Errors in Al Gore’s An Inconvenient Truth

By | July 19, 2007

 
 
 
Historical temperatures: The film promotes as factual the discredited 1,000-year “hockey stick” temperature chart by which certain palaeoclimatologists had sought to demonstrate the non-existence of the mediaeval warm period, whose existence the 1995 report of the Intergovernmental Panel on Climate Change had illustrated clearly. Accordingly, the film presents today’s temperatures as being unprecedented in recent times, when it is known – and well evidenced throughout the peer-reviewed scientific literature – that the mediaeval warm period was real; global; and up to 3C warmer than the present. McIntyre & McKitrick (2003, 2005) were the first to demonstrate the errors in the “hockey-stick” graph. Their work was subsequently supported by the Wegman report (2005) for the US House of Representatives, and by a report of the National Academy of Sciences in the US, which found that the graph had “a validation skill not significantly different from zero” (NAS, 2005).

> Hurricanes: The film showed heart-rending pictures of the New Orleans floods. The purpose was to demonstrate a link between increased hurricane frequency and global warming that is not supported by the facts. It has long been known, and is repeatedly asserted in the documents of the UN Intergovernmental Panel on Climate Change, that there is no evidence for any link between warmer climatic conditions and the frequency of hurricanes (IPCC, 2001, 2007). Though it is theoretically possible to make a case for some amplification of the intensity of individual tropical cyclones as the climate-relevant surface or mixed layer of the ocean warms, it is known (Lyman et al., 2006) that in the previous two years, including the year of the New Orleans hurricane, the surface layer of the ocean had lost some 20% of the heat which it had acquired over the previous 30 years. If the film had adhered to the published scientific literature, including the documents of the Intergovernmental Panel on Climate Change, the claim of a connection between anthropogenic climate change and Hurricane Katrina could not responsibly have been made.

The Arctic: The film asserted that at present the Arctic is experiencing unprecedented warmth. In fact, Arctic temperatures in the 1930s and 1940s, like temperatures throughout North America, were as warm or warmer than they are today (Briffa et al., 2004), and there is some historical evidence (including a letter from one of the Popes in the Vatican archives describing how at the end of the mediaeval warm period “the ice hath come in from the north”), that the Arctic was warmer than the present in mediaeval times. The film did not explain that Arctic temperature changes are more closely correlated with changes in solar activity than with changes in atmospheric CO2 concentrations (Soon, 2005). The film inaccurately said polar bears are drowning due to melting ice when in fact 11 of the 13 main groups in Canada are thriving, and polar bear populations have more than doubled since 1940, when the Arctic was at its warmest in recent times (Taylor, 2006). Further evidence for the thriving polar-bear populations is in a recent report by the World Wide Fund for Nature, in which a graph is displayed showing that in those places where temperature has increased the polar-bear population has increased; in those places where it has declined the polar-bear population has declined; and that in the majority of the Arctic where there has been no recent trend in temperatures the polar-bear population has remained stable.

The Antarctic: The film asserted that the Antarctic was warming and losing ice but failed to note that this is only true of a small region, the Antarctic Peninsula, and the vast bulk of the continent has been cooling and gaining ice: indeed, some of the Antarctic glens are suffering environmental damage arising from decreases of up to 2C in temperature over the past 30 years (Doran et al., 2004). The film mentioned the disintegration of the Larsen B ice shelf, but did not mention pre-existing and recently-confirmed peer-reviewed scientific research establishing that 1,000 years ago the ice shelf did not exist (Pudsey & Evans, 2001, 2006). The film said that Greenland’s ice is in danger of disappearing. In fact, the average thickness of the Greenland ice shelf has been increasing by 2 inches per year thoughout the past decade (Johannesen et al., 2005). The Intergovernmental Panel on Climate Change (IPCC, 2007) concludes that neither Greenland nor Antarctica will make significant contributions to sea-level rise in the next century.

