So Informative

This is a hasty post as I'm currently living in fear for my life from some wasps that keep harassing me. I just wanted to throw it up on here because I think it's funny. Read this statement:

The figure above shows model runs for the A1B scenario (which is the only scenario with model runs readily available, though its 2016 CO2 concentrations are nearly identical to those of the A2 scenario). AR4 projections between 1970 and 2016 show warming quite close to observations, only 8% higher.

This was in regard for a 2007 set of climate models. It turns out models used for a 2007 report managed to get temperatures largely correct for the period of 1970-2016. Who would have guessed?

You can see the full article in question here if you want to. If you do, you'll see it claims to examine how good a job climate models of the past have done. There are a number of technical I would raise problems with what they've done, but I don't know how worthwhile it would be. I mean, the central result of the article is given in this table:

Which says things like, climate models used for a 2013 report did a decent job of projecting temperatures from 1970-2016. I think we'd all be shocked if that weren't true. If you're looking at projecting temperature change over a ~45 year period and you already know the results for more than three decades, you better do a pretty good job.

The article also provides visual comparisons, explaining:

(Note, these model/observation comparisons use a baseline period of 1970-1990 to align observations and models during the early years of the analysis, which shows how temperatures have evolved over time more clearly.)

Climate models are run by people who know what the climate has been like. If model hindcasts end in 2000, why not have the model and observed temperature series aligned at 2000? That would show how the models change compared to hwo the temperature series change. That has obvious value. Maybe other decisions are justifiable as well, but why would you ever use the 1970-1990 period? (And why 21 years anyway?)

And why would you write this as your final paragraph:

Environmental scientist Dana Nuccitelli helpfully provided a list of past model/observation comparisons, available here. The PlotDigitizer software was used to obtain values from older figures when data was not otherwise available. CMIP3 and CMIP5 model data was obtained from KNMI Climate Explorer.

With a link for the word "here" which doesn't link to any actual webpage or reference. The link's URL is:

https://skepticalscience.com/search.php?Search=Predictions_150

Which is a dynamically created webpage in response to a search query, "Predictions_150." It is fairly bizarre to offer search queries as references since they link to a page which doesn't exist (as it is created only when the user visits it) and will necessarily change over time without any record.

But most importantly, and this is me burying the lede as hard as I can because I don't really feel like having a discussion of the point, why does the article say something the authors must know is incredibly misleading? The article says of one projection it considers:

Broecker also did not take other greenhouse gases into account in his model. However, as the warming impact from methane, nitrous oxide and halocarbons has been conveniently cancelled out by the overall cooling influence of aerosols since 1970, this does not make that large a difference.

It is true greenhouse gases other than carbon dioxide would be expected to contribute to warming. It is also true aerosols are believed to have reduced the amount of warming we have seen. However, it is completely and utterly inappropriate to claim greenhouse gases other than carbon dioxide have "been conveniently cancelled out by the overall cooling influence of aerosols since 1970...."

The reason that is inappropriate is we don't know how strong the impact of aerosols have been. There is a great deal of uncertainty on that issue. It is currently one of the most crucial issues in the study of global warming. The latest Intergovernmental Panel on Climate Change ,a href="https://www.ipcc.ch/pdf/assessment-report/ar5/wg1/WG1AR5_Chapter08_FINAL.pdf">says this of it:

The RF due to aerosol–radiation interactions, sometimes referred to as direct aerosol effect, is given a best estimate of –0.35 (–0.85 to +0.15) W m–2, and black carbon (BC) on snow and ice is 0.04 (0.02 to 0.09) W m–2. The ERF due to aerosol–radiation interactions is –0.45 (–0.95 to +0.05) W m–2. A total aerosol–cloud interaction5 is quantified in terms of the ERF concept with an estimate of –0.45 (–1.2 to 0.0) W m–2. The total aerosol effect (excluding BC on snow and ice) is estimated as ERF of –0.9 (–1.9 to –0.1) W m–2. The large uncertainty in aerosol ERF is the dominant contributor to overall net Industrial Era forcing uncertainty.

