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Fundamental Flaws Debase IPCC 5th Assessment (‘Consensus Science’ on its death bed)

By Chip Knappenberger -- October 14, 2013

“The IPCC seems more intent on trying to maintain the now-dying consensus than in following climate science to its logical conclusion—a conclusion that increasingly suggests that human greenhouse gas emissions are less important in driving climate change than commonly held.”

Several weeks ago, the United Nations’ Intergovernmental Panel on Climate Change (IPCC) released the climate science portion of its Fifth Assessment Report (AR5). The AR5 is so burdened by fundamental flaws that it is worthless, or worse, misleading, as a resource to ground policy decisions regarding energy choices.

The IPCC seems to favor the output of computer climate models over that of hard observational science—science which indicates that computer models warm the earth’s temperature too fast for a given input of greenhouse gases to the atmosphere. Using climate models which are too sensitive to greenhouse gases leads to projections of future warming and all its resultant impacts—the meat of the IPCC report—which are too high.

By putting forth such projections, and ignoring the new science, the IPCC seems more intent on trying to maintain the now-dying consensus than in following climate science to its logical conclusion—a conclusion that increasingly suggests that human greenhouse gas emissions are less important in driving climate change than commonly held.

It should be clear that he IPCC has outlived whatever usefulness it may ever have had.  It is time to disband this central climate “authority” and disperse the assessment of climate science to a broader, more diverse community.

Unprecedented Criticism

The United Nations’ Intergovernmental Panel on Climate Change(IPCC) released its Fifth Assessment Report (AR5) to great fanfare. But more than ever before, there was also stinging criticism.

Much complaint was aimed at the IPCC’s defense of climate models— models which the latest observations of the earth’s climate evolution show to be inaccurate, or at least are strongly indicative that is the case.

There are two prominent and undeniable examples of the models’ insufficiencies:

1) Climate models overwhelming expected much more warming to have taken place over the past several decades than actually occurred; and

2) The sensitivity of the earth’s average temperature to increases in atmospheric greenhouse gas concentrations (such as carbon dioxide) averages some 60 percent greater in the IPCC’s climate models than it does in reality (according to a large and growing collection of evidence published in the scientific literature).

Had the IPCC addressed these model shortcomings head on, the flavor of their entire report would have been different. Instead of including projections for extreme climate changes as a result of continued human emissions of greenhouse gases resulting from our production of energy, the high-end projections would have featured relatively modest changes, and the low-end projections completely unremarkable.

Since changes in the earth’s temperature scale approximate linearly with a property known as the earth’s equilibrium climate sensitivity (how much the earth’s average surface temperature rises as a result of a doubling of the atmosphere’s carbon dioxide concentration), it is pretty straightforward to adjust the IPCC’s projections of future temperature change to bring them closer to what the latest science says the climate sensitivity is.

The latest science suggests the equilibrium climate sensitivity probably lies between 1.5°C and 2.5°C (with an average value of 2.0°C), while the climate models used by the IPCC have climate sensitivities which range from 2.1°C to 4.7°C with an average value of 3.2°C.

To make the IPCC projections of the evolution of the earth’s average temperature better reflect the latest scientific estimates, it is necessary to adjust them downward by about 30% at the low end, about 50% at the high end, and about 40% in the middle.

What the IPCC Should Have Done

The figure below shows what happens when we apply such a correction (note we maintain some internal weather noise). The top panel shows the projections as portrayed by the IPCC in their just-released Fifth Assessment Report, and the lower panel shows what they pretty much would have looked like had the climate models used to make them better reflected the latest science.


Figure 1. (Top) Temperature evolution from 1950 to 2100 as portrayed by the IPCC in its Fifth Assessment Report according to its worst case (red) and best case (blue) emissions scenarios (RCP8.5 and RC2.6, respectively). (Bottom) Temperature evolution from 1950 to 2100 from the same emission scenarios adjusted such that the equilibrium climate sensitivity values better matched the latest science.

The result of such adjustments is that the IPCC’s worst-case emissions scenario produces a global average temperature rise (from the 1986-2005 average) by the end of the century that has a centralized value of about 2.6°C, compared with a rise of 4.1°C given in the IPCC AR5. The more moderate (and probably more likely) emissions scenarios, once properly adjusted, produce a temperature rise by century’s end of only about 1.25°C (of which, about 0.15°C has already happened).

Since virtually all climate impacts are related to the change in the earth’s temperature, the smaller the future temperature increase, the small the resulting impacts. And another degree or so of temperature rise during the next 87 years is not going to lead to climate catastrophe.

Had the IPCC been more interested in reflecting the actual science rather than in preserving a quickly crumbling consensus (that human greenhouse gas emissions are leading to dangerous climate change that requires urgent action), its Fifth Assessment Report would have been a far different document, a much kinder and gentler one that the national news might have entirely ignored.

Appendix: Further Reading

The above post is reproduced in large part from “What the IPCC Global Warming Projections Should Have Looked Like published October 4, 2013, at Cato@Liberty.

For further reading on the travails of the IPCC, please see at the Cato blog, Cato@Liberty:

The IPCC AR5 Is in Real Trouble (July 26, 2013)

The IPCC Is Pretty Much Dead Wrong (September 19, 2013)

New IPCC Report Will Be Internally Inconsistent and Misleading (September 26, 2013)

Band-aids Can’t Fix the New IPCC Report (September 27, 2013)


  1. Ed Reid  

    We do not know the current global average surface temperature, nor do we know the ideal global average surface temperature. The Climate Establishment believes it can produce reasonable estimates of the temperature anomaly over periods of time within the instrumental temperature record, though that process requires “adjustments” to the data. Much of the data is likely not accurate in the first place to the left of the decimal point; regardless, the adjusted temperature anomalies are reported to two decimal place “accuracy”. Even more amusingly, projected future anomalies are expressed to one decimal place “accuracy”.

    Over the past several years, the US has built the Climate Research Network, which appears to be capable of producing data which can be used without adjustment. It is about time! Perhaps, at some point in the future, the rest of the globe could be similarly instrumented.

    The Climate Establishment might benefit from some degree of humility; and, the ability to distinguish between what it KNOWS and what it BELIEVES.

    To paraphrase former US SecDef Donald Rumsfeld: There are known knowns, known unknowns and unknown unknowns. Climate science appears well endowed with both known and unknown unknowns.


  2. ilma  

    It still puzzles me why the assumption still is looking at climate sensitiviyy to a doubling of CO2 (when the relationship is desvribed as linear) and not the sensitivity of natural CO2 sources/sinks to each degree of temperature change, as standard ocean chemistry and decaying of dead subtropical habitat material woukd strongly suggest that CO2 levels are an effect of what happens in the world, and not a cause.


  3. Martijn van Mensvoort  

    Thanks for this review of the IPCC 5th AR.
    Interesting to see that not much has changed since the IPCC 4th AR

    PS. I would like to add to Ed Reid’s comment that the so-called average of ‘land- and sea measurements’ is also basically a doubtful concept, because the sea temperatures actually involve sea water… and not the atmosphere above the sea water!

    What if the internal heat transport inside the ocean (after all, in most parts of the oceans warmth rises very slowly from the bottom towards the surface) the atmosphere was warmed up? We don’t really know what is exactly going on in the oceans… but what we do know is that ocean cycles are not included in the IPCC climate models!


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