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Ocean heat storage: a particularly lousy policy target + Update

Filed under: — stefan @ 20 October 2014

The New York Times, 12 December 2027: After 12 years of debate and negotiation, kicked off in Paris in 2015, world leaders have finally agreed to ditch the goal of limiting global warming to below 2 °C. Instead, they have agreed to the new goal of limiting global ocean heat content to 1024 Joules. The decision was widely welcomed by the science and policy communities as a great step forward. “In the past, the 2 °C goal has allowed some governments to pretend that they are taking serious action to mitigate global warming, when in reality they have achieved almost nothing. I’m sure that this can’t happen again with the new 1024 Joules goal”, said David Victor, a professor of international relations who originally proposed this change back in 2014. And an unnamed senior EU negotiator commented: “Perhaps I shouldn’t say this, but some heads of state had trouble understanding the implications of the 2 °C target; sometimes they even accidentally talked of limiting global warming to 2%. I’m glad that we now have those 1024 Joules which are much easier to grasp for policy makers and the public.”

This fictitious newspaper item is of course absurd and will never become reality, because ocean heat content is unsuited as a climate policy target. Here are three main reasons why.

1. Ocean heat content is extremely unresponsive to policy.

While the increase in global temperature could indeed be stopped within decades by reducing emissions, ocean heat content will continue to increase for at least a thousand years after we have reached zero emissions. Ocean heat content is one of the most inert components of the climate system, second only to the huge ice sheets on Greenland and Antarctica (hopefully at least – if the latter are not more unstable than we think).

AR5 Fig 3.2

Figure 1. Ocean heat content in the surface layer (top panel, various data sets) and the mid-depth (700-2000 m) and deep ocean (bottom panel), from the IPCC AR5 (Fig. 3.2 – see caption there for details). Note that uncertainties are larger than for global mean temperature, the data don’t go as far back (1850 for global mean temperature) and data from the deep ocean are particularly sparse, so that only a trend line is shown.

2. Ocean heat content has no direct relation to any impacts.

Ocean heat content has increased by about 2.5 X 1023 Joules since 1970 (IPCC AR5). What would be the impact of that? The answer is: it depends. If this heat were evenly distributed over the entire global ocean, water temperatures would have warmed on average by less than 0.05 °C (global ocean mass 1.4 × 1021 kg, heat capacity 4 J/gK). This tiny warming would have essentially zero impact. The only reason why ocean heat uptake does have an impact is the fact that it is highly concentrated at the surface, where the warming is therefore noticeable (see Fig. 1). Thus in terms of impacts the problem is surface warming – which is described much better by actually measuring surface temperatures rather than total ocean heat content. Surface warming has no simple relation to total heat uptake because that link is affected by ocean circulation and mixing changes. (By the way, neither has sea-level rise due to thermal expansion, because the thermal expansion coefficient is several times larger for warm surface waters than for the cold deep waters – again it is warming in the surface layers that counts, while the total ocean heat content tells us little about the amount of sea-level rise.)

AR5 Fig 3.1
Figure 2. Temperature anomaly in °C as a function of ocean depth and time since 1955. (Source: Fig. 3.1 of the IPCC  AR5.)

3. Ocean heat content is difficult to measure.

The reason is that you have to measure tiny temperature changes over a huge volume, rather than much larger changes just over a surface. Ocean heat content estimates have gone through a number of revisions, instrument calibration issues etc. If we were systematically off by just 0.05 °C throughout the oceans due to some instrument drift, the error would larger than the entire ocean heat uptake since 1970. If the surface measurements were off by 0.05 °C, this would be a negligible correction compared to the 0.7 °C surface warming observed since 1950.

Two basic ocean physics facts

Let us compare the ocean to a pot of water on the stove in order to understand (i) that heat content is an integral quantity and (ii) the response time of the ocean.

Imagine you’ve recently turned on the stove. The heat content of the water in the pot will increase over time with a constant setting of the stove (note that zero emissions correspond to a constant setting – emitting more greenhouse gases turns up the heat). How much heat is in the water thus depends mainly on the past history (how long the stove has been on) rather than its current setting (i.e. on whether you’ve recently turned the element up a bit). That is why it is an integral quantity – it integrates the heating rate over time. You can tell from the units: heat content is measured in Joules, heating rate in Watts which is Joules per second, i.e. per unit of time.

The water in the pot heats up much faster than the global ocean. The water in the pot may be typically ~10 cm deep and heated at a rate of 1500 Watt or so from below. But the ocean is on average 3700 meters deep (thus has a huge heat capacity) and is heated at a low power input of the order of ~1 Watt per square meter of surface area. Also it is heated from above and not well mixed but highly stratified. Warm water floats on top, which hinders the penetration of heat into the ocean. Water in parts of the deep ocean has been there for more than a millennium since last exposed to the surface. Therefore it will take the ocean thousands of years to fully catch up with the surface warming we have already caused. That is why limiting ocean heat content to 1024 Joules is not possible even if we stop global warming right now – even though this amount is four times the amount of heating already caused since 1970. Ocean heat content simply does not respond on policy-relevant time scales.

If you turn your setting on the stove higher or lower, what you immediately change is the rate of heating – the wattage. So would limiting the rate of ocean heat uptake be a suitable policy target? At least it would be responsive to policy at a relevant time scale, like surface temperature. But here reasons two and three come into play. The rate of heat uptake has even less connection to any impacts than the heat content itself. And the time series of this rate is extremely noisy.

ocean_bottom

Charles Saxon in the New Yorker on the impacts of deep ocean heat content on society.

So why do Victor and Kennel propose to use deep ocean heat content as policy target?

In a recent interview, David Victor has explained why he wants to “ditch the 2 °C warming goal”, as the title of his Nature commentary with Charles Kennel reads:

There are some other indicators that look much more promising. One of them is ocean heat content.

The reason that Victor and Kennel gave for preferring ocean heat content over a global mean surface temperature target is this:

Because energy stored in the deep oceans will be released over decades or centuries, ocean heat content is a good proxy for the long-term risk to future generations and planetary-scale ecology.

I criticized this because the deep ocean will not release any heat in the next thousand years but rather continue to absorb heat. In his response at Dot Earth, Victor replied that I had “plucked this sentence out of context”. However, in their article there simply is no context that would explain how “energy stored in the deep oceans will be released over decades or centuries” or how this would make it “a good proxy for the long-term risk”. This statement is plainly wrong, and Victor would have been more credible to simply admit that. Victor there further argues that “the data suggest [OHC] is a more responsive measure” than surface temperature, but what he means by that, given the huge thermal inertia of the oceans, beats me.

