It Really Should Go Without Saying, BUT…

OVERVIEW

In a good number of posts over the past few months, we have discussed and illustrated how poorly the coupled ocean-atmosphere climate models used by the Intergovernmental Panel on Climate Change (IPCC) in their 4th Assessment Report (AR4) simulate past global surface temperatures over different timescales: the past 30 years, the past century, etc. There are very few circumstances when and where the models simulate past surface temperatures with any degree of skill. Refer to the posts (most recent first) here, here, here, here, here, here, here, here, here, here, here, and here.

To support their belief in their climate models, the IPCC provided Figure 9.5 in Chapter 9 of AR4. We’ve addressed the graph in cell a of that illustration, showing how poorly the models replicate surface temperatures over the 20thCentury, primarily during the early warming period and early “flat temperature” period. (Refer to the first 4 posts linked as “here” above.) But we haven’t yet looked at cell b of Figure 9.5, which was their graph that showed how poorly the models hindcast global surface temperatures when the models were forced with natural forcings only; that is, when only Total Solar Irradiance and Volcanic Aerosols forcings were used.

Let’s see what the IPCC has to say about cell b of their Figure 9.5 from AR4.

DISCUSSION

The IPCC in AR4 provided Figure 9.5, cell b, (my Figure 1) as proof that climate models that are forced by only natural forcings (Solar and Volcanic Aerosols) are not able to recreate the global surface temperature warming that occurred during the latter part of the 20thCentury. Specifically, they stated in Chapter 9, under the heading of “9.4.1.2 Simulations of the 20th Century” [appropriate portion in bold face]:

“Figure 9.5 shows that simulations that incorporate anthropogenic forcings, including increasing greenhouse gas concentrations and the effects of aerosols, and that also incorporate natural external forcings provide a consistent explanation of the observed temperature record, whereas simulations that include only natural forcings do not simulate the warming observed over the last three decades.

Figure 1

And it’s very obvious that the models that include only natural forcings don’t replicate the surface temperatures during the late 20thCentury warming period. Very obvious. But the IPCC fails to discuss a few other things.

The IPCC’s climate models with only natural forcings don’t hindcast the observed warming of global surface temperatures during the early warming period of 1917 to 1944, Figure 2.

Figure 2

And the IPCC’s climate models with only natural forcings don’t simulate the cooling of global surface temperatures that took place during the early “flat temperature” period, Figure 3.

Figure 3

And the IPCC’s climate models with only natural forcings fail to simulate the reasonably flat temperatures during the mid-20thCentury “flat temperature” period, Figure 4.

Figure 4

And since we have already established that the IPCC’s climate models that include anthropogenic forcings cannot simulatethe warming of global surface temperatures that took place during…

1. the early warming period, (Source) or

2. the early “flat temperature” period, (Source), or

3. if the observed sea surface temperature data is replaced with the Hadley Centre’s corrected version, the IPCC’s climate models that include anthropogenic forcings cannot simulate the cooling that took place during the mid-20th Century “flat temperature” period (Source)

…then it should come as no surprise that the IPCC’s climate models without anthropogenic forcings can’t simulate the warming observed during the late warming period of 1976-2000 either, Figure 5.

Figure 5

The linear trend of the long-term (1901-2000) model mean of the models without anthropogenic forcings is basically flat, Figure 6, as it should be. Why would anyone think that the IPCC’s climate models forced with only Total Solar Irradiance and Volcanic Aerosol data could simulate the rises and falls in surface temperatures that took place over the 20thCentury?

Figure 6

SO WHY DOES THE IPCC INCLUDE BOTH SETS OF MODEL ENSEMBLES IN FIGURE 9.5?

