Sarewitz on Consensus

Writing in Nature this week, Dan Sarewitz reflects on his recent participation on the BPC Geoengineering Climate Remediation task force and why efforts to achieve consensus in science may leave out some of the most important aspects of science.  Here is an excerpt:

The very idea that science best expresses its authority through consensus statements is at odds with a vibrant scientific enterprise. Consensus is for textbooks; real science depends for its progress on continual challenges to the current state of always-imperfect knowledge. Science would provide better value to politics if it articulated the broadest set of plausible interpretations, options and perspectives, imagined by the best experts, rather than forcing convergence to an allegedly unified voice.

Yet, as anyone who has served on a consensus committee knows, much of what is most interesting about a subject gets left out of the final report. For months, our geoengineering group argued about almost every issue conceivably related to establishing a research programme. Many ideas failed to make the report — not because they were wrong or unimportant, but because they didn't attract a political constituency in the group that was strong enough to keep them in. The commitment to consensus therefore comes at a high price: the elimination of proposals and alternatives that might be valuable for decision-makers dealing with complex problems.

Some consensus reports do include dissenting views, but these are usually relegated to a section at the back of the report, as if regretfully announcing the marginalized views of one or two malcontents. Science might instead borrow a lesson from the legal system. When the US Supreme Court issues a split decision, it presents dissenting opinions with as much force and rigour as the majority position. Judges vote openly and sign their opinions, so it is clear who believes what, and why — a transparency absent from expert consensus documents. Unlike a pallid consensus, a vigorous disagreement between experts would provide decision-makers with well-reasoned alternatives that inform and enrich discussions as a controversy evolves, keeping ideas in play and options open.

Not surprisingly, Dan and I have come to similar conclusions on this subject.  Back in 2001 in Nature I wrote (PDF):

[E]fforts to reduce uncertainty via ‘consensus science’ — such as scientific assessments — are misplaced. Consensus science can provide only an illusion of certainty. When consensus is substituted for a diversity of perspectives, it may in fact unnecessarily constrain decision-makers’ options. Take for example weather forecasters, who are learning that the value to society of their forecasts is enhanced when decision-makers are provided with predictions in probabilistic rather than categorical fashion and decisions are made in full view of uncertainty.

As a general principle, science and technology will contribute more effectively to society’ needs when decision-makers base their expectations on a full distribution of outcomes, and then make choices in the face of the resulting — perhaps considerable — uncertainty.

In addition to leaving behind much of the interesting aspects of science, in my experience, the purpose of developing a "consensus" is to to quash dissent and end debate. Is it any wonder that policy discussions in the face of such a perspective are a dialogue of the like minded?  In contrast, as Sarewitz writes, "a vigorous disagreement between experts would provide decision-makers with well-reasoned alternatives that inform and enrich discussions as a controversy evolves, keeping ideas in play and options open."

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