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Lukewarmerism, a.k.a. Ignoring Inconvenient Evidence

Posted on 11 February 2013 by dana1981

In the context of global warming, the term "lukewarmers" refers to individuals who accept the scientific reality that human greenhouse gas emissions are a primary cause of the current global warming, but who believe that future global warming and the consequences of the associated climate change will not be as bad as the body of scientific evidence indicates.  Different "lukewarmers" have different justifications for this belief, but in general, for one reason or another they tend to find the evidence for relatively mild future climate change impacts more compelling than the evidence to the contrary.

Despite his lack of climate expertise, one of the most prominent self-proclaimed "lukewarmers" featured in the media is Matt Ridley, a science writer, businessman, and poor risk manager.  In its September 2012 edition, WIRED magazine published an article in which Ridley wrongly argued that virtually every environmental concern over the past half century has been overblown, and therefore concern about climate change must also be overblown.  Skeptical Science debunked that article, and that debunking was quoted in the November 2012 edition of WIRED, which also featured excerpts from some other letters and articles both praising and criticizing Ridley's piece.

Recently, Ridley attempted to address some of the many criticisms of his WIRED article.  In the process, he provided further evidence that "lukewarmer" positions tend to stem from ignoring most scientific research which does not support the desired conclusion — that the consequences of climate change will be relatively benign.  He then proceeded to cement that evidence by publishing a list of 10 'tests' that would persuade him that climate policy makes sense.  This document was published on the website of the climate science denying Global Warming Policy Foundation, and the references Ridley cited therein are almost exclusively from climate science denying blogs.

Lukewarm Selective Evidence

In his response to the criticisms of his WIRED piece, Ridley defended his irrational climate optimism by arguing that "some of the subplots of climate change have already proved exaggerated."  He lists a few examples that he views as "exaggerated subplots":

  • That a 'giant methane belch' from the Arctic ocean is unlikely to occur, even though the many climate scientists in Ridley's own cited source agree that Arctic methane releases will amplify global warming.

Clearly these are very weak points in supporting the argument that climate concerns are "exaggerated."  Meanwhile Ridley fails to mention the climate consequences which are occurring faster than expected, and climate scientists are already being too conservative in many of their predicitons, erring on the side of least drama.

Lukewarm Escalator

Ironically, Ridley also argued that even though sea level is rising at a rate at the very upper end of the IPCC projections, that sea level data support his argument because, he argues, sea level rise has been decelerating.  To support this claim, Ridley pointed to a blog post by Patrick Michaels, in which Michaels lived up to his reputation by deleting inconvenient data

Although his blog post was written in September 2012, Michaels (who likewise might be considered a "lukewarmer") only examined global mean sea level data for 1993 through 2011.  Global mean sea level rise has been accelerating over the past 150 years; however, the preponderance of La Niña events over the past 5 years and recent extreme flooding has caused a short-term slowing of the sea level rise.

Michaels and Ridley thus ignore the accelerating sea level rise over the past 150 years to argue that the rise is decelerating based on just a few years' worth of noisy data.  This type of argument has come to be known as going down the up escalator.  In the data over the past year which are conveniently excluded by Michaels and Ridley, global sea levels have risen rapidly as we have transitioned away from a La Niña phase (Figure 1).

Ridley sea level

Figure 1: University of Colorado global mean sea level data (seasonal signal removed, inverse barometer applied) with a 12-month running average through 2011 (blue) and January–November 2012 (red).

This is far from the first time that "lukewarmer" Pat Michaels has deleted inconvenient data, and Stoat has another example of Ridley caught red handed doing the same thing.

Lukewarm Feedback Confusion

In both his WIRED response and 'ten tests' document, Ridley claims there is no evidence that water vapor will significantly amplify global warming.  He is wrong – see our discussion here, a list of relevant scientific papers here, and a new paper by Dessler (2012) here.  The scientific literature and data consistently show that the water vapor feedback is a positive strong one, as we expect based on fundamental atmospheric physics. 

However, for some reason Ridley continues to lump the cloud feedback in with the water vapor feedback.  The cloud feedback remains one of the largest uncertainties in climate science; Ridley claims there is evidence that the cloud feedback will significantly dampen global warming, but provides no references to support his assertion.