My impression is this. Victor and Kennel appear to have been taken in by the rather overblown debate on the so-called ‘hiatus’,  not realizing that this is just about minor short-term variability in surface temperature and has no bearing on the 2 °C limit whatsoever. In this context they may have read the argument that ocean heat content continues to increase despite the ‘hiatus’ – which is a valid argument to show that there still is a radiative disequilibrium and the planet is still soaking up heat. But it does not make ocean heat content a good policy target. The lack of response to short-term wiggles like the so-called ‘hiatus’ points at the fact that ocean heat content is very inert, which is also what makes it unresponsive to climate policy and hence a bad policy target. So my impression is that they have not thought this through.

I agree with the criteria that a metric for a policy goal needs to be (a) related to impacts we care about (otherwise why would you want to limit it) and (b) something that can be influenced by policy. A more technical third requirement is that it must be something we can measure well enough, with well-established data sets going far enough back in time to understand baseline variability.

But it seems clear to me that global mean surface temperature is the one metric that best meets these requirements. It is the one climate variable most clearly linked to radiative forcing, through the planetary energy budget equation. The nearly linear relation of cumulative emissions and global temperature allows one to read the remaining CO2 emissions budget off a graph (Fig. SPM.10 of the AR5 Summary for Policy Makers) once the global temperature target is agreed. Most impacts scale with global temperature, and how a whole variety of climate risks – from declining harvests to the risk of crossing the threshold for irreversible Greenland ice sheet loss – depends on temperature has been thoroughy investigated over the past decades. And finally we have four data sets of global temperature in close agreement (up to ~0.1 °C), natural variability on the relevant time scales is small (also ~0.1 °C) compared to the 2 °C limit, and models reproduce the global temperature evolution over the past 150 years quite well when driven by the known forcings.

I find the arguments made by Victor and Kennel highly self-contradictory. They find global mean temperature too variable to use as a policy target (that is the thrust of their “hiatus” argument) – but they propose much more noisy indicators like an index of extreme events. They think global surface temperature is affected by “all kinds of factors” – and propose ocean heat content, which is determined by the history of surface temperature. Or the surface area in which conditions stray by three standard deviations from the local and seasonal mean temperature, which is a straight function of global surface temperature with some noise added. They argue surface temperature is something which can’t directly be influenced by policy – and propose deep ocean heat content where this is a hundred times worse. They say limiting warming to 2 °C is “effectively unachievable” – and then say “it’s not going to be enough to stop warming at 2 degrees“. I simply cannot see a logically coherent argument in all this.

martin-argo

My long-time friend and colleague Martin Visbeck launching an Argo float in the Pacific.

The bottom line

Should we monitor heat storage in the global ocean? By all means, yes! The observational oceanography community has long been making heroic efforts in this difficult area, not least by getting the Argo system off the ground (or rather into the water). That is no small achievement, which has revolutionized observational physical oceanography for the upper 2,000 meters of the world ocean. Currently Deep Argo is under development to cover depths up to 6,000 meters (see e.g. News&Views piece by Johnson and Lyman just published in Nature). These efforts need and deserve secure long-term funding.

Is ocean heat storage a good target for climate policy, to replace the 2 °C limit? Certainly not! I’ve outlined the reasons above.

 

[p.s. I am grateful that David Victor has apologized to me for comparing it to “methods of the far right” that I introduced him as a “political scientist” in my previous post (as in fact he is in the intro to his interview). This matter is now settled and forgotten, with no hard feelings.]

 

Update 21 October: I thank David Victor and Charles Kennel for responding to this article below. Answering this again would turn the discussion in circles – I’ve made my points and I think our readers now have a good basis to form their own opinion. Just one piece of additional data that might be informative, since Victor and Kennel below suggest to use the rate of heat content change for a well-measured portion of the ocean, rather than absolute heat content. Below I plotted the annual heat uptake of the upper 700 meters. (I already made this plot last week, it is the basis of me saying above that this measure is very noisy – the data can be downloaded from NOAA.)

ocean heat uptake

155 Responses to “Ocean heat storage: a particularly lousy policy target + Update”

  1. 101

    and Then There’s Physics –

    Thank you for your further reply.

    We are starting to move closer to agreement. However, we still have a fundamental disagreement. Let me try an analog.

    Consider a pot of water being heated on the stove. The heating coils are providing the forcing in Joules. If we measure the change over time of the Joules of heat in the water, we can, of course, obtain the energy imbalance (i.e. the warming). The feedbacks that result in the imbalance being less than the forcing are from evaporation, convective heat away from the water, etc).

    We can time slice this any time during the process and calculate the energy imbalance for that time period. This can then be directly translated into a flux convergence of heat over that time interval. This is just a requirement of energy conservation. We do not need a zero energy imbalance at the start to make this calculation of the average flux convergence.

    I do not see why you conclude this is different for the climate system.

    Perhaps, you want to calculate a T’ for the entire period of added greenhouse gases? In the NRC (2005) report, however, it is written that

    “T′ is the change in surface temperature in response to a change in heat content.”

    This must apply over any selected time period.

    On your weblog, since you insist on assuming I am wrong rather than just present your reasoning, I am going to avoid going there. As you admitted, you were wrong before, so you should be open to the idea that you may be again. The slams against me (and Judy Curry) detract from the value of your post.

    You also made one key error in your post that shows why you should discuss more. I am not using the IPCC definition of radiative forcing, but the basic physics use of this term. You are arguing as if I started from the IPCC definition which I am not.

    You make another error when you write

    ‘as the system adjusts, the radiative forcing doesn’t change”

    This is not correct. For example, if the vertical temperature and moisture profiles, clouds, etc change, the short and long wave radiative flux profiles including surface fluxes will change. This is an adjustment of the climate system to the change in radiative forcings and feedbacks.

    [Response: ATTP is correct as far as everyone else understands radiative forcings. There is a distinction between radiative forcings which are fixed and the climate changes (the feedbacks) that adjust on the way to a new equilibrium. Your definition of radiative forcing is non-standard, and so perhaps you should expand on what you think RF is. In the standard approach, RF is not a function of the subsequent evolution of the climate. – gavin]

    Roger Sr.

  2. 102
    Victor says:

    The Royal Society and the U.S. National Academy of Sciences are apparently in agreement with the estimates presented in the above post (https://royalsociety.org/~/media/Royal_Society_Content/policy/projects/climate-evidence-causes/climate-change-evidence-causes.pdf):

    “If emissions of CO2 stopped altogether, . . . sea level would likely continue to rise for many centuries even after temperature stopped increasing.”

