Criticisms of Al Gore's "An Inconvenient Truth"

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Al Gore's An Inconvenient Truth became a big part of the British secondary educational landscape when it was made part of the official curriculum. This was big victory for those who feel the world is in imminent danger because of anthropogenic global warming. However, the High Court of London recently said "not so fast." Steward Dimmock sued under Section 406(1)(b) of the Education Act 1996, claiming that the movie is a form or political indoctrination. That law says that school governing bodies and head teachers "shall forbid... the promotion of partisan political views in the teaching of any subject in the school".

The court ruled that 1.) in order to show this movie to the children teachers must make clear that the film is a political work and promotes only one side of the argument. 2.) If teachers present the film without making this plain they may be in breach of section 406 of the Education Act 1996 and guilty of political indoctrination. 3.) Nine inaccuracies have to be specifically drawn to the attention of school children.

I will use these nine cited inaccuracies as a jumping off point for my criticisms of An Inconvenient Truth, both the book and film. These nine inaccuracies are:

• The film claims that melting snows on Mount Kilimanjaro evidence global warming. The Government’s expert was forced to concede that this is not correct. more...


• The film suggests that evidence from ice cores proves that rising CO2 causes temperature increases over 650,000 years. The Court found that the film was misleading: over that period the rises in CO2 lagged behind the temperature rises by 800-2000 years. more...


• The film uses emotive images of Hurricane Katrina and suggests that this has been caused by global warming. The Government’s expert had to accept that it was “not possible” to attribute one-off events to global warming. more...


• The film shows the drying up of Lake Chad and claims that this was caused by global warming. The Government’s expert had to accept that this was not the case. more...


• The film claims that a study showed that polar bears had drowned due to disappearing arctic ice. It turned out that Mr Gore had misread the study: in fact four polar bears drowned and this was because of a particularly violent storm. more...


• The film threatens that global warming could stop the Gulf Stream throwing Europe into an ice age: the Claimant’s evidence was that this was a scientific impossibility.


• The film blames global warming for species losses including coral reef bleaching. The Government could not find any evidence to support this claim.


• The film suggests that sea levels could rise by 7m causing the displacement of millions of people. In fact the evidence is that sea levels are expected to rise by about 40cm over the next hundred years and that there is no such threat of massive migration.


• The film claims that rising sea levels has caused the evacuation of certain Pacific islands to New Zealand. The Government are unable to substantiate this and the Court observed that this appears to be a false claim.

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"Warmer Oceans, Stronger Hurricanes," Trenberth, Scientific American, July 2007

Hyperbole comes in many forms. This article in Scientific American came with a full page artist's rendering of a "future hurricane." I have shown a very small (to avoid copyright lawyers) copy of the picture below, with a blow up of one section. The caption for the picture in the magazine says "Future hurricanes could be more severe thanks to global warming." The blow up shows a giant hurricane bearing down on the Mediterranean and the East coast of the United States

Figure 1. The small picture at the left is a miniature version of the 8 inch by 11 inch full page artist's rendering of a "future hurricane" form page 44 of the July 2007 Scientific American. The right side shows a blow up of part of the picture.

The very first paragraph of the article reminds the reader of the 2005 hurricane season and, of course, Katrina. So, I use a pair of pictures below to compare Katrina to the imagined "future hurricane." The first is a satellite image of Katrina shortly before it made landfall near New Orleans. The second is a detail of the Scientific American picture. Note that the sizes of the images have been adjusted to give the same scale.

Figure 2. Detail of Scientific American picture of "future hurricane" with same scale as image of Hurricane Katrina in figure 3,below.

Figures 3. Satellite image of Hurricane Katrina just hours before making landfall at New Orleans. This image is on the same scale at the artist rendering of a "future hurricane" in figure 2, above.

Figure 4. Juxtaposition of the Scientific American "future hurricane" and the very real Katrina from the satellite image. I have removed land masses from both pictures. Both pictures are on the same scale, as in figures 2 & 3.

