It's official! You can stop worrying about "climate change" effects on the polar bears, seals, and walrus – they've seen it all before, including ice-free summers

Paleoclimate + genetic study confirms: Arctic species adapted to sea ice changes

Guest essay by Dr. Susan Crockford

A new paper that combines paleoclimatology data for the last 56 million years with molecular genetic evidence concludes there were no biological extinctions over the last 1.5M years despite profound Arctic sea ice changes that included ice-free summers: polar bears, seals, walrus and other species successfully adapted to habitat changes that exceeded those predicted by USGS and US Fish and Wildlife polar bear biologists over the next 100 years.


Cronin, T. M. and Cronin, M.A. 2015. Biological response to climate change in the Arctic Ocean: the view from the past. Arktos 1:1-18 [Open access]

Thomas Cronin is a USGS paleoclimatologist at the Eastern Geology and Paleoclimate Science Center, and Matthew Cronin is a molecular geneticist at the University of Alaska Fairbanks (see previous postshere and here about Matt’s work on the genetics of polar bear evolution).

From the Abstract:

Arctic climatic extremes include 25°C hyperthermal periods during the Paleocene-Eocene (56–46 million years ago, Ma), Quaternary glacial periods when thick ice shelves and sea ice cover rendered the Arctic Ocean nearly uninhabitable, seasonally sea-ice-free interglacials and abrupt climate reversals.

The final discussion and two summary graphics from this paper (copied below) are especially useful:

The Cenozoic ecosystem changes in the Arctic described above are summarized in Figs. 5 and 6 within the context of climate changes over different timescales. Several conclusions can be made.

First, a seasonally ice-free marginal and central Arctic Ocean was common not only during Greenhouse worlds of PETM and Early Eocene, but also during the Pliocene, the early Quaternary before the Mid-Pleistocene Transition, during MIS 11, MIS 5 and regionally during the early Holocene.

During orbital climatic cycles of the last few hundred thousand years, interglacial periods were characterized by perennial and at times seasonal sea ice cover and inhabited by marine ecosystems similar to those of the pre-industrial Holocene. Some species thought to be dependent on summer sea ice (e.g., polar bears) survived through these periods.

In contrast, during glacial periods the much smaller Arctic Ocean and much of the adjacent continents were covered with massive ice sheets, thick ice shelves, and sea ice making large regions virtually uninhabitable to most species that inhabit today’s Arctic.

Despite the scale, frequency and rapidity of Quaternary climate changes, Arctic marine ecosystems associated with sea-ice habitats were extremely resilient, adapting through geographic range expansion into the Arctic during warm periods, and south into extra-Arctic regions during glacial periods. The stratigraphic record of the last 1.5 Ma indicates that no marine species’ extinction events occurred despite major climate oscillations.

The Cenozoic sedimentary record is too incomplete to conclude that large climate transitions caused extinction of Arctic species, but hopefully future IODP coring will recover more complete records. More generally, future cross-discipline studies of Arctic species and ecosystems combining molecular methods and paleoclimate reconstructions will result in a better understanding of how biological systems respond to climate changes. [my bold]

Cronin and Cronin 2015 Fig. 5: Summary of Arctic Ocean biological and climatic events during the Cenozoic. Blue letters are marine mammal events, red are climatic events, green are biological events. See text and Supplementary Tables 1–3 and Supplementary references for sources.

Cronin and Cronin 2015_fig5

Cronin and Cronin 2015 Fig. 6: Summary of Arctic Ocean biological and climatic events during mid-to-late Quaternary orbital glacial-interglacial cycles. Blue letters are marine mammal events, red are climatic events, green are biological events. See text and Supplementary Tables 1–3 and Supplementary references for sources

Cronin and Cronin 2015_fig6


Compare above to my previous post here on my estimate of sea ice coverage at the height of the last Ice Age (Last Glacial Maximum, copied below):

NH Perennial and Annual Ice at LGM_JFBaichtal_PolarBearScience_sm

Figure 2. Approximate sea ice extent at the Last Glacial Maximum: blue is perennial sea ice (present year round) and white is seasonal sea ice at its maximum (late winter). Purple is open ocean; black and dark grey are continental ice sheets; cream areas are land bridges exposed by lower sea level. Sea ice added by J.F. Baichtal, from this image, labels added by SJ Crockford. Click to enlarge.