    The last four posts on my blog, Mole in the Ground, are devoted to the serious deficiency in critical thinking skills regarding this and other issues in today’s world. Everyone is invited to read, and comment. Irate responses are particularly welcome. :-)

    http://amoleintheground.blogspot.com/

  3. 103
    Mike Jonas says:

    “While the increase in global temperature could indeed be stopped within decades by reducing emissions, ocean heat content will continue to increase for at least a thousand years after we have reached zero emissions.”.
    Well if that’s correct, then OHC is a stupid measure to use for policy because it will only be available 1,000 years after the policy is needed. NB. There’s a very important “if” in there.

  4. 104

    In reply to Hank Roberts post #61:

    I said, “It is a fact that fresh water has a higher specific heat than salt water. However, salt water, because of the molecular adhesive forces of the sodium and chloride ions, requires more energy, despite having a lower specific heat, to release (evaporate) H2O and heat into the atmosphere. – See more at: http://www.realclimate.org/index.php/archives/2014/10/ocean-heat-storage-a-particularly-lousy-policy-target/comment-page-2/#comments

    “Hank Roberts says: 23 Oct 2014 at 4:05 PM > A.G. Gelbert> … it is a fact … Can you cite that? – See more at: http://www.realclimate.org/index.php/archives/2014/10/ocean-heat-storage-a-particularly-lousy-policy-target/comment-page-2/#comments

    Hank, here are the details. It is somewhat counterintuitive, but nevertheless, the science is indisputable. Salt water has a boiling point of 103 C whereas, relatively unsalty, pure H2O has a boiling point of 100 C. In theory, a liquid with a lower specific heat (salt water) should have a a lower boiling point, but it has a higher one. Plain water also requires less energy to evaporate than salt water.

    “Re: Why does plain water evaporate faster than saltwater?
    Date: Tue Nov 30 20:05:51 1999

    Posted By: Dan Patel, Undergraduate, Chemistry Major/Math Minor, University of Houston
    Area of science: Chemistry
    ID: 943484734.Ch
    Message:

    There are several approaches we could take to explain why pure water evaporates faster than saltwater, and some of them can become rather complicated. It would probably be easiest to explain what exactly is happening to the water and salt molecules themselves.

    Salt is what we call a nonvolatile substance. This means that it will not easily evaporate. Water is a slightly volatile substance, meaning that if left standing it will evaporate (go from the liquid to the gas phase).

    When we have pure water, there is nothing to prevent it from evaporating. That is, on the surface of the water there are only water molecules, and we know that evaporation takes place on the surface.

    When we have saltwater, the surface now contains both salt and water. Salt does not like to evaporate (because it is nonvolatile), so it will stay in the solution. The water will still evaporate, but not as quickly because now salt takes up part of the surface area at the top of the solution. Since the water molecules in salt water don’t have as much surface area to evaporate from as the water molecules in pure water, the water in salt water will take longer to evaporate.

    We can also look at the forces between the salt and water in saltwater. We call these intermolecular forces and they result from the attraction of the positive and negative parts of a water molecule to the positive and negative ions in salt. Salt is made up of ions, which are just atoms with either a positive or negative charge. This charge comes about when an atom has more or less electrons than it does protons. Sodium and chloride ions make up salt, and when we put salt in water, these ions separate from each other (we call this dissociation) and the salt dissolves. The chloride ions, which are negatively charged, are attracted to the partial positive charge on the hydrogen atoms in a water molecule while the positively charged sodium ions are attracted to the partial negative charge on the oxygen atom in a water molecule.

    When the water in saltwater tries to evaporate it has a harder time because now it has sodium and chloride ions holding it back. Remember that salt doesn’t like to evaporate so it tries to keep the water in the solution, too. In order for the water in saltwater to evaporate it needs more energy than pure water, so it will take a longer time to evaporate.

    Pure water, on the other hand, does not have to worry about intermolecular forces with ions. It does have something we call “hydrogen bonding,” which is basically a weak force between the negative and positively charged parts of a water molecule, but hydrogen bonding is not as strong as the forces between the water and ions in saltwater. In hydrogen bonding, the hydrogen atoms (which have a partial positive charge) of one water molecule are attracted to the oxygen atom (which has a partial negative charge) of another water molecule.

    The electrons in the bond between hydrogen and oxygen in water are not shared evenly. They spend more time closer to the oxygen atom, which is what gives it the partial negative charge. To get a good picture of how hydrogen bonding works, you can look up the following website:

    http://www.mc.maricopa.edu/users/belford/scc130/pp130/ch14/sld023.htm

    http://www.madsci.org/posts/archives/1999-12/944144707.Ch.r.html

  5. 105

    Jim Baird says “Since the essence of global warming is ocean warming, it seems to me there is no answer without the conversion of some of this heat to work and the removal of as much as possible of the rest to the safety of the deep oceans. – See more at: http://www.realclimate.org/index.php/archives/2014/10/ocean-heat-storage-a-particularly-lousy-policy-target/comment-page-2/#comments

    I fully agree. I think all nuclear and fossil fuels should be eliminated permanently from our civilization as sources of energy.

    http://renewablerevolution.createaforum.com/fossil-fuel-folly/fossil-fuels-degraded-democracy-and-profit-over-planet-pollution/msg1409/#msg1409

  6. 106

    Gavin – The way you (and the IPCC) have defined radiative forcing is not what is used by everyone in our community. Indeed I have defined radiative forcings in my modeling book in Section 7.3

    Pielke Sr, R.A., 2013: Mesoscale meteorological modeling. 3rd Edition, Academic Press, 760 pp. http://store.elsevier.com/Mesoscale-Meteorological-Modeling/Roger-A-Pielke-Sr/isbn-9780123852373/

    The radiative flux divergence is an instantaneous quantity (or only constant over one or a small subset of time steps) and does change over time depending on the temperature, humidity, clouds etc. I am sure that in your models it is computed the same way.

    Roger Sr.

    [Response: ‘radiative flux divergence’ is not ‘radiative forcing’. The definition of radiative forcing has been developed over many years and appears in much of the literature. If you want to talk about something else, with a definition you are supplying, you mught want to try and make that clear right at the beginning so that people don’t get confused and waste their time talking at cross purposes. – gavin]

  7. 107

    Secular Animist says, “It is self-evident that the warming that has already occurred is already having consequences that we don’t like, and has already ensured worse consequences that we will like a lot less. There is already a steady stream of “disasters” that are at least in part directly attributable to anthropogenic CO2 emissions. The mitigation policy goal is straightfoward: zero emissions, as soon as possible. – See more at: http://www.realclimate.org/index.php/archives/2014/10/ocean-heat-storage-a-particularly-lousy-policy-target/comment-page-2/#comments

    This is the only logical course of action. Thank you for saying it.

