List of errors in Lomborgs text:

GROUNDLESS DEROGATION
Page 2 bottom, page 4 top and page 4 bottom: "The World Wildlife Fund actually warns that polar bears might stop reproducing. . ."; "It has gotten much press that . . . Not mentioned though, is that . . " and "Yet we are told that global warming will make polar bears extinct, possibly within ten years. . "
Error:
Lomborg tries to paint a picture of the WWF as an organisation that issues vastly exaggerated claims. However, the quote on page 5 from Washington Post of what WWF said is not correct. WWF was quoted for saying that bears in Hudson Bay might stop reproducing by 2012. This is a correct citation of what scientists say (except that it should have been only the western Hudson Bay). But Lomborg distorts the citation even further and make us believe that WWF said that polar bears - worldwide - would go extinct within ten years. Actually, when you consult the WWF web pages, you see a very different picture. There is a balanced presentation of what populations are declining, now and formerly, and what populations are increasing, now and formerly. The news story on decline in the Western Hudson Bay is presented as just what it is - one story from one limited part of the distribution range. There is one page on hunting (this version was placed on the internet already when Lomborg was writing his book) stating that the main threat to polar bears remains over-hunting. Actually, you get much better and more balanced information on polar bears on the WWF web pages than the information in Cool it, which was outdated already when Lomborg wrote it. The distortion of what WWF says is so gross, and so evidently deliberate, that this is counted as ablatant error.

FLAW OF CITATION
Page 2 bottom: "The IUK Independent tells us . . . "
Flaw:
The source that Lomborg gives does not contain the cited sentence.

FLAW
Page 3 top: ". . . of the 20 distinct populations of polar bears . . . one or possibly two were declining in Baffin Bay; more than half were known to be stable; and two subpopulations were actually increasing around the Beaufort Sea."
Flaw:
This information is taken from the 13th specialist meeting in 2001. However, knowledge of population size and trends was still not very certain at that time, and declines because of changed ice cover were not yet clearly evident. Data from the 14th specialist meeting in 2005 are different: out of 19 populations, 2 are increasing, 5 are declining, 5 are stable, and for 7 the trend is unknown due to lack of data. Lomborg should have used the most recent evidence. The proceedings of the 14th specialist meeting were placed on the internet in November 2006. Lomborg has a reference to the polar bear specialist group homepage. This homepage put a message on 15-Dec-2006 telling that the proceedings from the 2005 meeeting in Seattle have been published and can be downloaded. We know that Lomborg was still writing on the polar bear issue in January 2007, so he had time to use the most recent information, but he did not.

FLAW
Page 3 top: ". . . more than half were known to be stable; and two subpopulations were actually increasing . . ."
Flaw:
This information is taken from the 13th specialist meeting in 2001. The number of populations known to be stable at that time was 8, which is less than half.

FLAW
Page 3 top: "actually increasing around the Beaufort Sea"
Flaw:
The most recent report says for the southern Beaufort Sea that although the point estimates (1,800 around 1997 and 1,525 after the turn of the century) "suggest a decline in numbers, the overlap of the current confidence interval with the previous point estimate prohibits an unequivocal statistical conclusion . . ". As for the northern Beaufort Sea, the report says that new data will be available in 2006. Until the new estimate appears, no conclusions can be drawn.

ERROR
Page 3: "Moreover, it is reported that the global polar-bear population has increased dramatically over the past decades, from about 5,000 members in the 1960s . . ."
Error:
This is not true. As evident from the book of  Uspenskii  (reference above), various estimates of the world population from the period 1957 to 1979 range between 10,000 and 20,000, with the 1957 estimate being in the upper part of this range. However, the true figures are not known with any certainty. Lomborg´s only source for the figures is an article in the New York Times, i.e. he has no reliable source. Considering that the estimate for 2001, based on more extensive data, is 21,500 - 25,000, there is probably a slight net increase up to 2001, but no evidence for a  dramatic global population increase.

