In Hot Water: Global Warming Has Accelerated In Past 15 Years, New Study Of Oceans Confirms

Argo buoy taking measurements. (Credit: Argo Project Office)

By Dana Nuccitelli via Skeptical Science.

A new study of ocean warming has just been published in Geophysical Research Letters by Balmaseda, Trenberth, and Källén (2013). There are several important conclusions which can be drawn from this paper.

  • Completely contrary to the popular contrarian myth, global warming has accelerated, with more overall global warming in the past 15 years than the prior 15 years. This is because about 90% of overall global warming goes into heating the oceans, and the oceans have been warming dramatically.
  • As suspected, much of the ‘missing heat’ Kevin Trenberth previously talked about has been found in the deep oceans. Consistent with the results of Nuccitelli et al. (2012), this study finds that 30% of the ocean warming over the past decade has occurred in the deeper oceans below 700 meters, which they note is unprecedented over at least the past half century.
  • Some recent studies have concluded based on the slowed global surface warming over the past decade that the sensitivity of the climate to the increased greenhouse effect is somewhat lower than the IPCC best estimate. Those studies are fundamentally flawed because they do not account for the warming of the deep oceans.
  • The slowed surface air warming over the past decade has lulled many people into a false and unwarranted sense of security.

The main results of the study are illustrated in its Figure 1.

Figure 1: Ocean Heat Content from 0 to 300 meters (grey), 700 m (blue), and total depth (violet) from ORAS4, as represented by its 5 ensemble members.

The Data

In this paper, the authors used ocean heat content data from the European Centre for Medium-Range Weather Forecasts’ Ocean Reanalysis System 4 (ORAS4). A ‘reanalysis’ is a climate or weather model simulation of the past that incorporates data from historical observations. In the case of ORAS4, this includes ocean temperature measurements from bathythermographs and the Argo buoys, and other types of data like sea level and surface temperatures. The ORAS4 data span from 1958 to the present, and have a high 1°x1° horizontal resolution, as well as 42 vertical layers. As the authors describe the data set,

ORAS4 has been produced by combining, every 10 days, the output of an ocean model forced by atmospheric reanalysis fluxes and quality controlled ocean observations.

Accelerated Global Warming

As illustrated in Figure 1 above, the study divides ocean warming into three layers for comparison – the uppermost 300 meters (grey), 700 meters (blue), and the full ocean depth (violet). After each of the Mt. Agung, Chichón, and Pinatubo volcanic eruptions (which cause short-term cooling by blocking sunlight), a distinct ocean cooling event is observed in the data. Additionally, after the very strong El Niño event of 1998, a cooling of the upper 300 and 700 meters of oceans is visible as a result of heat being transferred from the surface ocean to the atmosphere.

One of the clearest features in Figure 1 is the rapid warming of the oceans over the past decade. As we have previously discussed, the warming of the shallower oceans has slowed since around 2003, which certain climate contrarians have cherrypicked to try and argue that global warming has slowed. However, more heat accumulated in the deeper oceans below 700 meters during this period. The authors describe the ocean warming since 1999 as,

the most sustained warming trend in this record of OHC. Indeed, recent warming rates of the waters below 700m appear to be unprecedented.

Their results in this respect are very similar the main conclusion of Nuccitelli et al. (2012), in which we noted that recently, warming of the oceans below 700 meters accounts for about 30% of overall ocean and global warming. Likewise, this new study concludes,

In the last decade, about 30% of the warming has occurred below 700 m, contributing significantly to an acceleration of the warming trend.

The warming of the oceans below 700 meters has also been identified by Levitus et al. (2012) and Von Schuckmann & Le Traon (2011), for example.

Some ‘Missing Heat’ Found

Kevin Trenberth past comments about ‘missing heat’ drew considerable attention. The phrase refers to the fact that the heat accumulation on Earth since about 2004 (e.g. from warming oceans, air, and land, and melting ice) that instruments were able to measure could not account for the amount of global heat accumulation we expected to see, based on the energy imbalance caused by the increased greenhouse effect, as measured by satellites at the top of the Earth’s atmosphere.

These new estimates of deeper ocean heat content go a long way towards resolving that ‘missing heat’ mystery. There is still some discrepancy remaining, which could be due to errors in the satellite measurements, the ocean heat content measurements, or both. But the discrepancy is now significantly smaller, and will be addressed in further detail in a follow-up paper by these scientists.

