bold bit is what has been highlighted by the WUWT post. The indication is that Roger Pielke Sr. is suggesting that there might be a problem with data used to infer the heat content of the deep ocean. Indeed there might, as is probably always true, but they seem to ignore that he appears to be saying that energy is indeed going into the deep ocean – or at least he’s not questioning it particularly strongly.

What they’ve largely ignored, however, is the latter part of his comment which is much more significant – in my opionion. He is saying that we should not be using global surface temperatures to look for a planetary energy imbalance. Absolutely, only a small fraction of the excess energy is going into heating the surface and hence it isn’t a good indicator of whether or not global warming is happening. He then goes on to say that global surface temperatures are being used as the icon to convince policy makers about the significance (or lack therefore) of climate change. He’s essentially criticising, as far as I can tell, much of what is said on WUWT and suggesting (and I agree) that we should be using all of the available information when trying to determine if global warming is happening and what implications this has with regards to climate change.

Now, I don’t know much about Roger Pielke Sr. I get the impression that he is often regarded as a lukewarmer and has, apparently, been quite critical of the IPCC. I don’t know if his criticisms have any validity. I do get the impression that it might be a bit of scientific jealousy in that his science has not been as heavily used in the IPCC reports as maybe he would have liked (or that they’ve focused on science that he doesn’t necessarily agree with). Anyway, I have to say that I find some of what he says quite sensible and I certainly agree that only using global surface temperatures to determine whether or not global warming is taking place is ignoring an awful lot of other crucial information that should also be used. I don’t know if there are any problems with the data used to determine the heat content of the deep oceans. However, if we are able to determine the amount of excess energy coming into the climate system and if, once we’ve determined what its done, there is some “missing”, then it has to go somewhere. Energy conservation is one of the most fundamental principles of physics.

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One Response to Watt about Trenberth’s “missing heat”?

  1. There seem to be a lot of comments on WUWT asking how so much energy can get from the upper ocean to the deep ocean without being detected. I’m not quite sure what they think we should measure. You can’t really measure the velocity of energy. In fact, it is possible to have a region in which the energy is constant but in which there is an energy flux (i.e., as much energy is coming in as is leaving). Of course, the ocean isn’t infinite and so the extra energy should do something, but given the large heat capacity of the ocean, the effect will be small. It could change the temperature equally everywhere (but, given the energy we’re considering, only by a fraction of a degree) or it could change the gradient – but again this would, likely, be a very small change. I believe that one method is to measure the the change in sea level which is an indication of an expansion of the ocean due to the increased energy. There are also the ARGO buoys which do direct measurements of temperature and salinity, but these have only been in place for about 13 years. This is presumably what prompted Roger Pielke Sr’s comment about data quality in early years.

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