ERROR
Page 3: "Contrary to what you might expect . . . the two populations in decline come from areas where it has actually been getting colder over the past fifty years. . "
Error:
The two areas referred to are the Baffin Bay and Davis Streat areas, including the west coast of Greenland. Air temperatures in the latter area have declined during the period 1950-1970, but have increased gradually from 1970 onwards. That is, during the period when the population sizes of polar bears have declined, air temperatures have increased (see this link). At the east coast of Labrador, rises in air temperatures have come later, but they are clearly rising now (Przybylak (2000), cited by Lomborg. What is crucial to the polar bears, is that the sea ice does not break up too early in the summer. Data from 1979 onwards for these regions show that on average, the data of ice breakup has become ever earlier, i.e. the climate has become ever milder, contrary to what Lomborg says. This evidence is presented clearly in the paper I. Stirling & C.L.Parkinson (2006): Arctic 59: 261-275, which has been presented to Lomborg. Climate trends before 1979 are irrelevant, because the trend of the bear populations are not known so far back in time. Thus Lomborg writes something which he knows is irrelevant (before 1979) or wrong (after 1979), i.e. he misleads deliberately.
   It may be added that polar bear populations have been stable in the Southern Hudson Bay, where the climate has been slightly cooling for some period.

(GROUNDLESS DEROGATION)
Page 3: "Contrary to what you might expect and not something that was pointed out in any of the recent stories, the two populations . . . "
Comment:
Lomborg insinuates that "the recent stories" were not honest, omitting evidence that decline concurs with a cooling climate. But as the climate was actually warming, not cooling, during the periods when polar bears declined, this insinuation is groundless.

FLAW
Page 3: "Al Gore´s comment on drowning bears  . . in one of the increasing bear populations."
Flaw:
The episode of four drowned bears was related to a situation where many bears had already problems swimming in open water far from the nearest ice or land. See this link. Specialists say in the recent report (14th meeting) that "The primary concerns for this subpopulation are from climate warming that continues to expand both the expanse and duration of open water in summer and fall." And the population is probably decreasing, not increasing.

FLAW
Page 3 bottom, figure 1:
Flaw:
To construct this graph, Lomborg has combined data from two figures, one from Stirling et al. (1999), the other from Amstrup et al. (2006).  The left part is taken from Stirling, the right part from Amstrup.  In the period of overlap (1985 to 1997) the two curves do not agree fully. Unfortunately, in the Stirling et al.paper the graph is presented without explanatory comments. More original data are in the following paper: A. E. Derocher & I. Stirling (1995): Journal of wildlife management 59(2): 215-221. Here is a curve covering the period 1978 to 1992. Again, the data here do not agree fully with the two other curves. All three curves have error bars. The approximate population size for 1985 is given in Derocher & Stirling as 1,150 ± 600, in Stirling et al. (1999) as 1,500 ± 500, and in Amstrup et al. as 850 ± 300. Thus, a value in the range 1,000 - 1,150 is compatible with all three data sets. But Lomborg has chosen to use only the highest figure for that year, and to leave out any error bars. Likewise, for the low point in 1981, he could just as well have presented an alternative figure of 800 ± 400. Thus, the difference between 1981 and 1985 is not significant. And indeed, the paper by Derocher & Stirling says (p. 220): "Poulation size did not show any trend between 1980 and 1992". Having taught statistics, Lomborg should have been able to understand that the trend is not significant. But he has chosen to neglect reservations pointed out to him by experts in the field, and has draw his own false conclusions. If he had taken account of known facts on polar bear biology, he would have known that isolated populations can grow by maximally 3-4 % per year, and that growth by immigration from neigbouring populations is very limited. The population increase that Lomborg postulates can impossibly have occurred.
    So, the trend that Lomborg has stressed and dramatized - the leap upwards from 500 to 1,500 - is just a statistical artifact due to large uncertainties in the figures. Having taught statistics, Lomborg should have been able to understand that.
    Unfortunately others, including Rosing-Asvid, cited by Lomborg,  have taken the figures from Stirling et al. (1999) literally, without considering that a rise from 500 to 1,500 is impossible, and without considering the uncertainties involved . Over a period of four years, a polar bear population can maximally grow by about 15 %, i.e. there could have been a rise from e.g. 1,000 to 1,150, but certainly not from 500 to 1,500. 
    It is believed that the population was exposed to overhunting before hunting regulations in 1968, and it is believed therefore that it increased especially from the late 1960s and well into the 1970s. But the apparent increases that Lomborg refers to are statistical artifacts.