So what’s causing this transfer of heat to the deeper ocean layers? The authors suggest that it is a result of changes in winds related to the negative phase of the Pacific Decadal Oscillation and more frequent La Niña events.

Good News for Climate Sensitivity? Probably Not

Recently there have been some studies and comments by a few climate scientists that based on the slowed global surface warming over the past decade, estimates of the Earth’s overall equilibrium climate sensitivity may be a bit too high. However, as we previously discussed, these studies and comments tend to neglect the warming of the deep oceans below 700 meters.

Does the warming of the deep ocean support these arguments for lower equilibrium climate sensitivity? Probably not, as Trenberth explained (via personal communication),

it contributes to the overall warming of the deep ocean that has to occur for the system to equilibrate. It speeds that process up. It means less short term warming at the surface but at the expense of a greater earlier long-term warming, and faster sea level rise.

So the slowed warming at the surface is only temporary, and consistent with the ‘hiatus decades’ described by Meehl et al. (2011). The global warming end result will be the same, but the pattern of surface warming over time may be different than we expect.

The real problem is that in the meantime, we have allowed the temporarily slowed surface warming to lull us into a false sense of security, with many people wrongly believing global warming has paused when in reality it has accelerated.

Global Warming Wake Up Call

Perhaps the most important result of this paper is the confirmation that while many people wrongly believe global warming has stalled over the past 10–15 years, in reality that period is “the most sustained warming trend” in the past half century. Global warming has not paused, it has accelerated.

The paper is also a significant step in resolving the ‘missing heat’ issue, and is a good illustration why arguments for somewhat lower climate sensitivity are fundamentally flawed if they fail to account for the warming of the oceans below 700 meters.

Most importantly, everybody (climate scientists and contrarians included) must learn to stop equating surface and shallow ocean warming with global warming. In fact, as Roger Pielke Sr. has pointed out, “ocean heat content change [is] the most appropriate metric to diagnose global warming.” While he has focused on the shallow oceans, actually we need to measure global warming by accounting for all changes in global heat content, including the deeper oceans. Otherwise we can easily fool ourselves into underestimating the danger of the climate problem we face.

– This piece was originally published at Skeptical Science and was reprinted with permission.

47 Responses to In Hot Water: Global Warming Has Accelerated In Past 15 Years, New Study Of Oceans Confirms

  1. fj says:

    We don’t comprehend the full range of services the world’s oceans provide. We just know that we are huge.

    We don’t know how to predict the imminent collapse of marine ecosystems but we know that it is close to happening.

    We don’t even know how to characterize oceanic convection systems below 500 feet (last I heard; might be meters).

  2. mikkel says:

    Joe, a few years ago there was a paper that stated there was a good likelihood that surface temps would “pause” through about 2015 due to ocean cycles but then catch back up as the ocean released the heat. The hype was that warming would stop until 2020 due to the way the graph was presented and of course the “skeptic” sites never talked about what would happen after that.

    I remember you interviewed the author for clarification and he supported your initial reading.

    I haven’t been able to find it since, despite repeated attempts searching, which is a shame because it is an example of a prediction that what we are seeing would happen. Do you remember the paper?

  3. Scary – methane hydrates.

  4. Mike Roddy says:

    Thanks, Dana. A few dumb layman’s questions:

    1. As excess heat from the atmosphere accumulates in the ocean, does this process become more difficult over time based on the differential data for ocean and air temps?
    2. As Patricia notes, does this presage much larger methane releases from the Arctic Shelf?
    3. What determines when a heat saturated ocean begins to more rapidly transfer this excess heat into the atmosphere?

  5. Merrelyn Emery says:

    This data explains so much, the changing currents and heatwaves, everything swimming towards the poles at the rate of knots, the melting from below etc, beautiful, ME

  6. Lore says:

    Confirmation to Nuccitelli et al. (2012). The studies just keep adding up!

  7. David Goldstein says:

    Can somebody clear this up for me?…are the implications of this study that contrary to the specious claim that ‘global warming stopped 16 years ago’, things are actually worse than supposed- that, in fact, when the heat/energy does ‘cycle out’ of the oceans we are in for some serious surface temperature spiking? If this is the case then…this seems like very bad news.

