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Sunday, July 1, 2018

Myth: Polar Bear Population Numbers Imply that Man-Made Climate Change does not Negatively Impact Polar Bears

The outline for this post is as follows:
  1. The Myth and Its Flaw
  2. Context and Analysis
  3. Posts Providing Further Information and Analysis
  4. References

This is the "main version" version of this post, which means that this post lacks most of my references and citations. If you would like a more comprehensive version with all the references and citations, then please go to the "+References" version of this post.

References are cited as follows: "[#]", with "#" corresponding to the reference number given in the References section at the end of this post.




1.  The Myth and Its Flaw



Polar bear populations increased, so either scientists do not know that man-made climate change detrimentally affects polar bears or those detrimental effects are exaggerated.

Purveyors of this myth include Steven Crowder (via his blog), Sargon of Akkad (a.k.a. Carl Benjamin), Paul Homewood, Investor's Business Daily, The Daily Caller, The Globe and Mail, WattsUpWithThat, Susan Crockford, Climate Depot, and various other blogs. Crockford acts as the central node from which many myth proponents drew this myth.

The myth's flaw: Human release of greenhouse gases warms the Arctic. Warming-induced melting of Arctic sea ice detrimentally affects polar bears, and will likely do so in the future. These negative effects are mitigated by other factors, such as laws limiting polar bear hunting and changes in polar bear behavior. Highlighting these factors does not rebut evidence on how climate change detrimentally affects polar bears, anymore than pointing out factors that increase human population rebuts evidence on how smoking detrimentally affects humans. 



2. Context and Analysis



Suppose a group of people told you the following:

A1: "You cannot know that the polio vaccine was effective. After all, polio incidence began decreasing before the polio vaccine was introduced."

A2: "HIV and AIDS did not detrimentally affect people in India, sub-Saharan Africa, and elsewhere in the world. After all, human population increased in India, sub-Saharan Africa, and elsewhere since HIV first began infecting people."

A3: "People exaggerate how much smoking affects human health. After all, the human population increased even as the number of smokers increased."

Each of the aforementioned claims make a similar mistake: the claims assume that X has no effect (or that X's effect is exaggerated or unknown) simply because non-X things can also have a significant effect. For instance, claim A1 overlooks the fact that vaccines, improved sanitation, better access to medical care, etc. all contribute to reductions in infection and illness. The efficacy of one of these factors does not show that the others have no effect. Similarly, A2 and A3 fail since HIV, AIDS, and smoking detrimentally affect human health, even though human population increases overall due to other factors, such as medical advances.
(I discuss HIV/AIDS, smoking, and vaccination more in sections 2.3, 2.5, 2.6, 2.7, and 2.10 of "Myth: Attributing Warming to CO2 Involves the Fallaciously Inferring Causation from a Mere Correlation").

The following claim commits a similar mistake as A1, A2, and A3:

A4: "You cannot know that man-made climate change has negative effects on polar bears. And people exaggerate the effect of man-made climate change on polar bears. After all, polar bear numbers increased."

A4 represents the myth this blogpost focuses on. And just as with A1, A2, and A3, A4 fails because it assumes that X has no effect (or that X's effect is exaggerated or unknown) simply because non-X things can also have a significant effect. 

Some people might be shocked that myth proponents make such an obvious mistake in their defense of A4. But this should not be that surprising. To see why, note that defenders of A4 tend to be critics of mainstream climate science. And many critics of mainstream climate science resort to similar tactics and reasoning as anti-vaxxers, AIDS denialists, and denialists on the health risks of smoking. So it is unsurprising to see these groups make the same mistake on A1, A2, and A3 as myth defenders make on A4. 

(I compare these different forms of science denialism more in sections 2.3, 2.5, and 2.10 of "Myth: Attributing Warming to CO2 Involves the Fallaciously Inferring Causation from a Mere Correlation". The myth defender Steven Crowder deserves special mention here, since he defends the myth, publishes blogposts on how man-made climate change is a fabrication invented by leftists in order to grow the government, and makes nonsensical claims on HIV/AIDS. Crowder contradicts scientific evidence when he claims there was no AIDS epidemic, and when he states that one has virtually no chance of contracting HIV if one is neither a homosexual nor an IV drug user.)

So if the myth fails, then what is the relationship between man-made (a.k.a. anthropogenic) climate change and polar bears? Anthropogenic climate change comes with global warming, with especially large warming in the Arctic. This Arctic warming melts Arctic sea ice, along with increasing storm intensity, which breaks up sea ice further. Sea ice loss is strongly linked to worse health for female polar bears and their cubs, since the bears use the ice as a platform for catching prey in the sea.

Other factors, however, can influence polar bear survival in the short-term, leading to regional variation in polar bear population trends. Figure 1 below depicts a 2015 review of some of the relevant evidence on polar bear populations, though this paper leaves out much of the recently published evidence on polar bears:


Figure 1: A 2015 review of published evidence on polar bear populations in different regions. The columns of the table represent the following:  (column 1) region;  (column 2) population size, with a 95% confidence interval {except for the "Southern Beaufort Sea" value labelled "e", which represents a 90% confidence interval};  (column 3) year of the analysis estimating population size and trend;  (column 4) population trend {"seclining" for "Western Hudson Bay" is a typo and should read "declining"};  (column 5) reference number for the cited analysis;  (column 6) whether the bears in that region can be legally killed for the purpose of subsistence {"S"}, commercial use {"C"}, or neither {"none"} [1, table 1 on page 729].


