Can We Actually Even Tell if Humans Are Affecting the Climate? What if we did nothing at all?

telescoper:

Reblog of a post about the doctrine of falsifiablity and its relevance to Climate Change….following on from Monday’s post.

Originally posted on Watts Up With That?:

Essay by Charlie Martin

We know, with great certainty, that the overall average temperature of the Earth has warmed by several degreees in the last 400 years, since the end of the Little Ice Age. Before that was a period called the Medieval Warm Period; before that was another cold period, and back at the time of the Romans there was a long period that was significantly warmer — Southern Britain was a wine-growing region. What we’re a lot less certain about is why?

Of course, the “why?” here has been, shall we say, pretty controversial. It’s worth wondering about the controversy and about the social mechanisms through which science is done — I wrote about them during the Climategate controversy as the “social contract of science” — but that’s not what I want to talk about today. Instead, let’s talk about how a scientist thinks about these sorts of…

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35 Responses to “Can We Actually Even Tell if Humans Are Affecting the Climate? What if we did nothing at all?”

  1. Anton Garrett Says:

    Even a single human changes the climate; the question is by how much. This subject has led to some of the hottest (sorry) debates on this blog, and nowadays I prefer to give a brief personal trajectory. When I first heard of the issue I assumed that the scientists then being heard on the subject – essentially physicists – were right to be alarmed. But when I became aware of counter-arguments I looked into it for myself as best I could (trained theoretical physicist in unrelated field), and decided that those saying man-made global warming should not be feared anywhere were right. My view has not changed since then, but I continue to hunt for quality contributions on both sides of the debate – which is not easy when it has become so intermingled with politics. Watts’ blog is one that I read regularly.

    • You should really regularly read http://tamino.wordpress.com/ which often points out flaws in Watt’s blog. Some of Watts’s claims are real howlers, classics like cherry-picking etc, reminding me of Reagan using the Mercator projection to make the USSR look bigger.

      I actually worked in climate modelling for a while back in the 1990s ( http://www.geo.uni-bremen.de/geomod/index_e.html ) and can personally swear that the accusations of fraud are completely bogus. No, the data weren’t massaged to get a “desired” result in order to get more funding or whatever.

      I can’t help but point out that almost all global-warming “sceptics” are devoutly religious and/or politically conservative (and/or funded by the oil industry, but this doesn’t apply to you). Adopting a Bayesian approach, should one take into account such affiliations when gauging the probability of truth of a statement about AGW?

      Yes, there are otherwise credible scientists who are sceptics. This applies to creationism as well. Do we need to “teach the conflict” as long as there is one dissenting voice, or should we move on, just like we no longer take phlogiston as a serious explanation for combustion?

    • If you’re looking for quality contributions, why are you reading Anthony Watts? He does not even understand, for example, that different global temperature measurement datasets use different reference periods from which to measure the temperature anomaly.

      • Anton Garrett Says:

        I don’t even understand what you mean by different reference periods needing to be used by global temperature measurement datasets. A thermometer measurement is a thermometer measurement. I presume you are talking about proxy variables for temperature before we got thermometers, and that the relation between the proxy and the actual temperature is inferred (for other reasons) to differ in different periods?

      • A thermometer measurement is an estimate of the absolute temperature at a particular place at a particular time. Global temperature datasets use those direct measurements to estimate the temperature anomaly for the entire globe over periods of time, usually monthly and annual. The anomaly is the difference between the measured or estimated temperature, and the average value in some reference period. Global temperature datasets use anomalies rather than absolute temperatures because absolute temperature measurements are highly sensitive to local conditions, altitude etc, while anomalies are not. For example, the absolute temperature measured in a valley or on top of a nearby hill will be very different, while the anomaly will be very similar.

        NASA’s GISTEMP record expresses anomalies relative to the averages for 1951-1980. The Hadley Centre’s HADCRUT record gives them relative to the averages for 1961-1990. The RSS satellite temperature record states anomalies relative to 1979-1998, while the UAH temperature record states them relative to 1981-2010 averages.

        The averages during these different periods were not the same, so you can’t directly compare the four different temperature measurements without taking that into account. I am sure you can see how trivially simple it is to understand that. I’d say that anyone who can’t grasp this cannot have anything of value to contribute to climate science discussions. Anthony Watts often makes claims that show that he does not understand this.

  2. Brendan Says:

    Yes, a good commentator. Watts certainly has a solid grasp on how science is done.

    • Watts has no clue about how science is done. He promotes anything which he thinks supports his beliefs, regardless of whether it completely contradicts the previous “theory” he promoted. “It’s not warming and the warming is not because of humans and warming’s good for everything anyway” roughly sums up his output.

    • Wouldn’t it be wonderful if you read the actual column, which wasn’t actually written by Anthony anyway?

      • Of course, apologies – I did read the column, and was rather disappointed by a well written piece that ends hinging on the argument that the probability of the model given the data is the probability of the data given the model.

      • Anton Garrett Says:

        Brendan: the one increases monotonically with the other, and as for priors in this field, who knows??

  3. This makes me think there should be an “ironic reblog” or “sarcastic reblog” option :-)

  4. Anivegmin Says:

    Disregarding the merits or otherwise of the above essay I would have thought a university professor might be somewhat embarrassed to cross post from such an inept anti-science blog.

    • telescoper Says:

      I’m not at all embarrassed. People should read what’s out there and form their own opinions. It’s not the first time I’ve cross-posted something I disagreed with. I reblogged this item for two reasons:

      (a) It refers to the doctrine of falsifiability which, as I posted about on Monday, is not a very good description of how science works, and its application to global warming is illustrative and topical

      (b) Climate change always generates a lot of hits, which gave me a cynical motivation.

    • Anton Garrett Says:

      Inept? You are entitled to your opinion. But anti-science? Nonsense.

      • I don’t really won’t to get into a massive argument here, but do you really think that the typical post on WUWT has any particular scientific merit? From my reading of it, most posts either violate the basics laws of physics (Bob Tisdale and his inability to understand the basic laws of conservation of energy, for example), assume correlation means causation, or simply make no sense at all. That’s not to say that there aren’t some posts that have merit, but given how many there are it would seem remarkable if there were none.

      • Anton Garrett Says:

        If what you say is accurate (and I haven’t checked Tisdale but I dispute the other assertions) then those would be examples of ineptitude, not anti-scientific.

      • Indeed, I was intentionally not claiming anti-science. I’d be surprised, however, if you couldn’t find a large number of examples of correlation implies causation claims on WUWT posts (unless I don’t understand what the terms correlation and causation mean). I would, however, add that it is fairly clear that most who post on WUWT are very explicitly anti-climate-scientists (or at least anti published climate scientists). If this isn’t an indication of being at least partly anti-science, I’m not sure what is.

      • Anton Garrett Says:

        If you suggest that correlation is confused with causation at Watts’ blog then it is up to you to make the case. (Actually I think that the only meaningful definition of causation in physics is time-ordering.) But “anti-science” means someone who is against science; to such a person it does not matter whether science is done correctly or incorrectly. Whereas the climate wars are all about whose science is correct. When you take out the ad hominems and the funding counterclaims it is, as it should be, a scientific debate.

      • In a sense, it’s not really up to me to do anything. I was simply commenting that – IMO – there are a lot of posts on WUWT in which they claim to have determined how something works because they’ve fitted some line to some dataset. You are, of course, welcome to disagree.

        I’m not sure that if removing the ad hominens and funding counterclaims would actually produce a site that was genuinely engaging in scientific debate. Possibly, but it does seem that the ad hominens and the like seem to dominate as far as I can see.

      • Anton Garrett Says:

        I’d prefer to believe people whose line fits the data than people whose line doesn’t…

      • “anti-science” means someone who is against science; to such a person it does not matter whether science is done correctly or incorrectly

        That is the very definition of Anthony Watts. He promotes anything that supports his beliefs, regardless of whether it is physically plausible, or at all consistent with whatever he published 5 minutes before.

      • Anton Garrett Says:

        I don’t agree.

  5. I can understand the Martin point of view. However, quite apart from Peter’s earlier points on the incompleteness of falsiability arguments, there is another point to be made – which is that Charlie Martin may be looking at the question the wrong way round..

    Most physicists who study global warming say that instead of looking at a symptom (rise in global surface temperature etc) and casting around for the most likely cause, a better and simpler approach is to work from basic principles of physics. If we understand how the greenhouse effect works, and if we have established that the concentration of long-lived greenhouse gases in the atmosphere has increased by about 40% since pre-industrial levels, is there any good reason to suppose this has *not* affected global climate? That’s the basic question. Quantitatively speaking, every detailed climate model predicts that such an increase in GHG would indeed have a measureable forcing effect on climate. Once you know this, it is no great surprise to measure symptoms such as a slight rise in surface temperature, a rise in deep ocean temperature, a rise in sea level and a rise in ice-melt. This does not rule out the possibilty that some warming could also be part of a natural cycle, but that becomes something of a moot point; once a systematic change and its effect have been established there is no escaping the logic..

    • Anton Garrett Says:

      All that works fine in a dry atmosphere, and the calculation – about a century old – is an undergraduate one today. but in a damp atmosphere things are so much more complicated, due to water vapour condensing into cloud with accompanying latent heat transfer and cloud reflecting more sunlight into space than otherwise, that there is no chance of doing analytical calculations and I regard the best computer models as uncertain to the point of not being useful.

  6. I forgot to say: re falsification, actually there is a very interesting way of testing the whole greenhouse gas hypothesis, and the size of the effect. Since the 1970s, satellites have been measuring the heat emerging from our atmosphere into space. If no reduction had been observed in heat emitted at wavelengths associated with absorption by GHGs , the theory would be falsified. In fact, a pronounced dip in energy emiited at just those wavelenghts is clearly observable, a dip that has been growing steadily in tandem with the rise in atmospheric GHG concentration…quite a smoking gun

    http://www.skepticalscience.com/empirical-evidence-for-co2-enhanced-greenhouse-effect.htm

  7. Re clouds, this in indeed one of the great unknowns. However, cloud effects tend to be dynamic, rather than longlived, as you probably know. The current thinking is that cloud formation makes both a positive and negative contribution to global warming, with the negative contribution dominating slightly. I don’t see this as a reason to throw out the models, any more than one would throw out a model of the big bang when one parameter is not very well understood…

    • Anton Garrett Says:

      If you don’t know the value of the parameters then the models aren’t much use at predicting (as we have been finding out). And that is supposing that they take all relevant factors into account.

  8. My understanding is that it’s more a question of a systematic rise over many decades in many different observables such as surface temps, ocean temps, ice-melt and sea level, coupled with a drop in observables such as stratospheric temp and ir radiation into space.. The fact that the rise in the first of the four has slowed somewhat is of interest, but far from any sort of falsification because the realtion beween heat and temperature is complex, as I’m sure you know.
    In terms of a cause for such systematic changes, a measured significant increase in atmospheric GHGs is a very obvious candidate – thus efforts have focused on verifying or falsifying the theory. So far, the evidence is very much in favour of the assigning a major component of the warming to the GHG effect, within all the normal ups and downs of science.
    What is unusual about climate science is the resistance to these findings by a multitude of commentators who are not specialised in the field

  9. Addendum;I should say land-ice above, because the trend is clearer there. By the way, the point about reference periods RW makes has nothing to do with thermometers, it concerns the baseline reference chosen to measure against; of course one can portray all sorts of strange trends if one is willing to jettison agreed baselines and measure relative to an unrepresentative reference.

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