Update April 23 2010: I sent to both Kevin Trenberth and Josh Willis an e-mail that this post was presented today on my weblog. Below is the response from Josh (with his permission), along with my response.
Josh Willis’s e-mail
Thanks for the heads up. I think what Kevin was trying to say about the satellite sensors being able to track “the changes in net energy.” is that while the satellites do not yield a good estimate of the time-averaged radiative imbalance, they DO give a good estimate of the year to year fluctuations about that mean. This is my understanding anyway. So in terms of heat content, that means that the satellites are insensitive to the mean warming rate (i.e., the SLOPE of the OHC estimates). But the year to year variations are probably much more accurate. So if you integrate the satellite net flux over time to compare it with OHC, there is an ambiguity in the slope of the resulting curve, but it still contains useful information about the year to year accelerations in OHC.
That’s what Kevin was driving at, so I think your comment about the capabilities of the satellite data is a bit unfair:
“However, if the satellites ‘are not good enough to give accurate measurements of the net energy itself’ they be cannot expected to track ‘changes in the net energy’!”
I agree that the satallite does provide a good estimate of the intra-annual (e.g. monthly) variations of the outgoing long wave and incoming (and reflected) solar fluxes. However, the year to year variations in the annual averages is a much smaller value. Unless the errors in the shorter term values were completely random, the errors in the monthly (or shorter term analyses) will accumulate so as to contaminate the year to year analyzed changes.
The reason the OHC is so valuable is that the ocean itself does the averaging. With the satellite measurements, we are relying on the accuracy of the measured irradiances themselves.
I will post your comments below and my reply (and unless you tell me differently). I also sent to Kevin that I posted today, but have not yet heard back from him.
There is an article in the publication Physicsworld.com by Hamish Johnston who is the editor titled
Where has all the heat gone? [h/t Don Bishop! for alerting us to this]
The article starts with the text
“Two leading climate scientists have urged their colleagues to find the growing amount of “missing energy” that seems to be eluding climate sensors.”
It includes the text that
“Since 2001 scientists have used satellites to compare the amount of solar energy being absorbed by the Earth to the amount of infrared energy escaping from our planet. And just as predicted by the theory of manmade climate change, the amount of energy retained by the Earth has increased along with greenhouse-gas concentrations.
At first this extra energy seems to have boosted temperatures down here on Earth. Then something unexplained happened in about 2004 – and since then terrestrial measurements suggest that the planet is losing energy.
So are the satellites wrong? While Trenberth and Fasullo say that the satellites are not good enough to give accurate measurements of the net energy itself, they claim that the instruments are “sufficiently stable” to track changes in net energy, which are the important quantity.”
However, if the satellites “are not good enough to give accurate measurements of the net energy itself” they be cannot expected to track “changes in the net energy”!
The article also writes
“Trenberth told physicsworld.com that the discrepancy probably lies in the environment’s largest heat reservoir. “I would say that the missing heat is mainly in the ocean,” he argues.
Much of our understanding of how the oceans absorb energy comes from over 3000 “Argo floats” that gather temperature data at depths of up to 2000 m. However, Trenberth says he thinks that “oceanographers are fairly new at processing this kind of data and are still learning how to do it right”. He also points out of that some of the floats deployed in the Atlantic have been problematic. “
As has been documented on my weblog, however, e.g. see the e-mail exchanges between Kevin Trenberth and Josh Willis
the ocean data analyses are quite robust since at least 2005. There is not a significant amount of heat that is “missing” in the climate system. See also the excellent post on this topic by Roy Spencer
To his credit, Kevin has made a forecast that this issue will be resolved in the next year or two; i.e.
“Trenberth believes that it is crucial to understand when this energy will return to the upper ocean, where it would have a significant effect on climate. Scientists already know the Southern Oscillation involves the absorption of solar energy by the Pacific Ocean during “La Niña” years and its release into the atmosphere during “El Niño” years – leading to significant changes in weather patterns in the Americas.
An El Niño began in 2009 and looks set to continue in 2010. Trenberth believes that it might result in much of the missing energy resurfacing – but adds that current data gathering and analysis techniques mean that it could be a year or two before we know.”
This is a scientifically testable hypothesis and we should know by the end of 2011 if Kevin is correct or not.
Finally, I do support Kevin’s recommendation with respect to the reporting of ocean heat change data
“One can argue that we should develop a system to do this in closer to real time as part of the new climate services,” he said.
Hopefully, Physicsworld.com will publish a follow-up to their article with the more up-to-date information with respect to the confidence in the robustness of the ocean heat data since 2005.