The Department of the Interior is expected to announce soon that polar bears have been designated a threatened species under the Endangered Species Act. The justification for such a move will not be that polar bears are actually declining. Rather, the justification will be based on speculation that they may decline in the future as a result of global warming. Global warming, so the argument goes, is causing Arctic sea ice to melt, and, unless that process is arrested, polar bears will be unable to survive because they need Arctic sea ice to reach their primary source of food: seals.
As might be expected with a speculative scenario, there is uncertainty about whether it is actually true. However, there is certainty that if Interior goes through with the designation, it will give the department enormous power to regulate economic activity under a polar bear mitigation plan. Hopefully, before the government puts shackles on the economy, it weighs very carefully the significant uncertainties about whether the polar bear is actually threatened.
Ken Green of the American Enterprise Institute has a new paper detailing the many problems with the supposed global warming/sea ice/polar bear link. Green notes in particular that while there has been some evidence of sea ice loss in the Arctic, there is not enough evidence to conclude global warming is the culprit.
- An October 2007 NASA study concluded that changing wind patterns are responsible for sea ice loss. New wind patterns have compressed sea ice and moved it into the Transpolar Drift Stream which has taken the ice to lower latitudes where it has melted.
- A study reported in Nature in January 2008 reported that Artic heating has been happening higher in the atmosphere than predicted by global warming models. Meanwhile, the predicted warming at the earth’s surface has not been detected. Green comments: “What the data seem to indicate is that heat from the tropics is being transported to the Arctic by wind patterns that are not well understood.”
If global warming isn’t the cause of recent sea ice loss, then there is no reason to assume that the loss of sea ice is a long-term trend.
There are also significant uncertainties about how the loss of sea ice will impact polar bear populations. Analysts use a tool called population viability analysis (PVA), which is fraught with problems. Green writes:
Like various statistical models, PVA can be a useful tool in policy cost-benefit analysis, but its results are only as accurate as the data and the model assumptions that go into it. Polar bear populations are difficult to measure, in part because they travel so much, are sparsely populated, and live far from people. The highest-quality data on polar bears come from aerial studies and mark/recapture studies, in which scientists “mark” polar bears and estimate how many are in a population based on sightings of marked and unmarked animals. There are other methods of estimating polar bears, but the report describes those methods as having “unknown and in most cases inestimable errors.”
Of the nineteen subpopulations of polar bears, the IUCN reports estimates based on aerial or mark/recapture data for fourteen, but of these, only five are based on data collected after 1998. Twelve had sufficient data for the report to predict population trends, and of the five marked as declining, only two of these estimates were based on aerial or mark/recapture data from after 1998. Scientists have collected more recent data on polar bear populations, but from studies with more “inestimable errors.”
But, says Green, we do know that polar bears “have survived past periods of extensive deglaciation.”
Polar bear fossils have been dated to over one hundred thousand years, which means that polar bears have already survived an interglacial period when temperatures were considerably warmer than they are at present and when, quite probably, levels of summertime Arctic sea ice were correspondingly low.
Listing the polar bear as threatened would give government incredible power to control economic development. The government, therefore, should feel an obligation to demonstrate that the polar bear actually is threatened before it lists the polar bear as threatened. Congress, meanwhile, should revisit the whole concept of delegating power that is essentially a legislative power to an unelected government agency. If global warming is a problem justifying economic sacrifice, then Congress should feel an obligation to actually vote for such sacrifice.
Cross-posted at InsiderOnline.