In his WIRED response, Ridley does reference Gillett et al. (2012), which did not investigate the water vapor feedback.  The study found a relatively low net climate sensitivity (and thus a relatively low net feedback) when considering temperature data from 1851 to 2010, but found a sensitivity and feedback consistent with IPCC values when considering temperature data from 1901 to 2000.  The fact that their results differ while using different but overlapping timeframes is something of a red flag, and Gillett et al. specifically cautioned against over-interpreting their results.

"We therefore recommend caution in interpreting the scaled projections derived from this single model..."

Clearly Ridley did not heed their warning.  The body of scientific literature remains consistent with a climate sensitivity in the range of 2 to 4.5°C surface warming in response to a doubling of CO2, which means that the net feedback will be strongly positive, amplifying global warming.

The Rest of Ridley's Ten 'Tests'

The remainder of Ridley's ten 'tests' involve:

In every argument Ridley has ignored the inconvenient data and relied exclusively on information from climate denialist blogs, and he has presented the "lukewarmer" case as being based on a laundry list of long-debunked climate myths.

Ultimately the "lukewarmers" may be right, climate sensitivity may be on the lower end of the range of possible values, and maybe we will have sufficient time to reduce our greenhouse gas emissions enough to prevent catastrophic climate change.  But if the "lukewarmers" are right, it will not be because the temperature record is wrong, or because global warming magically stopped 16 years ago, or because aliens are driving SUVs on Mars, or any of these long-debunked myths.

If the "lukewarmers" like Ridley are right, it will be because we were very lucky that climate sensitivity happened to be near the bottom of the range of possible values, and because we eventually managed to reduce our greenhouse gas emissions despite efforts by people like Ridley to delay that from happening.  And if we are not so lucky, and catastrophic climate change does occur, history will not look kindly on the "lukewarmers" like Ridley who helped make it happen by cherrypicking data, ignoring inconvenient evidence, and persuading others to follow their preferred haphazard climate path.

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Comments 1 to 31:

  1. Steve Mosher recently defined "Lukewarmer" on WUWT as (reformatted for clarity)

    ... back in 2007 or 2008 we did a poll on Climate audit asking the question
    How much of the warming we see today is due to GHG?
    There was a distinct group of us that said ‘some, but not all ” heck even Willis said 30%

    We called ourselves Lukewarmers.

    Over the years a few of us have worked to define what we mean by Lukewarmer and what defines the position.

    1. Acceptance of radiative physics.
    2. Acceptance of a lower bound to sensitivity. basically the no feedback estimate is 1.2C per doubling. We think that the true sensitivity will be above 1.
    3. over/under line. The over under line is 3C. That is, if offered a bet that the climate sensitivity is either ‘between 1 and 3 or over 3, we take the under bet.

    ballpark:
    less than 1.     2 5%
        1.2 to 3.     50%
        3 to 4.5      45%
         4.5+          5%

    So if you believe that GHG can warm the planet and not cool it, and you think that the mean estimate of the IPCC of 3.2 is more likely high than low, then you are a lukewarmer. But you have to drop the crazy refusals over radiative physics.

    Note:

    • Lukewarmers dont have to attack the surface record, its probably correct to within .2C
    • We also dont have to slam models, or invent kook theories about the sun.
    • Everything we believe is well within the consensus and we think that you can change the consensus from inside the tent rather than attacking everything and everyone.
    • Focus on sensitivity, work to refine that. You see there is a debate in climate science, its a debate about sensitivity.
    • When folks start putting their effort into that ( instead of frittering away time on tangents then you will see changes.

    I find most ofthat innocuous, which suggest that "Lukewarmerism" is more of an emotional position with regard to scientific consensus than a fundamental scientific difference. Ridley and Michaels are definitely not "Lukewarmers" like Mosher.

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  2. @shoyemore Seems to me the IPCC fall just about within that definition of "lukewarmer"!

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  3. Ridley has recently been elected to the House of Lords and he is also on the GWPF’s Academic Advisory Council. 

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  4. Agreed with Dikran @2 - Mosher's definition of "lukewarmer" is pretty much where the IPCC already is, and close to where I am too.  Basically he says lukewarmers think the most likely equilibrium climate sensitivity value is maybe a smidge lower than the IPCC does.  That's an inconsequential distinction, and incompatible with the positions of Ridley and Michaels.

    HH @3 - yes, let's just hope that Ridley doesn't exert any significant influence over UK climate or energy policy from his new position.

