Study: Climate Models Replicate Temperature “Pause”

September 8, 2014

First point:  there is no “pause” in global warming – merely a temporary slowdown in the increase of one indicator, global surface temperatures. The planetary thermometer – namely, the oceans, continues to register an increase in global heat storage, as evidenced by continuing sea level rise.

Sea level Satellite record from the University of Colorado

That said, a new paper from Jerry Meehl at the National Center for Atmospheric Research sheds some light on how climate models are used, and can be employed to shed light on the way the earth indicates climatic change.  It’s a wrinkle in the way computer models handle  cyclical changes in Pacific Ocean temperature, referred to as the Interdecadal Pacific Oscillation, similar to the PDO (Pacific Decadal Oscillation), but covering the whole pacific.  The study may lead to better modeling and prediction going forward.

I talked to Meehl about a year ago while he was engaged in this research, and found his explanation to be lucid and useful.  Recommend the 7 minute excerpt above as a primer for the text discussion here.

National Center for Atmospheric Research:

If today’s tools for multiyear climate forecasting had been available in the 1990s, they would have revealed that a slowdown in global warming was likely on the way, according to new research.

The analysis, led by NCAR’s Gerald Meehl, appears in the journal Nature Climate Change. It highlights the progress being made in decadal climate prediction, in which global models use the observed state of the world’s oceans and their influence on the atmosphere to predict how global climate will evolve over the next few years.

Such decadal forecasts, while still subject to large uncertainties, have emerged as a new area of climate science. This has been facilitated by the rapid growth in computing power available to climate scientists, along with the increased sophistication of global models and the availability of higher-quality observations of the climate system, particularly the ocean.

Although global temperatures remain close to record highs, they have shown little warming trend over the last 15 years, a phenomenon sometimes referred to as the “early-2000s hiatus”. Almost all of the heat trapped by additional greenhouse gases during this period has been shown to be going into the deeper layers of the world’s oceans.

The hiatus was not predicted by the average conditions simulated by earlier climate models because they were not configured to predict decade-by-decade variations.

However, to challenge the assumption that no climate model could have foreseen the hiatus, Meehl posed this question: “If we could be transported back to the 1990s with this new decadal prediction capability, a set of current models, and a modern-day supercomputer, could we simulate the hiatus?”

To answer this question, Meehl and colleagues applied contemporary models in a “hindcast” experiment using the new methods for decadal climate prediction. The models were started, or “initialized,” with particular past observed conditions in the climate system. The models then simulated the climate over previous time periods where the outcome is known.

The researchers drew on 16 models from research centers around the world that were assessed in the most recent report by the Intergovernmental Panel on Climate Change (IPCC). For each year from 1960 through 2005, these models simulated the state of the climate system over the subsequent 3-to-7-year period, including whether the global temperature would be warmer or cooler than it was in the preceding 15-year period.

Starting in the late 1990s, the 3-to-7-year forecasts (averaged across each year’s set of models) consistently simulated the leveling of global temperature that was observed after the year 2000. (See image at bottom.) The models also produced the observed pattern of stronger trade winds and cooler-than-normal sea surface temperatures over the tropical Pacific. A previous study by Meehl and colleagues related the observed hiatus of globally averaged surface air temperature to this pattern, which is associated with enhanced heat storage in the subsurface Pacific and other parts of the deeper global oceans.

Although scientists are continuing to analyze all the factors that might be driving the hiatus, the new study suggests that natural decade-to-decade climate variability is largely responsible.

As part of the same study, Meehl and colleagues analyzed a total of 262 model simulations, each starting in the 1800s and continuing to 2100, that were also assessed in the recent IPCC report. Unlike the short-term predictions that were regularly initialized with observations, these long-term “free-running” simulations did not begin with any particular observed climate conditions.

Such free-running simulations are typically averaged together to remove the influence of internal variability that occurs randomly in the models and in the observations. What remains is the climate system’s response to changing conditions such as increasing carbon dioxide.