Dynamics of radiative transfer: The film showed a graphic designed to demonstrate the assertion that the ocean absorbs heat from the Sun, when in fact this is a schoolboy howler which ought not to be circulated in schools. The ocean takes nearly all of its heat from the atmosphere, without which, even though the Sun’s rays would strike the ocean surface without any intervening atmosphere or clouds, the ocean would entirely freeze over (Houghton, 2002). The film also suggested that as the Arctic ice-cap melts (as it has done before and may well do again) so much less of the Sun’s heat would be reflected back to space that warming would sharply accelerate. There is no warrant for such a suggestion in the documents of the Intergovernmental Panel on Climate Change, since the zenith angle of the Sun in the polar latitudes is so small that a change in albedo in the Arctic (or, for that matter, in the Antarctic) would contribute very little to warming of the planet. Changes in albedo were arguably significant at the last glacial termination, when much of the world’s land-mass (including the whole of North America and of Northern Europe) was icebound, but they are of far less significance today. The only counter-suggestion is in an unpublished paper by James Hansen, a scientist who has been a self-confessed financial contributor to Al Gore’s re-election campaigns: Hansen, however, provides no evidence for his assertions, which are based on theoretical computer modelling using radiative-forcing formulae that are substantially exaggerated compared with those stated in the reports of the Intergovernmental Panel on Climate Change (IPCC, 1995, 2001, 2007).

Sea level: The film said the rise in global sea levels would swamp Manhattan, Bangladesh, Shanghai and other coastal regions, and would rise 20ft by 2100. Graphic reconstructions showing aerial views of these cities and nations disappearing beneath the rising sea were displayed. However, the reports of the Intergovernmental Panel on Climate Change (1990, 1995, 2001, 2007) have at no point suggested that so large an increase in sea level could occur in the next century (though, on the evidence of the three previous interglacials, sea level will rise quite naturally by this amount in the coming millennia, before the next Ice Age commences). The UN’s previous report (IPCC, 2001) said that, under a population-increase scenario that most demographers regard as absurdly high, sea level might, at worst, rise by less than 3ft to 2100. However, Morner (2004), the world’s foremost expert on sea level changes, who has studied sea levels continuously for 30 years (see also Morner 1979, 1995, 2000), wrote that the IPCC’s then projections were an unjustifiable exaggeration. Accordingly, the Intergovernmental Panel on Climate Change (IPCC, 2007) has cut its high-end projection from 3ft to less than 2ft, and its best estimate is just 8in to 1ft 5in, which is a quarter to a third of the mean centennial sea-level rise since the end of the last Ice Age 12,000 years ago.

The tropics: The film falsely asserted that global warming is melting Mt. Kilimanjaro’s icecap. In fact, measurements of temperature in the vicinity of the summit have shown no increase over the past half-century, and the recession of the summit glacier is actually caused by atmospheric dessication from local deforestation, and pre-20th-century climatic shifts (Cullen et al., 2006). The film also implied that the retreat of a Peruvian glacier's retreat has been caused by global warming. However, the tropical Andes have been cooling since the 1930s and other South American glaciers are advancing; also, the normal state of the tropical Andes during the current or Holocene interglacial period has been ice-free except for the very highest peaks (Polissar et al., 2006), suggesting that considerable further recession of the glaciers of the tropical Andes is to be expected as an entirely natural process. In general, mountain glaciers worldwide have receded since photographic records first began about a century ago, but in a longer perspective (two centuries or more), the current recession of mountain glaciers is far from unprecedented (Bhat et al., 2007). Very few of the world’s 160,000 glaciers have been systematically studies for any length of time: the 9,575 Himalayan glaciers mentioned in Bhat et al. have been studied for at least 200 years thanks to the scientific surveys conducted by officials of the British Raj. The film attributed water loss in Africa's Lake Chad to anthropogenic climate change, though NASA scientists, after prolonged investigation, had concluded that local water-use increases and changing grazing patterns are probably to blame (Foley & Coe, 2001). The film suggested that increasing temperatures would lead to the spread of tropical diseases such as malaria, when it is known (Reiter, 2006) that the anopheles mosquito does not select its habitat primarily by reference to temperature: indeed, the mosquito was once prevalent in Europe and is still endemic in Siberia.

