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Is More Global Warming Hiding in the Oceans?

Posted on 22 June 2013 by dana1981

This is a re-post of an article in US News & World Report by Jeff Nesbit

The HMS Challenger set sail 135 years ago. It was the world's first scientific survey of ocean life. But the HMS Challenger also studied ocean temperatures along the way by dropping thermometers attached to Italian hemp ropes hundreds of meters deep – an effort that has been used as a baseline for global warming in oceans since pre-industrial times.

Now, according to a new study, U.S. and Australian researchers have combined the work of the HMS Challenger with modern-era climate science models – and have some surprising results. The study found we may be significantly under-estimating global warming's impact and heat content in the oceans; and sea level rise from global warming seems to be split 60/40, with 40 percent coming from expansion of sea water caused by warming, and the remaining 60 percent coming from melting ice sheets and glaciers.

The U.S. and Australian researchers who re-examined the HMS Challenger thermometer readings in light of modern supercomputer climate models say it provides further confirmation of human-produced global warming over the past century.

"Our research revealed warming of the planet can be clearly detected since 1873 and that our oceans continue to absorb the great majority of this heat," said Dr. Will Hobbs, the study's lead author and a researcher at the University of Tasmania's Institute for Marine and Antarctic Studies. "Currently scientists estimate the oceans absorb more than 90 percent of the heat trapped by greenhouse gases, and we attribute the global warming to anthropogenic causes."

The HMS Challenger expedition ran from 1872 to 1876, and was the world's first global scientific survey of life beneath the ocean surface. But, while it wasn't part of its central research mission, the Challenger also dropped thermometers deep into the ocean at different points. More than a century later, researchers used state-of-the-art climate models to get a more accurate picture of how the world's oceans have changed since the Challenger's voyage.

"The key to this research was to determine the range of uncertainty for the measurements taken by the crew of the Challenger," said Josh Willis, a study co-author who is a climate scientist at NASA's Jet Propulsion Laboratory. "After we had taken all these uncertainties into account, it became apparent that the rate of warming we saw across the oceans far exceeded the degree of uncertainty around the measurements. So, while the uncertainty was large, the warming signal detected was far greater."

Because it was the first expedition of its kind, there were a number of uncertainties around the HMS Challenger expedition 135 years ago. For instance, the Challenger could only drop thermometers in a limited number of areas in oceans. As it turns out, some of the places it chose – modern science now knows – are places that are warmer than usual.

The Challenger also could only guess about depths for the Italian hemp ropes that held the thermometers at the end – there were no unmanned submersibles in those days – and they also could only guess at the natural variations in temperatures that could occur in different ocean regions during the expedition.

To account for these sorts of uncertainties with modern era models, the researchers used the most conservative estimates they possibly could, taking into account the maximum possible variation from these uncertainties. Even taking this approach, the researchers found that global warming has clearly occurred in the world's oceans and is likely higher than what we know.

"Because we took the most conservative outcome, we are likely to have underestimated the true temperature rise," said Hobbs. "A simple analysis of our results suggests we may have underestimated the warming by as much as 17 percent. In fact many of the stations most prone to bias were in the Eastern Pacific - a region showing one of the strongest ocean warming trends - so the true warming may be even larger than that."

While discovering that there was an increase in warming in ocean temperatures in the past century, the researchers were also able to clearly show the amount of thermal expansion in sea level rise in the oceans before the 1950s. Prior to this research, climate models offered the only way to estimate the change.

"This research adds yet another suite of compelling data that shows human activity continues to have a dramatic influence on the Earth's climate," Hobbs said.

This research on ocean heat content comes at a critical moment in the discussion of global warming. A leading climate scientist, Dr. Kevin Trenberth, recently wrote in a blog post for The Conversation that we may be vastly under-estimating just how much global warming is hiding in the world's oceans – and that we may need to re-define the way we think about global warming.