  8. 108

    We have reached a good point in this thread to ask the following question:

    and Then There’s Physics

    If the radiative forcing is 2.29 Watts m-2 [if this is really the current forcing as listed in the IPCC report], what are the contributions of each of the radiative feedbacks, including the water vapor radiative feedback, that result in a value of 0.73 W m-2 as the radiative imbalance? Or pick a different time period than given in your comment.

    The uncertainties, of course, need to be included with each of these values.

    Roger Sr

  9. 109
    sidd says:

    Dr.Schmidt has indicated that Quick Latex works on this blog. Please do use it. I take the opportunity to point out that the term Q, usually denoting heat, is being used for a flux, the time derivative dQ/dt
    this confused me for a bit. Would be more understandable if people will use markup to write equations.

    (am trying the Quick Latex markup here, hope it works)
     \frac{dQ}{dt}

    sidd

    [Response: Need to add [ latex ] short codes. – gavin]

  10. 110

    Gavin – You write

    ‘radiative flux divergence’ is not ‘radiative forcing’

    The two are the same as I define in my modeling book and as a large segment of our community uses the two.

    I agree with you, however, that since the climate modeling community in which you are a member uses a different definition, this has resulted in confusion. (Your approach is more complicated than necessary, in my view, but it is your field to chose as you would like).

    However, now that my definition is clear, I hope comments can move forward to discuss the issues I am raising.

    Roger Sr.

  11. 111
    Joseph O'Sullivan says:

    I don’t enough about the science to make a confidently informed decision on who is right, but my take is Roger Pielke Sr. is disagreeing with some established principals in climate science without explaining himself.

    Roger Pielke Sr.’s comments remind me of the hypothetical scenarios that law professors used in class. They hinted, but didn’t say exactly what they meant, and our job as law students was to deduce what they meant. The goal was to get us to think, and these hypotheticals were teaching devices.

    RP Sr’s comments also remind me of some of the less then helpful tactics that lawyers use. They tend to be evasive with the intent of drawing out an argument and generally wasting time as a way to help a client’s case.

    I do remember when his blog was active when he commented on the Supreme Court case EPA v Mass where the court said the EPA was mandated to regulate greenhouse gas pollution. I know enough about the legal issues to tell his opinions were way off the mark.

  12. 112
    Chris Colose says:

    Rather than talk in circles, perhaps an equation is required in order to guide this discussion of what “radiative forcing” means. Here is a link and equation below (if it’s embedded correctly).

    Here, I take R to be the outgoing minus incoming radiation at TOA, x to be some feedback like water vapor, and “phi” to be the forcing parameter (e.g., log CO2/CO2_init), and T is temperature. The LHS goes to zero in equilibrium and the RHS is the radiative forcing (or negative radiative forcing), which is -4 W/m2 for doubled CO2. I’ve been explicit that x and T should be held fixed, or you can let the stratosphere adjust and other very rapid adjustments depending on your favorite version of forcing. The last two terms are feedbacks, with the final term being the Planck response.

    If Roger prefers a better working definition he should formulate it precisely. But, none of this (still) makes any coherent contact with the point of the thread about policy benchmarks…

  13. 113
    Eli Rabett says:

    Another exam in Prof. Pielke’s classroom. Perhaps a good place to start would be Prof. Pielke adopting the common nomenclature everyone else uses. if he wishes to discuss radiative flux divergence, all to the good, but don;t waste everyone;s time and patience talking about radiative forcing when you mean something else and yes, if you wish to communicate and not confuse, please use the agreed meanings of the field and not your personal dictionary.

  14. 114
    Hank Roberts says:

    I’m sure the argument for substituting a measure that’s less certain (has wider error bars) includes the need to delay any political decision because further research will be required to reduce the uncertainty.

    In that vein, a reminder from the original post:

    Ocean heat content … uncertainties are larger than for global mean temperature, the data don’t go as far back (1850 for global mean temperature) and data from the deep ocean are particularly sparse ….

  15. 115
    Steve Fitzpatrick says:

    Secular Animist,
    “It is self-evident that the warming that has already occurred is already having consequences that we don’t like, and has already ensured worse consequences that we will like a lot less. ”

    Sounds a bit like the self evident truths in the Declaration of Independence. Still, for some these consequences may not be so self evident. Can you point out what the consequences are that we don’t like?

  16. 116
    Eli Rabett says:

    Roger, perhaps before ATTP takes your exam, you might explain why you expect others to intuit your rather ideosyncratic definition of radiative forcing, and once having forced it into the open you expect that others would accept it.

  17. 117
    Joseph O'Sullivan says:

    From what I can tell Roger Sr is using different uses for terms that the climate science community has already agreed upon, but is not telling us upfront.

    It reminds me of the hypothetical scenarios that law professors use, where they hint at what the law is, but don’t outright say it. These hypotheticals are teaching devices, requiring student to deduce what the law is. The old adage is the goal is to get the students to think.

    It also reminds me the tactics that lawyers use when they are not upfront about their arguments and evidence, and force their opponents to spend time and effort to find out. It’s a way to make a case difficult and make it more likely to result in a decision or settlement in their favor.

    Roger Sr seems to be out of the scientific mainstream on this one, but I am not qualified to say if he is correct or not. When he had his own blog he made some comments criticizing EPA v Massachusetts, the Supreme Court case requiring the EPA to regulate greenhouse gas pollution. I knew enough about that to know that he was off the mark.

  18. 118
    Hank Roberts says:

    Amateur poking at Google and Scholar with this search
    q=distinguish+%22radiative+forcing%22+and+%22radiative+flux+divergence%22
    turns up quite a few papers that use both terms — “radiative flux divergence” and “radiative forcing” — and distinguish them.

    Many of those papers are interesting to this amateur reader.
    For one example, this:
    _____________________
    Divergent global precipitation changes induced by natural versus anthropogenic forcing

    http://www.nature.com/nature/journal/v493/n7434/full/nature11784.html

    Jian Liu, Bin Wang, Mark A. Cane, So-Young Yim & June-Yi Lee
    Nature 493, 656–659 (31 January 2013)

    doi:10.1038/nature11784

    Here we show in climate model simulations that the tropical Pacific sea-surface-temperature gradient increases when the warming is due to increased solar radiation and decreases when it is due to increased greenhouse-gas forcing.