Subsequently published research showed the following for polar populations in different regions:

  • Southern Hudson Bay: Worsening body condition, 2009
  • Western Barents Sea: stable population (a population increase that was not statistically significant), 2015
  • Barents Sea: fewer pregnant polar bears reaching traditional denning areas, 2012

Arctic ice loss also exposes polar bears (and their prey) to more pollutants, pathogens, etc., and causes polar bears to come on land earlier to catch prey; both of these factors adversely affect prey populations
. Polar bears coming on land earlier may increase the likelihood of polar bears interacting with, or attacking, humans. Polar bears can attempt to acclimate to sea ice loss and warmer temperatures, but these acclimation strategies are not working well in a number of regions. The National Aeronautics and Space Administration (NASA) acknowledges these risks to polar bears. So NASA debunks the myth, even though the myth advocate Steven Crowder gleefully cites NASA on other occasions.

Despite the aforementioned negative effects on polar bear populations, humans can help maintain polar bear populations by, for example, limiting hunting of polar bears through legislation. But these legislative responses do not change the fact anthropogenic climate change negatively impacts on polar bears, anymore legislation funding AIDS treatments means that AIDS has no negative impact on humans (as I discussed above with respect to A2). 

A 2008 Internet article discusses laws limiting hunting of polar bears; the myth defender Steven Crowder relies on this article. This article also discusses the flaws in people, such as Crowder, relying on 1970s estimates of polar population in order to claim that polar bear population increased. I do not place much credence on these types of Internet articles, since they lack much peer-reviewed scientific evidence, an important facet of contemporary science. But if Crowder is going to cite such a source, then he needs to acknowledge what it says. And that 2008 source says:

"The population of polar bears today is larger than it was in the 1970s, due mainly to legislation banning polar bear hunting, but exact numbers are unclear.
[...]
Furthermore, according to an essay by Scott L. Schliebe, polar bear project leader for the U.S. Fish and Wildlife Service, more sophisticated satellite and thermal technology exists today than was available during the 1970s, making previous population estimates less accurate than today’s approximations.
[...]
However, most figures regarding the number of bears in the 1970s are based on guesses.
[...]
So why place polar bears on the list of "threatened" species if their numbers have been growing? Many scientists believe that due to climate change and resulting environmental factors, the trend is reversing.
[...]
Polar bears rely on sea ice as a platform for hunting seals, their primary source of food, and global warming and climate change are projected to cause a severe decline in the amount of sea ice. This was the reason Kempthorne cited in his May 14 press conference: "First, sea ice is vital to polar bear survival," he said. "Second, the polar bear’s sea-ice habitat has dramatically melted in recent decades. Third, computer models suggest sea ice is likely to further recede in the future [2]."

As noted near the end of the aforementioned quote, Arctic sea ice declined, exceeding model-based average projections of this decline; this discrepancy between model-based projections and observations decreases, once one takes internal variability into account. Figures 1 and 2 below illustrate these points, with figure 1 coming from a 2007 study and figure 2 coming from a 2011 study:

Figure 2: Arctic September sea ice extent from observations and projected by climate models from the Fourth Assessment of the Intergovernmental Panel of Climate Change (IPCC AR4). The thick red line represents the observations, the solid thick black line indicates the average trend of all the models, and the dotted black line reflects the standard deviation. The colored, thin dotted lines represent individual model or model ensembles, with an asterisk marking models with more than one ensemble member [3, figure 1]. Subsequently published research showed much the same trend.


Figure 3: (a) Arctic sea ice trend in the late-summer from 561 AD to 1995 AD. Solid and dashed lines indicate the 40-year smoothed trends, and the red shading indicates the 95% confidence interval. The analysis combines proxy-based estimates with recent observations. (b) Ice-core-based estimate of Chukchi Sea ice cover; panel b is not the focus of my discussion, so I have not included the y-axis for panel b [4, figure 3a on page 511].

So scientists were justified in their points about Arctic sea ice decrease, and this was clear long before Crowder advocated the myth in 2016. Given this, why do Crowder and other myth proponents defend the myth using the clearly fallacious reasoning illustrated in point A4? The likely reasons become clear when one focuses on the relationship between human activity and Arctic warming.

Human industry released greenhouse gases such as carbon dioxide (CO2), causing a near-exponential increase in atmospheric CO2 levels at a rate not seen for tens of millions of years. Greenhouse gas increases cause warming that melts Arctic ice (I discuss greenhouse gases causing warming in "Myth: Attributing Warming to CO2 Involves the Fallaciously Inferring Causation from a Mere Correlation"). Melting sea ice affects polar bears in the ways I noted above. Thus polar bears became one public keystone for the effects on anthropogenic climate change. By defending their fallacious myth, myth proponents attempt to attack this keystone and thereby undermine public confidence in the science on anthropogenic climate change.

The myth proponent Steven Crowder also likely defends the myth for political reasons. To see why, first note that reducing anthropogenic greenhouse gas emissions (whether by government intervention or by other means) can limit Arctic warming and melting of sea ice, thus aiding polar bear populations. This is akin to how government-led agreements and/or legislation helped address other anthropogenic environmental and health issues, such as ozone depletion, acid rain, leaded products (such as gasoline and paint, with mixed results), smoking-related deaths, and mortality from failure to wear seat belts

So concern over polar bears could serve as one keystone rationale for government-led responses to anthropogenic climate change. Crowder likely wants to avoid this government-led response, since he publishes blogposts on how man-made climate change is a myth invented by leftists in order to grow the government. Thus it is not surprising that Crowder would use the myth to undercut the polar bear rationale for government-led action. Maybe a similar political motivation drives other myth advocates to defend the myth?





3. Posts Providing Further Information and Analysis





4. References


  1. "Arctic marine mammal population status, sea ice habitat loss, and conservation recommendations for the 21st century"
  2. https://www.factcheck.org/2008/06/polar-bear-population/
  3. "Arctic sea ice decline: Faster than forecast"
  4. "Reconstructed changes in Arctic sea ice over the past 1,450 years"

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