News media hype the latest polar bear scare based on discredited RCP8.5 climate modelling.
A paper published in Nature Climate Change on Monday (20 July) presents yet another version of the ‘polar bears are going extinct unless we stop driving cars’ prediction the public has been inundated with since 2007.
The outcome of this new model suggests that several polar bear populations in Canada (but especially Southern Hudson Bay, Western Hudson Bay, and Davis Strait), are particularly vulnerable to catastrophic decline over the next few decades and concludes that virtually all 19 subpopulations will be on their way to extinction by the end of the century unless the world drastically and immediately reduces its production of human-produced CO2.
The media have obliged by publishing uncritical model accounts: the BBC offered “Climate change: Polar bears could be lost by 2100”, while the New York Times suggested “Global warming is driving polar bears toward extinction, researchers say”. The activist conservation organization Polar Bears International (where co-author Steven Amstrup works) put it this way (in a video): “When will polar bear populations collapse? The answer is up to us.”
However, zoologist Susan Crockford has pointed out that the creators of this new model incorrectly used the widely discredited RCP8.5 climate scenario. The RCP8.5 climate forecast was recently exposed in a peer reviewed paper published earlier this year by Zeke Hausfather and Glen Peters as being an implausible ‘worst-case’ scenario that assumes an unrealistic 500% increase in coal and a 60C rise in global temperature by 2100. This alone is enough to discount the polar bear prediction as scientifically implausible.
Crockford also notes that the paper uses only polar bear data from Western Hudson Bay (a subpopulation that is far from typical) as a proxy for all polar bear subpopulations worldwide. For example, even in the 1980s (the ‘good times’ for polar bears), Western Hudson Bay bears spent the longest time on land during the summer but most females still managed to produce three cubs per litter and wean them at one and a half years of age, whereas females in all other locations typically gave birth to twins weaned at two and a half years of age.
The combination of inappropriately using Western Hudson Bay data as a proxy for the response of all other subpopulations of bears to future sea ice levels, coupled with the dependence of the model on the most extreme and now discredited RCP8.5 climate scenario, is all that’s needed to dismiss it as exaggerated-fear-mongering-by-proxy. Why would anyone believe that the output of this new model describes a plausible future for polar bears?”