However, the naturally occurring variability in 10 of those simulations happened, by chance, to line up with the internal variability that actually occurred in the observations. These 10 simulations each showed a hiatus much like what was observed from 2000 to 2013, even down to the details of the unusual state of the Pacific Ocean.

Meehl pointed out that there is no short-term predictive value in these simulations, since one could not have anticipated beforehand which of the simulations’ internal variability would match the observations.

“If we don’t incorporate current conditions, the models can’t tell us how natural variability will evolve over the next few years. However, when we do take into account the observed state of the ocean and atmosphere at the start of a model run, we can get a better idea of what to expect. This is why the new decadal climate predictions show promise,” said Meehl.

Decadal climate prediction could thus be applied to estimate when the hiatus in atmospheric warming may end. For example, the UK Met Office now issues a global forecast at the start of each year that extends out for a decade.

“There are indications from some of the most recent model simulations that the hiatus could end in the next few years,” Meehl added, “though we need to better quantify the reliability of the forecasts produced with this new technique.”

Reporting Climate Science:

However, when the individual ensemble members are examined it is apparent that some do simulate the pause, say the researchers led by NCAR’s Gerald Meehl. The analysis shows that 12 enemble members from a set of 262 recreated a pause between 2000 and 2012, ten between 2012 and 2013, nine continue through 2000 to 2014, six from 2000 to 2015, and six from 2000 to 2016, one of which from 2000 to 2017 continues to 2018 (a hiatus of 19 years), the scientists report.

The common factor linking the ensemble members that forecast the pause is that they feature a cooling of the Pacific Ocean sea surface temperatures; a negative phase of the Interdecadal Pacific Oscillation (IPO) – a long term 15 to 30 year cycle in sea surface temperatures affecting both the north and south Pacific. This contrasts with the overall average of the larger total set of all ensemble members that shows mostly warming in the tropical Pacific. In simple terms, if climate models are set up with an assumption that the IPO is in a negative phase then they can replicate the pause.

The authors write: “This is a compelling application of the result derived from other analyses, in that tropical Pacific surface temperatures in the negative phase of the naturally-occurring IPO can temporarily counteract the warming from increasing GHGs to produce a hiatus of warming in globally averaged surface air temperatures that can last for a decade or more, even as the climate system is still trapping excess heat of about 0.51.0Wm-2”.

On a technical note the authors say they analysed all available uninitialized CMIP5 climate model simulations, with all possible ensemble members for all four greenhouse warming scenarios adopted by the Intergovernmental Panel on Climate Change – the so called representative concentration pathways (RCPs). This amounted to 262 possible realizations from 45 models, with up to 10 ensemble members for the period 2000 -2020. These model simulations all start from some pre-industrial state in the nineteenth century, and use observations for natural (volcanoes and solar) and anthropogenic (GHGs, ozone, aerosols, land use) forcings through 2005 with the four RCP scenario forcings after 2005. They point out that for the period of the early 2000s, there is little difference among the RCP scenarios for this short-term time frame, so all were used.

Meehl et al Nature Climate Change:

The slowdown in the rate of global warming in the early 2000s is not evident in the multi-model ensemble average of traditional climate change projection simulations1 . However, a number of individual ensemble members from that set of models successfully simulate the early-2000s hiatus when naturally-occurring climate variability involving the Interdecadal Pacific Oscillation (IPO) coincided, by chance, with the observed negative phase of the IPO that contributed to the early-2000s hiatus. If the recent methodology of initialized decadal climate prediction could have been applied in the mid-1990s using the Coupled Model Intercomparison Project Phase 5 multi-models, both the negative phase of the IPO in the early 2000s as well as the hiatus could have been simulated, with the multi-model average performing better than most of the individual models.


17 Responses to “Study: Climate Models Replicate Temperature “Pause””

  1. […] First point: there is no "pause" in global warming – merely a temporary slowdown in the increase of one indicator, global surface temperatures. The planetary thermometer – namely, the oceans, cont…  […]

  2. This is fascinating just for the impact on the propaganda.  For several years, a talking point I’ve been seeing is that climate models can’t reproduce the “hiatus”.  Well, climate models are now confirmed to have reproduced it.  That talking point is going to fall out of favor pretty quickly.