Conclusions: The film concluded that the human contribution to recent warming, if continued, would prove dangerous worldwide. However, the Sun has been hotter, for longer, in the past 50 years than in any similar period in at least the past 11,400 years (Solanki et al., 2005). And numerous peer-reviewed papers (the most recent include Soon and Baliunas, 2003, Buentgen et al., 2006, Chilingar et al., 2006, and Bhat et al., 2006) have come to the conclusion that anthropogenic warming accounts for no more than a third of recent warming; that the anthropogenic signal cannot be clearly detected against the background of natural climate variability, and that the anthropogenic contribution to temperature increase could be as little as 0.1C since 1750. The Intergovernmental Panel on Climate Change (IPCC, 2007) has cut its estimate of the entire anthropogenic contribution to climate change since 1750, so that it now stands at just 1.6 watts per square metre, or 0.84C, over 250 years. Finally, the film made great play of a short essay (Oreskes, 2004) that had reviewed abstracts of 928 scientific papers published between 1993 and 2003 inclusive, not one of which had been found to oppose the “consensus”. In fact, the “consensus” was defined in the essay in an extremely limited sense, as follows: that it was likely that more than half of the warming over the past 50 years – i.e. more than just 0.2C of warming – was anthropogenic. A further analysis showed that only 1% of the papers reviewed explicitly endorsed even this very limited “consensus”; almost 3 times as many were explicitly against (Peiser, 2006); and not one endorsed the alarmist definition of “consensus” advanced by Al Gore in the film. A subsequent review by Dr. Klaus-Martin Schulte (in draft and due for submission for peer review shortly), has found that of 539 papers published from 2004 to date only 9 explicitly endorse the “consensus” even if the limited sense defined by Oreskes is used. Some 68 papers either explicitly or implicitly reject the “consensus”. The film’s suggestion of scientific unanimity was simply false.

Summary Points:

·         Gore, aiming to undermine the significance of previous warm periods such as that of the Middle Ages, promoted the discredited 1,000-year “hockey stick” temperature chart (McIntyre & McKitrick, 2005).

·         Gore showed heart-rending pictures of the New Orleans floods and insisted on a link between increased hurricane frequency and global warming that is not supported by the facts (IPCC, 2001, 2007).

·         Gore asserted that today’s Arctic is experiencing unprecedented warmth while ignoring that Arctic temperatures in the 1930s and 1940s were as warm or warmer (Briffa et al., 2004).

·         Gore did not explain that Arctic temperature changes are more closely correlated with changes in solar activity than with changes in atmospheric CO2 concentrations (Soon, 2005).

·         Gore did not explain that the Sun has been hotter, for longer, in the past 50 years than in any similar period in at least the past 11,400 years (Solanki et al., 2005).

·         Gore said the Antarctic was warming and losing ice but failed to note, that is only true of a small region and the vast bulk of the continent has been cooling and gaining ice (Doran et al., 2004).

·         Gore mentioned the breakup of the Larsen B ice shelf, but did not mention peer-reviewed research which suggests the ice shelf did not exist 1,000 years ago (Pudsey & Evans, 2001).

·         Gore hyped unfounded fears that Greenland’s ice is in danger of disappearing. In fact its thickness has been growing by 2 inches per year for a decade (Johanessen et al., 2005).

·         Gore falsely claimed that global warming is melting Mt. Kilimanjaro’s icecap, actually caused by atmospheric dessication from local deforestation, and pre-20th-century climate shifts (Cullen et al., 2006).

·         Gore made assertions of massive future sea level rise beyond any supposed scientific “consensus”, when in fact little increase in the rate of sea-level rise is to be expected in the coming century (Morner, 1995, 2004).

·         Gore implied that a Peruvian glacier's retreat is due to global warming, failing to state that the region has been cooling since the 1930s and other South American glaciers are advancing (Polissar et al., 2006).

·         Gore blamed global warming for water loss in Africa's Lake Chad, though NASA scientists had concluded that local water-use and grazing patterns are probably to blame (Foley & Coe, 2001).

·         Gore inaccurately said polar bears are drowning due to melting ice when in fact 11 of the 13 main groups in Canada are thriving, and polar bear populations have more than doubled since 1940 (Taylor, 2006).

·         Gore said the ocean absorbs heat from the Sun, when in fact the ocean takes nearly all of its heat from the atmosphere, without which the ocean would freeze over (Houghton, 2004).

·         Gore said a review of 928 scientific papers had shown none against the “consensus”. In fact only 1% of the papers were explicitly pro-“consensus”; almost 3 times as many were explicitly against (Peiser, 2006).

·         Gore showed a link between changes in temperature and in CO2 concentration in the past 500,000 years, but did not admit that changes in temperature preceded changes in CO2 concentration (Petit et al., 1999).