"Rising surface temperatures are just one manifestation. Melting Arctic sea ice is another. So is melting of glaciers and other land ice that contribute to rising sea levels. Increasing the water cycle and invigorating storms is yet another," wrote Trenberth, who is a senior scientist at the National Center For Atmospheric Research in Boulder, Colorado.

"But most (more than 90 percent) of the energy imbalance goes into the ocean, and several analyses have now shown this. But even there, how much warms the upper layers of the ocean, as opposed to how much penetrates deeper into the ocean where it may not have much immediate influence, is a key issue," he continued.

Trenberth and some of his colleagues recently published a new analysis of their own which shows that, in the past decade, roughly 30 percent of global warming heat may be hiding below 2,000 feet in the world's oceans – essentially, in the bottom half of most of the oceans where very little observational research has been done. That's a significant analysis – because there has been virtually no research on missing heat at the deepest depths of the world's oceans (below 700 meters).

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Comments

Comments 1 to 18:

  1. There is also a good lecture available through UCTV's Perspectives on Ocean Science:

    "135 Years of Global Ocean Warming - Perspectives on Ocean Science"

    http://www.uctv.tv/shows/135-Years-of-Global-Ocean-Warming-Perspectives-on-Ocean-Science-23999

    Perspectives on Ocean Science
    Date: 9/12/2012; 56 minutes
    A new study comparing past and present ocean temperatures reveals the global ocean has been warming for more than a century. Join Dean Roemmich, Scripps physical oceanographer and study co-author, as he describes how warm our oceans are getting, where all that heat is going, and how this knowledge will help scientists better understand the earth's climate.

    Learn how scientists measured ocean temperature during the historic voyage of the HMS Challenger (1872-76) and how today's network of ocean-probing robots is changing the way scientists study the seas. (#23999)

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  2. It's well gone time for the governments to spend the resources required to measure ocean heat content accurately so that its increase is known from year to year. Same for the major freshwater (the other 2.5% of where "global warming" goes).

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  3. Do you think it is possible to take a very small sample of data from 135 years ago, manipulate it a bit and then compare it to Argo data and then draw a conclusion of any relevance?

    just some questions?

    How was the equipment calibrated?

    What was the margin of error in the original data?

    Was the process of measuring the data the same for each and every measurement?

    How accurate was the hemp rope for measuring depth?

    Was the data reported correctly and consistently?

    Was the data rounded up or down or did they measure down to 3 decimal places?

    What were the currents at the time, could this have an effect on the results?

    Too many variables combined with a very small sample means this comparison is a futile exercise.

     

    Cheers

     

     

     

     

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  4. Donthaveone - if you are interested in the answers to your questions (the tone of your post suggests probably not), then I suspect that a good place to look for them would be the original study, which appears to be this one:

    http://onlinelibrary.wiley.com/doi/10.1002/grl.50370/abstract

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  5. Dikran,

    How could you possibly tell by the tone of my post what my intentions are?

    Thanks for the link.

     

    Cheers

     

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  6. Just checked the link and it is paywalled and the abstract does not provide any answers to my questions therefore they still stand unanswered.

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    Moderator Response:

    [DB] Only the unitiate use Google; the Wise use Google ScholarScholar, like a wise Rabbit, finds all...like this.

  7. Donthaveone @6 equals, in translation, "The world has an obligation spoon feed me for free any information I desire."  Perhaps Donthaveone would be better of reflecting that his questions don't stand unanswered.  Rather, he is merely too lazy (or skinflint) to seek out the answers when provided.

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  8. donthaveone did you try emailing the corresponding author of the paper to ask for a preprint?  Scientists are generally quite pleased to hear of people wanting to read their work and will happily send them a preprint.  Most journals are happy for authors to do this (if in doubt you can consult SHERPA/RoMEo - in this case JGR is a "green" journal in the sense the author can archive both pre- and post-prints, meaning there is no copyright problem preventing the author from sending you a copy).  Sometimes if you want to find out answers, you do have to do a little bit of work for yourself.


