Al Gore's global warming movie, "An Inconvenient Truth," aims to call attention to the dangers society faces from climate change, and suggests urgent actions that need to be taken immediately. It is based on a slide show on climate Gore has presented to audiences worldwide over 1000 times in the past 15 years, but it is not purely a documentary. Gore's movie is an advocacy piece that is part documentary, part biography, and part campaign ad. I'll discuss all three of these aspects below. In brief, Al Gore has the right idea--climate change is an urgent issue that requires immediate action, and his thoughtful movie is a welcome addition to the usual array of mindless Hollywood summer fare. However, the movie has flaws. The presentation of the science is good, but not great--I rate it a B, which is the rating I give the movie as a whole. The excessive details on Al Gore's life make the movie too long, and his insistence on using the movie as something of a campaign ad detracts from its message. However, this is a very important movie, as was recognized in the 2007 Oscars, where it won best documentary. It's a movie everyone should see.
An Inconvenient Truth as a biography of Al Gore
The creators of the movie presumably thought that simply presenting Gore's slide show would be too dull, so they decided to give the movie some human interest by interweaving a biography of Al Gore's life. Al Gore has led an interesting life, but "interesting" and "Al Gore" are not words one can often put together. Al Gore is boring, and the 20 minutes or so of biography presented in An Inconvenient Truth is too much for a movie that is 1 hour and 36 minutes long. For example, I didn't really need to see the road where Al Gore totaled his car when he was 14 years old, or a replay of his loss in the 2000 election. On the other hand, some details of his past were interesting and relevant, such as the fact that he took college courses in the late 1960s from Harvard's Dr. Roger Revelle. Revelle and Dr. Charles Keeling were the pioneers in measurements of atmospheric CO2, and thus Gore got a very early exposure to the now infamous "Keeling Curve" (Figure 1), showing the build-up of atmospheric CO2. This early exposure to the significant impact humans were having on the atmosphere deeply affected Gore, and in the movie he details efforts he made to call attention to the issue long before most people had heard of it, back in the 1970s and 80s. Gore's slide show appropriately displays many graphs of the Keeling Curve, as it is probably the most important and most famous finding in climate change science.
Figure 1. The Keeling Curve is a record of CO2 measurements taken at he top of Mauna Loa volcano in Hawaii since 1958.
The science of An Inconvenient Truth
The science presented is mostly good, and at times compelling, but there are a few errors and one major distortion of the truth. Gore does an excellent job focusing on the most important issues, and usually presents them with a minimum of hype and distortion. The only exception to this comes in his treatment of global warming and extreme weather events such as hurricanes.
Basic global warming science
Gore begins the science part of his talk with a very easy to understand presentation on the basics of how the greenhouse effect works. His speech is clear, the graphics top notch, and he spices it up with a hilarious two-minute cartoon depicting roughneck global warming gases preventing poor Mr. Sunbeam from escaping Earth's atmosphere. Gore addresses the argument of skeptics who claim that the Earth is too big for humans to affect by showing Space Shuttle photos of how thin the atmosphere really is compared to the vast bulk of our planet. "The problem we now face is that this thin layer of atmosphere is being thickened by huge quantities of carbon dioxide," he asserts, which is not correct. The build-up of CO2 has virtually no effect on the density or thickness of Earth's atmosphere. The correct thing to say would have been, "The problem we now face is that this thin layer of atmosphere is being made more opaque to the transmission of infrared radiation (heat) by huge quantities of carbon dioxide."
Gore shows an impressive series of "then and now" images documenting the widespread retreat of many glaciers over the past century. Most dramatically, he shows Tanzania's Mt. Kilimanjaro, whose 11,000 year-old glaciers are almost gone. While not all the world's glaciers have retreated in the past century, Gore's presentation is an effective and reasonable way to show how global warming has affected the majority of the world's glaciers. Greenhouse skeptics, including Michael Crichton in his State of Fear book, are fond of bashing those who use Mt. Kilimanjaro as a poster child for demonstrating global warming. They cite scientific research showing that the glacial retreat on Mt. Kilimanjaro is due to drying of the atmosphere (PDF File), not global warming. However, as discussed at great length in a realclimate.org post, the research which supposedly supports the skeptics' claims has been widely misquoted and misinterpreted, and much of Kilimanjaro's melting can indeed be ascribed to warming of the atmosphere since 1960.
Gore does an excellent job discussing the Greenland and Antarctic ice caps. Again, Gore's graphics are superb, and he does a nice job narrating. He shows animations of what a 20-foot rise in sea level would do to Manhattan, Florida, India, and China. A 20-foot sea level rise is what we expect if all of Greenland or all of the West Antarctic Ice Sheet were to melt. Such a 20-foot rise is not expected by 2100, and it would have been appropriate for Gore to acknowledge that the consensus of climate scientists--as published in the most recent report by the United Nations' Intergovernmental Panel on Climate Change (IPCC)--is that sea level is likely to rise between 4 and 35 inches, with a central value of 19 inches, by 2100. He should have also mentioned that temperatures in Greenland in the 1930s were about as warm as today's temperatures, so the current melting of Greenland's glaciers does have historical precedent. Nevertheless, the risk of a catastrophic melting and break-up of the Greenland or West Antarctic ice sheets is very real, when we consider that sea level before the most recent ice age was 15 feet higher than it is now. Gore is right to draw attention to what might happen if sea level rose 20 feet.
