Hottest Decade on Record Would Have Been Even Hotter But for Deep Oceans — Accelerated Warming May Be On Its Way

A composite of all the major global temperature records via Skeptical Science.

The last decade was easily the hottest on record.  We’ve known that sulfate aerosols (from volcanoes and/or Chinese coal) and the “the deepest solar minimum in nearly a century” masked the rate of warming somewhat.

Even so, NASA’s Goddard Institute for Space Studies (GISS), which probably has the best of the long temperature datasets, reported the 12-month running mean global temperature reached a new record in 2010.  As a NASA analysis found: “We conclude that global temperature continued to rise rapidly in the past decade” and “there has been no reduction in the global warming trend of 0.15-0.20°C/decade that began in the late 1970s.”

But other datasets appeared to show a slight slowing in the rate of warming, though even that may have been due to flawed data, as in the case of the UK’s Hadley Center.

Scientists have long known that the overwhelming majority of human-caused warming was expected to go into the oceans (see figure below).  And many have suspected that deep ocean warming has also been masking surface warming.

Now a new study led by led by the National Center for Atmospheric Research (NCAR) finds that may indeed be the case:

The planet’s deep oceans at times may absorb enough heat to flatten the rate of global warming for periods of as long as a decade even in the midst of longer-term warming….

The study, based on computer simulations of global climate, points to ocean layers deeper than 1,000 feet (300 meters) as the main location of the “missing heat” during periods such as the past decade when global air temperatures showed little trend. The findings also suggest that several more intervals like this can be expected over the next century, even as the trend toward overall warming continues….

“This study suggests the missing energy has indeed been buried in the ocean,” [coauthor Kevin] Trenberth says. “The heat has not disappeared, and so it cannot be ignored. It must have consequences.”

These potential consequences include accelerated warming in the coming decade and melting of  the West Antarctic Ice Sheet. Let’s take these two in order.

The heat may have been carried deep into the ocean by overturning circulations, which can plunge surface water from the subtropical regions into the ocean’s depths. The burying of warmer water also corresponds with La Nina weather patterns, which are born from cooler-than-average surface water temperatures in the tropical Pacific. And over the last decade, La Nina conditions have dominated, Trenberth said.

That the heat is buried in the ocean, and not lost into space, is troublesome, Trenberth said, since the heat energy isn’t likely to stay in the ocean forever, perhaps releasing back into the atmosphere during a strong El Nino, when sea surface temperatures in the tropical Pacific are warmer than average.

“It can come back quite fast,” he said. “The energy is not lost, and it can come back to haunt us, so to speak, in the future.”

I asked Trenberth whether we might see a decade where warming is a tad faster than expected, and he emailed me, “Yes.”  Once the decade of slower warming “is over, the subsequent warming can play catchup.”

This idea that the ocean can mediate periods when human-caused global warming is faster and slower is not new.  Indeed, Dr. Mojib Latif, head of the Ocean Circulation and Climate Dynamics Division at the Leibniz Institute of Marine Sciences, came to the exact same conclusion in a widely misunderstood 2008 article (see “Nature article on ‘cooling’ confuses media, deniers: Next decade may see rapid warming”).

Here was Latif’s Nature “forecast” — the green dashed line (click to enlarge) — notice the accelerated “catch up” surface warming this decade:

For more explanation of this figure, see here.

A key point from recent observation is that whatever slight slowing in global warming some groups may have observed in the past decade, it was primarily in the surface temperature data set.  The oceans kept warming (see “Sorry Deniers, the Oceans are Still Warming as Predicted“):

Figure 1:   Revised estimate of global ocean heat content (10-1500 mtrs deep) for 2005-2010 derived from Argo measurements. The 6-yr trend accounts for 0.55±0.10Wm−2. Error bars and trend uncertainties exclude errors induced by remaining systematic errors in the global observing system. See Von Schuckmann & Le Traon (2011).  Via Skeptical Science.

