On “the real holes in climate science”

[This post is based on a question I got in response to a previous post but thought it deserved a short post on its own as there’s a few interesting points.]

There’s been a lot of bad press recently for climate science but a lot of has focused on very minor issues. For example, most of the coverage on the UEA CRU email leak/theft/hack (so-called climategate) has focused on what some of the “skeptic” community wished was in the emails rather than what was really there. The Guardian has gone over some of the issues from the leak in depth in a recent series of articles, although this seems like a lot of focus on old issues. As Prof. Phil Jones himself said in a recent interview in The Sunday Times: “I wish people would read my scientific papers rather than my emails”. Glaciergate was equally blown out of all proportion given that the original claim only appeared in one sentence in a 3000 page report.

In the midst of all this, Nature printed a nice feature looking at the real big gaps in climate science (Schiermeier 2010), but it is behind a paywall, which is a shame because it’s a good piece. So, I thought I’d provide a very quick summary here.

Regional climate prediction

We still don’t have sufficient computing power to run models at high enough resolution to make projections on the scale that would be useful to policy makers. This is clearly required to make big infrastructure decisions.


Projections of precipitation patterns are really hard to make as they depend on temperature changes, circulation changes, radiative balance changes and pollution (and, therefore, cloud condensation nuclei) changes. Yet precipitation changes will probably have the biggest impact on society.


The effect of aerosols (i.e. small solid particles or liquid droplets suspended in the atmosphere) is a big unknown. Different types do different things and its not really certain whether they have a generally cooling effect – by reflecting away solar radiation – or a warming effect – by promoting more cloud growth and trapping more terrestrial heat. That said, any cooling effect would be very unlikely to reverse the warming impact of greenhouse gases.

The tree-ring controversy

This relates mostly to the “hockey stick” graph and the reliability of the palaeoclimate data we use to put our current climate into perspective. It’s important that we learn from past climate changes as we only have one atmosphere and can’t do experiments with it. But it is not easy to get palaeoclimate data (tree rings, ice cores, sediment cores) or to interpret them properly.

So what is the “consensus”?

In a certain sense, when people talk about the “scientific consensus about climate change” they really mean little more than our understanding of the greenhouse effect, our impact on it and that things are very likely to get messy in the future. All the details are still very much under investigation.


ResearchBlogging.orgSchiermeier, Q. (2010). The real holes in climate science Nature, 463 (7279), 284-287 DOI: 10.1038/463284a

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10 Responses to “On “the real holes in climate science””

  1. Lite om de verkliga problemen som klimatforskningen dras med « Geobastard Says:

    […] en GLOBAL uppvärmning. Sverige är ju världen!) Artikeln ligger bakom Natures betalsystem men en geolog på nätet har vänligen sammanfattat de viktigaste punkterna. In the midst of all this, Nature printed a nice […]

  2. scienceofdoom Says:

    On aerosols, you said: “That said, any cooling effect would be very unlikely to reverse the war[m]ing impact of greenhouse gases.”

    And yet AR4 (2007) proclaims we have now increased to a “medium low level of understanding” of aerosols, and puts the range of impacts between zero and cancelling out the radiative forcing from CO2.

    Who knows how TAR (2001) with a “very low level of scientific understanding” of aerosols (their words) could have been so confident.


    My belief is that the attempts to claim more certainty for the science than is actually there is one of the biggest causes of AGW skepticism among the scientifically literate. Better to explain the gaps. The risks. The likelihoods. Anyway just a comment.

    • andyrussell Says:

      Ok, I’m not an expert on aerosols so here is the key figure on radiative forcing from the IPCC report (which doesn’t have an indication understanding level apart from the errors bars, which are large for aerosol direct and indirect effect). The important point is that even with those large error bars on aerosols, the range of the “Total net human activity” is entirely on the positive side of the plot:

      Radiative forcing from IPCC AR4

      There’s much more info on the relevant pages of the IPCC WG1 report.

      • scienceofdoom Says:

        I think the reason that the range bars on the “total net” comes out as an only positive range comes down to how the “net range” is calculated.

        Or perhaps it comes down to the politics..

        Do you really think that – First – with error bars so large, that we are accurate on the error bars? And, Second – that we can just do a root mean square or some such calculation on errors to work out the real unknown range? We aren’t working out the means and standard deviations of independent rolls of a pair of dice. We can assume we are but it’s just a statistical assumption that we don’t actually know is true.

        That’s really my point. Aerosols are not well understood, their effect is a negative, possibly large enough to wipe out CO2 warming – according to those IPCC skeptics.

        But you appear to be saying well, hold on, if we add on tropospheric ozone, CH4, N2O and halocarbons as well as the solar irradiance unknown the aerosol unknown isn’t *quite* negative enough..

        Are we splitting hairs or making progress?

        The problems for the outsiders, like me, is we read the chapters, we think, ok nice summary of the science so far very interesting work, then we read the confident conclusion and think that we are reading politics not science.

        I’m not saying that aerosols will wipe out CO2, I have no idea, maybe they will do nothing. The science is not “settled”.

        (And as a footnote: The science is very clear on the radiative forcing of CO2, I am a total believer. I think the error bars are spot on and getting smaller because it is well-understood physics with very few places of ignorance).

      • andyrussell Says:

        Well, the theme of the post was the holes in climate science. I don’t see a problem in admiting that aerosol science is not well understood. Maybe the IPCC presentation of it isn’t perfect.

      • scienceofdoom Says:

        I wonder why Nature didn’t mention the biggest gap (or maybe you precised their article?)

        The ghosts of climates past. Although I do hear a lot of “consensus” people saying how well understood the mechanisms behind past climate change are. But I have read a few papers and the writers didn’t profess the same confidence. Was it the Milankovitch cycles, can that slight increase in insolation at 65’N really explain it? Or was it the melting of the Laurentide ice sheet? Or other changes in the global ocean circulations? Or solar changes? What caused these big cold snaps, and then the warm snaps?

        Perhaps it’s just the fact that reconstructing past climate is so difficult that the answers are harder to come by, but if you had to pick a top three from the skeptics this would definitely be there.

        Then you have the related problem of the predictability of climate – like the THC. When will it change direction? Do the current GCMs incorporate it? No. So it won’t happen in the next 100 years? Maybe. We’re not sure when or if.

        Ok, I’m paraphrasing and perhaps out of touch with climate scientists. Maybe when and how the THC changes direction is all nailed now. But the climate predictability problem would be top 3 among the skeptics.

      • andyrussell Says:

        The Nature feature had 4 themes. The final one – The Tree Ring Controversy – discussed most palaeoclimate sources but concentrated on the hockey stick and divergence as it related to the CRU emails more. I absolutely agree that non-linear feedbacks are very difficult to understand but that isn’t a good reason to write off the whole of palaeoclimatology.

        Taking a step back, sure, it’s not easy to interpret these palaeo sources but I still find it amazing that we can know anything about past climates! It is really clever. Some of the details need a bit of work but the field as a whole adds something to the climate change debate.

  3. scienceofdoom Says:

    I also think you missed the biggest gap, but maybe that is Nature’s fault..

  4. Accretionary Wedge #22: Flash Wedge! « The Accretionary Wedge Says:

    […] a post from Andy Russell summarizing where the real holes are in climate science: https://andyrussell.wordpress.com/2010/02/10/on-the-real-holes-in-climate-science/ (Hint: It’s not what the cranks would have you […]

  5. IPCC AR5 WG1 author shake up « Our Clouded Hills Says:

    […] and aerosols” get their own chapter and regional climate change is mentioned, which are key areas that need addressing. Irreversibility is also now […]

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