Polar Bears and Sea Ice: Sorting it Out

87514496A recent post I wrote to highlight a radio discussion of the current plight of polar bears, drew a challenge from Russell Steele, one of our regular readers. Steele questioned some of the scientific conclusions underlying dire predictions for the bears.

To help sort some of this out, I asked for responses from two highly regarded scientists in the field. Here’s a response to the specific reader challenge from Mark Serreze, Director of the National Snow & Ice Data Center, in Boulder, CO:

It is unclear what Mr. Steele is trying to get at with reference to the seasonal cycles in sea ice extent from the AMSR-E data. The AMSR-E data, while valuable, only go back to 2002. Through combining SSM/I and SMMR satellite data with other information sources for earlier years, we have a decent record of Arctic sea ice extent going back to the early 1950s. The relevant issue is the long-term decline in end-of-summer (September) ice extent evident in this record, with the extreme September minima of recent years (represented in the short AMSR-E record) serving as exclamation points. The observed rate of September ice loss exceeds expectations from nearly all climate models.

I also turned to Waleed Abdalati. Now director of the Earth Sciences Observation Center at the University of Colorado, Abdalati is a veteran of the Cryospheric Sciences and Terrestrial Hydrology programs at NASA, and one of the most articulate people I’ve heard speak on the subject of polar ice. He offers the following:

I am not an expert on polar bears, but I do think it is safe to say that
 their primary habitat, the Arctic sea ice, is severely threatened.  I, and 
most of my colleagues believe we are well on our way to an ice-free Arctic
 in summer any time between this decade and the next 40 years.

 is because of two things:  1) it will be decades before the ocean has 
finished its response to present-day greenhouse forcing, so the impacts of 
what we’ve done already have not been fully realized; and 2) the loss of
 sea ice is self-compounding: when it starts to shrink, exposing a 
darker more (heat) absorbing ocean underneath, the likelihood of its continued
 shrinking is greater (ice melts, exposes darker ocean, absorbs more heat, 
melts more ice, exposes darker ocean, and so-on).

Of course the flipside
 of this is that as ice starts to grow, it is more inclined to grow, but
 against the backdrop of the increased warming, the former is far more likely 
than the latter. Finally, as thick multi-year ice disappears, it is
 replaced with thinner and younger ice that is more vulnerable to surface 
melt from the atmosphere, bottom melting from sea water, and being carried
 away to lower, warmer latitudes by ocean current and wind.

So back to the polar bears: If their habitat disappears and they are unable 
to hunt seals, their main source of food, they seem to stand little or no
 chance of survival. I am not a wildlife biologist but its hard for me to 
believe they as a population can sustain themselves on land and with only a
 seasonally-present ice cover. In some cases, the fact that they face more
 challenges on sea ice than in the past, has driven them to forage inland,
 creating the illusion in some people’s minds that their populations are 
increasing, because there are more sightings on land. Who knows? Maybe 
they’ll evolve to hibernate in late summer, when there is no ice, and hunt
 the rest of the year.

There is an added effect that doesn’t get much attention.  There was a 
fascinating study by a Canadian Biologist (Ian Stirling) and a sea ice
 expert (Claire Parkinson) [Stirling, I., and C.L. Parkinson. 2006. Possible 
Effects of Climate Warming on Selected Populations of Polar Bears (Ursus
maritimus) in the Canadian Arctic. Arctic 59(3): 261-275.], which suggested 
that the bears are also losing weight, and approaching the weights at which 
they have historically not been able to bear cubs.  So not only is the
population threatened by starvation, the ability to replenish the population
 seems diminished.

I don’t believe we can say anything with absolute certainty,
 so I, myself would not make the statement that the polar bears are doomed–but I will say that the outlook for them, in my view, looks very, very bad.

Polar Bears and Sea Ice: Sorting it Out 22 December,2009Craig Miller

16 thoughts on “Polar Bears and Sea Ice: Sorting it Out”

  1. I will admit up front that I am not ice or polar bear expert, however I am capable of reading and evaluating the work of experts in their fields of study.

    Dr Mitchell Taylor, a biologist with Nunavut Territorial, has been researching into the status and management of  polar bears in Canada and around the Arctic Circle for 30 years, as both an academic and a government employee.

    More than once since 2006 he has made headlines by  insisting that polar bear numbers, far from decreasing, are much higher than they were 30 years ago. Of the 19 different bear populations, almost all are increasing or at optimum levels, only two have for local reasons modestly declined.

    Dr. Mitchell Taylor, wrote a letter on April 6th, 2006 to the U.S. Fish and Wildlife Service and I have included some excerpts below:

    At present, the polar bear is one of the best managed of the large arctic mammals. If all the arctic nations continue to abide by the terms and intent of the Polar Bear Agreement, the future of polar bears is secure.