  8. Jack Burton says:

    It is a bit amazing that so many would discount the role of the oceans. They are after all the majority of the global surface area, and deep. A warming earth would by every law of physics see most warming go into the oceans. Air temperatures are isolated from deeper water, so as that water warms it can act as a natural heat sink that limits surface air temperatures. Heat sinks are well understood.
    We will have hell to pay when currents and natural sea churning eventually brings up this trapped heat. This could begin to happen at any time.
    Naturally the deniers are ecstatic with the limited surface air temperature warming. This is great for their PR campaign. I just in fact read a great article by some Geology professor who has written in detail his study of climate data which show conclusively that we are in experiencing global cooling and it is accelerating. This scientist uses his geology credentials as evidence that HE can interpret the evidence and prove global cooling is underway. This man is amazing! His article is on Global Research, somehow an anti globalization site picked up this denier’s piece. I believe because some anti globalization people believe global warming will be used to expand a one world government led by banks and neo-liberal economists, and their military arms NATO and the US military.

  9. BBHY says:

    @David Goldstein, it is actually much worse than that. When only a tiny fraction of this heat that is being stored in the oceans is released it will make 1998 seem like the sort of minor warming that prompts the daffodils to sprout.

    The oceans store tremendous amounts of thermal energy and they hold on to it for a very long time. This means that even if after we cease all CO2 emissions entirely, we will still have decades of Arctic melting, glacier melting, Greenland melting, sea level rising, permafrost melting and methane emissions to deal with.

    We have to stop this path that we are on and get on the new clean energy path that we know is the right way. We have to do it now, right away, before it gets any worse.

  10. fj says:

    Currently at plus 0.8 ºC and with all that’s happened and much more heat sequestered deep in the world’s oceans it’s difficult how anyone can talk about 2 ºC or 4 ºC as any sort of linear progression of changes caused by huge amounts of distributed kinetic energy easily concentrated at any given time by unforeseen events or phenomena as we are starting to see now.

  11. Joe Romm says:

    I’ll look for it.

  12. Yes, basically the next time we have an El Niño or two, it’s going to be really hot at the surface.

  13. Well, I’m no oceanographer. I think this means we’re going to get a lot of surface warming when we start to get a few El Niños, and when PDO transitions to its next positive phase.

  14. David Goldstein says:

    Hey, BBHY:
    thanks for that. I am a blogger for the Huffington Post- have had 3 climate change articles so far. I am writing up another right now that incorporates the implications of this study. I’ll post it one CP once it is accepted for publication over at HuffPost.

  15. Camburn says:

    Quick question:
    1. What current drew this heat from the top 700 meters of the ocean to the 2000 meter and deeper depth.
    2. How many data points below 2,000 meters did the XBT buoy data provide?
    3. What are the error bars of the original data points?
    4. What are the error bars of the output of the reanalysis model?
    5. Has the reanalysis model been verified?

  16. Colorado Bob says:

    Katrina-level storm surges have more than doubled due to global warming
    By Dr. Jeff Masters
    Published: 2:08 PM GMT on March 25, 2013

    Projecting into the future, the model predicts that if the global climate warms as expected by 2°C before the end of the century, Katrina-level storm surge events will become ten times more common, and a Katrina-level surge will occur, on average, every 2 years, instead of every 20 years. Since sea level is steadily rising due to global warming, these future storm surges will also be riding in on top of an elevated ocean surface, and will thus be able to do even greater damage than in the past.

  17. The heat had to be going somewhere. Oceans cover 3/4 of the earth’s surface, and therefore get 3/4 of the radiative forcing (give or take a little for variable cloud cover, arctic albedo, etc.).

    That’s why I completely discounted all the denier’s nonsense about how the planet isn’t warming up. Maybe the surface temperatures haven’t changed a lot in recent years, but the cryosphere has changed an enormous amount, as, apparently, has the world ocean — and don’t forget evaporation, i.e., a 4-5% global increase in atmospheric water vapor.

    Meanwhile, even the small change to overall surface temperature that’s happened so far has caused incredible changes.

    A hard rain’s gonna fall…

  18. Merrelyn Emery says:

    Yep, and the answer is blowin’ in the wind, ME

  19. jyyh says:

    Camburn’s been reading fringe science again…
    1.downwelling areas that have been warmer than previously (North Atlantic, Central north Pacific, Antarctic gyres…), so it’s hard to specify one current.
    2.are you saying you think increased submarine volcanism is the reason for this increase in marine heat content? Or maybe you think deep ocean clathrates have started to release methane that warms the ocean up so it’s not us?
    Please provide evidence of either
    3. a)increased amounts of volcanic sulfur on the areas of increased heat content or
    4. b)anoxia caused by the decomposition of methane in the layer of ocean that has warmed (as deepwater horizon may have locally contributed to this, i’d prefer the evidence to be collected near northern mid-Atlantic rift, mid-northern Pacific and from inside the antarctic oceanic gyres.) the heat hasn’t come out of the ocean yet, and since there’s entropy, I’d expect the nights to warm more than days, winters more than summers, and poles more than tropics. This model doesn’t change the physics of water, air, or the greenhouse gases, and doesn’t require further evidence described in 3 and 4.