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“A new paper that combines paleoclimatology data for the last 56 million years …”
Only 56 millions years?
Clearly a cherry-picked length of time probably designed to obscure the unprecedented nature of what is happening now.


Hey, don’t give the liberals any ideas….they think of enough silly stuff on their own !


My bad.
Unfortunately, for me, silly stuff is my specialty although I’m not silly enough to be a modern (progressive?) liberal.
In my rare non-silly moments I’m more of a Classic Liberal. Here in the US it is very possible that very many of us are Classic Liberals, but many just don’t know that they are because the Main Stream Medial labels them differently.


JFK would be embarrassed by today’s liberals (progressives / socialists ) …
” Ask not what your country can do for you, but what you can do for your country ” …


True dat.


I believe you guys are speaking of illiberal regressives . . so I suggest you start calling them illiberal regresives. People will get it ; )

Explain “clearly”.


You think you are joking but it is quite true! If they had gone back 56,000,001 years it totally destroys their argument. And DNA is not in the GCMs so you can’t use arguments from DNA. That would make you a big D-word. /totally not sarc.


Hmmm…who is this mysterious ” Guest ” blogger ??


Well, at the top it says “Guest essay by Dr. Susan Crockford”.

Marcus attempts at humor are do not seem to be working !!! LOL
[Ah! “But ’tis better that you hue more, or rue less? That is the question, lest yew wood eschew the rumor of humor no less than no more.” .mod]


Neither is my typing….ARRrrrrggggg…….


; )


Dr. Susan Crockford
Not so mysterious:

Sceptical Sam

Marcus, you are a fool. Can’t you read?


I go to her web site everyday, it was a bad attempt at a joke because only I understood it !! DOH !…


I got it…..but then, what does that say about me???


Latitude…it might mean you have had 2 more beer than I have !!

Folks, having a useful comment that’s later in the reply stream is better than making a dumb comment that’s early in the stream. Take the time to think (and proofread) before you comment.

Sceptical Sam

OK Marcus. My bad. Please accept my apology.
I owe you a beer.


Everybody stay calm.
The post was written by “the mysterious Dr. Susan Crockford”.
Everybody happy now?


Is she a tall mysterious amazonian?

B Cyr

who is Susan Crockford…University of Victoria adjunct professor Susan Crockford doesn’t seem interested in discussing the monthly payments she appears to receive from the climate denying Heartland Spinstitute.
“Crockford would not respond to emails, and refused to speak with the Martlet,” reports a UVic student newspaper attempting to probe the payments.
The Heartland Institute’s Denialgate documents indicate that the spinstitute gives Crockford $750 per month. She is one of three Canadian university professors on the denier dole at Heartland, along with Madhav Knandekar and Mitch Taylor.
She is also NOT a full-time professor and is NOT involved in climate science at all.

B Cyr,
Posting under an anonymous handle, you have nothing of substance to offer on the topic at hand so you try to denigrate my reputation.
So very childish.
Dr. Susan Crockford, zoologist


replies show a real need for an official sarcasm emoticon.



Does this mean that the global warming fanatics will stop using white color phase brown bears, excuse me, polar bears, in ads?


Yep, just after they stop using images of backlit steam from cooling towers as proof of “carbon” pollution. 😉

Bill Murphy

Well, since most leftist journalists think the Rankine cycle has something to do with permanent press laundry, I’m not holding my breath on either one.

Gunga Din

I’m not sure if I should be relieved or not.
Does this mean a polar bear might come knocking on my door here in Ohio or not? 😎


They don’t knock.


u.k……your thinking of Kodiaks and John Candy !

A new paper that combines paleoclimatology data for the last 56 million years with molecular genetic evidence concludes there were no biological extinctions over the last 1.5M years despite profound Arctic sea ice changes that included ice-free summers …

Hey, wait a minute! If the planet was a lot hotter in the distant past way before industrial society arrived — where did the SUVs come from that caused all that heating back then? Where did the man-made CO2 come from to “fry us”?? Dang, it is almost like someone with a PhD is saying that there is natural variation and mankind does not yet know exactly what causes it. Heaven forbid!
(OK, we could be talking about SUV driving ancient space aliens I suppose)


..It was Dino farts back then !!!