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  5. In fact, rather than "lukewarmer", I'd characterize Mosher's position as "pretty darn warmer".

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  6. shoyemore:

    Do you have a link for that?

    Just like M Jourdain in the play le Bourgeois Gentilhomme who was surprised to hear he had been speaking prose all his life and never knew it, so it is that I am now shocked to discover that I have been a lukewarmer all along, at least by Steve Mosher's definition. 

    The 50% of Lukewarmers who would vote for a most likely climate sensitivity between 1 and 3 is a broad church encompassing contrarian extremists like Ridley, as well as the IPCC consensus. There's a factor of three over that particular range—a lot of uncertainty by any but Judith Curry's standards—and it implies a huge difference in climate outcomes from mild to very serious.

    I think that what truly unites Lukewarmers is not any internal consistency of scientific opinion, but rather their desire not to be seen as so stupid to deny basic science and, at the same time, not being able to admit that the dirty hippies were right all along.

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  7. shoyemore @1, it is interesting to compare the IPCC AR4 with Mosher's definition:

    "Analysis of models together with constraints from observations suggest that the equilibrium climate sensitivity is likely to be in the range 2°C to 4.5°C, with a best estimate value of about 3°C. It is very unlikely to be less than 1.5°C. Values substantially higher than 4.5°C cannot be excluded, but agreement with observations is not as good for those values. Probability density functions derived from different information and approaches generally tend to have a long tail towards high values exceeding 4.5°C. Analysis of climate and forcing evolution over previous centuries and model ensemble studies do not rule out climate sensitivity being as high as 6°C or more. "

    (Original emphasis)

    In the contrained language of the IPCC, that means that thre is a less than 10% chance that the Climate Sensitivity is less than 1.5 C per doubling of CO2.  There is a 66% chance it lies between 2 and 4.5 C per doubling, and that the probability does not fall of as quickly above 4.5 C as it does below 2 C.

    The IPCC did not publish a PDF for its own assessment, but the right skew of probabilities means that a climate sensitivity between 3 and 4.5 C is more probable, on their assessment than a probabiltiy between 2 and 3 C..  That is, although 3 C is the modal value, the median and mean values probably lie between 3 and 4.5 C.

    Because Mosher has not used the same demarcations, and because his assignment of probabilities is inconsistent, with a total probability greater than 1.025, direct comparison is difficult.  It is clear that somebody accepting IPCC values would preffer the upper half of the bet between the climate sensitivity being between 2 and 3 C, or 3 and 4.5 C,   As the probability of greater than 4.5 C is greater than the probability less than 2 C, and hence greater than the probability of between 1 and 2 C, they would also take the upper half of Mosher's proffered bet.  Hence I disagree with both Dikran and Dana that Mosher's opinion that the IPCC just about fall within the opinion of luke-warmer.

    Having said that, I finde Mosher's definition of "lukewarmer" strange.  It is strange both because most self avowed lukewarmers I have known have been quite clear that:

    1) The probable CS is around 1.5 C per doubling (very close to Mosher's lower limit); and

    2) The climate sensitivity is sufficiently low that no major action need be taken to mitigate climate change.

    Indeed, "lukewarmer" seems to be a badge for saying, "I'm not so foolish as to deny well established physics, but let's do nothing to protect the future".  I should note that both Lindzen and Monckton who purport to believe the most probable cliimate sensitivity is 0.5 C per doubling also claim to be "lukewarmers".

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  8. Although it's been released in Jan 2013, the University of Colorado mean sea level data seems only to extend until late 2012. The last data point is for 2012.8590 (That is 859/1000 of the year, or something like the 313th day of 2012).

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  9. Pierre-Normand @8 - right you are, thanks.  Figure caption updated accordingly.

    Tom @7 - I still think that's a pretty minimal difference between the IPCC and Mosher positions.

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  10. dana @9, I think that has more to do with the fact that Mosher has been shifting towards the IPCC position over time.  I doubt many of his "fellow" lukewarmers would still recognize him as one.  But though he has shifted towards the IPCC position, he does not want to give up that title, so he has expanded the range of "lukewamer" positions to the right.  Indeed, he has expanded it so far that his estimate of the probability of a climate sensitivity between 3 and 4.5 C is likely greater than the IPCCs. His estimate of for greater than 4.5 C is, however, much lower.

