Down the up escalator: cherry picking for the global temperature trend you want

Here is a graph I’ve wanted for a long time.  It shows how you can get the answer you want out of the global temperature data series.  Just pick the right start and finish point and, presto, the temperature is rising, or falling, or flat.

It’s why denialists keep insisting that global warming stopped in 1998.

Courtesy Skeptical Science: http://www.skepticalscience.com

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9 thoughts on “Down the up escalator: cherry picking for the global temperature trend you want

  1. Hugh

    Name one prominent “denialist” who, contra the soi-disant “realists”, denies there has been global warming since the 1970’s.

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  2. Hugh

    And:
    Robert K. Kaufmann, Heikki Kauppi, Michael L. Mann and James H. Stock:
    “Given the widely noted increase in the warming effects of rising greenhouse gas concentrations, it has been unclear why global surface temperatures did not rise between 1998 and 2008.”
    “Reconciling anthropogenic climate change with observed temperature 1998–2008” PNAS July 5, 2011

    So Michael Mann is a “denialist”, too?

    As an interested spectator of the debate, I’m not qualified to pontificate as to whether or not there has been warming over the last 10 to 15 years, let alone whether it’s been a warming that is significant from an AGW perspective. But my suggestion would be: if we eliminate terms like “denialist”, with its negative historical connotations, there might be room for more constructive dialogue on this issue. Assuming we want constructive dialogue of course.

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  3. Pingback: Cherry Picking 2 | Better Nature: commentary by Geoff Davies

  4. Geoff Davies Post author

    Hugh – Bob Carter. See my more recent post.

    One loose comment does not invalidate everything. I think these people would concede it was a loose comment, unlike many “sceptics”.

    I use the term “denialist” for people who deny what the observations obviously say. There is plenty of room to debate the details of climate science, but claims that global warming has stopped, or that there is no evidence we are causing it, are not consistent with observations, as you can read in my post “Still warming …”

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  5. Hugh

    Thanks, Geoff.

    1. Bob Carter denies there has been global warming from 1973? Quotes, please (forgive me, but I can’t see how your subsequent post establishes this – it’s all about the last decade or so, as far as I can tell). If he does, he’s a very unusual “denialist”. Most “denialists” I’ve read concede warming over that time, and to me rightly so. But I’m prepared to be corrected.

    2. So there are “loose comments” in peer-reviewed pieces on global warming? (Note too that the “loose comment” is in fact the fundamental premise of an entire peer-reviewed treatise.) How are us muggins to sort out what’s loose-comment-dross and what’s gold-standard-science in peer-reviewed articles? Tony Abbott’s ridiculed distinctions between verbal interviews and what’s written down don’t seem to apply. 🙂

    3. Re. use of the term “denialist” – your response begs the question. If locked-on AGWers such as Michael Mann can make “loose comments” about a pause in the warming (in peer-reviewed articles, with colleagues), doesn’t that suggest there may be at least some doubt about whether warming has proceeded apace over the past decade or so? (I make these comments having read, but not been convinced by, the subsequent post. Disclosure – I’m not a scientist.)

    Cheers,

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  6. Geoff Davies Post author

    Since 1973? Well it’s true I don’t know anyone saying that, and I didn’t imply anyone was.

    Science progresses by self correction. There is always room for doubt.

    As I have written more than once on this site, the issue for the world is not whether every last smidgin of doubt has been removed, because then it will be far too late. The issue is “What is our best estimate of the prospect of global warming”. The IPCC provided a rather conservative answer – it is highly likely.

    See my comment after Cherry Picking 2. I don’t propose to continue this seminar.

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  7. Hugh

    Dr Davies, thanks – I’m relieved re. your statement about Bob Carter & other ‘denialists’.

    The implication is not from your own words, but from the graphs, taken together with their titles. One of the two graphs is headed “How Realists View Global Warming” and it shows the trendline rising from 1973. The manifest implication of the title is that “Denialists/skeptics” don’t accept this graph/trendline. But they do – as you’ve rightly acknowledged. The correct title of that graph should be something rather more underwhelming: “How Realists and Denialists view global warming since 1973”. True, the denialists also see significance in the latest non-warming phase of the second graph – so the second graph (possible with the last trendline going back to 1998 as per Mann &c above) is to that extent reasonably captioned. It’s not logically incompatible for them to acknowledge both graphs. But the juxtaposition of the two graph/trendlines, with the titles, certainly misrepresents their position and is not helpful to the debate. I appreciate your forbearance – I don’t intend to harass, and take the hint. All the best.

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  8. Greig

    Choosing the period from 1972 to present is also cherry picking. If you had chosen the 30 year period from 1940-1970 it would have shown that temperatures were trending downward, and this occurred while CO2 levels were rising, so demonstrating the obvious: that the correlation between CO2 and temperature has some significant complexities.

    In the future when we plot the graph from 2000-2030, will it show an upward trend? Geoff suggests that the “realists” (e.g. the IPCC) would predict that it is “highly likely”. The “denialists” would probably say that we don’t have enough information to predict the future.

    Which answer aligns better with the objective application of science? Answer: Neither. It is all just meaningless cherry-picking.

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  9. Geoff Davies Post author

    Hugh – I agree the wording on the graphs is too general – “denialists” rather than “some denialists”. Also the point of the graph is to emphasise that taking too short a window can give misleading results. The earlier steps are not to be taken literally, which I think most people would appreciate.

    Grieg – I agree 1940-1970 is a question. However it doesn’t change the 40-year trend since than that gets misrepresented by some as “global warming stopped in 1998”.

    Regarding the 1940-1970 episode, it’s mainly a northern-hemisphere phenomenon (see http://data.giss.nasa.gov/gistemp/graphs_v3/ ), which indicates it’s not “global” cooling and is why James Hansen argues for northern-hemisphere particulates being a cause. He also acknowledges the direct measurements that would confirm/test this were not funded until recently.

    We should bear in mind that the evidence for global warming is not confined to one data set. It is confirmed by independent observations (see http://www.skepticalscience.com/10-indicators-of-a-human-fingerprint-on-climate-change.html ). The most direct is the imbalance between energy arriving and energy leaving the Earth.

    If the air temperature is not rising at the moment (and La Niña tends to cool the Earth a bit), the extra heat must be going somewhere – presumably the oceans. That would fit the continuing trend of more intense storms. Either way we suffer effects. And if El Niño returns, very nasty heat, drought and fires are likely to result.

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