Tag Archives: observations

Abrupt summer sea ice decline has not affected polar bear numbers as predicted

Yes, Arctic sea ice has declined since satellite records began in 1979 but polar bears have adjusted well to this change, especially to the abrupt decline to low summer sea ice levels that have been the norm since 2007.

Global pb population size sea ice 2017 July PolarBearScience

Some polar bear subpopulations have indeed spent more time on land in summer than in previous decades but this had little negative impact on health or survival and while polar bear attacks on humans appear to have increased in recent years (Wilder et al. 2017), the reasons for this are not clear: reduced summer sea ice is almost certainly not the causal factor (see previous post here).

Ultimately, there is little reason to accept as plausible the computer models (e.g. Atwood et al. 2016; Regehr et al. 2016) that suggest polar bear numbers will decline by 30% or more within a few decades: even the IUCN Red List assessment (Wiig et al. 2015) determined the probability of that happening was only 70%.

Arctic sea ice has never been a stable living platform (Crockford 2015): it shifts from season to season, year to year, and millennia to millennia. Without the ability to adapt to changing conditions, Arctic species like polar bears and their prey species (seals, walrus, beluga, narwhal) would not have survived the unimaginably extreme changes in ice extent and thickness that have occurred over the last 30,000 years, let alone the extremes of sea ice they endured in the last 200,000 years or so.

Some biologists continue to hawk doomsday scenarios for polar bears due to summer sea ice loss but the truth is that their previous predictions based on sea ice declines failed so miserably (e.g. Amstrup et al. 2007) that it’s impossible to take the new ones seriously — especially since the basic assumptions that caused the first predictions to fail have not been corrected, as I’ve stated in print (Crockford 2017:27):

In summary, recent research has shown that most bears are capable of surviving a summer fast of five months or so as long as they have fed sufficiently from late winter through spring, which appears to have taken place since 2007 despite marked declines in summer sea ice extent.

The assumption that summer sea ice is critical feeding habitat for polar bears is not supported.

Recent research shows that changes in summer ice extent generally matter much less than assumed in predictive polar bear survival models of the early 2000s as well as in recent models devised to replace them (Amstrup et al. 2010; Atwood et al. 2016a; Regehr et al. 2015; Regeher et al. 2016; Wiig et al. 2015), while variations in spring ice conditions matter more.

As a consequence, the evidence to date suggests that even if an ‘ice-free’ summer occurs sometime in the future ­ defined as sea ice extent of 1 million km2 or less (Jahn et al. 2016) ­ it is unlikely to have a devastating impact on polar bears or their prey. [my bold]

The abrupt drop in summer sea ice that occurred in 2007 was not predicted by experts to occur until mid-century yet the predicted decimation of polar bears worldwide expected under those conditions (a loss of 2/3 of the global total, to only about 6660-8325 bears) not only did not happen, it did not come even close to happening (Crockford 2017; see also my recent books, Polar Bear Facts & Myths, and Polar Bears: Outstanding Survivors of Climate Change, sidebar).

Instead, the global population grew from about 22,550 bears in 2005 to about 28,500 bears in 2015. And while this might not be a statistically significant increase (due to the very wide margins of error for polar bear estimates), it is absolutely not a decline.

The present reality is that low summer sea ice cover since 2007 has not caused polar bear numbers to decline and therefore, polar bears are not a species in trouble. This suggests that even if the Arctic should become briefly ice-free in summer in the future, polar bears are likely to be only minimally affected and not become threatened with extinction. Polar bears are outstanding survivors of climate change: recent research and their evolutionary history confirm this to be true.

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W Hudson Bay polar bears won’t have an early breakup year, according to sea ice charts

There is still a huge swath of highly concentrated thick first year ice (>1.2m) over most of Hudson Bay this week (19 June 2017) and even in the NW quadrant (the closest proxy we have for Western Hudson Bay), the weekly graph shows levels are greater than 2016, when WHB bears came off the ice in good condition about mid-July. All of which indicates 2017 won’t be an early sea ice breakup year for WHB polar bears.

Hudson Bay weekly ice stage of development 2017 June 19

There is thick first year ice (>1.2m, dark green) in patches along the west coast in the north and south. Thick first year ice also extends into Hudson Strait and Baffin Bay, with some medium first year ice (0.7-1.2m thick, bright green) along the central and southern coasts of WHB.  Note the red triangles incorporated into the thick ice of Hudson Strait in the chart above: those are icebergs from Greenland and/or Baffin Island glaciers. A similar phenomenon has been noted this year off northern Newfoundland, where very thick glacier ice became mixed with thick first year pack ice and were compacted against the shore by storm winds to create patches of sea ice 5-8 m thick.