    In fact, I think his high estimate for 3-4.5 C is the real story here.  The disaterous future consequent on greenhouse emissions that is currently predicted assumes a climate sensitivity of 3 C per doubling of CO2.  Mosher things there is nearly a 50/50 chance it is worse than that.  Why, then, is he not demanding urgent action to mitigate climate change?

     

    Andy Skuce - Mosher's comment.

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  11. " But though he has shifted towards the IPCC position, he does not want to give up that title, so he has expanded the range of "lukewamer" positions to the right. "


    And consider this:


    "Everything we believe is well within the consensus and we think that you can change the consensus from inside the tent "

     

    If one's opinion lies within the consensus, the need for changing the consensus is driven by ... what, exactly?

     

    Tom Fuller has also in the past said he thinks sensitivity is about 2.5, i.e. dead-on with NASA GISS Model E's 2.4-2.7 range.  He's made a big deal of James Annan's work to diminish the high tail of uncertainty as though this is somehow counter to the mainstream view (Annan thinks sensitivity lies within 2.5-3C, though he agrees that higher values can't be entirely ruled out).

     

    I think that lukewarmerism is just obfsucation - claiming a difference where non exists in order to appear to accept the science in order to support their political position that nothing need be done (or not much needs to be done).

     

    I think it's just an effort to paint the mainstream view as being that sensitivity is > 3C and likely considerably higher, that calls for action are based on that view, and then "reasonably" extrapolating that accepting a lower value (say 2.5-3) means no immediate action need be taken ...

     


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  12. Tom @10 - I entirely agree.  Mosher's move towards the IPCC/consensus has been quite noticeable, and as a result he's become less and less popular amongst the contrarians.  It does seem like he's holding onto this 'lukewarmer' label just to distinguish himself rom the consensus position somehow.

    I also very much agree that if you believe there's a ~50% chance equilibrium sensitivity is 3°C or higher, you should be pushing hard for urgent action on climate change.

    And that dovetails very well with my next post coming up on Wednesday, looking at future climate change in various sensitivity and emissions scenarios.  Stay tuned, that's going to be a good one.

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  13. Lukewarmism is a nonesense idea that is designed to artificially polarise the debate into discrete camps. It is a premeditated selection of the minimum defensible sensitivity and creating an argument around that rather than an open process of bringing evidence to the table. 

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  14. dorlormin,

    That's exactly right. Someone who derives their conclusions from the evidence can't help but arrive at the obvious value:

    There is still uncertainty, sure — for example, the sensitivity is probably temperature-dependent since certain feedbacks only exist within certain temperature ranges (e.g. in terms of albedo, highly-reflective ice can only exist up to a certain temperature; vegetation can only exist up to a certain temperature, etc.) which means the past values may not be exactly the same as the future, but that's still the best information we have, and saying "Well, it was high in the past, but we're now pushing it into a regime unknown for tens of millions of years and we don't know what it will be under those circumstances, so let's assume it's lower!" doesn't seem like good risk management!

    Choosing to ignore that and instead assume a sensitivity a-priori (or using a technique that is fundamentally unable to give you an accurate answer while ignoring those that do) is not scientific, no matter how "scientific" the proponents feel they are because they have grudgingly agreed to accept every other piece of evidence leading up to that last one, which is just one step too far for them. It's as if they think this last obstacle to action is impenetrable, so they're willing to concede everything else, but you get the feeling that if you push too hard on the last one they'll take a step backwards and proclaim "But CO2 is a trace gas anyway! UHI! Sun!". :-)

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  15. Interesting reading over at fuller's.   Self-congratulation on scientists like Annan accepting the lukewarmer position that climate sensitivity is ... about 3C.

     

    The delusion over there seems real.  They really seem to believe that the consensus position has been 4C or more, and all of the calls for action are based on sensitivity at that level.

     

    While sensitivity in the "about 3C" range, even if a bit lower as Model E and other results might suggest, has been, of course, the basis for policy arguments that we must take definite action if we want to restrict warming by 2100 to 2C over preindustrial levels.

     

    The disconnect with reality, history of climate science, history of the political calls for action is just ... stunning.

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  16. In the case of Mosher and Fuller, I wonder if the need to distance themselves from the consensus view despite their actually sharing the consensus view is related to the fact that they wrote and profited from a book that accused leading climate scientists of scientific fraud?