RF stands for radiative forcing, a measure of how much impact things have on the planet's energy imbalance, which in turn is used to estimate their effect on global temperatures. The RF given by the IPCC for greenhouse gases other than carbon dioxide is approximately ~1.0 (for carbon dioxide alone, it is ~1.8) 1.0 is approximately the middle-point of the IPCC range, meaning it could be aerosols have conveniently cancelled out the warming influences of those other greenhouse gases.

But "could be" is not "has." It might be aersols have cancelled out the warming influence of those other greenhouses gases. Or they might had a negligible effect as the uncertainty range for the overall impact of aerosols extends almost to 0. Or it might be that aerosols have not only canceled out those greenhouse gases but also canceled out a significant portion of the impact carbon dioxide has.

If aersols have had an RF of -.1, then they would have cancelled out only 10% of the impact of those other greenhouse gases. If aerosols have had an RF of -1.9, then they would have cancelled out the ~1.0 RF of the other greenhouse gases and .9 of the ~1.8 RF of carbon dioxide. Either of those scenarios is acknowledged as possible by the climate science community as a whole. As are all the possibilities in-between. This article ignores all of them.

The author of this article knows everything I just said. He might know it better than I do. I don't know why he'd do something like tell us how models initialized to 2005 perform over the period of 1970-2016 when that ~45 year period includes ~35 years where the modelers used actual, measured data. I don't know why this author would state with certainty the effect of aerosols, the issue which may well have the greatest amount of uncertainty in understanding global warming.

What I do know is some people will view this post as "nitpicking." What I also know is if you think global warming is a serious threat to humanity, you should be "nitpicking" everything that gets written about it to make sure the most accurate and best information gets out there while minimizing the amount of skepticism and confusion errors and inaccuracies can cause.

I don't know that anyone advocating for action to address global warming would care about the points raised in this post. I don't even know that "skeptics" would. What I do know is every time I open a new article by such and such researcher with obvious problems and even outright misrepresentations, I dismiss global warming concerns a bit more.

If people tolerate shoddy work on the obvious stuff, I have no reason to think their standards are higher for work which takes more effort to examine. If global warming is a major threat to humanity, the last thing anyone should do is tolerate shoddy work. These two points combined show why I scoff at global warming advocates.

5 comments

  1. The author is Dana Nucitelli. He has a history of producing work of the same quality as Lewandowsky (including involvement in Cook 2013). Far be it for me to shoot the messenger, well, at least not until after the message has been proven to be rubbish... 😀

  2. The author isn't Dana Nuccitelli. It's Zeke Hausfather. Zeke thanks Dana at the end of the post for providing references (as quoted in my post), but otherwise, Dana isn't connected to this piece.

    By the way, Zeke responded to me on Twitter saying:

    Brandon, the point I was making was that a CO2-only estimate from the 70s will be reasonably accurate since aerosols largely offset non-CO2.

    Not that aerosols exactly cancel non-CO2 GHGs 100% all the time with no uncertainty...

    While I have no reason to believe his intended point was anything other than he says, it is clearly not what he wrote in his piece. My response was:

    And you could have easily made that point by saying using a phrase like, "some or all." You didn't. You stated a totality, with certainty.

    If that wasn't your intent, okay. You made a mistake. Mistakes can be called and fixed.

    It should be interesting to see if he directly acknowledges what he wrote was incorrect and tries to fix it. I'm cynical so I expect he won't. I expect neither he nor anyone else who recognizes what he wrote was incorrect/misleading to do a thing about this. That's been the result in most cases in my experience. My experience is people usually refuse to squarely deal with errors/mistakes.

    But I hope to be pleasantly surprised.

  3. Believe me, there are few negative things you could say about Dana Nuccitelli I wouldn't agree with. Of all the Skeptical Science members, I would rate him the most dishonest.

  4. Perhaps Zeke was making a Freudian slip or Kinsleyan gaffe, that aerosol effect is an input parameter used to tune the output of the model.

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