  20. Andy Lee Robinson says:

    David, you’re welcome to use the iconic Arctic Death Spiral too, if you haven’t already seen it:
    It helps to get the message across very clearly.

  21. Paul Klinkman says:

    The need to study deep ocean temperature rises may be especially true with the polar ocean. The Arctic Ocean can act as a decades-long heat sink, preventing thick ice from accumulating on the ocean surface in winter, which then allows the ocean to be uncovered in summer, so that solar heat penetrates the ocean all summer and the deep ocean grows ever warmer.

    If the Arctic ice pack is headed toward catastrophe this summer, what’s the best forecast for ten or twenty years from now? Scientific minds are curious and we want to know these things, in the same way that we want to know where in general the hurricane is going to hit in five days, even if we don’t know exactly.

    Is the Arctic pack ice going to suddenly return? No! Is it going to stay the way it is? I doubt it. Well then, what’s our best 20 year forecast?

  22. wili says:

    I also seem to recall an article about ocean turnover being quicker than once thought. But perhaps that was regarding CO2 sequestration. And iirc the focus was on the southern oceans. I’ll look around a bit and see what pops up.

  23. wili says:

    “what’s our best 20 year forecast?”

    Rough, and getting rougher.

    Actually, I think the science is still trying to catch up with the events as they unfold more and more rapidly than anything the earlier models had predicted.

    Recall, that none of the Arctic Ice models used in the ’07 IPCC report came anywhere remotely close to predicting the rate of Arctic ice loss that we have witnessed since then. So scientists weren’t mostly focused on what the consequences would be of an event that was not supposed to happen for many decades to centuries.

    Note that there are two components to the issue:

    –What are the direct effects of an ice free Arctic Ocean on _atmospheric_ circulation?

    –What are the effects of it on _ocean current_ circulation?

    The former, from what I’ve seen, has gotten a bit more attention than the latter (which has gotten little-to-no attention, as far as I’ve seen).

    We know that all that open water will mean more evaporation. That evaporated moisture will have to fall somewhere, and since the opening will happen first in the fall in the far north, it will fall mostly as snow, much of it on the surrounding land surface.

    This could paradoxically lead to cooling of continental interiors due to albedo shift. In fact that is likely part of the reason for this year’s cool winters in much of central North America and Eurasia.

    Dr. J. Frances and others have proposed other effects, like more and longer blocking patterns, such has those that created the western drought and the never-ending British rain this summer.

    But it’s a huge, comlex system that we don’t fully understand.

    I expect that more and more we will be seeing ever-more intense and destructive climate patterns that we will be less and less able to predict or understand (this even if the repugs weren’t actively eviscerating the relevant scientific programs, essentially condemning us to fly blind into the rapidly worsening sh!t storm we have created).

  24. Camburn says:

    Your answer does not answer the questions.

    How many data points below 2,000 meters were used?

    You don’t know what currents, but maybe someone does?

    Where in my question did volcanoes enter? Do you think volcanoes are all of a sudden large heat sources?

  25. Joan Savage says:

    Prompted by you and Patricia, I went looking for a recent map of the Arctic Ocean bathymetry. A great deal of it is over relatively shallow (less than 100 meters) shelves such as the Laptev Sea, where the methane bubbles are detected.

    I think a big question regarding ocean heat accumulation below 700 meters is where else clathrate thawing could develop?

    The temperature/pressure nomographs for clathrate instability show that clathrates at great depth (pressure) can still destabilize at warm enough temperatures.
    Here’s a nomograph –

  26. Mark E says:

    “what’s our best 20 year forecast?”

    More talk than action, gradually giving way to decreasing winter food stores until…..

    We have not just high food prices, but empty shelves.

    At which point we do a crash program which is only minimally effective towards adaptation, and everyone says “Don’t blame me, I was a climate hawk ‘way back when we could of still done something!”

  27. Jim Baird says:

    What is needed is to disappear ocean heat permanently, which can be accomplished by converting it to work. The ocean is simultaneously the largest hot and cold reservoir on planet and thus the perfect host for thousands of small heat engines.