A 2009 NOAA-led study, “An observationally based energy balance for the Earth since 1950” (subs. req’d, release here) concluded:

[S]ince 1950, the planet released about 20 percent of the warming influence of heat-trapping greenhouse gases to outer space as infrared energy. Volcanic emissions lingering in the stratosphere offset about 20 percent of the heating by bouncing solar radiation back to space before it reached the surface. Cooling from the lower-atmosphere aerosols produced by humans balanced 50 percent of the heating. Only the remaining 10 percent of greenhouse-gas warming actually went into heating the Earth, and almost all of it went into the ocean.

Note that this Journal of Geophysical Research-Atmospheres study was done “without using global climate models.”

“Total Earth Heat Content [anomaly] from 1950 (Murphy et al. 2009). Ocean data taken from Domingues et al 2008.”

There is a second consequence of ocean warming, of course.  As Climate Progress reported last December, “Deep ocean heat is rapidly melting Antarctic ice“:

“Warm waters carried by the Antarctic Circumpolar Current are brushing the ice front in the western part of the continent, in the area of the Bellingshausen Sea.”

Antarctica is disintegrating much faster than almost anybody imagined — see “Nothing in the natural world is lost at an accelerating exponential rate like this glacier.” In 2001, the IPCC “consensus” said neither Greenland nor Antarctica would lose significant mass by 2100. They both already are.  As Penn State climatologist Richard Alley said in March 2006, the ice sheets appear to be shrinking “100 years ahead of schedule.”

A presentation at the fall 2010 meeting of the American Geophysical Union sheds some light on the underlying cause of this rapid melt — the ice is being attacked from the bottom.  Discovery News had the story:

Global warming is sneaky. For more than a century it has been hiding large amounts of excess heat in the world’s deep seas. Now that heat is coming to the surface again in one of the worst possible places: Antarctica.

New analyses of the heat content of the waters off Western Antarctic Peninsula are now showing a clear and exponential increase in warming waters undermining the sea ice, raising air temperatures, melting glaciers and wiping out entire penguin colonies.

“In the area I work there is the highest increase in temperatures of anywhere on Earth,” said physical oceanographer Doug Martinson of the Lamont-Doherty Earth Observatory. Martinson has been collecting ocean water heat content data for more than 18 years at Palmer Island, on the western side of the Antarctic Peninsula.

And that was updated in a June post, Ocean Currents Speed Melting of Antarctic Ice, as “Seawater Appear[s] to Boil on the Surface Like a Kettle on the Stove.” The news release by Columbia University’s Earth Institute explained:

Stronger ocean currents beneath West Antarctica’s Pine Island Glacier Ice Shelf are eroding the ice from below, speeding the melting of the glacier as a whole, according to a new study in Nature Geoscience. A growing cavity beneath the ice shelf has allowed more warm water to melt the ice, the researchers say—a process that feeds back into the ongoing rise in global sea levels. The glacier is currently sliding into the sea at a clip of four kilometers (2.5 miles) a year, while its ice shelf is melting at about 80 cubic kilometers a year – 50 percent faster than it was in the early 1990s – the paper estimates.

This new study, “Stronger ocean circulation and increased melting under Pine Island Glacier ice shelf” (subs. req’d), gives us a better understanding of just how PIG is being undermined from underneath: “We conclude that the basal melting has exceeded the increase in ice inflow, leading to the formation and enlargement of an inner cavity under the ice shelf within which sea water nearly 4◦C above freezing can now more readily access the grounding zone.

Here is a particularly remarkable observation the scientific team made one day:

One day, near the southern edge of Pine Island Glacier Ice Shelf, the researchers directly observed the strength of the melting process as they watched frigid,  seawater appear to boil on the surface like a kettle on the stove. To Jacobs, it suggested that deep water, buoyed by added fresh glacial melt, was rising to the surface in a process called upwelling. Jacobs had never witnessed upwelling first hand, but colleagues had described something similar in the fjords of Greenland, where summer runoff and melting glacier fronts can also drive buoyant plumes to the sea surface.

As Trenberth said, “The heat has not disappeared, and so it cannot be ignored. It must have consequences.”

Finally, some of you may recall a certain controversy from a certain email:

The discovery of the heat, which the researchers say is likely locked deep in the ocean, sheds light on a controversial email that was written by one of the study’s co-authors, Kevin Trenberth, in 2009. The email was one of hundreds that hackers stole from a server at the University of East Anglia nearly two years ago.

