Several climate scientists have now examined the alleged errors in An Inconvenient Truth. At RealClimate Gavin Schmidt (NASA Goddard Institute for Space Studies) and Michael Mann (director Penn State Earth System Science Center) write:
First of all, “An Inconvenient Truth” was a movie and people expecting the same depth from a movie as from a scientific paper are setting an impossible standard. Secondly, the judge’s characterisation of the 9 points is substantially flawed. He appears to have put words in Gore’s mouth that would indeed have been wrong had they been said (but they weren’t). Finally, the judge was really ruling on how “Guidance Notes” for teachers should be provided to allow for more in depth discussion of these points in the classroom. This is something we wholehearted support – AIT is probably best used as a jumping off point for informed discussion, but it is not the final word. …
Overall, our verdict is that the 9 points are not “errors” at all (with possibly one unwise choice of tense on the island evacuation point).
William Connolley (British Antarctic Survey) responds to Schmidt and Mann:
I think its too kind; e.g. on SLR and Katrina Gore is misleading; on evacuation he is simply wrong. But the lake Chad bit was interesting.
Michael Tobis (University of Texas Institute for Physics) writes:
I’ve watched the relevant scenes, and though I find the polar bear sequence a bit silly, I can find nothing whatsoever wrong with what Gore says in substance or in emphasis in eight of the nine cases.
The troublesome case is where Gore says:
“that’s why the citizens of these Pacific nations have all had to evacuate to New Zealand”
There is certainly no case where all the inhabitants of a nation have evacuated, to date, although the prospect does not seem remote. This astonishing fact does not seem to faze the critics of the movie in the least. …
Arguably, there is some subset of Pacific Islanders who have ‘all evacuated’ in the loose, emphatic sense of ‘all’. I can certainly imagine a context in which the statement, with a little slack for Gore’s vernacular, would be reasonable. …
Other than that out-of-context evacuation comment, I can see nothing wrong with what Mr. Gore said or how the film presented it.
In fact the judgement systematically refers to “errors” (using
inverted commas, which the media have generally ignored), and has some
wise words to say on the distinction between presenting and promoting
partisan views, and the balanced presentation of controversial issues
(which he decides does not require equal “air-time” for views which
are held only by small minorities). However, in his analysis of the
“errors”the judge has also expressed unwarranted confidence on
several issues which are still the subject of considerable uncertainty
among the scientific community. It would be fair to say that Al Gore
presents the more extreme (concerned) end of the range of scientific
opinion on several issues, and implies stronger evidence than is fair
on several others. However, overall the film still achieves an
exceptionally high standard of scientific accuracy, and it is
regrettable that the judge has triggered a media storm by the
injudicious use of the term “errors”. Lawyers know not to rely on
ordinary commas to make their meaning clear; now judges must learn not
to rely on inverted commas either. …
Overall evaluation from John Shepherd: In only three cases [lake
Chad, Katrina, drowning polar bears] can it realistically be argued
that the film presents an overstated or unreasonable argument, and in
only one case (hurricanes) is that in relation to a major issue. In no
case is there a scientific “error” as such. In three cases [sea level
rise, thermohaline circulation, Kilimanjaro] Gore presents a view
which represents the more extreme end of the range of scientific
uncertainty. In the remaining three cases the Gore presentation is
essentially correct. To refer to “nine scientific errors” is therefore
itself a very considerable misrepresentation of the facts.
Endorsement by Chris Rapley: The view of climate scientists with whom
I have spoken (and my view also) is that Al Gore’s grasp of the
climate change issue is remarkable, and his ability to communicate it
quite exceptional. Having said this, there are some points Al makes in
Inconvenient Truth which a scientist would generally hedge with
caveats or avoid, because they are scientifically controversial,
uncertain, or too complicated to explain accurately and
succinctly. The snows of Kilimanjaro are a good example. As is the
case for almost all localised or regional climatic changes, the loss
of the ice cap has not formally be attributed to human actions. That
does not mean that it is not – simply that convincing evidence for the
link has not been presented. Even so, expert scientists working on the
issue have their views, and it seems that in this case Al’s comments
may have been influenced by these. The other issues raised in the
court case are to a greater or lesser degree of the same nature. The
bottom line, as the judge noted, is that the message delivered by Al,
that climate change is real, now, and driven mainly by humans, is
“broadly correct”. John Shepherd’s excellent detailed analysis of the
issues addressed by the judgement comes to the same conclusion. I am
pleased to endorse and recommend John’s evaluation.
