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Polar Bear Population Projections: Reliability in the Face of Uncertainty

Tuesday, March 6, 2012 @ 7:30 PM-9:00 PM

Featured Speaker: Steven C. Amstrup, PhD, Senior Scientist, Polar Bears International

In 2007, Steven Amstrup’s research team at the US Geological Survey projected that by mid-century we would lose two-third’s of the world’s polar bears and that there was reasonable chance they would be extinct by the end of the century if we continued to follow greenhouse gas (GHG) emissions business as usual. More recently, Steven and his colleagues have shown that preventing polar bear extinction is largely a matter of controlling greenhouse gas rise.

Given the natural chaos in the climate system, many have questioned how we could reliably predict what populations might be like in 50 or 100 years. After all, we cannot even predict next week’s weather! The answer to this apparent paradox lies in the concept of threshold exceedence. The persistent climate forcing that results from growing atmospheric GHG concentrations requires a directional response in earth’s climate-that is, the earth must warm. Polar bears depend on sea ice for catching their marine mammal prey. A warmer world will hold less sea ice habitat. Natural variations in weather and climate mean we cannot predict the first summer the Arctic will be ice-free or the first year the mean Cleveland temperature will be 2 degrees higher than it is now, but without GHG mitigation, crossing both thresholds is assured. The farther into the future we look the greater the likelihood these and other critical thresholds will have been crossed.

The most trustworthy climate models are consistent in predicting summer sea ice disappearing between the middle and the end of the century. Even if those models are wrong, the sea ice eventually will disappear without mitigating GHG rise. Warming will constrict polar bears into ever smaller and more vulnerable areas. Seasonal and annual fluctuation in the weather and climate mean that in the short term, some years will be bad for polar bears and some will be better. In the long run, without GHG mitigation, all years will be bad for polar bears and they ultimately will disappear. The good news is that it is not too late to prevent this from occurring. Prompt mitigation will prevent much sea ice loss and preserve sustainable polar bear populations over a majority of their current range. Join Polar Bears International senior scientist, Steven Amstrup for the good news on why it’s not too late to prevent the demise of the polar bear.

Location: Saint Louis Zoo Living World Auditorium. Parking is FREE in the Zoo North Lot.

FREE and OPEN to ALL. Adults, teachers, middle and high school students, and the general public are invited to attend these no-cost lectures on topical issues in science. For more information call 314-646-4544 or 314-533-8586. Registration not required.

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Date:
Tuesday, March 6, 2012
Time:
7:30 PM-9:00 PM
Event Category: