by Eric Steig

Along with various Seattle business and community leaders, city planners and politicians, a large group of scientists from the University of Washington got a chance to preview the new film, An Inconvenient Truth, last week. The film is about Al Gore’s efforts to educate the public about global warming, with the goal of creating the political will necessary for the United States to take the lead in efforts to lower global carbon emissions. It is an inspiring film, and is decidedly non-partisan in its outlook (though there are a few subtle references to the Bush administration’s lack of leadership on this and other environmental issues).

Since Gore is rumored to be a fan of RealClimate, we thought it appropriate to give our first impressions.

Much of the footage in Inconvenient Truth is of Al Gore giving a slideshow on the science of global warming. Sound boring? Well, yes, a little. But it is a very good slide show, in the vein of Carl Sagan (lots of beautiful imagery, and some very slick graphics and digital animation). And it is interspersed with personal reflections from Gore that add a very nice human element. Gore in the classroom in 1968, listening to the great geochemist Roger Revelle describe the first few years of data on carbon dioxide increases in the atmosphere. Gore on the family farm, talking about his father’s tobacco business, and how he shut it down when his daughter (Al Gore’s sister) got lung cancer. Gore on the campaign trail, and his disappointment at the Supreme Court decision. This isn’t the “wooden” Gore of the 2000 campgain; he is clearly in his element here, talking about something he has cared deeply about for over 30 years.

How well does the film handle the science? Admirably, I thought. It is remarkably up to date, with reference to some of the very latest research. Discussion of recent changes in Antarctica and Greenland are expertly laid out. He also does a very good job in talking about the relationship between sea surface temperature and hurricane intensity. As one might expect, he uses the Katrina disaster to underscore the point that climate change may have serious impacts on society, but he doesn’t highlight the connection any more than is appropriate (see our post on this, here).

There are a few scientific errors that are important in the film. At one point Gore claims that you can see the aerosol concentrations in Antarctic ice cores change “in just two years”, due to the U.S. Clean Air Act. You can’t see dust and aerosols at all in Antarctic cores — not with the naked eye — and I’m skeptical you can definitively point to the influence of the Clean Air Act. I was left wondering whether Gore got this notion, and I hope he’ll correct it in future versions of his slideshow. Another complaint is the juxtaposition of an image relating to CO 2 emissions and an image illustrating invasive plant species. This is misleading; the problem of invasive species is predominantly due to land use change and importation, not to “global warming”. Still, these are rather minor errors. It is true that the effect of reduced leaded gasoline use in the U.S. does clearly show up in Greenland ice cores; and it is also certainly true that climate change could exacerbate the problem of invasive species.

Several of my colleagues complained that a more significant error is Gore’s use of the long ice core records of CO 2 and temperature (from oxygen isotope measurements) in Antarctic ice cores to illustrate the correlation between the two. The complaint is that the correlation is somewhat misleading, because a number of other climate forcings besides CO 2 contribute to the change in Antarctic temperature between glacial and interglacial climate. Simply extrapolating this correlation forward in time puts the temperature in 2100 A.D. somewhere upwards of 10 C warmer than present — rather at the extreme end of the vast majority of projections (as we have discussed here). However, I don’t really agree with my colleagues’ criticism on this point. Gore is careful not to state what the temperature/CO 2 scaling is. He is making a qualitative point, which is entirely accurate. The fact is that it would be difficult or impossible to explain past changes in temperature during the ice age cycles without CO 2 changes (as we have discussed here). In that sense, the ice core CO 2 -temperature correlation remains an appropriate demonstration of the influence of CO 2 on climate.

For the most part, I think Gore gets the science right, just as he did in Earth in the Balance. The small errors don’t detract from Gore’s main point, which is that we in the United States have the technological and institutional ability to have a significant impact on the future trajectory of climate change. This is not entirely a scientific issue — indeed, Gore repeatedly makes the point that it is a moral issue — but Gore draws heavily on Pacala and Socolow’s recent work to show that the technology is there (see Science 305, p. 968 Stabilization Wedges: Solving the Climate Problem for the Next 50 Years with Current Technologies).

I’ll admit that I have been a bit of a skeptic about our ability to take any substantive action, especially here in the U.S.

Gore’s aim is to change that viewpoint, and the colleagues I saw the movie with all seem to agree that he is successful.

In short: this film is worth seeing. It opens in early June.