Imagine the size of the SUVs that the dinosaurs must have been driving.


It was Fred Flintstone wot dun it.

Dish it out, those polar bears can suck it up. A 700km. swim through the freezing Arctic waters is nothing to them. They could even manage a whole Warmista Scientist before breakfast.


“They could even manage a whole Warmista Scientist beforeFOR breakfast.”
Fixed it for ya….and Remember, Only forest fires prevent Bears…


In contrast, during glacial periods the much smaller Arctic Ocean and much of the adjacent continents were covered with massive ice sheets, thick ice shelves, and sea ice making large regions virtually uninhabitable to most species that inhabit today’s Arctic.
well, you think?


This post needs the most famous ice graph of all…..comment image?w=640&h=491&h=491


…and this one from the 1990 IPCCcomment image

DD More

Lat with Atude – Don’t forget to add the wording with that graph.
Changes and fluctuations in Arctic seaice extent have been analysed by Mysak and Manak (1989); they find no long term trends in sea-ice extent between 1953 and 1984 in a number of Arctic ocean regions but substantial decadal time scale variability was evident in the Atlantic sector. These variations were found to be consistent with the development, movement and decay of the “Great Salinity Anomaly” noted in Section 7.7. Sea-ice conditions are now reported regularly in marine synoptic observations, as well as by special reconnaissance flights, and coastal radar. Especially importantly, satellite observations have been used to map sea-ice extent routinely since the early 1970s. The American Navy Joint Ice Center has produced weekly charts which have been digitised by NOAA. These data are summarized in Figure 7.20 which is based on analyses carried out on a 1° latitude x 2.5° longitude grid. Sea-ice is defined to be present when its concentration exceeds 10% (Ropelewski, 1983). Since about 1976 the areal extent of sea-ice in the Northern Hemisphere has varied about a constant climatological level but in 1972-1975 sea-ice extent was significantly less.
About where we are now.

Gloateus Maximus

But now-Arctic marine mammals probably thrived in the then-icy North Pacific and North Atlantic Oceans during the LGM.

Gloateus Maximus

Arctic seals and walruses from Eemian Interglacial (Sangamonian) South Carolina:
They also inhabit the Eastern Seaboard of the US not only during warm interglacials but cold glacial maxima as well.


In a much shorter time frame, arctic sea ice extent may have been at similar levels or less compared to recent years in the 1930s and the 1950s. We do not have satellite data, but there is proxy average temperature from Svarlbard where the huge fluctuations in temperature are likely influenced by the sea ice extent.
What is more, the recent rise in temperatures might be partly influenced by the location of the thermometer next to a runway tarmac, near to aircraft exhaust gases.

David Ball

I am highly sceptical that polar bears can do science.

Gunga Din

If Mann can do it, why not polar bears?

Gunga Din

Forgot the “8-)”.


Gunga old soul,
If the mann can – surely our favourite climate bunny can . . . .
That said – if mann can, but didn’t get a Nobble – why should our beloved climate bunnies?
PS – I was a full [very full, after dinner] resident of the Glorious EU when it won some sort of Nobel – for what, I know not, but could look up, I suppose. Given the interest . . . .
Obviously I have a small share.
I’ll look to Wikithingy to validate my claim after my editing . . . .

Dr Crockford, I’m afraid that your estimate of the land ice sheets in figure 2 is a bit too high. See for instance fig 1 on page 1335:

The land ice sheets were already drawn in on that figure – see the original post. I only estimated the sea ice extent because no one else ever does. All they do is show the lowered sea level but that’s only part of the story.
Dr. Crockford

Robert B

The other part would be the sea level rise? Polar bears might not care but seals and pinnipeds might.
I was reading a summary of some work by an Australian scientist ( a Yank working here) who has been reported to be under investigation for fraud.
He claimed 10 years ago that the sea levels must have risen 5m in 20 years to inundate a forest of mangroves, about 9000 years ago. At least amazing that coral survived but surely that would have caused stress to species who like to breed on favorite beaches.

