Yesterday, the BBC published a story that gave the two most alarmist polar bear researchers on the planet a forum to market their ‘polar bears are doomed’ message. This time the desperation shows: watch how these biologists move the goal-posts, make claims so misleading they border on lies, and pretend they don’t have big, big trouble with their predictive models.
SOME HIGHTLIGHTS FROM “Will polar bears become extinct?”
Amstrup has a big problem — experts say his model is lousy science:
“The best estimates we’ve got indicate that we’ll probably lose somewhere around two-thirds of the world’s bears somewhere around mid-century, just based on the simple fact that we’re losing sea ice,” says Andrew Derocher, a professor of biological sciences at the University of Alberta and past chair of the International Union for the Conservation of Nature’s (IUCN) Polar Bear Specialist Group.” [my bold]
The “best estimates” Derocher refers to are results of a model that depended on one man’s opinion (Steven Amstrup’s) to provide most of the “facts” feed into the computer. Amstrup’s model may be the best they’ve got but IUCN experts say it was bad science and the PBSG won’t get away with using it again.
The PBSG have been told in no uncertain terms by their parent organization [the IUCN] that Amstrup’s model will not be acceptable as a valid argument for having polar bears retain their current status of ‘vulnerable’ (equivalent to USA ‘threatened’).
A new polar bear assessment is due by June 2015 (7 months from now) and the IUCN is demanding an argument with numbers – a model or models that include population estimates and so-called “vital rates” (like cub survival and size of litters) — numbers the PBSG still doesn’t have for many subpopulations.
If the PBSG can’t generate a scientifically sound model over the next 7 months, the Red List status of the polar bear will be demoted. PBSG biologists, including Derocher and Amstrup, are scrambling to come up with something before then because without future threats, polar bears are doing just fine.
[Note that the Commission on Environmental Cooperation, an arm of the North American Free Trade Agreement (NAFTA), also said Amstrup’s model was weak science (pdf here, link here) — it’s not just the IUCN that thinks so]
The problem of generation time
“Current bear population numbers aren’t really the problem. It is what is going to happen to bears in the future, Derocher says. He cites the international standard to consider conservation of a species, that of using the “three generation rule” looking forward in time. For polar bears, three generations is somewhere in the 36- to 45-year timeframe. In this timeframe, scientists predict rapid declines in sea ice.” [my bold]
This is actually the first time I’ve seen these researchers admit that three generations can be as few as 36 years, although this still ignores the work by Cronin et al. 2009, who determined it was as short as 30 years.
The petition to list polar bears as threatened in the USA in 2008 used a 3 generation time frame of 45 years (15 years per generation). Shortening that time frame to 30-36 years means the predictive models have to show a significant decline in population numbers coinciding with a decline in sea ice over a much shorter period of time.
Recall the admission earlier this year by sea ice experts (discussed here), that “the range at which you reach an ice free Arctic [in summer] will likely happen over a 20 year period and that there was no exact date.”
How a plausibly accurate, statistically sound prediction correlating future polar bear population decline with sea ice declines can be made over the next 30-36 years when the error bars for future sea ice declines are up to 20 years wide beggars belief.
More claims about WHB sea ice based on unpublished data
“When I first started working in Hudson Bay in the early 1980s, the sea ice would have already formed along the shore quite nicely by now,” Derocher says. “There were years when the bears were gone in the first week in November, but this year it is unlikely that we see any significant sea ice for at least a couple of weeks.“
In the last 30 years, bears have increased the amount of time they are on land by almost 30 days – staying another day longer each year – according to Amstrup. That means the bears are coming ashore to face food shortages before they have stored enough fat to last through the season, he says.” [my bold]
As I’ve noted again recently, none of the recent data Derocher refers to here has been published in any form, including the sea ice data. I’ve already addressed recent Western Hudson Bay sea ice changes here, here, and here.
But let’s bring this right up to date: see Figs. 1-3 below that show freeze-up on Hudson Bay this year is ahead of last year, which was an early freeze-up year, not late.
A claim so misleading it borders on a lie:
“Not all the bear populations are suffering though, Amstrup says. Bears in the higher latitudes, such as those in the Davis Strait, are thriving. With warming, annual ice cover replaces the thick multilayer ice, making it more suitable for seals, the polar bears’ main food supply.” [my bold]
Less than half of Davis Strait is further north than Western Hudson Bay (Fig. 4) and certainly has not seen multiyear ice replaced by annual ice cover – Davis Strait has always been covered in annual (1st year) ice that melts every summer. Yet, Davis Strait bears are thriving despite sea ice declines as severe as those experienced by WHB bears.
Moving the future global temperature goal posts:
“We don’t have any evidence that polar bears have experienced anything more than about a degree and a half temperature rise during their whole evolutionary history,” Amstrup says.
And, according to most of the predictive models we will be close to 2 degrees Celsius warmer for a global mean temperature within 50 years, and certainly within 100 years, Amstrup says. “Polar bears just simply haven’t experienced warming like this,” he says.”
Previously (and again in this piece), Amstrup said it was not the ultimate amount of warming but the rate of warming that really threatens polar bears, which I countered here [11,500 years ago, it warmed about 5-100C within 30 years or less, compared to the 30C over 30 years seen in the Arctic so far]
Now Amstrup also claims that although polar bears survived a global mean temperature one degree Celsius warmer than today during the Eemian Interglacial without an discernible repercussions, they are doomed if the global temperature reaches “close to 2 degrees Celsius” warmer than today. Perhaps a difference of a few tenths of a degree at most, if you take scientific error into account as you should. That’s a pretty sharp threshold for disaster.
Amstrup’s 2008 model that predicted declines in polar bear population over the next century generated Eemian-like sea ice conditions at the end of the century (i.e., ~ 1 degree Celsius warmer than today) – where did this “close to 2 degrees Celsius” escalation of warming come from?
They say it’s all about the sea ice but forget the bears:
“It is really quite simple and I come back to it time and time again: It’s just the habitat loss issue,” Derocher says. “If there’s not enough ice, we won’t have bears.”
Derocher makes it sound simple and all about what the ice does but it’s clearly not: polar bear biologists predicted Davis Strait and Chukchi Sea bears would be the first to suffer from the effects of profound sea ice declines in summer but both populations not only failed to suffer, they have thrived. Western Hudson Bay (WHB) and Southern Hudson Bay (SHB) have about the same changes to length of the ice-free period in summer, yet SHB bears are stable and WHB bears are only “likely stable” (according to the latest Canadian assessment, see Fig. 4 above).
All in all, a sad example of polar bear biologists desperately trying to save their message of doom, which really has to make you wonder: do they really want the bears to be OK?
Read the whole story BBC here.
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