Book review: Cool It: The Skeptical Environmentalist’s Guide to Global Warming by Bjørn Lomborg.
This book eloquently counters many popular myths about how much harm global warming is likely to cause, but is sufficiently partisan and one-sided that it will do more to polarize the debate than to resolve disagreements. Many of his criticisms of the alarmists are correct. Reading this book in combination with writings of his opponents will give you a much better perspective than reading only one side of this debate.
Selective reporting gives the impression that global warming is causing more deaths, but Lomborg reports that warming will cause reduced deaths for the foreseeable future, mainly through reduced cold-related cardiovascular deaths. He claims warming won’t cause a net increase in deaths until at least 2200, but I expect that uncertainty about medical innovation makes predictions more than a few decades ahead not credible. Even for the next few decades, he exaggerates the evidence. What he calls “The first complete survey for the world” covers the entire world, but only tries to model the effects of the 6 types of disease for which global information is available, and its authors clearly deny knowing whether other diseases have important effects. Lomborg claims there will be 1.4 million fewer deaths in 2050 due to global warming, but he seems to get that number from the effects of only two disease types, whereas the paper he cites predicts 849252 fewer deaths from 6 disease types.
He is often too dismissive of the possibility of technological improvements. For instance, he claims that sticking to Kyoto commitments through the 21st century “would get ever harder”, yet I can imagine a variety of ways it could get easier. He mentions specific dollar costs for complying with Kyoto for a century without hinting at the large uncertainties in those guesses.
In one place he analyzes Kyoto as if it were a foreign aid program, and says that it would do 16 cents of good in developing countries for every dollar spent. I assume he considers this an argument against Kyoto. Since 16 cents might help a person in a developing country more than a dollar helps a person in a developed country, and there is some reason to suspect that few large aid programs are more than 16 percent efficient, it could easily be considered a weak argument for Kyoto.
Sometimes he’s blatantly careless, such as when he talks about “reducing [hurricane] damage by almost 500 percent”.
He appropriately criticizes the Stern report’s use of a suspiciously low discount rate (which has major implications for how much we should do now), but he doesn’t provide a clear explanation of that issue, nor does he say what his preferred model uses (a review on Salon says it uses a 6 percent discount rate, which I suspect only makes sense if we assume a higher economic growth rate than most experts expect).

Book review: An Inconvenient Truth: The Planetary Emergency of Global Warming and What We Can Do About It by Al Gore
I read An Inconvenient Truth in book form rather than watching the movie because I’m generally suspicious of attempts to convey serious arguments via film, and expected that the book version would have better references to the sources of his claims. Alas, this is merely a movie copied to paper, and his idea of a technical reference is a label such as “source: science magazine”.
This may be more scholarly than what a typical politician would produce, but it’s poor scholarship compared to what I’d expect from a typical college professor, even allowing for the goal of reaching a wide audience by keeping it simple.
The book is full of exaggerations and misleading impressions (but is usually not explicit enough to be clearly false). It is hard to say whether the book is helping by offsetting myths from the other extreme or whether it is adding to the confusion. Gore does deserve some credit for bringing more attention to a fairly serious problem.
Much of the book is pictures showing examples of climate changes, which don’t by themselves say whether we’ve experienced anything more than normal fluctuations. The movie may have reached people who thought climates were more stable than that, but I doubt the book will.
His main attempt to show evidence that CO2 emissions cause warming is a graph showing CO2 levels and temperature over the last 600,000 years. It sure looks like there’s a strong correlation. But my crude attempts at comparing the timing of the changes suggest that temperature changes precede CO2 changes more often than they follow them. I can imagine ways that the correlation could be caused by temperature changes causing changes in CO2 levels. I don’t see how a non-expert can tell what this correlation implies except by relying on authority (experts seem to think the causation works in both directions).
So that leaves him with only appeals to authority to back up his claims. He’s more credible there. His claim of a scientific consensus is approximately right. He lists the “percentage of articles in doubt as to the cause of global warming: 0%”. The paper he’s apparently referencing is responsible enough to use words such as “likely” rather than claiming an absence of doubt. Peter Norvig‘s analysis of some of those papers concludes at least 4 of those papers expressed doubt. But that difference is probably too subtle to matter to the people this book is targeting.
Gore is quick to blame big oil for the popular press’s false impressions of scientific controversy. The possibility that controversy sells stories appears to be at least as strong an explanation, but blaming the people Gore’s trying to convince would be rather inconvenient.
Pages 183 to 196 appear designed to create fears that sea levels could rise 18 to 20 feet suddenly and unpredictably. He doesn’t say anything about how fast experts think this might happen (which seems to be over many decades). The hints he gives are the mention of an ice shelf than unexpectedly broke up in 35 days, and some maps Greenland which appear to suggest the ice there could vanish in the next decade. The difference between an expected sea level rise over many decades and an unexpected rise over less than a decade makes a big difference in how well people could adapt to it. (The mass migrations in China recently demonstrate the feasibility of adapting to sea level changes in a decade or two). Gore appears to be contributing to fears of changes that are way outside the expert consensus.
Gore underestimates human ability to adapt to climate change (much as those on the other extreme underestimate human ability to invent affordable ways to reduce carbon emissions). For example, he implies that quick efforts to mitigate global warming are the only way to deal with the risks of drinking water shortages. But I see signs that cheaper desalinization is a more promising approach.
His graph on page 276 of “U.S. renewable energy future” is strange. Renewability has a weak connection to global warming solutions, but the possibility that nuclear power might be desirable seems too inconvenient to him. His forecast for biomass looks too optimistic, his forecast for solar after 2020 looks too pessimistic, and his forecast for wind shows strange fluctuations.
Gore repeats the myth that frogs won’t jump out of water that’s slowly brought to a boil, and claims that sometimes people make the same mistake. “Sometimes” is too uninformative to refute, but the most relevant research that I can think of suggests that at least political experts are biased toward sounding alarms too often.
He claims it’s “absolutely indisputable” that global warming is a “planetary emergency”. Yet nothing he says implies that stopping global warming is as urgent as reducing poverty, war, or disease.
Ph.D. economists seem fairly confident that the effects of global warming will be small.
There are substantial disputes among experts about how much of the global warming problem we should try to solve now (see Hal Varian’s comments, Tyler Cowen’s comments and Arnold Kling’s comments). But you won’t find any hint of that controversy in An Inconvenient Truth (in part because it’s hard to describe in ways that laymen can understand).
Gore recommends doing many things to slow down global warming a bit (but may leave many with the impression that his plans would do more than that – if it were an emergency as he says, wouldn’t he recommend more?).
Some of these steps are clearly good even if their effects on the climate are trivial.
For some (recycling and locally grown food) I’ve seen conflicting claims and can’t tell whether objective analyses exist.
Some are misleading. He claims a “fuel-cell vehicle (FCV) that uses pure hydrogen produces no pollutants”, which would be true if we had a convenient source of pure hydrogen. But on this planet, hydrogen requires energy to create, and only acts as a battery, so FCVs cause pollution if energy production causes pollution.
I recommend Ron Baily’s review for additional criticisms.
Disclosure: I own stocks in oil companies and in a company that serves the photovoltaic industry.