Compare the above to what the ice looked like last year at this time (2016 20 June, below). There is more open water in the east this year (where few WHB bears would likely venture anyway) but less open water around Churchill and Wapusk National Park to the south than there was in 2016:

Hudson Bay ice age weekly at 20 June 2016

We won’t know for several more weeks if most WHB bears will come ashore at about the same time as last year (early to mid-July) or whether they will be in as good condition as they were last year (because winter conditions may not have been similar).

But so far, sea ice conditions are not looking as dire as the weekly “departure from normal” chart (below, 19 June 2017) might suggest (all that “less than normal” red and pink, oh no!!):

Hudson Bay weekly departure from normal 2017 June 19 Continue reading

Science behind the video Polar Bear Scare Unmasked – updated paper now available

Announcing the publication today of Version 3 2 of my paper that tests the hypothesis that polar bear population declines result from rapid declines in summer sea ice, updated with recently available data. Version 2 provides the scientific support for the information presented in the GWPF video published yesterday, “Polar Bear Scare Unmasked: The Sage of a Toppled Global Warming Icon” (copied below).

Crockford 2017 V3 title page graphic 3

[The graphic above was created by me from the title page and two figures from the paper]

Updated 1 March 2017: I added an important reference to the paper below that got overlooked in previous versions (the work of Armstrong et al. 2008, see this post), making Version 3 the latest and most up-to-date.

Crockford, S.J. 2017 V3. Testing the hypothesis that routine sea ice coverage of 3-5 mkm2 results in a greater than 30% decline in population size of polar bears (Ursus maritimus). PeerJ Preprints 2 March 2017. Doi: 10.7287/peerj.preprints.2737v3 Open access. https://doi.org/10.7287/peerj.preprints.2737v3

Version 3, published 2 March 2017, adds an important reference; Version 2, published 28 February, incorporates additional reviewer comments and suggestions received on Version 1, as well as the updates noted above.

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New paper updates lack of trend in W Hudson Bay breakup/freeze-up dates to 2015

A newly-published paper shows that there has been no trend in the time Western Hudson Bay polar bears spent onshore between 2001-2015 due to sea ice conditions at breakup or freeze-up (previously available to 2010 only), despite the marked decline of global sea ice since 2007.


Figure 3 from Castro de la Guardia and colleagues (2017) showing freeze-up and breakup dates and ice-free days 1979-2015 for Western Hudson Bay. Figure with caption, copied below, explains symbols.

Previously, a 2007 paper by Eric Regehr and colleagues for WHB bears up to 2004, which was used to support the US bid to list polar bears as ‘threatened’ with extinction, concluded that between 1984 and 2003, bears were spending 3 weeks longer onshore than they did in the 1980s.

The big news from Castro de la Guardia et al. (2017) is that polar bears spent longer onshore from 1979-2015 by … 3 weeks. That is, no change from the situation in 2004. Wow!

Note the population size of the entire WHB subpopulation has also not declined since 2004 and is currently estimated at about 1030, based on a 2011 aerial survey (Stapleton et al. 2014).

Thanks to Andrew Derocher for the heads-up tweet.

From the abstract (my bold):

We found that the ice-free period in this region lengthened by 3 ± 0.8 wk over the period 1979−2015. Polar bears migrated onshore 2 wk earlier and offshore 1 wk later in the period 2005−2015 than in 1980−1989.

Here is the region in question, illustrated by Fig. 1 from the paper:

castro-de-la-guardia-et-al-derocher-2017-fig-1a-locationThe significant information contained in this paper is breakup and freeze-up dates and length of the ice-free period data for 2010-2015, which has been unavailable until now. More excerpts and comments below, including Figure 3 with its caption. Continue reading

New paper asks: Has recent sea ice loss caused polar bear populations to crash?

A paper published today finds that predictions of polar bear population crashes due to summer sea ice loss are based on a scientifically unfounded assumption.


[The graphic above was created by me from the title page and two figures from the paper]

Specifically, this paper of mine addresses the basic premise upon which predicted population declines linked to modeled habitat loss made by polar bear specialists back in 2006 and 2008 (by the International Union for the Conservation of Nature, IUCN, and the US Fish and Wildlife Service, USFWS), and concludes that when assessed as a testable hypothesis against data collected since then, it must be rejected.

The forum for this paper is PeerJ Preprints,  which I found while looking for recent research papers about ringed seals. I discovered that Canadian ringed seal biologist Steven Ferguson recently used this service, which is free, open access, accepts review commentary, and will show up on Google and Google Scholar searches.

Ferguson et al. 2016. Demographic, ecological and physiological responses of ringed seals to an abrupt decline in sea ice availability. DOI:10.7287/peerj.preprints.2309v1 Pdf here. https://peerj.com/preprints/2309/

I decided that if this publication forum was good enough for Ferguson and his Arctic research community, it was good enough for me.