Scientific American's "future hurricane" is bigger than the continent of North America. It is so big that it stretches from northern Brazil to southern Canada. It is as large as the North Atlantic Ocean. This is clearly extreme visual hyperbole, but it is also a metaphor for much of the global warming debate, where preposterous exaggerations and extrapolations abound.

Those who are convinced that we are headed for a future of giant hurricanes due to increased CO2 might consider the following journal articles to mitigate the effects of the seemingly endless fear mongering so common in the global warming debate:

1. In Low Atlantic hurricane activity in the 1970s and1980s compared to the past 270 years, Nyberg, et. al., point out that "reliable observations of hurricane activity in the North Atlantic only cover the past few decades." It is not possible to say, based on this short set of data, if the variation that has been seen during these few decades is greater than should be expected over longer time scales. However, they developed a proxy for both sea surface temperature and vertical wind shear covering 270 years. (Vertical wind shear is inversely related to hurricane formation). The result shows that "the average frequency of major hurricanes decreased gradually from the 1760s until the early 1990s, reaching anomalously low values during the 1970s and 1980s." It seems clear that the upswing in hurricane activity seen from the beginning of the satellite era to the present is largely a consequence of the beginning of the satellite era being at the low point of hurricane activity for the last 270 years.

2. The article in Nature, Intense hurricane activity over the past 5,000 years controlled by El Nin˜o and the West African monsoon," by Donnelly and Woodruff of the Woods Hole Oceanographic Institution in Massachusetts echos the concern that "the instrumental record is too short and unreliable to reveal trends in intense tropical cyclone activity." To overcome these limitations they used sediment deposits in coastal lagoons of the Caribbean to gauge hurricane activity on the century and millennial time scales over a 5000 year period. They found the frequency of intense hurricanes varied widely on these time scales during the past 5,000 years and that the frequency appears to be governed by the El Nin˜o/Southern Oscillation and the strength of the West African monsoon." Additionally, " sea surface temperatures as high as at present are not necessary to support intervals of frequent intense hurricanes."

3. The short instrumental record of hurricane activity was a motivation for Miller, et. al. in their 2006 Proceedings of the National Academy of Sciences paper, "Tree-ring isotope records of tropical cyclone activity." As trees grow, the oxygen isotope ratios of the water at that place and time are locked into their rings. It is also known that the precipitation of tropical cyclones and hurricanes have oxygen isotope ratios that are greatly different that more common causes of precipitation. Miller, et. al., examined long leaf pines (pinus pulustris) in Georgia because they have shallow roots and a distinct early season growth and late season growth in their rings. these combine to give a precise temporal fix on isotope ratio variation. Their study covered 1770 to 1990. Their analysis of the tree ring oxygen isotope data shows very close agreement with the instrumental data for the southeastern United States after 1940, verifying the efficacy of their method for earlier times. The overall results indicate "systematic, decadal- to multidecadal-scale variations" in the isotope ratios, and consequently variations in the number of hurricanes. Hurricane activity appears to have peaked in the 1770s, 1800s to 1820s, 1840s and 1850s, 1865 to 1880, and the 1940s to 1950s. The quietest decades are the 1780s through 1790s, and the 1970s. The 1970s saw the beginning of satellite tracking of hurricanes. The fact that there has been an upswing in hurricanes in the satellite record is much less alarming when you consider that the 1970s was one of the least active decades (at least for the southeastern United States) in over 200 years.

Kevin E. Trenberth, "Warmer Oceans, Stronger Hurricanes," Scientific American, July 2007, p44-51. (Get copy here.)

Johan Nyberg, et. al., "Low Atlantic hurricane activity in the 1970s and 1980s compared to the past 270 years," Science, Vol 447, 2007. (Get copy here.)

Jeffrey P. Donnelly & Jonathan D. Woodruff, "Intense hurricane activity over the past 5,000 years controlled by El Nin˜o and the West African monsoon," Nature, Vol 447, 24 May 2007 (Get copy here.)

Dana L. Miller, et. al., "Tree-ring isotope records of tropical cyclone activity," Proceedings of the National Academy of Sciences, PNAS, Vol. 103, no. 39, September 26, 2006 (Get copy here.)