    For the same global surface temperature increase the latter pattern produces less rainfall, notably over tropical land, which explains why in the model the late twentieth century is warmer than in the Medieval Warm Period (around ad 1000–1250) but precipitation is less.

    This difference is consistent with the global tropospheric energy budget12, which requires a balance between the latent heat released in precipitation and radiative cooling.

    The tropospheric cooling is less for increased greenhouse gases, which add radiative absorbers to the troposphere, than for increased solar heating, which is concentrated at the Earth’s surface.

    Thus warming due to increased greenhouse gases produces a climate signature different from that of warming due to solar radiation changes.

    (added para. breaks for readability online – hr)

  19. 119
    Erich Zann says:

    So all the heat that was going to raise temperatures in the atmosphere by 2C is going into the oceans. The large heat capacity of the oceans means that the time constant will be a couple of hundred years, about the same timescale as a) we run out of fossil fuels and b) the CO2 lifetime.

    Alright this is probably wrong. So give me a simple engineering model of what is going on. Also, do we know the sign of the net effect of clouds on temperature yet?

  20. 120
    ...and Then There's Physics says:

    Roger,

    I understand your reluctance and am always to consider I might be wrong. I do think, though, that if you want to use the equation that you include in Judith Curry’s post, then you should be using that standard definitions, or rewrite the equation to be consistent with your definitions. As Gavin points out, you seem to using the forcing to mean radiative flux divergence, rather than as it is normally defined.

    If the radiative forcing is 2.29 Watts m-2 [if this is really the current forcing as listed in the IPCC report], what are the contributions of each of the radiative feedbacks, including the water vapor radiative feedback, that result in a value of 0.73 W m-2 as the radiative imbalance? Or pick a different time period than given in your comment.

    If you’re happy to ignore uncertainties, then this is how I would do it.

    Anthropogenic forcings = 2.29W/m^2

    Planck response = 4 epsilon sigma T^3 dT

    If I assume epsilon = 0.6, T = 288 K, and sigma is the Stefan-Boltzmann constant, then the Planck response would be 3.6 W/m^2 per 1.1 degrees (so about what we expect for a doubling of CO2). If I then assume dT = 0.85 degrees (i.e., how much we’ve warmed) that gives a Planck response of 2.8 W/m^2.

    Therefore to still have a radiative imbalance of about 0.73 W/m^2 that implies feedbacks (water vapour, lapse rate, clouds) of

    feedbacks = 0.73 – 2.29 + 2.8 = 1.24 W/m^2.

    This would then be 1.5 W/m^2/K. Of course this is the sum of the water vapour, lapse rate and cloud feedbacks. I wouldn’t know how to extract the individual feedbacks.

    From the figure in your Judith Curry post, the Planck feedback was -4.2 W/m^2/K and the sum of the other feedbacks was 3 W/m^2/K. If I repeat my calculation using a Planck feedback of -4.2W/m^2/K, then the other feedbacks sum to 2W/m^2/K, again less than the figure in your post but not that surprising since we know that these energy budget estimates give mean TCR and ECS estimates that are lower than those from climate models.

    So, either feedbacks really are lower than climate models suggest, or these energy budget estimates are unable to capture the full picture (inhomogeneities, non-linearities), or internal variability has produced some cooling that is currently resulting in them underestimating these values (of course, it could have produced some warming which would make the climate models even more discrepant).

    Having said that, of course, Gavin has recently published a paper showing that more recent forcing estimates can bring climate model results more in line with observations, so I’m not convinced that the discrepancy between these energy budget estimates and observations is all that significant an issue at this stage.

    Of course, as you say, we should really be including uncertainties and doing this properly, but that’s more than I can manage at 9am on a Sunday morning while watching the roundup of the weekend’s football.

  21. 121
    Tommy Skoog says:

    It´s better we change debate instaed change CO2 levels seems to be the method. specialy to make it uninteresting for common people. or to difficult to understand. Then politician can discus instead of doing something. Mother earth won´t disscus. I.e it looks like this time IPCC came with its report it was no debate because it was only a long presentation list of which person should say something. Dr … Professor… and no one realy couldn´t make it a importent issue for voters. perfect planned from UN or who was it.

  22. 122
    phil mattheis says:

    gavin’s inline response to Roger Pielke, Sr at 25 Oct 2014 @ 5:03 PM:
    “If you want to talk about something else, with a definition you are supplying, you might want to try and make that clear right at the beginning so that people don’t get confused and waste their time talking at cross purposes. – gavin
    ========================================

    I’m a bit suspicious about this new interest in using ocean heat content to define global warming. Pielke Sr’s statement “We do not need the 2C threshold as the primary metric to diagnose global warming” is a handy straw man. He changes that value’s meaning as a projected likely minimum consequence of our current reality, as well as prohibitive maximum not to be exceeded, into a marker that could just prove warming might be happening. I doubt this is an accidental or poorly reasoned misuse of terms, but more a shifting of goalposts; confusion as a feature, not a bug.

    If current weather patterns persist to end of the year (esp with any amount of el nino action), 2014 is likely to be the new ‘hottest year’ on record. Thus would begin the end of ‘the hiatus’ in surface temp as the simplistic distraction it has been. Time to look for other candidates.

    Pielke’s suggestion that “we can diagnose the current value of global ocean heat content and the value of ocean heat content some time ago (i.e. any two time slices) with sufficient spatial and temporal accuracy…” assumes there is no noise in that system, and that a simple single number at each time will be broadly representative, and comparable, and useful.

    No doubt we need better understanding of OHC dynamics in storing and masking the continued radiative imbalance. But that is not a simple process, and OHC is not a simple unitary variable.

    I happily leave the math to others at the front-lines, for yall to beat out the many problems with OHC measurement: conflict resolution of data gathered by different methods, determination of regional and seasonal influences on local variability (noise), stratification of ocean depths into functional categories, identification of mixing zones and tipping points in the direction and magnitude of heat flow, relative impact of fresh vs saline, etc.
    It seems likely that we’ll be awhile waiting for OHC data to be dependably and widely available, just to inform modeling and analysis. Proposing its use as a measure of proof for AGW seems premature at best; lots of ‘developing field’ points of academic conflict as distraction, abundant justification of more delay in accepting that reality.