  28. Mark E says:

    And here comes Jim, seeking profits for his patents and spreading ecological lies to line his pockets.

    At realclimate awhile back folks really thumped his shameful marketing ploy, whereby Jim falsely claims ocean energy converted to work results in a net cooling of the planet instead of just moving the energy from one part of the climate system to another.

    Are there no other ecological scolders among us?

    See comment thread here

  29. Joan Savage says:

    I’m not a physicist by training, but I too am uneasy about the notion of “thousands of small heat engines,” in part because I think like the ecological economists: there are no externalities, everything counts.

    The one solid way that the net heat increase can dissipate from the earth’s biome is radiation to space.

    The most comprehensive way to prompt release of excess heat from over 150 million square miles of ocean is cooler air temperature, creating a gradient that would favor upward movement of heat in the water column.

  30. Jack Burton says:

    Clearly another Public Relation employee has turned up. Another creative denial angle. Only a couple days ago a quite plausible and interesting angle of denial appeared in the comments section. The mystery man disappeared after a quick strike. Never heard from before, not heard from since.
    Now we see another very interesting denial strike, no back up evidence for support, simply some questions designed to divert attention from the evidence.
    Clearly the Fossil Fuel Industry has set it’s Public Relations Firm’s hired guns to troll this website. We shall see if our new friend sticks around eh?
    Totally entitled to post, he certainly is. But don’t try and BS me! I know how many professional PR trolls work for these firms. They are set up to respond to any climate report on any media outlet, the internet is monitored very carefully and their automatic search functions can key them to arrive in minutes. The Think Tank portions of the PR firm supplies the post, the operative posts it under fake name and Poof! Is gone.
    Call me a liar if you will, but who really is the liar??????

  31. pinroot says:

    A ‘reanalysis’ is a climate or weather model simulation of the past…

    Well, if the model says it’s so, it must be so. No longer any such thing as GIGO with these new-fangled models.

  32. Mark E says:

    Thanks Joan;

    Jim, you can count on my passionate support if you can figure out how get the “waste” BTUs out to space. And I will want to invest too, not just talk it up. But until then I wish you would stop spreading marketing hype that defy the laws of thermodynamics.

  33. David Goldstein says:

    Thank you, Andy.

  34. mikkel says:

    Yup, that was it. Thanks.

  35. Mulga Mumblebrain says:

    That would be ‘beautiful’ as in… ‘Now and in time to be, Wherever green is worn, Are changed, changed utterly, A terrible beauty is born’.

  36. Mulga Mumblebrain says:

    It looks as if, while the soft denialists still prattle on about ‘tipping-points’, that, in fact, the ‘points of no return’ have already been passed.

  37. Mulga Mumblebrain says:

    And the Dunning-Kruger mob, brandishing their pitch-forks, starts screeching, ‘Why didn’t you warn us? Why didn’t you make us listen’, egged on by the Rightwing MSM.

  38. Paul Klinkman says:

    Realistically, poor Jim isn’t going to line his pockets. He has no market for selling energy generated 20 miles off of the north coast of Alaska, except maybe to Shell Oil, and they already have oil. He has no way of economically servicing his machines in the middle of the Alaskan winter. Somebody has to keep the machines from being crushed by (not so thick these days) pack ice and then sinking. When the pack ice moves, will a floating machine’s anchor on the sea bottom be dragged along to Siberia or to deep water? There may be other show stoppers, such as Jim underestimating how hard it will be to create usable power from marginal temperature differences.

  39. Mulga Mumblebrain says:

    It’s the GIGOLOs (GIGO Lying Outrageously) that we have to look out for, isn’t that so?

  40. fj says:

    Just with a cursory (mis?) understanding of this stuff it seems that tropical cyclones might serve as giant air conditioners with terrific cooling potential considering the dynamics and thermodynamics; with large scale distributed kinetic energy converted to the concentrated kinetic energy in powerful winds and heat constantly transitioning between heat of vaporization to heat of fusion and back again.

  41. Mark E says:

    Except Jim’s main target deployment area isn’t in those waters

  42. fj says:

    Forget heat of fusion

  43. fj says:

    Just transitioning through the heat of vaporization phase change in both directions.

  44. fj says:

    Concentrated kinetic energy is converted back to heat with frictional losses.

  45. fj says:

    The potential of applications might lead to new areas of applied science perhaps, nonlinear geoscience inclusive of innovations similar to squeezed-light soliton stuff at geophysical scales.