by Judith Curry

The public seems to have gotten the memo that climate scientists believe that humans are warming the planet, and the warming is dangerous. They also don’t seem to care.

For some context, see the numerous CE posts on the subject of ‘consensus‘, particularly my paper No Consensus on Consensus.

Climate scientists and others that are alarmed about AGW seem very concerned by consensus denialism that attacks the expert consensus on climate change, that has allegedly resulted in a gap between the scientific consensus and the public consensus about climate change.

During the past few weeks, there have been some interesting articles that shed light on the topic of consensus.

Cultural cognition

Dan Kahan has a series of excellent posts on the public perception of consensus, see particularly They’ve already gotten the memo! What the public think ‘climate scientists believe.’ Excerpts:

I’ve explained in a couple of posts why I think experimental evidence in support of “messaging” scientific consensus is externally invalid and why real-world instances of this “messaging” strategy can be expected to reinforce polarization.

But here is some new evidence that critically examines the premise of the “message 97%” strategy: namely, that political polarization over climate change is caused by a misapprehension of the weight of opinion among climate scientists.

It isn’t.

Overwhelming majorities of both Republicans and Democrats are convinced that “climate scientists believe” that CO2 emissions cause the temperature of the atmosphere to go up—probably the most basic fact scientific proposition about climate change.

In addition, overwhelming majorities of both Republicans and think that “climate scientists believe” that human-caused climate change poses all manner of danger to people and the environment.

Thus, they correctly think that “climate scientists believe” that “human-caused global warming will result in flooding of many coastal regions.”

Again, these are the responses of the same nationally representative sample of respondents who were highly polarized on the question whether human-caused climate change is happening.

“Belief in human-caused global warming” items measure “who one is, what side one is on” in an ugly and highly illiberal form of cultural status competition, one being fueled by the idioms of contempt that the most conspicuous spokespeople on both sides use.

As I’ve explained, the responses that individuals give to such items in surveys are as strong an indicator of their political identity as items that solicit self-reported liberal-conservative ideology and political-party self-identification.

What individuals know—or think they know—about climate science is a different matter. To measure it, one has to figure out how to ask a question that is not understood by survey respondents as “who are you, whose side are you on.”

Same here: ask “what do climate scientists believe,” and the parties who polarize on the identity-expressive question “do you believe in global warming? do you? do you?” and you can see that there is in fact bipartisan agreement about what climate scientists think!

Climate change consensus: who cares?

The Guardian has an article by Adam Corner Who cares about climate change consensus? Excerpts:

This doesn’t mean that it is impossible to communicate about the consensus effectively – simply that the scientific consensus alone cannot overcome deep-rooted political divides. Messages about the consensus must be provided by communicators whose cultural credentials are congruent with the audience they are speaking to. Like every other aspect of the climate change debate (from newspaper articles to perceptions of extreme weather), communicating the consensus is an unavoidably politicised challenge.

In fact, this idea gets to the heart of why debating the precise proportion of scientists who endorse the mainstream position on climate change is ultimately a distraction. The more pressing challenge is creating a massively expanded social reality for climate change – one in which the things that people love and wish to protect are clearly linked in their minds to policies for confronting climate change.

Until the issue resonates with the hopes and aspirations of more than just a narrow band of campaigners and sceptics, pointing to a row of nodding scientists and expecting this to catalyse public concern is not going to get us far – no matter what the ‘magic number’ attached to the consensus is.

What consensus means to climate scientists

Roz Piddock has a post at the Carbon Brief entitled Dispelling myths and silently shaping progress: What consensus means to climate scientists. Excerpts:

Consensus is complicated. And reducing a complex question to a simple number is going to be fraught. So why do it? We asked climate scientists what consensus means to them, if it can be measured and how they use consensus in their own work.

Another point worth noting is that in pursuit of a single number to capture consensus, the answer you get depends on the question you ask, explains Professor Kevin Trenberth, climate variability expert at the US National Centre for Atmospheric Research:

“Very small changes can change the perceived consensus easily. 97% of scientists may agree that global warming from humans is happening but add any qualification like its timing or magnitude and it would change.”

Nuances aside, the scientists we spoke to generally tended to see the value of emphasising the broad strength of consensus for communication purposes. Andrew Dessler, professor of atmospheric sciences at Texas A&M University, explains:

“After all, if you’re looking for an expert medical opinion, and you find out that 97 per cent of the specialists agree about the course of treatment, you can be justly confident that that’s the best advice that medicine can give you”.

In fact, consensus isn’t a word you’re likely to hear being discussed in scientific circles, Dessler tells us.