    Finally, the inherent inertia of heat energy added into the deep oceans makes OHC comparable to [CO2] in the atmosphere – increases in either are better avoided than retrofit. So, increased attention to OHC measurement and analysis? Absolutely. Is OHC the new best parameter for diagnosis or setting policy, not so much (or much at all).

  23. 123
    Chris Dudley says:

    Roger (#98),

    The increased area under heatwave is a consequence of global temperature rise. So, if you want to have a damage metric, that is fine, but this one works back to the average global surface temperature and thus the policy limit on that well measured quantity is well justified.

    The damage metric I find most morally compelling is species extinction since it elevates us above our own survival interest if we make that our focus. The latest IPCC report indicates we have a small cushion in future emissions in this regard if we will undertake to do some cleanup work down the road. The moral cost of failed stewardship may be the step too far that brings the further human costs crashing down around us. The 2 C limit is useful in this in that we must act on it now, which begins a process that could lead to stronger action to protect biodiversity. The 2 C limit requires China to finally make some climate commitment.

    I urge you to join 350.org in calling for a path that reduces the concentration of carbon dioxide in the atmosphere that is both compatible with the 2 C limit and also avoids species extinction.

  24. 124
    ...and Then There's Physics says:

    Roger,
    Actually, I made the same mistake in my previous comment that I’ve been suggesting that you made in the post on Judith Curry’s blog (knew I shouldn’t do this first thing on a Sunday morning). The terms should all be changes over the relevant time interval. If one considers the period used by Otto et al. (2001-2010 relative to 1860 – 1879) then the change in temperature is 0.75K, the change in system heat uptake rate is 0.65W/m^2 (0.73 – 0.08) and the change in anthropogenic forcing is 1.95W/m^2.

    The Planck response would then be 2.4 W/m^2 and the feedbacks would then be

    Feedbacks = 0.65 – 1.95 + 2.4 = 1.1 W/m^2 (or 1.1/0.75 = 1.5 W/m^2/K).

    Of course, you can consider other assumptions and include the uncertainties, but that is how I would compute the feedbacks.

  25. 125

    #88 et seq, ‘impacts’–

    Disasters for which some level of formal attribution to climate change exists include the 2003 European heat wave, the 2010 Russian heatwave (that one has mixed results), and the 2012 American drought. Those three events alone represent many tens of thousands of premature deaths, and more than a hundred billion dollars of losses.

    Moreover, inundation events such as Superstorm Sandy have been shown to have been exacerbated by the several-inch sea level rise which had occurred to date. Add those in and you have thousands of additional lives lost and well over a hundred billion in losses.

    It’s quite clear that actual costs of climate change so far must exceed attributed costs, as indirect effects can’t be reliably accounted for–for example, the Arab Spring uprisings have been politically ‘attributed’ in part to food shortages linked to drought, linked in turn to climate change. Those uprisings led directly to the present Syrian conflict, which is a massive humanitarian disaster. The American Meteorological Society likened this situation to driving: speeding (climate change) increases risk, even though proximate causes may include texting drivers (human action or inaction) or wet roads (bad meteorological luck.)

    Then there are effects which are likely to prove negative, but which are difficult to quantify. For example, there is little or no doubt that the loss of Arctic sea ice which we are observing is due to anthropogenic warming. Yet many of its probable consequences can’t be captured well in purely economic analyses.

    Taking everything together, I think it’s a reasonable, conservative estimate to say that the small warming seen so far has cost hundreds of thousands of lives and hundreds of billions of dollars. Given that impacts are expected to scale non-linearly, and that some are irreversible on humanly meaningful timescales, caution would seem to be very well justified.

  26. 126

    #115, Steve Fitzpatrick–I hope my previous comment puts sufficient flesh on the bones of SA’s summary statement.

  27. 127
    Bob Loblaw says:

    For all of those wishing to follow Roger Pielke down his rabbit hole of “flux divergence”, please note that he has a history discussing ocean temperatures here at RealClimate, where he seemed incapable of recognizing the important difference between “flux” and “flux divergence”. Perhaps he was using his own idiosynchratic definitions then, too.

    As for using OHC instead of surface temperature as a diagnostic – is there anyone out there willing to take a bet that if such a switch was made, that very soon afterward the bleat from the contrarians would be that the OHC content record is too short, and we need to wait until we have more data before doing anything? In other words, delay, delay, delay.

  28. 128
    MARodger says:

    Roger A. Pielke Sr. @97.
    You say to me “I am sorry but I am missing your point.” I take this to be a step in the right direction as @73 you were saying of me “Unfortunately, you miss the point,” when au contraire, I fear it is you who are indeed ‘missing the point.’
    You say @97 you “used the Wielicki et al.(2013) paper” to source you feedback values. Within the discussion paper that you’ve had posted on the planet Climateetcia, you put it thus:- “Wielicki et al. (2013; their figure 1; reproduced below) has radiative feedbacks.” And @97 you are suggesting that I consider “other better current estimates of the global average radiative feedbacks are available.”
    This is all incorrect. You did not “use” Wielicki et al. (2013) because that paper is not the true source of that data. @93 I point you to the actual source of that data – Boden et al. (2008). I do not in any way refer to different data of any form. Read my comment @93. It is all set out there.

  29. 129
    Hank Roberts says:

    In pielkeclimatesci.wordpress.com/2008/04/22: Guest Weblog By Roy Spencer of the University of Alabama at Huntsville titled “Internal Radiative Forcing And The Illusion Of A Sensitive Climate System“ I found

    I tentatively propose the following definition:

    Internal radiative forcing refers to any change in the top-of-atmosphere radiative budget resulting from an internally generated fluctuation in the ocean-atmosphere system that is not the direct result of feedback on temperature.

    If I understand Dr. Pielke’s posts he’s arguing here for the same uncertainty as Spencer has been?
    See http://www.yaleclimateconnections.org/2011/09/the-science-behind-the-spencer-braswell-paper/

  30. 130

    and Then There’s Physics –

    Thank you for your reply. However, what is the magnitude, specifically, of the water vapor radiative feedback?

    Roger Sr.

