Sunday 10 May 2015

Climate change: the science is settled

The slogan "the science is settled" is mainly a rhetorical tool of the mitigation sceptics: A nice strawman to shoot down. When someone does say "the science is settled", what they are telling is "I do not want to talk to you about this".

Climatology is a mature science by now:
The basic results have not changed in decades,
the basics are based on natural science, where clear answers are possible,
a lot of scientists are involved,
climatology is well networked into the other sciences and
colleagues from other disciplines regularly contribute.

In such a situation, I find it perfectly normal for a citizen or politician to respond to outlandish claims of mitigation sceptics with: "Listen chap, you and I are both not qualified to discus such details. For me it is good enough that almost all scientists agree that there is a problem. If you really have a problem with some detail of the science, go write a scientific paper about it, but do not bother me with it." Or for short: "The science is settled".

You will have to search long and hard to find a scientist saying "the science is settled". Mostly because that is not how we scientists think: we are working on trying to improve our understanding and focus on the interesting parts that are not well understood. But when someone claims to have refuted the greenhouse effect, I feel perfectly entitled to say "the science is settled".

Some people even claim that greenhouse gasses cool the atmosphere. Sorry my life is too short to waste on such people. Some people even claim that the increases in CO2 are not man made. Sorry my life is too short to waste on such people.

Not only is there an overwhelming consensus on these topics, these are also topics that are pure natural science and they deal with the present or recent past. For such questions, an overwhelming consensus signals that the evidence is clear. I do not overestimate myself and think I can just barge in and explain the local experts what they are doing wrong. If someone else wants to do so, fine, they can write a scientific article about it. If they do not have the skills to write a scientific article, it is a legitimate question how it is possible that they are so sure that the science is wrong.

When someone asks me about the removal of non-climatic changes (inhomogeneities) from climate data, I can naturally not just answer "just trust me". That is my field of expertise and people have a justified expectation that I am able to answer such questions.

There are limits to this expectation. Eric Worrall recently asked on this blog: "How do you know the climate didn't actually cool?". And also did not provide any arguments. That signals such a degree of extremism that it makes no sense to talk to someone like that. A similar question from a scientist would also be another matter, but Worrall comes from a group that is known for misinformation and deceit. A reasonable answer would thus be: "the science is settled". Because it was here at my blog and he is somewhat known in mitigation sceptical circles, I actually mentioned the various lines of independent evidence that the world is warming. Then he was no longer interested in the discussion.

"The science is settled" is especially well suited for politicians. And they seem to have picked up this strawman lately. Seepage? Mass media are important for politicians and a short snappy slogan makes it more likely that your message is transported. Politicians are unfortunately supposed to extrude confidence and thus prefer not to explicitly say that they are not qualified. Good scientists should know the humble limits of their expertise. They can signal that they are good at science by acknowledging that the "question" is not their field of expertise. Unfortunately, scientists are also humans and some age groups and some fields of study seem to have more problems with admitting any limits.

Politicians may also like it that the slogan is rather ambiguous. The greenhouse effect itself is well understood. That greenhouse gas concentrations are increasing due to human activities is well understood. That CO2 emissions from fossil fuels, deforestation and cement are the main reason also. That it will continue if we do not change our energy system is also clear. However, what the future will exactly bring, how much the temperature will increase exactly is uncertain, if only because no one can predict how much CO2 we will emit before action is taken.

Also which impacts will be how big is quite uncertain. That is actually what worries me most. We are taking the climate system, on which our civilisation depends, outside the range we understand. There will be many (unhappy) surprises. The uncertainty monster is not humanities friend.

Thus, dear reader, please do not ask me why CO2 is a greenhouse gas, why the greenhouse effect does not cool the atmosphere, or even less interesting mitigation sceptical questions from the list of Skeptical Science. The science is settled!! But feel free to ask any questions on homogenization methods, about non-climatic changes in the historical stations measurements or why I am sure the climate is not cooling.

[UPDATE. Just remember a memorable quote by Justin Haskins, a blogger and editor at Heartland, a pro smoking and fossil fuel think tank: “The real debate is not whether man is, in some way, contributing to climate change; it’s true that the science is settled on that point in favor of the alarmists.” If he can, anyone can use the slogan: the science is settled.]

Related reading

The US Republicans signal that the science is settled, that there is no need for further climate research and in doing so put the American public in harms way.

Climatology is a mature field

A collection of early citations on settled science

Thou shalt not commit logical fallacies


  1. I think scientists should not hesitate to say "the science is settled *enough* for policy purposes."

  2. Great blog. I do feel that whether on climate science or almost any science requiring communication with politicians or public, you highlight persistent Communication issues. In our complex world, it feels like we need to develop new tools. Not sure the IPCC "highly likely" etc usage is sufficient. We need as you do to distinguish different qualities of uncertainty. Unhealthy lifestyle will almost certainly reduce your life expectancy, but the fact I cannot predict exactly when does not make this untrue. Truth and uncertainty can sit side by side.

  3. VV wrote: "... I actually mentioned the various lines of independent evidence that the world is warming. Then he was no longer interested in the discussion. "

    Here's one aspect I don't hear discussed much, but I believe worth mentioning more often.

    Rational science is a constructive Learning Process -
    Be it the experts in a specific field,
    or the interested but under-educated layperson such as myself.

    Being caught in an error, or being confronted with new information that conflicts with our(my) understanding is embraced as a learning opportunity rather than being defined as a personal attack upon my convictions, as the denialist crowd seems to assume.

  4. Steve Bloom: "the science is settled *enough* for policy purposes."

    I am happy to say that about the case for mitigation, but as a citizen. That is a value judgement.