    What do the propaganda mills have ready to replace it… and how many believers will they lose when they’re suddenly told we’ve always been at war with Eastasia, not Eurasia?

    • dumboldguy Says:

      Two excellent video clips, text, and graphics.

      So, if I’ve got this right, we are now making one of the known unknowns into a known known? And just by looking at the numbers a bit differently? How come it took so long?

      What do the denier propaganda mills have to replace it, asks E-Pot?. IMO, they are not going to replace it anytime soon, but will just keep parroting the same “talking points” and beating the same old dead horses—-“the hiatus is real, models are just models, models are easily manipulated, models are sometimes wrong, Michael Mann and Al Gore suck eggs”, etc.

      That will go on until El Nino arrives (maybe) and things return to “normal” as the ocean gives up its heat. Even then, the deniers will sow FUD for a few years until it becomes so obvious that denial is no longer possible. In the meantime, fossil fuels burn, CO2 goes up, tides go in and out, the greedy rich get richer, and the chances of turning things around in time decrease (in spite of Meehl’s “bright-sidedness).

      • j4zonian Says:

        Denying delayalism is a defense-in-depth strategy. It uses a diabolically brilliant combination of High-Command coordinated sequential multiple lines of defense and the more front line throw everything against the wall and see what sticks approach in a fascinating way, worthy of study like ant colony decision-making or disease bacterial replication.

        When outright denial doesn’t work, other tactics are used, including geoengimagicalism, technological optimistic techno-hyping of non-solutions like supposedly non-dirty coal, hydrogen, nuclehead reactors, etc. Specific day-to-day responses will continue to be fabricated in Koch factories and distributed by paid shills and volunteer dupes–Climategate is one example. Personal attacks are always good for a few months of delay–Gore, Mann, Hansen, Kayhoe, Tyson, whoever comes forward and has credibility. Swift-boating, Rathering (aka Danrathering, aka sucker-baiting, as in fake documents to discredit a truthful investigation of a real problem), and ever-louder shouting will no doubt continue to be used.

        Denial is always at the root–denial by the delayers to themselves that climate catastrophe is real, dangerous, caused by humans and can be stopped by changing energy sources, production practices and lives; and denial that the allegedly “free” market has utterly failed and is a major proximal cause of this problem and many others. Looking deeper than that, it becomes clear that inability to feel connection and thus denial of connection is always the physio-psychological problem at the root. That’s endemic to those we call conservatives but it’s also an impulse we all struggle with. It’s a symptom of faulty child-raising, and no one’s was perfect.

        As the jarring gap between reality and conservative fantasy becomes more obvious (really, how much more obvious do you think it can be than it already is?) there will be increasing rigidity, then finally a collapse into what might be called despair. It’s also surrender; in AA terms it might also be called rock bottom, although I find that concept flawed. In Buddhist terms, that’s one place where Beginner’s Mind is found, and while it may come too late for the planet, it may be early enough that we can still save a lot that we love, for our children and grandchildren. We should be prepared for that moment in individuals and society as a whole so we can nurture them through the dark times it engenders, so they, and we, can come out the other side with more connection to each other, reality, and our energy and determination.

        A few resources to find out more about aspects of this: George Lakoff’s Don’t Think of an Elephant and other works; Thomas Moore’s Care of the Soul and Moore and Gillette’s King, Warrior, Magician and Lover (and each subsequent volume) has some interesting appendices. Years ago there was a fascinating Scientific American article on how ants pick routes; Honeybee Democracy and the Buzz About Bees are also excellent with some relevance here. The theoretical work behind using google to pinpoint early signs of epidemics might also be useful. To become attuned to the early signs of collapse in others and skilled in emotional first aid/peer counseling will be increasingly needed by society. To embed those skills in networks like Transition Towns, permaculture communities and Joanna Macy’s The Work That Reconnects alumni would increase our effectiveness and feeling of strength, safety, resolve and connection.

    • We cannot predict PDO, ENSO etc.; therefore, in the models they are simulated as random.
      Now hindcast model runs with Observed PDO, ENSO (not random) shows the so called “hiatus”.