In the email, Trenberth wrote, “The fact is that we can’t account for the lack of warming at the moment and it is a travesty that we can’t.”

Climate change skeptics immediately seized on the email as proof that global warming wasn’t real. But from the beginning, Trenberth argued that he was referring to holes in scientists’ ability to measure how heat moves through the climate system.

I discussed Trenberth’s response at the time here.  I emailed Trenberth to ask, “Does this close the chapter on your ‘travesty’ comment?  He replied:

It helps close the chapter, but more observational studies are needed.  We plan to do those but await better datasets.

29 Responses to Hottest Decade on Record Would Have Been Even Hotter But for Deep Oceans — Accelerated Warming May Be On Its Way

  1. We are insulting the environment faster than we are understanding it

    Stephen Schneider back in 1979

  2. Rob Honeycutt says:

    Deep ocean heat content sounds a bit like a climate land mine. You don’t know where it is. You don’t know quite how to find it. You know it’s there. And you know it’s just a matter of time until we all find out exactly where it is.

  3. Chris Winter says:

    So let me get this straight: Overturning circulation during La Niña periods carries warmed ocean surface waters below 100 m depth. Heat stored at those depths can come back into the atmosphere during an El Niño or — as it is currently doing — can melt ice it comes in contact with at the poles.

    Is that about right?

  4. Jacob says:

    Could this deep ocean heat have anything to do with the occasional washing ashore of dead animals who reside in deeper ocean waters? Giant squids and other animals.

    It seems reasonable, whether or not it is the case.

  5. glen says:

    The people over at posted new reports on Greenland: Greenland meltdown

  6. Joan Savage says:

    I’d like to hear comments on that, too. Over 2400 scientific articles pop up on a search of “Antarctic Circumpolar Current and ENSO and heat.”

  7. Joe Romm says:

    That would be 300 m (1000 ft) and that might be the elevator explanation. But ocean circulation patterns are a bit more complex than that.

  8. Mauri Pelto says:

    The hottest decade was also seen in the mountain ranges of the world as recorded by the glaciers monitored for mass balance and reporting to the WGMS. As I report in BAMS State of Climate 2010 (68-69) the decadal mean annual balance for glaciers was -198 mm in the 1980’s, -382 mm in the 1990’s, and -730 mm for 2000-2009.

  9. Joan Savage says:
    “Most of the West Antarctic Ice Sheet is grounded below sea level, in places over 1.5 miles below sea level.”

    The Diapycnal and Isopycnal Mixing Experiment in the Southern Ocean
    has a graphic that shows water from the North Atlantic is part of an isopycnal upwelling of Lower Circumpolar Deep Water (LCDW) which reaches about 70 S latitude.

    So Atlantic warmth has ways to get to the Antarctic. How that might fit with the ENSO in the Pacific Ocean would be fascinating to learn.

  10. Gnobuddy says:

    At current melt rates, how long will it be before melting polar ice exposes enough dark seawater to account for more global heating (via decreased albedo) than human fossil-fuel usage does? Does anyone have a reasonably scientific estimate?

    It seems that, even ignoring all other positive feedback mechanisms, this would mark a definite tipping point, a point at which humans are no longer driving the current climate change, and nature has taken over the drivers seat. And with the increasingly rapid meltdown of both polar icecaps, this particular tipping point appears to be approaching a century or more ahead of “schedule”, or rather, ahead of the predictions from our yet incomplete thermal models.


  11. dan p says:

    Good question. The answer seems to be that the forcing due to an ice-free arctic is significant but smaller than even today’s level of greenhouse gas forcings.

    There was a recent paper: estimating. They say current forcing (from already melted Arctic ice) is 0.1 W/m^2, an ice-free summer (possible in 10-20 years) would be 0.3 W/m^2, and a completely ice-free Arctic (imaginable later this century) would be 0.7 W/m^2.