Stung by the criticism he received for not doing any fact checking on the judge’s decision, Michael Dobbs did what he should have done in the first place and checked with a climate scientist, Martin Parry (Co-Chair IPCC, Working Group II). Parry felt that the judge was right about Kilimanjaro, lake Chad and thermohaline circulation, and “technically correct” on Katrina and coral bleaching. Dobbs also had a comment from a NOAA coral reef scientist who backed Gore on coral bleaching.
While there is some disagreement amongst the scientists, if you look at the details, much of the disagreement is not about the science, but about what Gore said, and what counts as an error. This was not helped by the media misreporting the judge’s findings as “AIT has nine errors”, when the judge actually found that there were nine points which were either errors or departures from the mainstream. (The judge doesn’t say which were which, but a little reading between the lines suggest that he thought that sea level rise and evacuation were errors and the other seven were departures from the mainstream.)
So let’s look at the score on each of the nine points:
Sea-level rise: Four votes for Gore. Shepherd and Rapley say he has scientific support but at the extreme end of uncertainty, while Connolley thinks that Gore is misleading on this point. The difference of opinion here seems to be about what Gore said or implied. The judge and Connolley think that although Gore doesn’t say it, he implies it will happen in the immediate future. While I would have preferred that Gore had said something like: “We don’t know how long the ice sheets will take to melt, maybe it will be 100 years, maybe it it will be a 1000”, I don’t think that it would have made much difference to the impressions gained by viewers of the movie. In any case, all the scientists agree that this is not an scientific error.
Island evacuation: Five votes for Gore. Tobis says it’s an editing error, while Connolley thinks that Gore is simply wrong. The differences here aren’t about the science but about how to interpret what Gore said. Connolley takes the strictest interpretation, while the others are more generous.
Thermohaline circulation: Three votes for Gore. Shepherd and Rapley say he has scientific support but at the extreme end of uncertainty, Connolley thinks that Gore is misleading on this point, while Parry says the judge is correct. Again, the difference is not about the science, but how to judge what Gore said. The people voting for Gore say that he is correct to say that it’s a possibility, while the ones saying that he is extreme/misleading think that his presentation makes it appear more likely than it is. I would have preferred that he had said that this was a possibility and not something that is likely, but I suspect that this would have made little difference to viewers. In any case, this certainly is not an scientific error.
Graph of CO2 vs temperature: Unanimous agreement that Gore is right and the judge is wrong.
Snows of Kilimanjaro: Three votes for Gore. Shepherd and Rapley say he has scientific support but at the extreme end of uncertainty, Connolley thinks that it is uncertain that the receding glacier is because of global warming, while Parry says the judge is correct. Once again the differences aren’t about the science, but how strictly you judge what Gore said. They all agree that mountain glaciers are receding worldwide because of global warming, and that there is scientific evidence that Kilimanjaro is also receding because of global warming. I think that there were better examples he could have chosen, but it makes no difference to his main point. In any case, this certainly is not a scientific error.
Drying lake Chad: Four votes for Gore. Shepherd and Rapley and Parry say that the judge is correct. Again, everyone agrees that there is scientific evidence that global warming is partially responsible for the drying — the differences seem to be about whether the evidence is strong enough fir Gore to use it as an example. In any case, this certainly is not a scientific error.
Katrina: Three votes for Gore. The other four agree with the judge. This one is also about how you interpret Gore. He never says that warming caused Katrina. Katrina is used as an example of the damage that stronger hurricanes could do and of the consequences of ignoring warnings from scientists. The scientists voting for the judge think he implies it. In any case, this certainly is not a scientific error.
Drowning polar bears: Five votes for Gore. Shepherd and Rapley agree with the judge, but they don’t seem to be aware of the study that supports Gore here. In any case, this certainly is not a scientific error.
Coral bleaching: Six votes for Gore. Parry says that the judge might be technically correct. I think that this one goes for Gore.
Overall, there were only three points where a majority felt that the judge was right: thermohaline, Katrina and Kilimanjaro, and none of these were scientific errors, but rather cases where Gore should have said a little more about what was going on.