    Polar bears are believed to have evolved from grizzly bears during the Pleistocene era some 200-250,000 years ago (Amstrup 2003). Polar bears were well developed as a separate species by the Eemian interglacial approximately 125,000 years ago. This period was characterized by temperature fluctuations caused by entirely natural events on the same order as those predicted by contemporary climate change models. Polar bears obviously adapted to the changing environment, as evidenced by their presence today. That simple fact is well known and part of the information contained in the reference material cited throughout the petition, yet it is never mentioned. This fact alone is sufficient grounds to reject the petition. Clearly polar bears can adapt to climate change. They have evolved and persisted for thousands of years in a period characterized by fluctuating climate. No rational person could review this information and conclude that climate change pre-destined polar bears to extinction.

    The petition admits that there is only evidence for deleterious effects from climate change for one polar bear population (Western Hudson Bay [WH]) at the southernmost extreme of polar bear range (Fig. 1). The petition argues that the likelihood of change in other areas is reason enough to find that polar bears should be regarded as a species at risk of imminent extinction. I hope the review considers the precedent set by accepting this argument. Climate change will affect all species to some extent, including humans. If the likelihood of change is regarded as sufficient cause to designate a species or population as “threatened,” then all species around the world are “threatened.”

    With hunting no longer allowed, bear populations have increased 4-5 times. Here is some data: 1950 = 5,000 |1965-1970 = 8,000=10,000 |
    1984 = 25,000 | 2005 = 20,000 -25,000.

    Dr. Point to problems with the projections from one group to other groups in the region. J. Scott Armstrong, Kesten C. Green and Dr Willie Soon evaluated the forecasting method and procedures.

    The paper Abstract:

    Polar Bear Population Forecasts: A Public-Policy Forecasting Audit

    J. Scott Armstrong The Wharton School, University of Pennsylvania, Philadelphia, Pennsylvania 19104, armstrong@wharton.upenn.edu Kesten C. Green Business and Economic Forecasting, Monash University, Victoria 3800, Australia, kesten@kestencgreen.com Willie Soon Harvard-Smithsonian Center for Astrophysics, Cambridge, Massachusetts 02138, wsoon@cfa.harvard.edu

    Calls to list polar bears as a threatened species under the United States Endangered Species Act are based on forecasts of substantial long-term declines in their population. Nine government reports were written to help US Fish and Wildlife Service managers decide whether or not to list polar bears as a threatened species. We assessed these reports based on evidence-based (scientific) forecasting principles. None of the reports referred to sources of scientific forecasting methodology. Of the nine, Amstrup et al. [Amstrup, S. C., B. G. Marcot, D. C. Douglas. 2007. Forecasting the rangewide status of polar bears at selected times in the 21st century. Administrative Report, USGS Alaska Science Center, Anchorage, AK.] and Hunter et al. [Hunter, C. M., H. Caswell, M. C. Runge, S. C. Amstrup, E. V. Regehr, I. Stirling. 2007. Polar bears in the Southern Beaufort Sea II: Demography and population growth in relation to sea ice conditions. Administrative Report, USGS Alaska Science Center, Anchorage, AK.] were the most relevant to the listing decision, and we devoted our attention to them. Their forecasting procedures depended on a complex set of assumptions, including the erroneous assumption that general circulation models provide valid forecasts of summer sea ice in the regions that polar bears inhabit. Nevertheless, we audited their conditional forecasts of what would happen to the polar bear population assuming, as the authors did, that the extent of summer sea ice would decrease substantially during the coming decades. We found that Amstrup et al. properly applied 15 percent of relevant forecasting principles and Hunter et al. 10 percent. Averaging across the two papers, 46 percent of the principles were clearly contravened and 23 percent were apparently contravened. Consequently, their forecasts are unscientific and inconsequential to decision makers. We recommend that researchers apply all relevant principles properly when important public-policy decisions depend on their forecasts.

    From the sum total of the above, I have concluded that that the Polar Bears are doing fine and the studies used by the alarmist are flawed.

    The majority of the information above is posted on the Watts Up With That Blog, along with more articles questioning the science used to create alarmist propaganda that the polar bears are endangered.

  2. As much as I appreciate the rigor of some of these comments, let’s try to keep the length down to something reasonable. I know it’s hard when you’re trying to make a case–but might I suggest summarizing and pointing us to sources that help make your case, rather than duplicating that info in the comments field.
    Comments that contain URLs will go briefly to moderation to keep the spam down, but we try to get to those promptly and clear them for posting.
    Thanks! I continue to be impressed by the caliber of our discussions here.