It’s interesting how the lowered sea levels leave the Greenland Sea as the only access to the Artic as far as ocean currents under the ice. Considering the current and projected positions of the continents, the planet may be in this Ice Age for quite a long time in geologic terms.

Thank you, the reason that I pointed out the discrepancy between the land ice estimates is because it nullifies the ice volume / sea level calculations as well as the benthic isotope stages (Shackleton 1967). There wasn’t nearly enough total ice mass for that, just large mammoth steppes instead.


I’m not saying, I’m just saying that a horse named “Anthonysgotgame” is gonna run at Santa Anita in about 10 minutes, the odds are currently 9/2 probably gonna go up a bit, maybe 6-7 to one.


Not a good result, dang it.


u.k. why do you always bet on the same horse if it keeps losing ??

Bill Illis

I wanted to note the Arctic PETM temperature of +25.0C that they are quoting is a complete fabrication.
Climate science has a particular capacity to misuse the dO18%% isotope data from this time period (well actually any time period but particularly the PETM and the Cenozoic time period) .
The dO18 isotope data they are using has a change of -4%% which in the Arctic would signify a local temperature change of only +12C for example (+6C on a global basis considering 2X polar amplification).
Greenland dO18%% changes by 10%% in an ice age (for a temperature change estimated at 10C using the proper formula or 25C in some climate science misused forums) so how could 4%% in the PETM indicate 25C in the Arctic.
The dO18%% values they are using (primarily Zachos 2001) were collected from all over the world and all of the oceans and the proper dO18% to Temp C conversion formula for this data in the Arctic (considering 2X polar amplification) would be just +12C in the PETM.
I have spent a lot of time working with these data sources and it just bugs me how often it is misused on purpose because it has been pointed out to the community many times on how it should be used.

Smokey (can't do much about wildfires)

@Bill Illis, I totally get when a pet peeve gets poked, but methinks one doth protest a bit much in this particular case.
Fig. 3 of the paper clearly shows that the dO18 proxy is only one of multiple global proxies used, and it is listed as a “global” proxy, rather than a specifically Arctic one. Further, the same figure shows a number of separate specifically Arctic proxies which were used as well. Finally, just to be a bit picky, I don’t see anyplace in the paper where they claim the PETM was 25C; Fig. 2 appears to indicate an average temperature of perhaps ~22.5C, with dips down under 20C. Perhaps I’m missing the reference? (They do show the ETM2 as having a spike above 25C; was that what you were looking at?)
If the authors have used ALL of their proxies incorrectly, then you might certainly have a significant complaint (one which I would appreciate seeing quantified), but it at least appears as though they have covered their bases on this particular point.

John F. Hultquist

On Fig. 2, note the Appalachian Mountains show as light yellow.
Many years ago I learned of the concept of Pleistocene glacial refugia across the Appalachian Mountains. I was raised in Western Pennsylvania where the up slope of the strata from farther west started making hills on which I roamed. We lived 25 miles east of the Allegheny River but frequently crossed into the glaciated landscape to the west, and north into New York State.
As a very young reader about nature, I was pleased than my little part of the world had acted as a refugia. It still pleases me, although now I’m in WA State and, again, close to the glacial advances – just not living where there was ice.
The funny thing is – I never worried about Polar Bears, or the other animals mentioned.
Thanks for confirming this boyhood belief.

Gary Pearse

As always Dr. Crockford, an island of sanity in a sea of new world order climate science. I have one issue with the Cronin/Cronin conclusions, though:
”during glacial periods the much smaller Arctic Ocean and much of the adjacent continents were covered with massive ice sheets, thick ice shelves, and sea ice making large regions virtually uninhabitable to most species that inhabit today’s Arctic.”
If this is meant to suggest that the habitat had shrunk, I think not. These animals would move southward with the sea/ice boundary and actually have an expanded habitat. I’m not a wildlife biologist, but surely the sea lions and harbour seals that are found today down to Los Angeles/San Diego were once part of or related to the arctic fauna. I imagine polar bears were found down the coasts of the US forty-eight east and west (they occasionally come ashore in Newfoundland today). Certainly mammoth skeletons (are they not tundra animals?) are found in these southerly localities.
I think the ability of a polar bear to swim 600-800km must have utility and this suggests to me that they can handle low Arctic ice and can easily depart if the basin ice is perennial for an extended period. Why do ‘mainstream’ specialists ignore the significance of the Churchill, Manitoba polar bears whose habitat is totally ice free for many months and is relatively warm during the summer when they speculate on the disasters of low ice extent?