FLAW
Page 3 bottom, note 26 to figure 1: "Stirling points out (personal communication) that . .
Flaw:
What Stirling tried to explain to Lomborg is that there are large uncertainties in population estimates based on capture-recapture data. For a long-lived species like the polar bear, the uncertainties are especially large when only capture data from a single year are utilised for each point estimate. For instance, when a bear has been captured in 1984 and 1986, it must have been present in 1985 too, but this information is lost when the 1985 population estimate is based only on data from that particular year. There exist mathematical procedures by which data from neighbouring years are also utilised (the Jolly-Seber method); this method has not been used by Stirling, but he has handed the data over to other scientists (Amstrup et al.) who have reanalysed the data by utilising mulit-year data sets. This means that the estimates arrived at by Amstrup et al. are more reliable than those published by Stirling et al. In addition, the apparent increase during the early 1980s is also explained by the fact that sample sizes and area covered were increasing rapidly, that is, data for 1981 did not cover the whole region, which of course means that the population estimate is too low. If the first estimate (Derocher & Stirling 1995) included only captures from the core region, and later estimates included a few additional captures made at the periphery of the region, where the chance of recapture is low, then this would have the effect to lower the recapture rate and thus boost the population estimate. Thus, using data from the first years when the study area is extended will cause population estimates to be unrealistically high, but including data from subsequent years, when these bears are recaptured, will tend to reduce the population estimates to more realistic levels.
    Lomborg should know all this, as he has corresponded with several scientists on the issue. He has probably not understood the mathematical problems involved, but at least he has understood that the low estimates for the early 1980s are biased to the low side. He conceals this insight at the end of note 26 (and leaves it out completely in the American version of the book), and on page 4 he writes as if he did not know this.
   Those readers who care to look up note 26, are met with the following sentence: "Stirling et al. are coming out with a new data set, but they would not share it . . . " At first sight, this may look as if Stirling is an unkind person. Actually, he was the person who sent the paper by Stirling et al. (1999) to Lomborg, and he urged a colleague to write additional explanation to Lomborg, and to promise to send an additional paper when this was published.

  
GROUNDLESS DEROGATION
Page 4, top: ". . the western coast of Hudson Bay. . . Not mentioned, though, is that the population research . . "
Error:
As explained in relation to Figure 1 and to note 26, the data for the early 1980s are so uncertain that the apparant trend for a population increase is not significant. This is a good reason why scientists have not focused on trends during this period. But Lomborg twists the evidence to throw unjustified suspicion on the scientists. As he knows that the trends for the early 1980s are too uncertain, this is a case of deliberate unjustified derogation.

ERROR
Page 4, top: ". . . Here, the population has soared from just 500 in 1981 . . ."
Error:
As explained in relation to Figure 1, this is not true. There is no statistically significant trend between 1981 and 1985. It should be fundamental for a person who has taught statistics not to proclaim that an important trend has been observed, without checking if the apparent trend could possibly be due to statistical variation, which is certainly the case here, because the postulated rise could impossibly have occurred in the real world.
    As Lomborg has corresponded with the scientists, he knows all this. What he writes is deliberately misleading.

FLAW
Page 4: "it means we have lost about 15 bears to global warming each year, whereas we have lost 49 bears each year to hunting."
Flaw:
With this sentence, Lomborg either demonstrates a blatant lack of understanding of ecology, or purports to lack this understanding. In a stable population, it is possible to obtain a `sustainable yield´, because the population each year produces a surplus of young, some of which will die from natural causes if they are not shot by man. Calculations are made by wildlife biologists to find the size of the `sustainable yield´, i.e. how many bears may be shot each year without causing the population to decline. Permits are then issued to shoot this amount of bears, with the local inuit population receiving most of the permits. However, if conditions get worse, the bears produce less young, and the sustainable yield decreases. That is, the increased melting of sea ice means that the population tolerates less hunting than before. So harvesting the sustainable yield does not imply a lasting reduction of the population (a "loss"), whereas a decline in the size of the sustainable yield is indeed a loss, to the polar bear population and to the people hunting them.