    It was Mosher who, years ago, before ClimateGate, coined the term Michael "Piltdown" Mann as part of the CA-led attack on MBH 1998/99 and the "hockey stick", in essence claiming that his work on climate reconstructions was a fraud on the level of Piltdown Man.

    Perhaps portraying the mainstream as having moved to their view, rather than the obvious fact that their view has moved to be in line with the mainstream (regarding climate sensitivity to a doubling of CO2, at least) is easier than admitting that their earlier claims of scientific fraud were unwarranted.

     

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  17. Andy Skuce @6

    You will find Steve Mosher's definition of Lukewarmerism in the comments to this post - reasonably early on.

    http://wattsupwiththat.com/2013/02/01/encouraging-admission-of-lower-climate-sensitivity-by-a-hockey-team-scientist/#comment-1214225

    I am still at a loss to define "Lukewarmers" - there seems to be agreement on teh fundamentals of the science, but a difference in the response. Some, like Richard Tol and Pielke Jnr, just seem to take a different tone - Tol for example is on the "academic board" of the science-denying Global Warming Policy Foundation, but supports a carbon price for all the right reasons. Others (Judith Curry) desire to be "bridge builders", but turn out to be anything but. My own suspicion is that they just get a kick out of running with the foxes and hunting with the hounds at the same time.

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  18. Graph 3 from Stoat's post "the sleepwalkers"

     

    Perhaps this is too simplistic but, from the graph aboove, which was taken from Stoat's post "The Sleepwalkers", from the height of the MWP to the depths of the LIA seems to only be about 0.9°C which is what a lot of the lukewarmers expect we are going to get, with their favoured low sensitivity figure.

    But, eyeballing, that would put us about 0.7°C on top of the peak of the MWP which suggests that such an apparently small increase (which the lukewarmer types represent as insignificant) would actually be quite a big deal in terms of the changes to the planet, no? From the LIA to the MWP was certainly a big change to the climate in the northern hemisphere…

    Do they shoot themselves in the foot by backing an approximately 1 °C rise figure? If they have already accepted up to 3°C sensitivity, as Moshers and co's self-description seems to suggest, then surely it is an open and shut case for them to agree that any rise between 1-3°C has got to be extremely risky?

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  19. Nick Palmer...  First thing I notice about that graph, even without going to Stoat to see it, is the phrase "Adapted from Ljundquist, 2010."  I would bet my bottom dollar that graph actually comes from the Idso's website, CO2science.

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  20. It needs to be stressed that climate sensitivity is not a limit on warming. A climate sensitivitiy of 2C does not mean that there will only be 2C of warming. Warming will continue as more CO2 is added to the atmosphere. Nor is there any guarantee that we won't face a terrible catastrophe before warming reaches 2C. Storm damage, crop damage, the advance of insect pests have all reached terrible levels today when we've only experienced around .9C of warming.

    Ask a "luke-warmer" if they'd play Russian Roulette with 3 live bullets out of 6.

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  21. This graph also shows up at Stoat:

    http://scienceblogs.com/stoat/2013/02/07/the-sleepwalkers/

    WMC comments:

    "So now we know how MR proposes to support his assertions: provide evidence that doesn’t cover the period in question, and erase information that contradicts his assertions – even when that comes from the very refs he is quoting"

    http://www.flickr.com/photos/belette/8454321768/

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  22. Nick Palmer - maybe the lukewarmers can explain why global sea level (a proxy for the volume of global land-based ice and therefore global temperature) during the Medieval Period was static during that time and only began to rise appreciably in the 19th century?

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  23. Rob Honeycutt@19

    Yup it does come from a denialist source.That is why I think it can be used against lukewarmers - Judo uses the enemy's strength against himself - to make the argument powerfully that even 1°C of warming is likely to have far reaching effects.

    Connolley put in the data that was sneakily missed out - see below

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  24. Nick...  Yup.  And I believe this is the original source of the colored and doctored version:

    http://www.co2science.org/education/reports/prudentpath/ch1.php

    You can catch these pretty easily when they pop up because most of the Idso's MWP Project graphs are doctored in various ways.  The always add in their own notations of where MWP, LIA, etc occur.  They delete any aspect of the original that might be inconvenient and then they add the notation "Adapted from..."