    As to how can I tell intentions from the tone of a post?  Well that is kind of what language is for.  Ending posts that ask multiple question with a statement that shows you have already made up your mind "Too many variables combined with a very small sample means this comparison is a futile exercise." is a pretty good indication that the questions were merely rhetorical and you are not really interested in the answers.  Ending posts with "cheers" is also a fair indicator - it does come accross as being somewhat sarcastic, especially following rhetorical questions.

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  9. donthaveone SkS is primarily intended for discussion of science, if you want to engage in rhetoric, or blogsphere bitch-slapping, then you would be better off elsewhere.  If nothing else, please read the comments policy, especially the item about sloganeering, which basically gives posters a requirement to be willing and able to discuss the science supporting their position.

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  10. I can hint Donthaveone, that easy answers to most of their gishgallop @3 can be found in Dean Roemmich video posted by citizenschallenge@1. Very nice and informative video at your fingertips requiring little effort: no need to spend energy looking for the publication and learning all of those terms and acronyms without what you won't understand the publication anyway.

    In this video, Dean has shown in very simple words, that the amount of ocean warming between Chalenger and Argo is most likely underestimated. This is a simple answer to your gishgallop about "uncertainty". Have you genuinely checked it after citizenschallenge@1, you would not need post your questions, or you would post a reasonable questions, e.g. fow the uncertainty was measured and what is the confidence level of the final conclusion. But instead, you prefer to conclude:

    "Too many variables combined with a very small sample means this comparison is a futile exercise"

    That's pure nonsense. In statistics, any sample greater than 1 can be analysed and the confidence of how the sample represents the population be concluded. But you are clearly not interested how. I concur with Dikran.

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  11. My institution gives me access to the paper. In it I see that it builds heaving on "135 years of global ocean warming between the Challenger expedition and the Argo
    Programme, Dean Roemmich,W. John Gould& John Gilson 2013"
    which is publically available. It answers most if not all of Donthaveone's queries but funnily enough they dont leap to the same conclusion. Worth reading.

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  12. I am sorry maybe i misunderstood what the point of SKS was.

    dana1981 posted a newspaper story which in a nutshell claimed OHC data taken some 120 years ago was compared to current day Argo data and from this comparison it was then stated that the comparison shows the OHC has risen by an amount and this was due to AGW. The newspaper story gave no indication of how this comparison was achieved.

    I was of the opinion that such a comparison was unrealistic in terms of both number of samples and methodology and stated such in the hope of generating a discussion point however this did not occur, instead i was told my "tone" was not acceptable and you cannot end a post with the word "cheers" i would be fascinated to know what is the correct way of ending a post DiKran?

    Following on from this a moderator made this statement

    (-Moderation complaints snipped-)?

    To Dikran,

    You stated in 9

    (-blockquote snipped-).

    (-Inflammatory snipped-). In regards to discussing science well i have asked questions regarding the science around this issue, have you even attempted to respond to those questions?

    To scaddenp in 11,

    Thankyou very much for the link i have not read the paper as yet but i will and respond to you in time.

    Regards?

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    Moderator Response:

    [DB] Firstly, you were given a direct link to the openly-available submitted version of the paper in the previous moderator's comment.

    Secondly, familiarize yourself with this site's Comments Policy before posting further comments.  This is NOT an option.

  13. Mod,

    I have read the comments policy and i do accept i erred when i copied and pasted a statement for which i appologise, i did not complain to a moderator i merely asked what the word meant as i did not recognise it. I have no idea what was inflammatory but if a mod feels it is then so be it.

    In response do  the mods feel it is acceptable to percieve ones tone and then make unsubstantiated comments based on that perception?

    Also do the mods feel it acceptable that one can claim the use of the word "Cheers" when ending a post to be an indication of ones true intentions?