  3. Russ, you cut-and-paste from denialist propoganda sites and then pretend it’s some sort of representation of the literature and expert opinion. As you well know, it isn’t.

    Craig, did you ask a PB expert for input?

  4. I did not–partly because I don’t know any (apart from Ellis, who is a journalist) and partly because Russ’ initial challenge seemed to be based on sea ice melt, not bear populations.
    I thought that the two experts adequately addressed the sea ice issue but now it seems that the challenge has shifted to the current status of bear populations. I believe that was addressed in the original post, using a credible source.

    1. Russ refers to a biologist with the Canadian territory of Nunavut, who was the center of a flap last summer, when he was reportedly turned away from a meeting of scientists, for his minority views on anthropogenic global warming, an assertion that was denied by a colleague who chaired the meeting.
      I am not in a position to assess Taylor’s work on bear populations per se versus those with differing conclusions–but it does seem remarkable that his conclusions are nearly (pardon me) the polar opposite of the PBSG’s. Taylor does not have a high profile online but his views are summarized succinctly in a letter he wrote to the Toronto Star in 2006. A 12-page letter he wrote to the US Fish & Wildlife Service in April of that same year is also available for download online, for those interested in digging deeper.

  5. The information in the first post seems more than sufficient, Craig. Did you read and listen to all of that, Russ, or are you just trying to keep an argument going? In any event, from tyhe further links above, the salient point about Taylor seems to be that until his recent retirement he was an employee of the Nunavut government, which is deeply interested in avoiding reductions in polar bear hunting quotas. Follow the money, Russ!

  6. Yes, yes follow the money. If global warming were just a natural cycle the AGW money stream would dry up and go away. There is too much money on the table, to admit to a natural cycle, so the hoax continues.

  7. Ya the guy just hangs out with Polar bears for 30 yrs but what does he know compared to the scientists in East Anglia-

    certainly not surprised to hear he was turned away, since he was going to say their all fine and no need to waste any more money at this time – jeeezzz what a crackpot

  8. Quoting Russel Steele
    “More than once since 2006 he has made headlines by insisting that polar bear numbers, far from decreasing, are much higher than they were 30 years ago.”

    Making headlines is meaningless. Is there scientific literature and/or publicly available data that support the claim? I don’t know if there is or not, but discussion should be focused on science and data rather than claims and headlines.

  9. Thank you, Dr. Abdalati.

    As the Taylor letter quoted by Russ correctly states, the polar bear listing is based primarily on expectations of the impacts of further warming on the bears. Simply put, more warming => less sea ice => less polar bear habitat => fewer polar bears, and no habitat => no polar bears in the wild.

    But he goes off the rails when he claims “This period [the last interglacial] was characterized by temperature fluctuations caused by entirely natural events on the same order as those predicted by contemporary climate change models.” Wrong. The models project temperatures beyond that level, more than enough to result in a seasonally sea ice-free Arctic. The only question is how quickly we will see that outcome. Given the recent behavior of the ice, probably it won’t be long.

  10. Speaking of future temperature projections, Craig, I wanted to draw your attention to Robinson (2009), a recent paper with major implications for the Arctic and California. The focus of the paper is on Arctic warming, but note the other major feature of the SST reconstruction on page 7. With lags due to the time needed to warm up the oceans and melt a substantial part of the ice sheets, that reconstruction is our climate future given *current* CO2 levels, let alone the 500 ppm+ that more and more seems unavoidable. (Also see Lunt et al, a just-published companion paper, for discussion of the larger implications.)

    While we should not lose track of the main concern, which is the huge danger posed by melting the Arctic’s stock of frozen carbon too quickly for the climate system to buffer it, this seems like a good opportunity for you to do a California-centric story tieing in these results with the recent Montanez paper.

  11. Steve Bloom:
    “As the Taylor letter quoted by Russ correctly states, the polar bear listing is based primarily on expectations of the impacts of further warming on the bears. Simply put, more warming => less sea ice => less polar bear habitat => fewer polar bears, and no habitat => no polar bears in the wild.”

    So what you are saying is you agree with Dr Taylor and Russ there is no current issue with the Polar bears. Just might be one someday if a few what if’s happen, glad we have this clarified and can move on.

  12. “Primarily,” Dixon. Learn to read. The polar bears are not lacking in current problems.

Comments are closed.


Craig Miller

Craig is a former KQED Science editor, specializing in weather, climate, water & energy issues, with a little seismology thrown in just to shake things up. Prior to that, he launched and led the station's award-winning multimedia project, Climate Watch. Craig is also an accomplished writer/producer of television documentaries, with a focus on natural resource issues.

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