…and its inconvenient truth:

Based upon early drafts of the AR5, the IPCC seemed prepared to dismiss the pause in warming as irrelevant ‘noise’ associated with natural variability. Under pressure, the IPCC now acknowledges the pause and admits that climate models failed to predict it. The IPCC has failed to convincingly explain the pause in terms of external radiative forcing from greenhouse gases, aerosols, solar or volcanic forcing; this leaves natural internal variability as the predominant candidate to explain the pause. If the IPCC attributes to the pause to natural internal variability, then this begs the question as to what extent the warming between 1975 and 2000 can also be explained by natural internal variability. Not to mention raising questions about the confidence that we should place in the IPCC’s projections of future climate change.

Nevertheless, the IPCC appears to be set to conclude that warming in the near future will resume in accord with climate model predictions.

Why is my own reasoning about the implications of the pause, in terms of attribution of the late 20th century warming and implications for future warming, so different from the conclusions drawn by the IPCC? The disagreement arises from different assessments of the value and importance of particular classes of evidence as well as disagreement about the appropriate logical framework for linking and assessing the evidence – my reasoning is weighted heavily in favor of observational evidence and understanding of natural internal variability of the climate system, whereas the IPCC’s reasoning is weighted heavily in favor of climate model simulations and external forcing of climate change.

The models are utterly useless, as a basis for public policy. In fact, to the degree that people don’t understand this, they’re worse than useless.

[Update a few minutes later]

Related: no ice-free Arctic this year. Mazlowski is falsified.

2 thoughts on “The IPCC”

  1. But if you ignore the last several (10?) years the models are very good. And if you ignore certain tree stands the hockey stick is unassailable.

    Similarly, if you ignore the dead rats, smoking is provably harmless.

  2. A few points from the “Maslowski is falsified” link:

    1) “The minimum ice extent was the sixth lowest* in the satellite record, and reinforces the long-term downward trend in Arctic ice extent.” Not in the link, but the other lowest years were in the 2000s, including last year’s all-time record low.

    2) “The minimum extent was reached two days earlier than the 1981 to 2010 average minimum date of September 15.”

    Looks more like a dead cat bounce to me.

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