Drought and heat waves
An excellent discussion of the most serious climate change issue our generation is likely to face, the threat of increased drought and reduced water supplies, is presented. Gore makes reference to the extreme heat wave that affected Europe during the summer of 2004, and I was glad to see that he didn't blame the heat wave on global warming--he merely said that more events of this nature will be likely in the future.
Hurricanes and severe weather
The biggest failure in the movie's presentation of science comes in the discussion hurricanes and severe weather events. The devastation wrought by Katrina is used to very dramatic effect to warn of the dangers climate change presents. We are told that Katrina grew "stronger and stronger and stronger" as it passed over the warm waters of the Gulf of Mexico that were heated up by global warming. We are told that global warming is increasing the intensity of hurricanes, but not provided information on the great amount of uncertainty and vigorous scientific debate on this issue. Graphs showing recent record insurance losses from natural disasters are presented, but no mention is made of how increasing population and insistence on building in vulnerable areas are the predominant factors causing recent high insurance claims from disasters such as Katrina. Gore points to some unprecedented events in 2004 as evidence of increasing severe weather events worldwide--the record 10 typhoons in Japan, the most tornadoes ever in the U.S., and the appearance of Brazil's first hurricane ever. However, examples of this kind are meaningless. No single weather event, or unconnected series of severe weather events such as Gore presents, are indicative of climate change. In particular, the IPCC has not found any evidence that climate change has increased tornado frequency, or is likely to. Gore doesn't mention the unusually quiet tornado season of 2005, when for the first time ever, no tornadoes were reported in Oklahoma in the month of May.
Gore presents many other important aspects of climate change, including the threat of abrupt climate change leading to a shut-off of the Gulf Stream current, the increase in damaging insect infestations and tropical diseases, loss of coral reefs, loss of ice in the polar ice cap, and melting of permafrost in the Arctic. All of these issues were presented with sound science.
An Inconvenient Truth as a campaign ad
Gore has repeatedly said that he currently has no plans to run for president again, and that this movie was created as part of his life-long passion to protect the environment. Gore undoubtedly does care very deeply about the planet, but this movie very much looks like a campaign ad. We are shown many scenes of Gore being applauded, Gore traveling the globe to present his slide show, and Gore working to uncover evidence of Republican shenanigans to alter or suppress climate change science. Gore is portrayed as a humble and tireless crusader for good. If the movie is not intended to promote his political ambitions, then it is certainly intended to benefit the Democratic Party. All this gets in the way of the movie's central message.
At the end of the movie, we are presented with the same image that Gore started the movie with, that of a beautiful river in the wilderness. Throughout the movie, Gore emphasizes how beautiful and special our planet is, and he does an effective job conveying this. He also makes a powerful case that something can and should be done to protect the planet, and it is worth hearing his message, even if the science is flawed and the messenger does get in the way of the message. Overall, the movie rates 2.5 stars--definitely worth seeing, but you might want to wait until the DVD comes out.
At the end of the movie, Gore presents some tips on how everyone can contribute, and points people to his web site, www.climatecrisis.net. However, I would recommend that people who want to get educated about climate change get their information from web sites not associated with a politician; perhaps the least politicized source of information is the latest scientific summary (PDF File) of the Intergovernmental Panel on Climate Change(IPCC), a group of over 2000 scientists from 100 countries working under a mandate from the United Nations in the largest peer-reviewed scientific collaboration in history. It will only take you about 20 minutes to read through their conclusions, and it is something every citizen on the globe should educate themselves on.
Should "An Inconvenient Truth" be shown in schools?
According to a recent blog posted at realclimate.org, "An Inconvenient Truth" has a become a required part of the science curriculum in some countries. One of the producers of the film, Laurie David, recently offered 50,000 free copies of the $19.99 DVD to National Science Teachers' Association (NSTA) for use in U.S. classrooms. The NSTA turned down the offer on the grounds that the NSTA has a 2001 policy against "product endorsement", and a fear that distributing the film would place "unnecessary risk upon the [NSTA] capital campaign, especially certain targeted supporters." Realclimate.org points out that one of these targeted supporters is oil giant ExxonMobile, and questions whether concern about losing funding from ExxonMobile influenced the decision not to take the free movies. I don't have a problem with the NSTA rejecting the free movies on the grounds that Al Gore's presentation is politicized. However, as pointed out in the realclimate.org post, NSTA does not offer much content on climate change in their list of recommended materials. One of the recommended books, "Global Warming: Understanding the Debate" has no business being on their recommended reading list. This book is written by Kenneth Green, a fellow of the American Enterprise Institute (AEI). This fossil-fuel funded think tank recently offered $10,000 to any scientist willing to criticize the recent landmark 2007 Summary of Policy Makers (PDF File) climate change report issued by the United Nations sponsored Intergovernmental Panel on Climate Change (IPCC). AEI offered to award the money to scientists who would "thoughtfully explore the limitations of climate model outputs", as explained in an article in the UK Guardian. Given the lack of quality climate change education material available to teachers, NSTA needs to seriously rethink their recommended offerings on this important subject.