ERROR
Page 4: " In 2006, a polar bear biologist from the Canadian government . ."
Error:
The biologist referred to is Mitchell Taylor. The quote may be seen in full in this link. He does not work for the Canadian federal government, but for the government of the Nunavat territory, where local interests in allowing large quotas for beer hunting probaly have a greater weight.

FLAW
Page 4: "we hear vastly exaggerated and emotional claims that are simply not supported by the data."
Flaw:
The claims are not exaggerated, and they are supported by the data.

ERROR
Page 4 bottom and note 33: " Yes it is likely that disappearing ice will make it harder . . and that they more often will take up a lifestyle similar to that of brown bears . ."
Error:
In note 33, Lomborg writes: "The Arctic Climate Assessment finds it likely that disappearing ice will make polar bears take up `a terrestrial summe lifestyle similar to that of brown bears . .´ ". But here follows the original text in the assessment report (Symon, Arris and Heal 2005 p. 509; Berner is not among the editors): "It is difficult to envisage the survival of polar bears as a species given a zero summer sea-ice scenario. Their only option would be a terrestrial summer lifestyle similar to that of brown bears, from which they evolved. In such a case, competition, risk of hybridization  with brown bears and grizzly bears, and increased interactions with people would then number among the threats to polar bears." Thus, in the cited text, the eventual survival of polar bears on land is presented as a hypothetical possibility, fraught with several difficulites. It is certainly not presented as something "likely".

ERROR
Page 4 bottom: "But over the past forty years, the population has increased dramatically. . "
Error:
As stated above, this is not true.

FLAW
Page 4 bottom: ". . and the populations are now stable."
Flaw:
This might have been true up to 2001, but in 2005 it was no longer true.

(COMMENT)
Page 4 - 5: "In general, the Arctic Climate Impact Assessment projects that the Arctic will experience increasing species richness . . . "
Comment:
Lomborg usually accuses biologists of focusing on negative trends and ignoring positive trends. But the ACIA report presents in a neutral way positive as well as negative trends. There is no obvious bias. But Lomborg can always twist his text in such a way that we are left with the impression of overly pessimistic environmentalists - also in this case when they make a neutral contribution. On the other hand, Lomborg himself is not neutral here. He only cites those parts of the text on pages 997-998 that deal with positive trends, and ignores all text dealing with various species that will probably decline or go extinct. He ignores that species disappearing from the Arctic will disappear completely from the globe, whereas species that will immigrate to the Arctic already exist elsewhere - that is he ignores the risk that the total number of species on the globe will decline.

(COMMENT)
Page 5 top: ". . the plight of the polar bears shows "the need for stricter curbs on greenhouse-gas emissions . . "
Comment:
The cited newspaper article did not exactly say so. The reason given in the article for the need for curbs is rather that the polar bear are indicators of climate change in the Arctic areas, and that these areas provide a bellwether of what´s coming to the rest of planet Earth.

GROUNDLESS DEROGATION
Page 5 top: "Even if we accept the flawed idea of starting to count bears at Hudson Bay at close to the maximum in 1987. . ."
Flaw:
The idea is not flawed.The population around Hudson Bay did not have an aberrant size in 1987. The study of population trends starts with those years when data are sufficiently certain.

FLAW
Page 5: "Thus, if we care for stable populations of polar bears, dealing first with the 49 shot ones might be both a smarter and a more viable strategy."
Flaw:
This is nonsense due to Lomborg´s lack of understanding of the concept of sustainable yield (as explained above). If we want a stable population, we can shoot 49 bears annually without compromising the stability. If the 49 bears were not shot, a similar number of bears would die from other causes. On the other hand, when the environment becomes less favourable, then the sustainable yield decreases, and the number of bears shot annually will have to be reduced to avoid an acceleration of the ongoing decline.