Crockford, S.J. 2017. Testing the hypothesis that routine sea ice coverage of 3-5 mkm2 results in a greater than 30% decline in population size of polar bears (Ursus maritimus). PeerJ Preprints 19 January 2017. Doi: 10.7287/peerj.preprints.2737v1 Open access. https://peerj.com/preprints/2737/  (pdf here).

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As polar bear populations fail to decline with sea ice, message of doom intensifies

If 10 years of summer sea ice levels expected to kill 2/3 of the world’s polar bears by 2050 hasn’t had an impact, why would anyone expect a bit less summer ice will do the job?


The more the polar bears fail to die in droves, the shriller the message from activist polar bear researchers – via willing media megaphones – that the great death of the bears will soon be upon us, just you wait and see!

Some big media guns were out this past week spreading the prophesy of doom fed to them by the polar bear researchers most committed to the “threatened with extinction” narrative: The New York Times, The Atlantic, The Guardian. The desperation is becoming palpable as the public catches on to their epic failure.

In 2007, the sea ice dropped to a level the experts said wouldn’t be reached until mid-century, and since then, it has remained at that low level (about 3-5mkm2, give or take some measuring error). And in 2007, US Geological Survey (USGS) biologists said with absolute confidence that when sea ice levels reached that point, 2/3 of the world’s polar bears would be gone.

No bears at all would remain, they said, in Western Hudson Bay (the Churchill bears), Southern Hudson Bay, Foxe Basin, Davis Strait, Baffin Bay, Southern Beaufort, Chukchi Sea, Barents Sea, Kara Sea, and the Laptev Sea:  ten out of 19 subpopulations would be extirpated if sea ice levels in most years dropped to the summer lows in the 3-5 mkm2 range.

On the basis of that prediction, polar bears were declared ‘threatened’ with extinction by the US Fish & Wildlife Service (USFWS) under the Endangered Species Act (ESA).

But nothing of the kind happened. There are still lots of polar bears – and not even struggling-to-survive bears but lots of fat healthy bears everywhere across the Arctic, in what were considered by USGS biologists to be the most vulnerable regions of all: Western Hudson Bay (i.e., Churchill), Chukchi Sea and Southern Beaufort (Alaska) and the Barents Sea (Norway).

This is the truth the world needs to hear: the experts were wrong. Polar bears have not been driven to the brink of extinction by climate change, they are thriving. This is the message of each of my two new books (one of which is appropriate for kids of all ages, see the sidebar).

In turns out that polar bears are much more resilient to changing levels of sea ice than data collectors assume and the proof is in the current healthy populations everywhere. Continue reading

No correlation between freeze-up dates for WHB sea ice & Churchill temperatures

This is a follow-up to my last post and this time, I’ll address the implied correlation between freeze-up dates for Hudson Bay and Churchill temperatures in November that is being made by folks who should know better .


Monday, 14 November 2016 a.m, over at Polar Bears International [my bold]:

“As a new week starts in Churchill, the weather is the warmest we’ve ever seen at this time of year. The tundra is muddy, with remnant patches of snow, and the bay is ice-free.” PBI Blog (no author designated)

Well, that may be true for the last few years – the high on 14 November 2016 (-1.20C) was the highest since 2012.

Andrew Derocher made a similar statement on the 4th (my bold):

There’s no sea ice anywhere in Hudson Bay yet—not even in the northern part of the Bay where ice should be forming. It’s above freezing today and if the forecast holds, it will be a record high for this date. It was 10 degrees colder last year at this time.”

Derocher is being unscientifically vague here and also misleadingly cites highs and lows as if they were the same. In fact, according to weather records kept by Environment Canada, for 4 November 2016 at Churchill, the daily high was +1.50C (compared to –1.50C in 2015). The daily low in 2015 was -15.30C, a 10 degree difference. The next-highest temp. for that date since 2012 was +0.70C in 2014 – hardly an earth-shattering difference.

However, if you are trying to draw conclusions about climate, you should go back at least 60 years (two climate periods of 30 years each). Temperature records for Churchill go back to 1943, which can be used to assess the claim for the 14th of November made by PBI.

According to weather records kept by Environment Canada, for 14 November at Churchill, the year with the highest temperature was 1975 (+2.20C):


That was Monday. But as of yesterday, the weather recorded – and the forecast for the following week (17-23 November) was quite different, as the screencap below shows:


The final recorded max. for yesterday (Thurs. 17 Nov) was -9.70C vs. a min. of -17.70C. So, a bit warmer during the day than predicted but as cold as expected overnight.

And for today, the current temperature in Churchill, as I write this is, is -190C (-310C with the wind chill) and the year with the highest temperature recorded for 18 November was 1944 (0.00C) – which was also the highest temperature for the 19th, recorded in 1943.

Ice maps and historical background below. See last post for recent multi-year comparison.
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