A post by Alec Rawls at WUWT Taking Keating’s $30,000 skeptic challenge seriously, part 1 has renewed some interest in a challenge to disprove the theory of human-induced global warming. This post is not about Alec’s post; it provides my general comments about Keating’s challenge to skeptics.
Keating’s challenge is simply a publicity stunt. It is a waste of his time and yours, even with Keating’s new criteria:
The basic tenets of AGW are these two IPCC conclusions:
It is extremely likely (95-100%) that human influence has been the dominant cause of the observed warming since the mid-20th century.
Climate sensitivity is likely in the range 1.5°C to 4.5°C and extremely unlikely (95-100%) less than 1°C.
So if someone was able to scientifically disprove these two extremely likely / unlikely statements, then that should suffice.
The IPCC’s beliefs about the human influence on climate and on climate sensitivity are based on climate models that were never established to simulate Earth’s climate. Recall Kevin Trenberth’s blog post Predictions of Climate at Nature.com’s ClimateFeedback. Kevin wrote (my boldface):
In fact there are no predictions by IPCC at all. And there never have been. The IPCC instead proffers “what if” projections of future climate that correspond to certain emissions scenarios. There are a number of assumptions that go into these emissions scenarios. They are intended to cover a range of possible self consistent “story lines” that then provide decision makers with information about which paths might be more desirable. But they do not consider many things like the recovery of the ozone layer, for instance, or observed trends in forcing agents. There is no estimate, even probabilistically, as to the likelihood of any emissions scenario and no best guess.
Even if there were, the projections are based on model results that provide differences of the future climate relative to that today. None of the models used by IPCC are initialized to the observed state and none of the climate states in the models correspond even remotely to the current observed climate. In particular, the state of the oceans, sea ice, and soil moisture has no relationship to the observed state at any recent time in any of the IPCC models. There is neither an El Niño sequence nor any Pacific Decadal Oscillation that replicates the recent past; yet these are critical modes of variability that affect Pacific rim countries and beyond. The Atlantic Multidecadal Oscillation, that may depend on the thermohaline circulation and thus ocean currents in the Atlantic, is not set up to match today’s state, but it is a critical component of the Atlantic hurricanes and it undoubtedly affects forecasts for the next decade from Brazil to Europe. Moreover, the starting climate state in several of the models may depart significantly from the real climate owing to model errors.
The models, therefore, cannot be falsified. And if the models cannot be falsified, no one can meet Keating’s two criteria.
Additionally, the likelihoods in the two criteria are subjective, based on beliefs, not on quantitative analysis. Box TS.1 Treatment of Uncertainty on page 36 of the Technical Summary (18MB .pdf) of the IPCC’s 5th Assessment Report begins (my boldface):
Based on the Guidance Note for Lead Authors of the IPCC Fifth Assessment Report on Consistent Treatment of Uncertainties, this WGI Technical Summary and the WGI Summary for Policymakers rely on two metrics for communicating the degree of certainty in key findings, which is based on author teams’ evaluations of underlying scientific understanding:
- Confidence in the validity of a finding, based on the type, amount, quality and consistency of evidence (e.g., mechanistic understanding, theory, data, models, expert judgement) and the degree of agreement. Confidence is expressed qualitatively.
- Quantified measures of uncertainty in a finding expressed probabilistically (based on statistical analysis of observations or model results, or expert judgement).
Expert judgment is, of course, subjective. Unfortunately, the report does not identify whether the confidences and uncertainties of specific findings were determined through analysis or through “expert judgement”.
A further discussion with clarifications can be found in the IPCC’s July 2010 Guidance Note for Lead Authors of the IPCC Fifth Assessment Report on Consistent Treatment of Uncertainties.
It is impossible to disprove any likeliness that is subjective.
Once again, anyone responding to Keating’s challenge is wasting their time.