by Judith Curry

I have a fairly lengthy op-ed that has been published in The Australian.

The piece is titled Consensus distorts the climate picture. Unfortunately, it is behind paywall. An editorial on the piece can be found [here], which is publicly accessible. And yet another article in The Australian Climate Consensus Skewing Science, which is also publicly accessible.

Below is a short essay with my original title that conveys the main points made in my op-ed.

The IPCC’s ‘inconvenient truth’ — a pause in surface warming for the past 15+ years

Publication of the IPCC AR4 in 2007 was received with international acclaim. The vaunted IPCC process – multitudes of experts from over a hundred countries over a period of four years, examining thousands of refereed journal publications, with hundreds of expert reviewers – elevated the authority of the IPCC AR4 to near biblical heights. Journalists jumped on board, and even the oil and energy companies neared capitulation. The veneration culminated with the Nobel Peace Prize, which the IPCC was awarded jointly with Al Gore. At the time, I joined the consensus in supporting this document as authoritative: I bought into the meme of “don’t trust what one scientist says; rather trust the consensus building process of the IPCC experts.”

Six and a half years later and a week before the release of the IPCC 5th Assessment Report (AR5), substantial criticisms are being made of leaked versions of the Report as well as of the IPCC process itself. IPCC insiders are bemoaning their loss of their scientific and political influence. What happened?

The IPCC was seriously tarnished by the unauthorized release of emails from the University of East Anglia in November 2009, known as Climategate. These emails revealed the ‘sausage making’ involved in the IPCC’s consensus building process, including denial of data access to individuals who wanted to audit their data processing and scientific results, interference in the peer review process to minimize the influence of skeptical criticisms, and manipulation of the media. Climategate was quickly followed by the identification of an egregious error involving the melting of Himalayan glaciers. These revelations were made much worse by the actual response of the IPCC to these issues. Then came the concerns about the behavior of the IPCC’s Director, Rachendra Pachauri, and investigations of the infiltration of green advocacy groups into the IPCC. All of this was occurring against a background of explicit advocacy and activism by IPCC leaders related to CO2 mitigation policies.

The IPCC does not seem to understand the cumulative impact of these events on the loss of trust in climate scientists and the IPCC process itself. The IPCC’s consensus building process relies heavily on expert judgment; if the public and the policy makers no longer trust these particular experts, then we can expect a very different dynamic to be in play with regards to the reception of the AR5 relative to the AR4.

But there is another more vexing dilemma facing the IPCC. Since publication of the AR4, nature has thrown the IPCC a ‘curveball’ — there has been no significant increase in global average surface temperature for the past 15+ years.

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.

Scientists do not need to be consensual to be authoritative. Authority rests in the credibility of the arguments, which must include explicit reflection on uncertainties, ambiguities and areas of ignorance and more openness for dissent. I have recommended that the scientific consensus seeking process be abandoned in favor of a more traditional review that presents arguments for and against, discusses the uncertainties, and speculates on the known and unknown unknowns.

The growing implications of the messy wickedness of the climate change problem are becoming increasingly apparent. Lets abandon the scientific consensus seeking approach in favor of open debate and discussion of a broad range of policy options that stimulate local and regional solutions to the multifaceted and interrelated issues surrounding climate change.