  31. 131
  32. 132

    Gavin – On the definition of what is “radiative forcing” as used others in the climate community, it is of the form I have used in my posts and comments. It is not an outlier as a number of commenters have erroneously claimed. As one example (where even Mike Mann was a co-author, as well as myself) see

    National Research Council, 2005: Radiative forcing of climate change: Expanding the concept and addressing uncertainties. Committee on Radiative Forcing Effects on Climate Change, Climate Research Committee, Board on Atmospheric Sciences and Climate, Division on Earth and Life Studies, The National Academies Press, Washington, D.C., 208 pp. http://www.nap.edu/openbook.php?isbn=0309095069
    where text in the Executuve summary reads
    “A climate forcing is an energy imbalance imposed on the climate system either externally or by human activities. Examples include changes in solar energy output, volcanic emissions, deliberate land modification, or anthropogenic emissions of greenhouse gases, aerosols, and their precursors. A climate feedback is an internal climate process that amplifies or dampens the climate response to a specific forcing. An example is the increase in atmospheric water vapor that is triggered by an initial warming due to rising carbon dioxide (CO2) concentrations, which then acts to amplify the warming through the greenhouse properties of water vapor. Climate forcings are usefully subdivided into direct radiative forcings, indirect radiative forcings, and nonradiative forcings. Direct radiative forcings directly affect the radiative budget of the Earth; for example, added CO2 absorbs and emits infrared (IR) radiation. Indirect radiative forcings create an energy imbalance by first altering climate system components (e.g., precipitation efficiency of clouds), which then lead to changes in radiative fluxes; an example is the effect of solar variability on stratospheric ozone. Nonradiative forcings create an energy imbalance that does not directly involve radiation; an example is the increasing evapotranspiration flux resulting from agricultural irrigation.”

    Radiative forcing is specifically described here as changes in radiative fluxes

    The report than goes on to define radiative forcing as you and others have presented.
    However, the report continues with the text in a section with the header

    “EXPANDING THE RADIATIVE FORCING CONCEPT’

    “Despite all these advantages, the traditional global mean TOA radiative forcing concept has some important limitations, which have come increasingly to light over the past decade… it diagnoses only one measure of climate change—global mean surface temperature response—while offering little information on regional climate change or precipitation. These limitations can be addressed by expanding the radiative forcing concept and through the introduction of additional forcing metrics. In particular, the concept needs to be extended to account for (1) the vertical structure of radiative forcing, (2) regional variability in radiative forcing, and (3) nonradiative forcing. A new metric to account for the vertical structure of radiative forcing is recommended…”

    My goal in proposing OHC changes and assessing the radiative imbalance in terms of radiative forcings and feedbacks is modified by this view.

    Ocean heat content changes are specifically presented in the report; i.e.

    “TOA radiative forcing is relatively easy to compute, generally robust across models, straightforward to use in policy applications, directly observable from space, and also inferable from observed changes in ocean heat content. It provides an extremely useful metric for climate change research and policy.”

    The report recommended

    “Long-term, accurate observations of changes in the heat content of the oceans are also needed as a continuous record of globally averaged radiative forcing.”

    I hope this clarifies why a different approach than a number of you use is advantageous to moving forward in the assessment of global warming of the climate system. Why not use both approaches?

    If you want to build consensus for optimal policy decisions, all assessment approaches should be used. Emphasizing the assessment of risk on a 2C threshold based on your approach, with social and environmental risk a derivative of this, is not effective use of what we know about the climate system, in my view.

    Roger Sr.

  33. 133
    Hank Roberts says:

    P.S., if Google Scholar has it right, Dr. Pielke hasn’t ever cited that paper by Held and Soden.
    As it’s been cited by over 500 subsequent papers, it might be worth a look, re his question.

    Remember, the problem with Spencer and Brasewell 2011 was that “it essentially ignored the scientific arguments of its opponents”.

  34. 134
    Eli Rabett says:

    Gavin,

    http://www.codecogs.com/latex/eqneditor.php

    is a useful and free website for generating AMS-latex code. Would it work here??

  35. 135

    “Radiative forcing is specifically described here as changes in radiative fluxes” – See more at: http://www.realclimate.org/index.php/archives/2014/10/ocean-heat-storage-a-particularly-lousy-policy-target/comment-page-3/#comment-614973

    As this musician reads it, no–RF is described as *causing* a change in fluxes. So are feedbacks; but feedbacks and forcings are not thereby the same.

  36. 136

    Hank Roberts – Your search is incomplete. We cited

    Held, I. M., and B. J. Soden (2006), Robust responses of the hydrological cycle to global warming, J. Clim., 19(21), 5686 – 5699

    in our paper

    Wang, J.-W., K. Wang, R.A. Pielke, J.C. Lin, and T. Matsui, 2008: Towards a robust test on North America warming trend and precipitable water content increase. Geophys. Res. Letts., 35, L18804, doi:10.1029/2008GL034564. http://pielkeclimatesci.wordpress.com/files/2009/10/r-337.pdf

    That is more recent than the Held and Soden (2000) paper.

  37. 137
    ...and Then There's Physics says:

    Roger,
    However, what is the magnitude, specifically, of the water vapor radiative feedback?
    Why is this specifically important? I can see why it’s interesting to know, but why would being able to tell you this be some kind of resolution to our discussion? Alternatively, what does me not be able to tell you the water vapour feedback specifically imply? The Wieliki et al. (2013) figure in your Climate Etc post indicates that water vapour feedback should be around 2W/m^2 (which is about the same as Soden & Held 2006). But there’s also lapse rate and clouds. It’s clearly very difficult to disentangle these different feedbacks. I think I’ve given you an estimate for the total feedback response (ignoring uncertainties), but how would it be possible to tell you the water vapour feedback specifically? You wouldn’t be asking an impossible question, just so that you can then go “Aha” would you?

  38. 138
    Hank Roberts says:

    Wang et al. (2008) got some interesting attention. Cited by six
    http://scholar.google.com/scholar?q=DOI%3A+10.1029%2F2008GL034564
    three science papers, and three by J.S. Johnston about corrupt climate science.

    Hm.

    Global Warming Advocacy Science: a Cross Examination
    JS Johnston – 2010 – scholarship.law.upenn.edu

    The Cost of Cartelization
    JS Johnston – Institutions and Incentives in Regulatory Science, 2012 [PDF] from climatecorruption.info

    [PDF] INSTITUTE FOR LAW AND ECONOMICS
    JS Johnston – 2010 – climatecorruption.info

  39. 139
    Hank Roberts says:

    Aside: Held and Soden (2006) has, Google Scholar finds, been cited by more than 950

  40. 140
    Eli Rabett says:

    Roger,

    While ATTP is responding to another of your questions, perhaps you might respond to one of Eli’s. What is the time for the water vapor feedback to respond to a greenhouse gas forcing?