    This compares to a net of 1.6 W/m^2 for current forcings, which will only increase going forward. Substantial, but not enough to put the Arctic in control of our climate. I don’t think any projections of Antarctic sea ice have it vanishing very soon thanks to that cold, cold continent.

  12. dan p says:

    I should mention those numbers come with substantial uncertainties due to potential changes in cloud cover (due to more moisture in the air above that open water). That would likely serve to reduce their reported forcings but the paper didn’t claim to model it.

  13. Gnobuddy says:

    Dan, thank you for the reply. It is hard to find any good news related to climate change these days, and this is at least better news than I was expecting. I had been wondering if the expected ice-free Arctic summers by 2030 would already mark a definite point of no return.

    I’m aware that many other positive feedbacks exist, and that it’s quite possible the real tipping point is either imminent or possibly has already been passed (as James Lovelock thinks).


  14. Spike says:

    Indeed as the oceans soak up heat and warm they will eventually cease to do so as rapidly, allowing the surface to warm and importantly stay warm for centuries. Solomon’s paper on irreversible global warming due to carbon dioxide stated

    “Following cessation of emissions, removal of atmospheric carbon dioxide decreases radiative forcing, but is largely compensated by slower loss of heat to the ocean”

  15. Colorado Bob says:

    Gnobuddy –
    One other thing is happening with the loss of the polar albedo. That water will be transporting the extra energy . The currents up there are going to be doing “new and different” things.

  16. Colorado Bob says:

    Flowing tongues of rock, ice and dirt on move in Alaska arctic

    “We were totally surprised,” Grosse said. “The flow is pushing over trees in front of the lobe and burying vegetation like a bulldozer.”

    Using images from aerial photography and satellites, the researchers mapped three moving masses near Coldfoot that are creeping toward the Dalton Highway. Comparing snapshots from different years, they found that the lobes are now moving downhill about 3 meters (about 10 feet) per year. Last spring, Daanen returned from a Dalton Highway road trip with GPS data that was a bit more dramatic.

    “There’s one just south of the three we surveyed earlier that moved 10 meters (about 30 feet) during the last year alone,” Grosse said.

  17. Peter Mizla says:

    Perhaps the question to be asked here, is how much longer can the oceans absorb heat? C02 continues to rise at a rate unknown in earths history- and is now the highest in nearly 20 million years,

    Yes the oceans are still cold after over 50 million years of cooling since the early Eocene, but have they ever faced this an extreme forcing of this magnitude?

  18. Lewis Cleverdon says:

    Gnobuddy –
    back last spring there was a paper discussed here on CP concerning the current impact of cryosphere decline. (Sadly I didn’t record the url).
    It reported that current albedo loss provides a forcing equivalent to around 30% of current anthro-CO2 emissions. This was apparently a radical increase in estimate, roughly doubling the previously accepted level, due to more advanced analysis and new data. I’ve yet to see any refutation of that paper, but if you find one, I’d like to read it.

    As you remark, albedo loss is only one of the five major feedbacks and the point of their independent self-reinforcing acceleration has to be very close, given that natural carbon sinks’ annual intake varies between 20% to 50% of our CO2 output.

    The best definition of that ‘tipping point’ I’ve seen is when the feedbacks’ combined CO2e outputs exceed the natural carbon sinks’ capacity (Gribben, “Hothouse Earth” 1990) after which even a total ending of anthro-CO2 output no longer ends the increase of airborne CO2 stocks.

    Recognizing just how fully committed we are to passing that milestone of the sinks being swamped – due both to our ongoing GHG outputs and particularly to the interactive feedbacks’ response to the four massive ‘pipeline’ warmings over at least the next four decades – is what has lead me to asserting the necessity of deploying Albedo Restoration technologies during a prolonged global effort for effective Carbon Recovery.

    Plainly, ending our GHG outputs ASAP is entirely necessary but no longer sufficient to resolve the predicament we face.



  19. Mauri Pelto says:

    The Arctic Ocean’s biologic response has been rising productivity.

  20. Peter Mizla says:

    from what? & where?

  21. Joe Bftsplk says:

    The way Trenberth and NCAR are discussing their findings has problems which contribute to the ability of deniers to pretend that global warming is not happening.