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    Moderator Response:

    [DB] Per the Comments Policy :

    No profanity or inflammatory toneAgain, constructive discussion is difficult when overheated rhetoric or profanity is flying around.

     

    For those genuinely wishing to engage others on the science of climate change...and the denial of it, then Skeptical Science is the place to do that.  However, please note that posting comments here at SkS is a privilege, not a right.  This privilege can be rescinded if the posting individual treats adherence to the Comments Policy as optional, rather than the mandatory condition of participating in this online forum.  The Comments Policy is a common set of rules that everyone here observes and abides by.

    Lastly, please note that moderation policies are not open for discussion.

    Please take the time to review the Comments Policy and ensure future comments are in full compliance with it; this will allow yourself to participate in a rich discussion.  Thanks for your understanding and compliance in this matter.

  14. To scaddenp,

    I read the paper you provided, it does detail potential errors in the readings from the Challenger and the authors appear to do thier best to take these errors into account.

    They say all the errors add a warm bias to the measurements therefore the Challenger data is reduced in magnitude, obviously the larger the reduction the larger the trend over the 135 years becomes.

    So i suppose it comes down to how much confidence you have in the data and according to the authors i would say that is not too much when they say

    Obviously, these local differences may represent any timescale in the 135-year intervalfrom a transient meander of the Gulf Stream in 1873 to a long-term change in the current's latitude. Similarly, regional to ocean-scale differences may be affected by interannual to decadal15,16 variability, including in the deep ocean17, and hence our Challenger-to-Argo difference based on stations along the Challenger track must be viewed with caution.

    That said i found it an interesting study and according to the authors the results show a warming on centenial time scales

    The larger temperature change observed between the Challenger expedition and Argo Programme, both globally (0.33 C +/-0.14, 0-700 m) and separately in the Atlantic(0.58 C +/-0.12) and Pacific (0.22 C+/-0.11), therefore seems to be associated with the longer timescale of a century or more. The implications of centennial-scale warming of the subsurface oceans extend beyond the climate system's energy imbalance.

    What the authors are saying is that the positive trend in OHC can be extended right back to the 1870's (Challenger data).

    In summary, this paper uses data that cannot be considered accurate but if we were to accept these results as they are the trend shown in this data is similar to other studies and tthey show the trend extends back well before man could have started to change the climate through CO2 emissions. This paper is not a new discovery, this paper adds to what is already known and that is OHC and therfore SLR has been increasing at a steady rate for well over a century.

    I believe the headline "Is more global warming hiding in the ocean" to be an inaccurate description of what the paper discusses and declares.

    Thanks again for supplying the paper

    Cheers

     

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  15. The period 1550 -1850 was known as "Little Ice Age", appears drop maybe 0.5 degrees C just eyeballing graphs. So, I do not see how finding that ocean  heat was less ~1870 A.D. than previously thought leads to the conclusion of increased anthropogenic warming 1873–1955 unless the prior computations include a quantitative assessment of what the ocean heat change would have been during that period with no anthropogenic warming.

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  16. If you're interested in helping out with on-going, crowd-source research using old ship logs you can "hop aboard" one of these vessels and help transcribe the data at OldWeather.  I'm aboard the US Concord which sailed all over the world in the late 1800s.

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  17. Donthaveone, the paper I linked included the discussion of the errors and raises a number of issues. The article however is about a followup pape which further delves into those questions and uses combination of both data and ocean thermodynamic modelling to look at spatiala and temporal variability. It is unfortunate that no freely accessible version exists yet but you could follow up with the authors as suggested above. 

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  18. I would also say that paper is interesting for what it doesn’t find. While the authors are correctly cautious about their findings, and point to alternative explanations, they do indeed find significant ocean warming and not a “same as” picture that the “its just a natural cycle” crowd would have expected. By itself the comparison doesn’t “prove” anything but the findings are consistent with current climate theory.

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