Let’s return to the Summary for Policymakersfrom the IPCC’s AR4. The fourth bullet-point paragraph under the heading of “Understanding And Attributing Climate Change” (page 10) reads [my bold face]:

“It is likely that there has been significant anthropogenic warming over the past 50 years averaged over each continent except Antarctica (see Figure SPM.4). The observed patterns of warming, including greater warming over land than over the ocean, and their changes over time, are only simulated by models that include anthropogenic forcing. The ability of coupled climate models to simulate the observed temperature evolution on each of six continents provides stronger evidence of human influence on climate than was available in the TAR. {3.2, 9.4}”

The bracketed reference to chapter/section 9.4 would bring the interested reader the portion of Chapter 9 and Figure 9.5 (See Figure 7) that was quoted earlier. I’ll provide them again so you don’t have to scroll up the webpage (my boldface):

“Figure 9.5 shows that simulations that incorporate anthropogenic forcings, including increasing greenhouse gas concentrations and the effects of aerosols, and that also incorporate natural external forcings provide a consistent explanation of the observed temperature record, whereas simulations that include only natural forcings do not simulate the warming observed over the last three decades.

Figure 7

And Figure 9.5 and the IPCC’s discussion of it confirm the statement from the Summary for Policymakers. So that section in chapter 9 did its job.

But there are some who might think cell b of the IPCC Figure 9.5, combined with the visual noise of the individual ensemble members in yellow in cell a, are intended as distractions. They draw the reader’s attention away from how poorly the models simulate observed global surface temperatures over the entire 20thCentury. In other words, it appears as though the IPCC drew the reader’s attention to the “last three decades” because that’s the only period when the climate models forced with anthropogenic forcings consistently align themselves with the observation-based global surface temperature data.

SOURCE

The HADCRUT observation-based surface temperature data is available through Monthly observationswebpage at the KNMI Climate Explorer. The data for the multi-model ensemble mean of Figure 9.5 cell b were replicated using the X-Y coordinates of Microsoft Paint.

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About Bob Tisdale

Research interest: the long-term aftereffects of El Niño and La Nina events on global sea surface temperature and ocean heat content. Author of the ebook Who Turned on the Heat? and regular contributor at WattsUpWithThat.
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9 Responses to It Really Should Go Without Saying, BUT…

  1. hswiseman says:

    Anyone with a shred of professional responsibility would be embarrassed to participate in this willful deception.

  2. Bob Tisdale says:

    dallas says: “Bob? You missing a rock”

    Yeah, but I’m missing Tisdale 7, not 2.

    Thanks for the link. I hadn’t seen that yet.

  3. Joe's World says:

    Bob,

    This is what I have been trying to explain to you.
    Temperature data has no meaning on a changing planet.
    Focus on temperature data and ignoring everything else has put science in jeopardy on collapsing from stupidity just to follow a man man protocol of generating a calculation on the whole planet and staying within the fields of temperature exclusively for a minor period of Earth time.

  4. Pascvaks says:

    In the real Universe vibrations cancel and/or amplify one another, at the IPCC you’re allowed to take or leave what you like; indeed, you’re allowed to invent, or create out of nothing, and “settle” whatever you wish. I guess it really is true that money can buy anything or anyone. We must remember that when we wish to build (or destroy) something it’s always best to hire an engineer.

  5. Bob,
    Don’t worry, I heard all these problems will be solved in AR5………

  6. Hmmm says:

    You aren’t including error ranges in either observations (which grow with time) nor models.

    It’s quite clear from the graphs that the models fit the 20th century, including the recent few decades of warming, a hell of a lot better with manmade contribution than without. And the biggest gap is in the last few decades.

  7. Bob Tisdale says:

    Hmmm says: “You aren’t including error ranges in either observations (which grow with time) nor models.”

    You’re welcome to do any additional anaylses you’d like.

    Hmmm says: “It’s quite clear from the graphs that the models fit the 20th century, including the recent few decades of warming, a hell of a lot better with manmade contribution than without. And the biggest gap is in the last few decades.”

    But since the models with anthropogenic forcings show no skill at hindcasting, as shown in the previous two posts, your point is?

  8. Pingback: The IPCC AR4 Models Of 20th Century Surface Temperatures With And Without Anthropogenic Forcings | Bob Tisdale – Climate Observations

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