Bart Verheggen’s Survey of Climate Scientists

In the Spring of 2012, the Netherlands Environmental Assessment Agency PBL held a survey among 1868 scientists studying various aspects of climate change, including physical climate, climate impacts, and mitigation. The main results of the survey were published in an article in Environmental Science and Technology (ES&T) in August 2014: “Scientists’ views about attribution of global warming”. It showed that there is widespread agreement regarding a dominant influence of anthropogenic greenhouse gases on recent global warming. This agreement is stronger among respondents with more peer-reviewed publications.” That should not be surprising–there’s no question that most climate scientists feel that way. While I question the extent of dominance of AGW on overall warming, if it turned out to be 50% I would not be overly surprised.

However, there are other areas covered by the survey that are well worth exploring. A supplemental report detailing the findings has been recently released.

First, as a professional market researcher I would like to compliment the research team on their methodological choices and execution of the survey. As one who has been very sharply critical of other research on climate scientists (in particular Lewandowsky, Cook, Anderegg, Prall et al), it is refreshing to see someone taking care to get it right. In that respect, Verheggen, PBL et al is a return to good primary research as exemplified by von Storch, Bray et al in 2008. The results from the two surveys have a lot in common and should be considered mutually reinforcing.

On to the survey findings. Starting with the sexiest topic first, the question of attribution was explored in the survey. 66% of the respondents said that 50% or more of global warming since the mid-20th century can be attributed to human induced increases in greenhouse gases. As 19% responded ‘don’t know’ or ‘unknown’, it is clear that only a small minority has the opinion that GHGs caused less than 50% of recent warming. In fact, only 12% indicated that GHGs caused between zero and 50% of warming since the middle of the 20th century.

An interesting follow-up question was asked of those who felt AGW caused more than 50% of recent global warming. “What confidence level would you ascribe to the anthropogenic GHG contribution being more than 50%?” Similarly, those who ascribed less than half of recent warming to GHGs were asked about their level of confidence.

Those who think GHGs caused more than half of recent warming are far more confident in their perceptions than those who think GHGs caused less than half the warming.

Eighty-nine percent (89%) of those who attribute more than half of recent warming to GHGs said it was ‘virtually certain,’ ‘extremely likely’or ‘very likely’. In sharp contrast, only 45% of those who felt that GHGs had caused less than half of recent warming expressed similar levels of certainty.

I hope to continue with this analysis in subsequent posts. For now, I would suggest that it is fairly clear that there is a very real consensus among climate scientists about the role of human emissions of greenhouse gases in warming since 1945 and that those scientists who form the consensus are far more confident in their perceptions than those who doubt it.

17 responses to “Bart Verheggen’s Survey of Climate Scientists

  1. If I were going to analyze this study, I would start with figure 6. Only 16% listed climate observation as an expertise. 27% listed climate impacts.
    See if they will give you the cross tabs.

  2. As a fellow lukewarmer I am quite open to the idea that over half of warming is due to manmade CO2.
    However, I would be interested in how many of the scientists questioned had a role that was in any way based on the assumption that warming has a manmade component, rather than being entirely natural. Because if we should discount the views of sceptics who are linked with the fossil fuel industry (as we are often told we should), then shouldn’t we discount the views of those whose job depends on warming being anthropogenic?

    • Hi Alex, I don’t think we’re at the stage where that level of distrust is appropriate. I trust scientists. My real problem is with the activists who steal the microphone out of the scientists’ hands and pretend to speak for them.

      • Agreed; my point (probably badly expressed) is that among those activists there is a tendency to argue that those with a financial interest in fossil fuel usage should be ignored or even silenced. However, surely much of the current funding of climate science (and those scientists studying, for example CCS) is based on Climate Change being dangerous and anthropogenic and those scientists therefore have a financial interest in Climate Change being largely human-caused. If we don’t ignore the opinions of the second group (and we shouldn’t) we shouldn’t ignore the first group either.

      • I have to agree with Alex here. I’ve worked in contract research. You deliver what you’re paid to deliver.

      • Tom,
        You mean like Peter Gleick? Or ATTP (a scientist and academic, after all)?
        Or perhaps Mann?
        They should be trusted exactly how far.

  3. Tom, while I have always acknowledged and appreciated your expertise in the field of “market research” – and I certainly share your views on the utterly shoddy work of Lewandowsky, Cook, Anderegg, Prall et al – I still have a problem with your declarations in the above to the effect that (my bold -hro):

    Those who think GHGs caused more than half of recent warming are far more confident in their perceptions than those who think GHGs caused less than half the warming.

    And:

    those scientists who form the consensus are far more confident in their perceptions than those who doubt it.

    I don’t dispute that “perceptions” may well be a very valid – and worthwhile -indicator in market research pertaining to consumer products and/or services. However, I am very far from convinced that “perceptions” – regardless of who might hold or express them – should be construed as an indicator of scientifically valid findings (of any kind)!

    For the record – while I appreciate that your mileage and that of others may well vary – my definition of “perception(s)” matches that of Google, which begins as follows:

    per·cep·tion
    pərˈsepSH(ə)n/
    noun
    the ability to see, hear, or become aware of something through the senses.
    “the normal limits to human perception”

    the state of being or process of becoming aware of something through the senses. […]

    If – as the movers and shakers at the UN and the EU (not to mention the former’s ever-increasing armies of NGO advocates) would have the rest of the world believe – the purported “dangers” of increased emissions of CO2 are merely based on “perceptions”, then perhaps we need something somewhat more scientifically solid – and valid – than mere “perceptions” … Regardless of who might hold, profess and/or espouse ’em!

    In short, the view from here, so to speak, is that what the world needs now is fewer “perceptions” and more solid evidence of the purely scientific (i.e. non-Climateer and non-pseudo-statistical) kind.

  4. By the way, do they have a similar survey about a consensus amongst physicists about the existence or nature of dark matter? I wrote a comment at CPI stating I had serious doubts about it and the pig went ballistic. He even devoted a post to tearing up my simple comment. Some people take these controversies so seriously one would think their whole careers hang on the balance.

  5. Pingback: Verheggen’s Consensus: Not 97%, not 47%. It’s 66%. | The Lukewarmer's Way

  6. Pingback: PBL survey shows strong scientific consensus that global warming is largely driven by greenhouse gases | My view on climate change

  7. Pingback: More on Verheggen et al: Great Survey. Pity about the report… It’s still 66%. | The Lukewarmer's Way

  8. Pingback: PBL survey shows strong scientific consensus that global warming is largely driven by greenhouse gases | Enjeux énergies et environnement

  9. Pingback: PBL survey shows strong scientific consensus that global warming is largely driven by greenhouse gases

  10. Pingback: The Lukewarmer's Way

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