    I have not looked into the economic or political case for mitigation, but I would expect that they only include climate change impacts we understand sufficiently to put a price on it. Many impacts are not well understood and we will certainly have forgotten many impacts. For example, ecosystem that provided services to mankind we never realised. Like much of the of functioning of the human body only becomes clear when we are sick, which is one reason to study rare deceases. Addition currently unknown impacts would make the case to do something stronger.

    As I argued in my own last post, the science is far from settled when it comes to adaptation. That requires locally accurate information, which is a lot harder than just getting the global statistics right. Adaptation is also policy and there the science is far from sufficiently settled.

  5. Richard Erskine, especially when the "highly likely" that mankind is responsible for climate change is an enormous underestimation of the statistical likelihood.

    The probability was *subjectively* reduced to take into account that maybe something has influenced the climate we completely did not think of. It is completely clear that the alternatives we considered are not strong enough and do not give the right spatial patterns.

    Such a magical force X can maybe also be called an uncertainty, but is of a completely different kind than the normal statistical uncertainty.

  6. citizenschallenge, it is clear that the mitigation sceptics keep themselves in a deliberate state of underinformation and misinformation. It is unfortunately not possible to check, but I would be willing to bet a fortune that less than 1% of the readers of Watts Up With That and similar or worse blogs has ever read a book about the climate system written by a mainstream scientist.

    If a mainstream blog links to me, even if it is a small blog judged by its number of comments, I normally get much much more traffic than when a mitigation sceptical blog links to me. As William M. Connolley says: They do not go out much.

    To afraid of cognitive dissonance. Given the broad range of opinions among mitigation sceptics, but almost no internal debate, we can guess that they know that they are wrong. They just are against mitigation and think they can oppose this best by claiming that they are not convinced about the science. Scientists are just collateral damage.

  7. Victor, you speak as if you think scientists should not interpret the science in the context of the approved global policy determination of avoiding dangerous climate change. Really?

  8. Steve Bloom, no I have no problem with scientists interpreting the science and giving policy advice. Likely somewhat in general terms because policy is not the strength of most scientists.

    Journalists often ask questions that cross the line from science to policy. It gives a strange impression when a scientists would not be willing to answer policy questions at least in general terms. That sounds as if the science is not solid enough for policy, while I agree with you that it is.

    However, I prefer to clearly distinguish between two roles, the scientist who explains our current understanding of the climate change as objectively as possible and the citizen who has subjective values and policy preferences. When James Hansen writes political sections in his articles in the scientific literature, he is mixing those two realms, which is something I do not like.

    And it also depends on how specific the policy questions are.

  9. it is clear that the mitigation sceptics keep themselves in a deliberate state of underinformation and misinformation. It is unfortunately not possible to check, but I would be willing to bet a fortune that less than 1% of the readers of Watts Up With That and similar or worse blogs has ever read a book about the climate system written by a mainstream scientist.

    Victor, there may be “sceptics” in the deliberately underinformed category, but I don’t think the evidence points to that being the dominant category, at least in the blogospheric climate “debate”.

    Many “sceptics” are actually extremely well-informed, but don’t process the information rationally - when faced with a fact that is too uncomfortable to accept... ...rejects it instead, insisting that it is not true despite what may be overwhelming evidence.

    For instance, the anthropogenic nature of our current CO2 rise is a clearly proven fact, yet even professors of climatology choose to refuse to accept this. Underinformed, they are not.

    …I am not convinced by simple mass balance attribution arguments based on current observations. I think it unlikely that 100% of the increase in atm CO2 is caused by humans. It is not unreasonable to start from a point of 50-50 (Fred’s conclusion) and see if you can falsify natural variability as large as 50%. It may not be 50%, but I don’t think it is 0%.

    Some “sceptics” of course, are simply contrarian.

  10. Isn't that what Ben Santer did with his "finger print" studies?

  11. verytallguy, they really do not know much at science or climate science. Maybe you have to be a scientist to notice. Most got stuck with the first topic they "studied": the greenhouse effect or the temperature trend. Even when it comes to the temperature trend there are maximally a few who understand how homogenization methods remove non-climatic trends.

    The complaints they may have may sound complicated, but that is another matter. If you want to change and contribute to science, you first have to understand it. That is almost always missing.

    I am not sure if the quote from Judith Curry is an argument for your position.

    citizenschallenge, you could also call studies where the CO2 increase comes from attribution studies, but the work of Ben Santer is about what is traditionally called attribution studies, the question where the temperature increase comes from.

  12. Hi Victor,

    That last notion - a group of experts present at the same time and location with a quick bouncing of ideas that is missing in the virtual world where discussions go much slower and many are not present - is an interesting one.

    The peer review process also does not really fit this description. Yet personal experience is that exactly that - having a group of experts together discussing ideas - can be extremely valuable, stimulating and provide a fast track for sharpening ideas.

    In the past that would happen on conferences and workshops, but with an ever expanding research community and conferences such possibilities, combined with more pressure to (quickly) publish the possibility of letting your ideas gradually mature, are becoming more and more rare.

    I could imagine that some form of pre-publication online discussion platform for experts and for example moderated by journal editors or journal staff might be something worth thinking about. Maybe also for continued post-publication discussion of papers. There would also have to be some reward for participatation of these experts, as they put in time/resources.

    As an example, I've played around with the idea of journals inviting experts on 'hot' topics to discuss this hot topic at an online platform - like with Climate Dialogue - where the discussion would count as peer-reviewed , i.e. get the same status as a research paper. The latter would provide incentives for experts to participate, which was an issue when running Climate Dialogue.


    Cheers, Jos.


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