“The only time I hear about “consensus” is in the public debate over climate. Scientists never ever talk about consensus – by going to meetings and reading the peer-reviewed literature, you can figure out what your colleagues think”.

Though it may not be much of a conversation topic among scientists, consensus as a concept has a fundamental place in driving scientific progress. Dessler continues:

“For each question that arises (e.g., is the earth warming?), there comes a time when the evidence is so overwhelming that the experts independently realize that the problem is essentially solved … At that point consensus exists on the answer and the question is no longer interesting – and scientists move on to the next interesting question”.

Arriving at a consensus – even if it’s an an unspoken one – drives scientific progress by taking research in new directions, Dessler adds:

“Consensus determines what we know, and it also determines what we don’t know. [It] also determines what the interesting questions are, which in turn determines what people work on …

A good example of a new and still very speculative field is whether diminishing Arctic sea ice is linked to Northern Hemisphere extreme weather. Professor Jennifer Francis, whose work proposing a connection prompted most of the research in this field, explains:

“Consensus comes in wherever there isn’t absolute proof of a theory, which is most of the time. In my work regarding links between rapid Arctic warming and changes in weather patterns, I would not say we have a consensus yet. When you do achieve consensus, it’s when a hypothesis transitions to a theory … This is a key distinction in science.”

There’s no doubt that consensus as applied in the scientific world is a complicated concept. Each time consensus pops up in the media, it raises interesting questions about how to measure it and what expressions of consensus mean in different scientific, social and political contexts.

However we choose to talk about consensus, all we’re really doing is exploring how to present scientific facts to different audiences. The facts themselves don’t change. That an overwhelming consensus exists among scientists about human-caused climate change isn’t in doubt. But then again, it never was.

Victor Venema

Victor Venema has a post 5 reasons scientists do not like the consensus on climate change. The post is trying to understand dissent from the consenus, and the negative reaction to The Consensus Project (Cook and Lewandowsky). Excerpts:

1. Fuzzy definition. One reason is that the consensus is hard to define.

2. Scientific culture. By defining a consensus and by quantifying its support, you create two groups of scientists, mainstream and fringe. This does not fit to the culture in the scientific community to keep communication channels open to all scientists and not to exclude anyone.

3. Evidence. Many people, and maybe also some scientists, may confuse consensus with evidence. For a scientist, referring to a consensus is not an option in his own area of expertise. Saying “everyone believes this” is not a scientific argument.

4. Contrarians. The concept “consensus” is in itself uncomfortable to many scientists. Most of us are natural contrarians and our job is to make the next consensus, not to defend the old one. Even if our studies end up validating a theory, the hope and aim of a validation study is to find an interesting deviation, that may be he beginning of a new understanding.

JC reflections

So . . . as per Dan Kahan, the public has gotten the message that there is a consensus among climate scientists about dangerous anthropogenic climate change.

As per Adam Corner, debating the precise proportion of scientists who endorse the mainstream position on climate change is ultimately a distraction from the public acceptance for policies to confront climate change.

As per Roz Pittock, climate scientists don’t pay much attention to the idea of consensus in context of their research.

As per Victor Venema, scientists don’t like the consensus on climate change, but presumably have been sold a bill of goods that consensus is needed for ‘action’?

So . . . why all the angst about ‘consensus’? We have Sir John Houghton and Steve Schneider to thank for this, the idea being one of ‘speaking consensus to power.’ Most of the so-called climate change consensus is a second-order consensus; relatively few scientists actively work on problems of climate change detection and attribution.

From my paper No Consensus on Consensus:

The climate community has worked for more than 20 years to establish a scientific consensus on anthropogenic climate change. The IPCC consensus building process arguably played a useful role in the early synthesis of the scientific knowledge and in building political will to act. We have presented perspectives from multiple disciplines that support the inference that the scientific consensus seeking process used by the IPCC has had the unintended consequence of introducing biases into the both the science and related decision making processes, elevating the voices of scientists that dispute the consensus, and motivating actions by some consensus scientists and their supporters that have diminished the public’s trust in the IPCC.

The growing implications of the messy wickedness of the climate change problem are becoming increasingly apparent, highlighting the inadequacies of the ‘consensus to power’ approach for decision making on the complex issues associated with climate change. Arguments are increasingly being made to abandon the scientific consensus seeking approach in favor of open debate of the arguments themselves and discussion of a broad range of policy options that stimulatelocal and regional solutions to the multifaceted and interrelated issues of climate change, land use, resource management, cost effective clean energy solutions, and developing technologies to expand energy access efficiently.