    The UCAR article you refer readers to isn’t as bad as the one the National Science Foundation issued a few days later ( ) which discussed the same research, but it has similar problems.

    Consider: Trenberth led the IPCC AR4 group that determined that the shortest time period over which the global average surface temperature data can be viewed that clearly shows the global warming “signal” emerging from the noise is 25 years. Why then does the NSF article I”m talking about then quote scientists talking about 10 year periods where “Earth’s temperature did not rise“. Why does the UCAR article you refer us to talk about “hiatus” periods of ten years or so in “global warming”?

    As Hansen points out if you choose your start and end date and a timeframe short enough you can make the data show anything. But we could make things clearer: there’s the planetary system as a whole, and then there is the average global surface temperature chart. We’ve got to be more careful when using terms that could apply to either thing.

    It can’t be that the way to talk about this NCAR study involves using phrases like “Earth’s temperature did not rise” during some ten year period, or there has been a “hiatus” in “global warming”. Obviously, the scientists know what they are referring to, but as we all know, their is a far bigger audience for their words out there.

    The way out is to be more careful in the use of terms. Trenberth calls the recent advances in observational capability, i.e. Argo floats etc, a “revolutionary” improvement which should allow scientists to explain far more of what until now they have had to call “natural variability”. Had his famous email described his frustration as being over why scientists can’t explain more of “natural variability” now that they have what looks like a sudden increase in good data avaliable, he might not have been so easily exploited by deniers who trumpeted that what he was writing about was that global warming is not happening.

    This recent NCAR computer modelling could be described as showing possible success in the quest to explain more of what’s been called “natural variability”, because their model shows ocean circulation patterns vary the rate of heat transfer to the deep ocean over fairly short, i.e. 10 year, periods in ways that could explain a ten year flatline in the Hadley average global surface temperature chart such as what that dataset suggests may have happened.

    One further note: Hansen believes all current state of the art computer models send too much heat into the deep ocean.

  22. Lewis Cleverdon says:

    Spike –

    given the calamitous outcomes of the long-term warming projected above, I’m interested as to why the author appears to imply that there will be global climate treaty to phase out anthro-GHG outputs, and no global effort at geo-engineering via Carbon Recovery to further limit the peak of airborne CO2 and to massively accelerate its recovery, and no global effort at Albedo Restoration to offset both the warming due to airborne GHGs and that due to marine emissions of stored heat.

    Have you perhaps omitted to include some overall qualification by the author that the projection would result from society’s failure to undertake commensurate action against global warming ?

    If not, is there perhaps some unspoken hankering for glorious imperial collapse at work here ? Or maybe just some group-think deference-of-mind that until rational solutions are proposed by an appropriate monarchial authority (such as the president) they should be disregarded as being unapproved, regardless of the extreme urgency of the situation ?

    If I sound blunt on this it is because statements such as this author’s dire projection get widely quoted among activists, thus spreading an entirely false assumption of the problems being intractable and hopeless, which robs people – most particularly the young and impressionable – of the morale to strive for their resolution.

    In this sense such unqualified projections by an highly qualified scientist can do far more damage to our campaigning capacity than can the denialism of several Rush Limbaughs.



  23. Gnobuddy says:

    Thanks for your reply, Lewis.

    It occurs to me that the fact that polar albedo increase might only be equivalent to some fraction of forcing from current anthro-CO2 emissions does not mean that it is automatically low enough not to trigger runaway change.

    In other words, we know anthropogenic CO2 emissions are so huge that they’re sufficient to trigger drastic climate change in a startlingly short period of time (geologically speaking). So it is quite possible that half as much forcing will also trigger drastic climate change, possibly in a slightly longer time span.

    The history of human attempts to control large areas of our environment and wildlife over prolonged periods have universally been disastrous, and I have zero confidence that any attempts at geo-engineering our global climate will have a happy outcome. Most likely we will either wildly undershoot, or wildly overshoot the forcing needed to establish any sort of human-friendly equilibrium state, and end up making things far worse than they already are.