      I can understand your confusion one, computer models improve all the time. Second you are confusion of the term “hindcast” because your hiny is in the same direction as our mouth.

      • dumboldguy Says:

        You say, “I can understand your confusion one, computer models improve all the time. Second you are confusion of the term “hindcast” because your hiny is in the same direction as our mouth”.

        That’s an “Omno-Speak” comment for sure, and rates a “WHAT?”. Who exactly are you talking to? Peter? E-Pot? Me? Who is confused about what? What’s a “hiny” and what’s the meaning of “it’s in the same direction as our mouth”? (and who is the “our” you speak of?)

        (And if the link was wrong the first time, isn’t it wrong the second time as well? THAT’S confusing)

        • I was replying to E-pot

          Second, I use a speech to text program. Hands only work like mittens with razorblades.

          Words like “an and you u you are your” and so on are problems for the program.

          It should be:

          “I understand your confusion with the term hindcast. Your hiny (BUT or backend) is in the same direction as your mouth.” A joke.

          Using voice editing can create odd things like pasts and premature posting. There should not be a link at all; it pasted from the other window (Crock YouTube) and posted during editing.

          • dumboldguy Says:

            Aulthet isreelyvury cunfoozing. ItheenkitzSwelthat u use a progrum….that perhaps inhibits rather than aids communication. Kind of like what my messages would look like if I don’t do at least a cursory proofread.

            (It would have been nice to know that a link (posted TWICE) was not something we needed to spend any time viewing)

      • APCS, two things:

        1.  I never used the term “hindcast”.
        2.  I’m not confused about the output of the climate models.  I recognize that there’s uncertainty (otherwise all the models would agree), but denial that they’ve got anything to tell us is O-log territory.

        I’m surprised that, as a regular reader here, you are so unfamiliar with the massive gap between the public perception of ACC science (55% perceived acceptance) vs. the climate science community (97% actual acceptance) and don’t see that the effect on the PUBLIC propaganda pushed by e.g. the Heartless Institute is going to be one of the most significant, if not THE most significant, results of this analysis.

        The amount of distortion they can get away with gets smaller all the time.  The questions for PUBLIC perception is how much the Overton window will narrow, and how soon?

        • “…don’t see that the effect on the PUBLIC propaganda pushed by e.g. the Heartless Institute is going to be one of the most significant, if not THE most significant, results of this analysis.”

          Reality doesn’t matter (to them) they will just make things up to fit their reality. There is a famous quote that reflects this denial.

          People don’t drink the sand because they’re thirsty. They drink the sand because they don’t know the difference.

          This report will have no affect on the general public perception of ACC science. Only when reality (weather) hit hard enough to pop the bubble will their reality change.

          • But reality does matter to them.  Few people are ready to be complete hermits.  When saying such things gets them laughed at, snubbed or avoided if not firmly corrected, most will get the impression that they’re on the wrong side.

  3. omnologos Says:

    This will only gain weight when foretold. Maybe in next decade.

    • redskylite Says:

      Programs and knowledge are evolving quickly, no need to wait so long as a decade. We no longer need our future to be foretold by oracles or witches, we can work it out for ourselves by looking at the past and using modern tools.

      Just stop our continued reliance on mining and burning fossil fuels and let Milankovitch cycles and nature dominate once more. We have endured ice ages before and can again.

    • dumboldguy Says:

      More mindless denial from “he who spouts illogical nonsense just for attention”.

      Let’s see. Climate change models have proven to be correct and even too conservative—-things are going more badly than the models predicted. We are constantly fine-tuning the models as our knowledge increases, and this “redo” shows that the “hiatus” is not due to any real cooling.

      This finding has weight RIGHT NOW for all but the terminally WIFI like Omno. “Maybe in the next decade”, says Omno? YGBSM

  4. […] but comes up a lot, recently on the Senate floor in a rant by denialist Senator Jeff Sessions.  No experienced scientist is surprised when the planet doesn’t conform exactly to what a partic… – and moreover, many indicators of planetary change are moving well ahead of projections made […]

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