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  25. Jeffrey @20 - we've got a post looking at future climate change under various sensitivity and emissions scenarios tomorrow.  It's going to be a good one, stay tuned.

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  26. Nick Palmer @ 23, the most germaine point is that luke warmers will insist that most of the rise in temperature from the depth of the LIA until about 1940 is natural in origen.  That, is also, the concensus position.  However, it means that the "lukewarmer" prediction for temperature increase above MWP conditions given only a doubling of CO2 is from 0.7 C assuming natural conditions return to those at the lowest point of the LIA, to 1.8 C above MWP (assuming they stay at current levels).

    Of course, on current trends we will significantly more than double atmospheric CO2.

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  27. Dana

     

    Good post as ever. One query, my very simplistic understanding is that in La Nina years more heat is retained in the ocean cooling the surface and in La Nino years more oceanic heat is transferred to the atmosphere cooling the ocean slightly. I had understood the sealevel drop in 2010 was due to very wet weather over large continental masses shifting c 1cm of water from the ocean to the land.

     

     

     

    Of course the thermal expansion coefficient of water is temperature dependent and the mix of heat between the upper and lower ocean layers would cause an effect – I could easily do a calculation, but I suspect there are already many papers on this?

     

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  28. StBarnabas @27 - you are correct.  If you click the "extreme flooding" link in the OP at the end of the 2nd paragraph in the Lukewarm Escalator section, that goes to a post by Rob Painting about research showing that the short-term pause in sea level rise was primarily caused by large flooding events.

    I'm not sure I understand your question about thermal expansion though.

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  29. Jeffrey Davis at 03:09 AM on 13 February, 2013

    "Warming will continue as more CO2 is added to the atmosphere" - this is so right - Luke warmer, skeptic denier - who cares. They have to be ignored as even a 0.9 C increase is already affecting food production, flowering times, animal survival (not just food source species) etc - something has to be done. Dana - sensitivity is now over - its all downhill unless actions are taken.

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  30. Dana
    Sorry I’ll try to be a bit clearer. I would have like a bit more time to look at the literature as it seems to me that sea level rise should be accelerating rather then being a fairly static 3.2 mm/y. Over the past decade there has been considerably accelerating ice melt – Greenland, glaciers Antarctica etc. I know that temporarily water can fall as rain dropping the sea level – but all the rivers run into the sea, why is it not rising faster.

    The substantive point is that sea level rise will depend on whether the heat goes into the top of the oceans or lower down. If the heat sticks near the surface the sea will normally rise a lot faster. (If there is a paper in this you heard it here first!) As you will be well aware there seems to be a lot more heat transfer to the lower ocean below 700m in the past few years, unless I have misunderstood. This would slow down sea level rise.

    The ocean cools as the deeper it gets. (normally anyway - The Med is well mixed below the thermocline and is a constant 15 degrees or so, but I understand the big oceans are  quite different).

    The thermal mechanism for sea level rise is driven by two constants Cp the specific heat capacity of seawater and Beta the thermal expansion coefficient. Heat is absorbed by seawater and the temperature rises.  As the temperature rises the water expands. So far so obvious, however both these terms are functions of salinity (typically about 35 ppt), pressure (depth) and of course temperature. In Practice Cp varies little with these parameters however Beta is very strongly temperature dependent and not very dependent on depth or salinity. It takes a lot more heat to expand cold water than hot. For fresh water Beta becomes zero at 4C and negative below that. Beta for seawater remains positive   right down to -2C where it freezes.

    I will try attaching a graph generated by using the seawater toolbox  (CSIRO, Nathan Bindoff 1993.) but essentially as water get hotter it expands faster.

    ThermalExpansion

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    Moderator Response: [RH] Fixed image width.
  31. St Barnabas @30, your graph is interesting when compared to this one of ocean temperature with depth:

    (Source)

    The important fact here is that since about 2005, gain in OHC (and hence temperature) at 0-700 meters has been much reduced.  That has been largely compensated by increased gain at 700-2000 meters, such that the 0-2000 meter OHC gain has only reduced slightly.  The important point is that an equal gain in temperature at 700-2000 meters will result in a lesser expansion to the equivalent gain at 0-700 m due to the lower average temperature; and hence the switch in where heat is accumulating will result in a decceleration in the rise in sea level, even if there were no change in gain in OHC.

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