    As an aside, one of the reasons why Hewlett-Packard became successful in its early days was the development of a sophisticated (for its day) method of controlling the amplitude of an audio oscillator. It’s not easy to accurately control the amplitude of a physical system controlled by even one single linear differential equation (like the one governing the HP oscillator), and it takes constant monitoring and adjusting to make it work.

    When it comes to something as incredibly complex as the entire planet’s weather, and its interaction with the planet’s life, forget about controlling it through human design and intent. It’s way, way too complex. There’s no way we will get it right.


  24. BBHY says:

    The last few years sea level has actually dropped. The water didn’t disappear of course, and it certainly didn’t turn into bigger ice sheets and glaciers. It went into the air, and a lot of it came back down on land masses. The extreme flooding experienced in various parts of the world are the predictable result.

    But doesn’t the evaporated water represent a huge amount of heat energy? Yet another store of heat that will continue to cause problems.

  25. Lewis Cleverdon says:

    Mauri –

    I note that the three numbers express a remarkably consistent progression of close to 1.91 per decade. I’m wondering if the annual data is steady enough to give confidence that this is the exponential trend of glacier decline, or whether it is so volatile as to imply that the apparent trend is no more than a numerical fluke of the start & finish dates ?

    Your thoughts on this would be much appreciated.



  26. Spike says:

    Who can doubt the current irresolution of any attempt to progress the issues you so rightly mention. I am reminded of Churchill’s description of government failure to act at an appropriate time in an earlier time of crisis

    “So they [the Government] go on in strange paradox, decided only to be undecided, resolved to be irresolute, adamant for drift, solid for fluidity, all-powerful to be impotent.”

    The paper quoted is certainly a timely warning of what will happen if this situation continues and merely serves to amplify Trenberths comment “The energy is not lost, and it can come back to haunt us, so to speak, in the future.”

  27. Lewis Cleverdon says:

    Gnobuddy –

    with respect, I think you mistake the role of Albedo Restoration. You rightly observe that managing the weather is beyond us – given its chaotic nature and sensitivity to initial conditions – right down to the butterfly’s wing – I’d suggest that it will always remain so.

    Yet managing the weather is not the objective. What we can do, and in fact are already doing inadvertently, is to restrain global temperature by deflecting insolation and thereby offsetting excess GHG stocks’ retention of heat energy.

    The ‘sulphate parasol’ that is now maintained by our fossil fuel emissions will decline as they are terminated (due to sulphates’ residency of about two years). According to Hansen that parasol is now cutting about half of the warming we’d otherwise experience.

    So the first question on Albedo Restoration is: – do we wish to see a doubling of global warming as GHG outputs are ended, or shall we research, develop and deploy a better means than sulphates to maintain the parasol ?

    And that question is not about managing the weather, but about controlling the excess global temperature that is driving climate destabilization.

    With regard to the overshoot risk, it is worth noting that the various technologies offer varied limitations of that risk. At one pole is ‘space mirrors’ whose permanent irretrievability would maximize the risk; at the other is ‘cloud brightening’ whose reflective effect is reliably rained out within a few days, and whose constant renewal by vessels at sea can be halted or relocated on command.

    If I knew of any less radical means of preventing the feedbacks accelerating out of control in response to the four known pipeline warmings (of which the ending of the sulphate parasol is one) I’d not be asserting the imperative need for Albedo Restoration. Limiting planetary temperature is evidently possible; what is still uncertain is how reliably it can be done. Yet given the plainly inexorable existential climate threat we face, refusing Albedo Restoration on grounds that it may be done badly is to decline the one remaining chance that science offers for resolving that threat.

    As such, I’d hope that you may at some point reconsider your outright opposition, and instead join the growing calls for the most stringent global oversight of the R,D&D of both Albedo Restoration and Carbon Recovery, as the necessary formal adjunct to a binding global treaty phasing out GHG emissions.



  28. Solar Jim says:

    Thanks Joe for another outstanding post, and thanks to all for outstanding comments.

    With atomic meltdowns, financial meltdowns, political meltdowns and polar ice cap meltdowns it seems “modern life” is becoming surreal. Perhaps a Spaceman will soon inform humanity that “Fossil Fuel” is a cookbook.