  41. 141

    A very recent paper denounces the idea of deep water warming:

    Deep-ocean contribution to sea level and energy budget not detectable over the past decade. By W. Llovel, J. K. Willis, F. W. Landerer and I. Fukumori
    in Nature Climate Change (2014) doi:10.1038/nclimate2387
    Received 27 June 2014, Accepted 26 August 2014 and online 05 October 2014

    Abstract

    As the dominant reservoir of heat uptake in the climate system, the world’s oceans provide a critical measure of global climate change. Here, we infer deep-ocean warming in the context of global sea-level rise and Earth’s energy budget between January 2005 and December 2013. Direct measurements of ocean warming above 2,000 m depth explain about 32% of the observed annual rate of global mean sea-level rise. Over the entire water column, independent estimates of ocean warming yield a contribution of 0.77 ± 0.28 mm yr−1 in sea-level rise and agree with the upper-ocean estimate to within the estimated uncertainties. Accounting for additional possible systematic uncertainties, the deep ocean (below 2,000 m) contributes −0.13 ± 0.72 mm yr−1 to global sea-level rise and −0.08 ± 0.43 W m−2 to Earth’s energy balance. The net warming of the ocean implies an energy imbalance for the Earth of 0.64 ± 0.44 W m−2 from 2005 to 2013.

  42. 142

    Re #140 A water vapor increase occurs when ocean surface temperature increase; e.g. see

    De-Zheng Sun, Yongqiang Yu, and Tao Zhang, 2009: Tropical Water Vapor and Cloud Feedbacks in Climate Models: A Further Assessment Using Coupled Simulations. J. Climate, 22, 1287–1304.
    doi: http://dx.doi.org/10.1175/2008JCLI2267.1
    http://journals.ametsoc.org/doi/abs/10.1175/2008JCLI2267.1

  43. 143
    Eli Rabett says:

    Roger Eli’s question was: What is the time for the water vapor feedback to respond to a greenhouse gas forcing? not what is the mechanism. Your answer is not responsive. Care to try again?

  44. 144
    Jim Baird says:

    Re #141 As the dominant reservoir of heat uptake in the climate system, the deep ocean is underutilized. This can be reversed with heat pipes that can be adapted to produce as much zero emissions energy as is currently derived from fossil fuels.

    Commenting on the Llovel study and the concurrent Lawrence Livermore study that suggests warming in the southern seas since 1970 could be far higher than previously deduced, eco-business – http://www.eco-business.com/news/oceans-greater-heat-explains-warming-pause/ – points out, “One urgent question that needs answering is how much longer the water near the surface can continue to absorb the extra heat which human activities are producing. Another is what will happen when the oceans no longer absorb heat but start to release it. The answers could be disturbing.”

    Moving near surface heat to the deep resolves this question and is the short and long term solution to global warming.

  45. 145
    Hank Roberts says:

    He’s beating his own drum.
    He’s not going to cut it open and show you what’s inside.

  46. 146

    #143 – I answered with a paper that discussed this issue in detail. Why not present your answer for us.

  47. 147
    Eli Rabett says:

    Roger, you could, of course, answer with an answer. That’s what you demand from others. Eli’s answer, somewhere in here

    http://scholar.google.com/scholar?hl=en&q=water+feedback+time+scale&btnG=&as_sdt=1%2C9&as_sdtp=

  48. 148
    mitch says:

    To Comment by Boris Winterhalter — 27 Oct 2014 @ 7:31 AM (currently 141. Llovel et al do not ‘denounce’ deep water warming. If you read the paper they say that the warming is within large error bars of zero.

    They measure deep water warming by water expansion, but they first must subtract the glacial/groundwater contribution to sealevel rise, and then subtract the seawater expansion from the layers above 2000 m. The result is a noisy zero, but could be as much as an additional 0.43w/m2 additional heating or significantly negative. So, they don’t say that there is no deep ocean heating, but that they cannot measure any heating with this ‘yardstick’.

  49. 149
    James@CAN says:

    Just as there is “noise” in data there is also “noise” in the course of argumentation. The “noise” is important as it gives us something to compare to; to think about. It is always there as a reminder to check and check again. Sometimes “noise” turns out to be something else overlooked.
    I encourage you all to continue with your “noisy” arguments as over time the facts will filter out and in the end you will all have contributed to getting at the facts which we desperately need.
    No idea or thought is too small or ignorant.. so much is at stake here and every angle should be explored, egos notwithstanding. Forgive, shake hands and never give up.
    Congratulations and thank you to all for working on these important matters! The science is fascinating. The correct information will surface and recognition that this is a group effort is paramount.
    Thank you for sharing with the world as we muddle through this process together.
    To those of us like me who want to know, all of your ideas are greatly appreciated.
    Sincerely, James.

  50. 150
    sidd says:

    Purkey(2014) in JGR:Oceans doi:10.1002/2014JC010180 is as expected, very nice. Careful comparison of sea surface height and GRACE can get you very far indeed. She (and trusty cohorts Johnson and Chambers) teases out the precise error introduced by neglecting steric change in each fraction of the vasty deep:

    “to evaluate the error introduced into the mass budget if the deep steric contributions below 700, 1000, 2000, 3000,and 4000 m are neglected, revealing errors of 65%, 38%, 13%, 8% and 4% respectively.”

    “the deep ocean steric expansion below 700 m equivalent to 65% of the ocean mass contribution to sea level, and 13% below 2000 m”

    As for SLR from adding water to the bathtub:

    “finds a global mass addition trend of 1.5 (±0.4) mm yr-1 from 1996–2006”

    Was a pleasure to read. Caveat: Arctic is neglected. Read the whole thing. Preferably her (and Johnson’s) previous work too which elucidates isotherm heave, which leads me to bring up another recent paper in GRL by Spence et al, doi:10.1002/2014GL060613

    “Here we show that a poleward wind shift at the latitudes of the Antarctic Peninsula can produce an intense warming of subsurface coastal waters that exceeds 2°C at 200–700 m depth.”

    This is a calculation using a grid of approx 11Km at 65S for the ocean model, barely enough to resolve the Slope, where the shelf takes a dive. The idea is that as the Westerlies compress the ring poleward, more warm CDW is forced up and into contact with ice shelf bases, which is Not Good News for coastlines. The last line of the paper is:

    “Given 21st century projections of the Southern Annular Mode and the mechanism outlined here by which it can intensely warm subsurface Antarctic coastal waters, current projections for global sea level rise may be significantly underestimated.”

    Oh dear.

    sidd

    PS: Everything i wrote above has to do with the part of the title before the colon: “Ocean Heat Storage”

    PPS: I agree that OHC is a lousy target.

    PPPS: I am also not enamoured of a target of 2C globally averaged surface temp rise over preindustrial.

    sidd