Missing Ocean Heat Study Reported On By Climate Wire – Response From Josh Willis

source of image – NOAA’s PMEL [note the data have not yet been updated for the last couple of years]

There is a Climate Wire report on a new Nature Geosciences paper.

The Climate Wire article reads [highlight added]

 Researchers puzzle over measurements of ocean-stored heat  (Monday, January 23, 2012)

Lauren Morello, E&E reporter

Earth’s “missing heat” might not be missing after all.

That’s the conclusion of a new study that examines how accurately satellites and floating ocean instruments track the flow of energy from the sun to Earth and back again.

Those measurements are at the heart of a puzzle climate scientists have been trying hard to crack: why, as greenhouse gas emissions rose and satellite data showed an increasing amount of energy trapped in the planet’s atmosphere, the amount of heat absorbed by the world’s oceans — a major heat sink — wasn’t rising as quickly.

One answer to the puzzle came from climate scientists Kevin Trenberth and John Fasullo of the National Center for Atmospheric Research, who coined the term “missing heat” — and later suggested it may be stored in the deep ocean, where there are few measurements to track the energy’s path.

But new research, published yesterday in the journal Nature Geoscience, argues that what Trenberth and Fasullo dubbed “missing heat” isn’t missing, after all — that the amount of radiation trapped in Earth’s atmosphere, as measured by satellite sensors, is consistent with measurements of heat absorbed by the ocean.

Any discrepancy falls within the margin of error on those measurements, say the study’s authors, led by NASA climate scientist Norman Loeb.

Part of the problem, Loeb said, is that the margin of error on the ocean measurements is large, a legacy of the early 2000s switch from an instrument originally developed in the the 1960s — the expendable bathythermograph, or XBT — to the more accurate Argo float.

Today, roughly 3,200 Argos are traveling the world’s oceans, collecting data as they repeatedly sink to prescribed depths, pop back up again and transmit the information they’ve collected to waiting satellites.

Diving into uncertainty

“Given that there’s a lot of uncertainty in the ocean measurements, given that there was this transition from XBT to Argo right around the time that satellite data and ocean data deviated, it raises a lot questions in my mind about whether you can say there is missing energy,” Loeb said.

His analysis examining the amount of solar radiation entering and leaving the atmosphere estimates the heat content of the upper ocean using three different data sets.

Loeb’s conclusion? That, if you consider the margin of error on the satellite and ocean measurements, the two data sources are in agreement — and there may not be any “missing energy.”

“It’s not to say that it’s not happening,” Loeb said. “It’s just that you can’t easily make that conclusion from the data.”

Not so fast, says Trenberth. “One of the key points of our paper was, when you try to do this inventory and things didn’t add up, if you take things at face value, that is an indicator by itself that the error bars are very large,” Trenberth said. “We were very aware of that — but they shouldn’t be that large.”

Trenberth said he also believes Loeb overestimated the error bars for the satellite data, which show the potential margin of error for those measurements.

But both scientists agree that the ongoing debate over the accounting of Earth’s energy budget demonstrates the need to improve monitoring of the Earth’s climate and to better understand sources of error in older measurements, like the ocean data collected for decades by XBTs.

“There are at least 10 estimates of upper ocean heat content,” Trenberth said. “They are all over the place, in spite of the fact that we have the best ocean observing system, with Argo floats, that we’ve ever had.”

My Request To Josh Willis of JPL for a response [Josh, as most of you already know, is an internationally well-respected expert on ocean heat content analyses]

Hi Josh

Would you be willing to comment on this for my weblog?


Josh’s Response

Hi Roger,

You bet.  You can post these comments on your blog.  However, since I comment on Kevin’s quote, perhaps you could be sure to include the paragraph below in its entirety.

I think that the Loeb et al. paper is an important step forward in our understanding of the Earth’s energy balance and our ability to observe it. As I have said for some time, I think a fair accounting of the uncertainties in the observations would cast serious doubt on the “missing heat” hypothesis, and I think the Loeb et al. paper confirms that.  I also disagree with Trenberth’s comment that the estimates of ocean warming are all over the place.  All the estimates that I am aware of agree quite well over the period from 2005 to the present, which is dominated by the Argo data.  It is true, however, that there are still large uncertainties for the period before 2005 due to unresolved biases in the XBT data.  But even with these biases, it is still possible to see the human-caused signal over a long enough period of time–like 15 to 20 years.

Hope this helps.

Cheers, Josh

My Comment: 

As I have urged in my papers

Pielke Sr., R.A., 2003: Heat storage within the Earth system. Bull. Amer.  Meteor. Soc., 84, 331-335.

Pielke Sr., R.A., 2008: A broader view of the  role of humans in the climate system. Physics Today, 61, Vol. 11, 54-55.

the assessment of ocean heat content changes is the robust approach to diagnose climate system heat changes (global warming and cooling). The ocean itself does the time and space integration needed to diagnose the accumulation or loss of heat to the climate system over time. Radiative fluxes as viewed from space is a much more difficult way to diagnose this heating. We should have the most confidence in the upper ocean data, particularly since 2005, as Josh reports.

The papers [with more on the way by these internationally well-respected climate scientists]

R. S. Knox, David H. Douglass 2010: Recent energy balance of Earth  International Journal of Geosciences, 2010, vol. 1, no. 3 (November) – In press doi:10.4236/ijg2010.00000.

D.H. Douglass. The Pacific sea surface temperature.  Physics Letters A (2011). doi:10.1016/j.physleta.2011.10.042

provide quantitative examples of the value of using this ocean data in order to improve our understanding of the climate system.

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