If you look at my blog post about the LGM sea ice extent in which the ice map appears (which I provided a link to in this post), I examined the potential area involved.
You have to keep in mind that the ice in the entire Arctic Basin and its margins would have been too thick to support mammalian life (even if a few bacteria survived), which excludes a huge area of habitat that is used today in summer and winter.
The ice down the North American continental margins during the LGM, as far as I have been able to determine, was merely a narrow strip of ice much like exists off Eastern Greenland today.
One might argue that the area of sea ice habitat was approximately equal during the LGM and today but I am not convinced the evidence supports a claim that there was MORE habitat for truly ice-dependent species like polar bears and ringed seals during the LGM.

Maybe I am reading sloppily, but this statement is either mis-worded or completely and stupendously wrong:
“A new paper that combines paleoclimatology data for the last 56 million years with molecular genetic evidence concludes there were no biological extinctions over the last 1.5M years…”
At 12,800 years ago there were over 30 genera in North America that went extinct at the beginning of the Younger Dryas. Dozens also went extinct, I am told, in Eurasia as well, but I honestly haven’t had time to check on that.
Included in the extinctions were at least two that are considered to have been cold weather animals – the Mastodon and the Mammoth. The latter included at least three different species of Mammoths.
There is so much in the journal literature on this that this author must have simply misstated this. The author must have been addressing only arctic animals. But the present scientific reality is that mammoths and mastodons were certainly arctic animals. In fact, the most recent date for a mammoth on the North American continent was at the edge of the Beaufort sea, dated to 10,000 calibrated years ago.
So, Arctic and extinct. Mammoths. MUCH less than 56 million years ago.
What is this author THINKING?

Oops! That last date should be 1.5 million years ago, not 56.

Perhaps poorly worded? It should have included the qualifier “of Arctic marine animals” – the paper deals with Arctic marine species, not terrestrial. I may have assumed that would be obvious since the rest of that sentence discussed sea ice changes, but apparently not.
That was MY summary statement, not the authors of the paper, so if it was too imprecise to be abundantly clear to all who read the entire sentence, it’s on me. I guess I could have done better.

susan – Ahhh

Susan –
Ahhh! Thanks! I THOUGHT it was just the wording not being precise enough. But I couldn’t be sure, so I thought I should speak up.
Do you have the option of going and editing it in the opening of the post?

this is a natural thing that happens, but idiots like to make money using the fear factor on global warming.
its all a myth, Al Gore has made millions on this scare tactics. people need to grow up and stop believing all this dome and gloom shit

Herb Ziegler

I read an interesting article the other day where it stated that schools have been teaching the global warming theory since the 1990’s. Students naturally believe everything that their teachers tell them and it is for this reason there are so many young folks convinced that global warming is caused by CO2. It would be nice if as the grew up they followed up the science and found out what the truth is.

I have begun taking the tack of simply stating that the science is weak, much weaker than anyone lets on, and has ALWAYS been weak. That it’s just not well done science. People that know me or meet me pretty quickly realize that I am a pretty scientific kind of guy, even if my science is weaker than many hear, so hopefully some day they can put those two things together and wonder just what it IS that Steve thinks is so bad.
And MAYBE, sometime, when the one science-minded guy in the room thinks global warming is bad science, one can perhaps hope that some one among them might realize that and – like you say – take a closer look.

johann wundersamer

Great read, Mr. Cronin, T. M. and Mr. Cronin, M.A. !
Thanks for the ever eloquent tough humor, Dr. Susan Crockford !
Regards – Hans