Climate Science Slowly Becomes Less Settled

Andrew Gelman, in a comment on the previous post, said that he believes the science of climate change is “much more settled” than I do. He’s right — in the sense that I believe the state of the world is different (less certain) than claimed. Andrew sees correct certainty; I see false certainty. Because science slowly becomes more accurate, I think the science will slowly shift toward “less settled” — a prediction I don’t think Andrew would make. Here’s an example of such a shift. According to the Mail on Sunday, Phil Jones

admit[s] that there is little difference between global warming rates in the Nineties and in two previous periods since 1860 and accept[s] that from 1995 to now there has been no statistically significant warming.He also leaves open the possibility, long resisted by climate change activists, that the ‘Medieval Warm Period’ from 800 to 1300 AD, and thought by many experts to be warmer than the present period, could have encompassed the entire globe.

Phil Jones slowly shifts.

12 Replies to “Climate Science Slowly Becomes Less Settled”

  1. Yes this was a stunning admission by Jones. Watch 90% of experts start backpedaling now.

    I’m going to make some popcorn, this should be fun to watch.

  2. 1. Are CO2 levels not rising to levels not seen in millions of years?
    2. Is the polar icecap not receding?
    3. Can we afford to “wait and see”, which will help decide whether we are now experiencing a period of global warming, and if so, how much of it (0-100) is caused by human activity?

    Sorry, I’m a pragmatist, I have to go with something, and the path we’re now on still gives the overwhelming impression that we’re slowing stewing ourselves. Are we acting on perfect knowledge? No. If science turns around and says “drill, baby, drill” and “burn, baby, burn”, then so be it. But it ain’t there now.

  3. Steve, the recent rate of warming is matched by the rate of warming during two previous periods before we started putting so much CO2 in the air. This suggests that CO2 doesn’t make a big difference. (If it did, the current rate of temp increase should be greater than ever before.) If the current global temp was unprecedentedly high OR the rate of warming was unprecedentedly high, then I would get really worried. But neither are true, as far as I can tell.

    “Is the polar icecap not receding?” The South Pole is not shrinking, as far as I know. During most of the Earth’s history and all of recent history, the polar ice cap has been shrinking half of the time. (It has been growing the other half.) That fact alone doesn’t mean a lot.

    “Can we afford to wait and see”? I think so. Overreaction is costly too. There are plenty of good reasons to reduce carbon emissions and I believe they will go down.

  4. Are Phil Jones’s actual words available anywhere, or do we have to rely on this paraphrase from The Daily Mail? Both of the claims about recent temperatures sound like they could be meaningless. The claim that two previous periods had similar warming rates is hopelessly vague and it’s not at all clear that it represents a shift in anything – temperature records have long shown a substantial increase from the 1910s to the mid 1940s, for instance. The claim about no statistically significant warming since 1995 could just be relying heavily on “statistical significance” and a small sample size.

    Googling around a bit… yep, that’s exactly what happened:

    Question: “Do you agree that from 1995 to the present there has been no statistically-significant global warming?”

    Jones: “Yes, but only just. I also calculated the trend for the period 1995 to 2009. This trend (0.12C per decade) is positive, but not significant at the 95% significance level. The positive trend is quite close to the significance level. Achieving statistical significance in scientific terms is much more likely for longer periods, and much less likely for shorter periods.”

  5. Vince, Jones’s exact words are in the link called “Phil Jones slowly shifts” but they only apply to one issue. Sure, 15 years is a relatively short period and statistical significance is arbitrary. The two earlier periods with similar rates of warming are spelled out in various places. They are pre 1900, if I remember correctly. Take my prediction as a prediction about what will happen over the next five-ten years. Obviously any shift so far is tiny.

  6. Those are his words for one of the three claims. I quoted his words for a second claim, and it’s clear that the article is being misleading: he wasn’t retreating at all. He was fed a leading question, and responded by noting that it was technically accurate and explaining why it’s misleading: it’s hard to make precise estimates of trends with data from a short period of time, so it’s no surprise that the increase in temperatures since 1995 isn’t quite statistically significant. I haven’t seen his words on the third claim, but I’d guess that it’s a lot like the second – he was fed a misleading question and agreed that it was technically accurate. He was probably relying on an updated version of these data, and it looks like you could pick out a couple 10-15 year periods before 1900 with upward trends similar to the trend over the past 40 years (one starting in the mid 1850s and one starting around 1890), but it’s not clear why anyone should care (it’s just as easy to pick out a decade with a downward trend, like by starting in the late 1870s).

  7. Seth, please do look up “confirmation bias”. You write very much as if you have never heard of it. You’re convinced that AGW is a load of hooey; so, to be scrupulous, you should be seeking out evidence that it’s real. If you could bring yourself to bother, you’d find plenty. Instead, you find yourself quoting from editorials and misquotes in the least scrupulous newspapers. That should worry you.

    Other warming periods not involving CO2 say nothing about the present trend. There are plenty of possible causes for warming, and if all of them were combined, then the rate would obviously be higher than it is; but they haven’t been. All we know much about is the trend we’re experiencing now where the temperature rise really is tracking CO2.

  8. If Seth is guilty of confirmation bias then he is certainly not the only one. It is one of the most common of logical errors. Very few people can approach a controversial topic with a fully unbiased and open mind.

    Particularly with global warming, many people have ideological preferences which will interact strongly with their beliefs about the topic. Those who distrust big business and favor government regulation will be inclined to welcome evidence for global warming. Those who hold the opposite views will tend to be skeptical. I find that there is a very strong correlation on this issue between people’s beliefs and their preferences.

  9. The full interview is now online.

    On the similar trends question, the interviewer picked out the time periods (1860-1880, 1910-1940 and 1975-1998) and he just ran some numbers that confirmed that they had similar temperature trends (around .16 degrees C per decade). This was a prelude to a few questions about how he can be so sure that the recent warming is human caused, then. He agreed with the IPCC report that it’s very likely to be human caused, gestured towards all the research that directly addresses that question of what factors are influencing the temperature, and seemed to get annoyed when he kept getting asked versions of the same question.

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