A frontier of climate science: the model-temperature divergence

Summary: Today Rud Istvan gives us a brief tour of a climate science frontier, as seen in a hot new paper. It’s a bit technical, an unavoidable aspect of real science. It’s controversial, an ingredient that helps science grow.  Don’t let activists on either side cloud your understanding of the science. There is a strong but narrow consensus among climate scientists; move beyond that and the questions multiply.  {2nd of 2 posts today.}

A challenge for climate science: model-temperature divergence:

Figure 2 from  “Why models run hot, results from an irreducibly simple climate model”.Figure 1 from MSLB. Medium-term global temperature trend projections from FAR {IPCC’s 1st report}, extrapolated from Jan 1990 to Oct 2014 (shaded region), vs. observed anomalies (dark blue) & trend (bright blue), as the mean of the RSS, UAH, NCDC, HadCRUT4 and GISS monthly global anomalies. Click to enlarge.

Lessons from the ‘Irreducibly Simple’ kerfuffle.

by Rud Istvan, posted at Climate Etc., 1 March 2015.
Reposted under their Creative Commons License.
Headings & some graphics added.

A controversial study

The Monckton, Soon, Legates, and Briggs paper “Why models run hot, results from an irreducibly simple climate model” appeared in the January 2015 Science Bulletin of the Chinese Academy of Sciences (CAS). Hereinafter MSLB.The paper discusses the divergence between climate models and observed temperatures, and develops the implications for climate sensitivity.

MSLB has created quite a kerfuffle. There was initial dismissal: it was claimed that Science Bulletin is an obscure journal with lax review standards, so the paper is no good. Bulletin turned out to be the Chinese equivalent of Science or Nature. Then came MSM efforts (NYT, Boston Globe, WaPo, even BarackObama.com) to discredit the authors. This has escalated into a more general attack on prominent skeptics like Christy, Pielke, and our gracious hostess. These attacks are growing ugly, for example from BarackObama.com on Feb 23: “Bad things are coming for these boys and girls. (Name list) Keep your eye on the media. Several stories.”  {Ed note: I don’t see any mention of this on at BarackObama.com or using Google.}

Dr. Trenberth of NCAR provided NYTimes reporter Gillis a MSLB rebuttal, posted at Matt Brigg’s blog.  Gillis did not report Brigg’s reply. Trenberth dismissed the simple model simply because it is simple — and said the ‘pause’ is insignificant natural variation. Yes, but the now 18+ year pause/hiatus is in very serious disagreement with CMIP5 climate model simulations using criteria set out by climate modelers themselves in 2011 [see Climate Etc]. Trenberth’s comments to the NYTimes are indefensibly misleading in my opinion, and provide a vivid object lesson about consensus climate ‘science’ and its reporting.

There was a saying among WWII Army Air Force bomber pilots: “If you are taking heavy flak, you are over the target”. What is it about this target?


B-17 in heavy flak

Climate Simulations vs Reality

CMIP5 climate model simulations continue to diverge from observed temperatures because of the ‘pause’. This suggests the GCMs {global climate model or general circulation model) are oversensitive to increases in CO2 – CO2 continues to increase ‘business as usual’ per RCP8.5, while temperature hasn’t. MSLB discusses this divergence shown by their Figure 2, and then offers a non-GCM way to understand why this is happening and what it means for climate sensitivity.

Figure 1 from “Why models run hot, results from an irreducibly simple climate model”Near-term global warming projection intervals from FAR (red arrows) and AR5 (expert assessment: green arrows), overlaid on the CMIP5 model projections based on the four RCP scenarios from AR5, which zeroed the models’ projections to observed temperature (black curve) in 1990. Based on AR5. Click to enlarge.

MSLB proceeds in three steps: (1) derives the ‘irreducibly simple’ climate sensitivity equation, (2) estimates the 5 required parameters from mainly IPCC sources, and then (3) uses both to debunk IPCC sensitivity estimates. The first two steps are useful and instructive. The last step is unfortunately partly wrong. This post covers that last step first.

What’s wrong with the MSLB study?

(1)  Background

Both IPCC AR4 (CMIP3) and AR5 (CMIP5) GCMs estimate the resulting equilibrium climate sensitivity (ECS) at +3.2C on average. There is substantial GCM model-to-model variance, for example in AR4 WG1 Table 8.2. This gives a ‘simple average’ multiplier of (3.2/1.2) ~ +2.67. AR4 gave a point (mode) estimate of +3.0C (~ +2.5).  AR5 only gave a likely range from +1.5C to +4.5C, and explicitly did not give a midpoint value, owing to the discrepancy between climate model and observationally derived values. GCMs derive feedback by doubling (or quadrupling) CO2, then simulating into the future at least 150 years.

… {skipping extensive and technical discussion.}

(2) Water vapor feedback fw

Water feedback
Climate Change and its Effects on the Global Ocean” by Nicole Del Monaco (2012).

Climate models produce a tropical troposphere hotspot that does not exist in reality. See Prof. John Christy’s presentation to APS. That is because modeled upper troposphere specific humidity is too high. The probable reason is the physical inability of coarse-resolution GCMs to simulate tropical convection cells (thunderstorms). They must be parameterized instead. Essays “Models all the way Down” and “Humidity is still Wet” (in Blowing Smoke provide details. CMIP3/5 climate models also underestimate the precipitation that removes atmospheric water vapor– by about half (citations in the essays).

Given these model/observation differences, perhaps the water vapor feedback is on the order of about half the climate models, notionally something like fw ~0.25.

(3) Cloud feedback fc

Cloud Feedback
From “Introduction to climate dynamics and climate modeling” by H Goosse et al. Click to enlarge.

Dessler’s 2010 clear/cloudy sky satellite paper actually suggests zero cloud feedback, contrary to what he claimed and what is on the NASA website. Essay Cloudy Clouds (in Blowing Smoke) provides much more detail. To a first order very rough observational approximation, cloud fc ~0. AR5 WG1 7.2 says it is uncertain, but certainly positive. (Phrased that crisply, the IPCC non sequitur is obvious). This provides a lesson on the consensus belief in models over observations, a belief deeply unsettled by the undeniable pause/divergence.

Combined, these observations suggest an ft on the order of (0.25), a little less than half the implicit IPCC f. Plug some ft like that into the irreducibly simple MSLB equation using the foregoing parameters, and out pops an ECS {equilibrium climate sensitivity}of about ~1.75. Or, just spot your preferred f on the x axis, and read ECS off the y axis of the Bode plot above. Use your own ‘red lines’. An f of about 0.25 provides an ECS remarkably similar to the Lewis and Curry result, which was derived using completely different and much more sophisticated methods.

Bottom line

The simple non-GCM models Trenberth dismisses have great utility. Observations now suggest Earth’s ECS is a bit more than half of what the IPCC has proclaimed as settled ‘GCM science’. Simple models like those discussed here can deconstruct f to suggest how and why. That unsettles the IPCC science. MSLB’s simple model has vociferously unsettled the ‘consensus’. Lower ECS silences the urgent, loud alarm to mitigate at COP21 in Paris — unless the consensus’ increasingly nasty public attacks succeed in silencing all the skeptics who point out simple stuff.

Also: here’s a response from Christopher Monckton.  Since it is longer than the original post, I am providing it as a pdf file.. In the comments below are the money paragraphs.  {Ed., it’s well worth reading.}


About the author

Chairman and Chief Executive Officer, Third Stream Bioscience, Inc. He has published three books: Gaia’s Limits, The Arts of Truth and Blowing Smoke: Essays on Energy and Climate. Rud has also authored frequent guest posts at Climate Etc.

Polar Ice Caps are melting

For More Information

(a) Reference Pages about climate on the FM sites:

  1. The keys to global warming.
  2. Studies & reports, by subject.
  3. My posts about climate change.
  4. See all posts about the pause.

(b)  About computer models:

  1. About models, increasingly often the lens through which we see the world.
  2. Confronting the Fundamental Uncertainties of Climate Change.
  3. Will a return of rising temperatures validate the IPCC’s climate models?
  4. We must rely on forecasts by computer models. Are they reliable?

7 thoughts on “A frontier of climate science: the model-temperature divergence

  1. Christopher Monckton’s reply to this article

    Some high points from Christopher Monckton’s reply. Headings added.

    The little-known shift in the IPCC’s temperature projections

    … Fig. 2 of our paper, which actually demonstrates that IPCC itself – under pressure from expert reviewers such as me, who told it that it would lose what little credibility remains to it unless it curbed its wild over-predictions – has very sharply reduced its near-term global-warming projections (though, of course, it has left its long-run predictions unaltered, for otherwise the game would be up).

    In the overheated days of 1990, it predicted warming over the coming decades on the interval [0.19, 0.43] K decade–1. By 2013, it had just about halved what it now calls its “projections” to [0.10, 0.23] K decade–1. And the real-world outturn since 1990, when IPCC’s central estimate was 0.28 K decade–1? Just half that, or 0.14 K decade–1. It was that persistent factor-of-two discrepancy between prediction and reality that led us to write our paper.

    About the Earth’s thermostat

    … The climate, therefore, is formidably thermostatic. Indeed, so narrow is the inferred temperature interval of the Earth’s climate that it is not much wider than that of a room-heating thermostat.

    Why is this? Because the atmosphere – a tenuous fluid medium – is sandwiched between two near-infinite heat-sinks, the ocean below and outer space above. No doubt there might be significant changes in the temperature of the atmosphere if there were significant changes in the input temperature from the Sun above or from the Earth’s molten core below; but, taking these inputs as broadly constant, such little heat as we are able to generate in the atmosphere will either be radiated harmlessly off to space or taken up into the ocean, which appears to have warmed during the ARGO decade at a rate equivalent to just 0.05 K decade–1 – well within the very large measurement and coverage uncertainties (each ARGO buoy has to try to monitor 200,000 km3 of ocean).

    Since the atmosphere has not warmed during the ARGO decade, it is not illegitimate to deduce that at least the upper or mixed stratum has not warmed during the past decade, for if it had done so the atmosphere – three orders of magnitude less dense than the ocean, and intimately mixed with it at its interface by tropical afternoon convection in low latitudes and baroclinic eddies in the extratropics – ought to have warmed too.

    … Mutatis mutandis, the climate, too, may suffer shocks – meteorites, supervolcano explosions, Milankovic changes in the orbital characteristics, etc., etc. In feedback amplification regime that looked anything like the Bode plot, IPCC’s implicit central estimate of 0.65 for the feedback sum is far too close to the singularity. There would have been several points in the past 810,000 years where a feedback sum that large would have driven the feedback-sum beyond unity, leading to violent results that are simply absent from the record.


    1. And the CO2 concentrations of 400 ppm, higher than they have been at any time in the past 400,000 years? MIT projects they will approach 750 ppm by 2100 with no sign of stabilizing. The last time carbon dioxide levels were apparently as high as they are today — and were sustained at those levels — global temperatures were 5 to 10 degrees Fahrenheit higher than they are today, the sea level was approximately 75 to 120 feet higher than today, there was no permanent sea ice cap in the Arctic and very little ice on Antarctica and Greenland.

      Not a worry?

    2. Gloucon,

      I don’t understand how your comment relates to this article, or to the study it describes. However, I’ll discuss the points you raise anyway. Note how I respond to quotes of your comment. Otherwise we must guess what specifics you are responding to. Spock is dead; nobody else here has telepathic powers.

      (1) “Not a worry”?

      I’m sad to see you’re not certain if we should worry. We could be doing so much today, but are blocked by the activists on the Left and Right who have politicized the issue for their own narrow goals.

      On the other hand, we face so many threats, so “worry” is not a binary quantity and so not useful to determine how we should prioritized these expenditures. How serious is the threat, with what uncertainty, with what timing? That’s why determining the sensitivity and feedback factors are so important. Note that the projected rise in temperature is not from increases in the trace amount of CO2 (that’s 400 parts per million), but a feedback — warming increases water vapor in the atmosphere, a powerful greenhouse gas. As described here, there is only a weak consensus on these details — and that has changed during the past decade (e.g.,, the sensitivity numbers have decreased).

      (2) You describe the Earth’s state outside a period of glaciation. Warmer, no polar ice. There have been 5 major “ice ages”. You assume a relationship between glaciation and CO2 levels. Can you provide citations showing that yours is the consensus view? In fact there are several overlapping theories, with variations in CO2 being one of many factors.

      (3) “global temperatures were 5 to 10 degrees Fahrenheit higher than they are today”

      Yes, past temperatures frequently swing by 5-10°F — by causes other than CO2. As shown in this graph of the past 450 thousand years (by Robert A. Rohde, lead scientists of the Berkeley Earth Surface Temperature project).

      [caption id="attachment_79912" align="aligncenter" width="564"]Ice Age Temperature Ice Age Temperature, by Robert A. Rohde. Wikimedia Commons graphic.[/caption]

      (4) “MIT projects they will approach 750 ppm by 2100 with no sign of stabilizing.”

      “MIT” is guessing at economic and technological trends over the distant future, an activity with proven poor record of success. (But a nice use of “appeal to authority” for this guess!) The IPCC’s long-term scenarios assume we burn off almost the entire fossil fuel deposits (coal, oil, natural gas, bitumen, etc) on this planet. While it’s possible that no tech replaces burning fossil fuels during the next 80 years, that seems unlikely imo. Even assuming that advances stop in solar and other renewables, we could “electrify” the Earth’s transportation system over two decades — replacing fossil fuels with next-gen nuclear power plants.

  2. One thing that comes out of these papers is that more complex models are no more reliable than simple models. This is a real warning sign that we’re not including all mechanisms or that we have too many (badly known) parameters to tweak.

    1. Social Bill,

      I agree. I have been playing with a post on that theme. We’re ignoring major signs that we’re in a weird space. Too many things we’re told are normal but that nobody predicted. Negative nominal interest rates, 5 years of 2.4% real GDP, a 15 year long pause in surface temperature warming — and odd results from models everywhere.

      “Toto, I’ve a feeling we’re not in Kansas any more.”

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