Amstrup rebutts unscientific audit

PBSG member and USGS senior polar bear scientist Steven Amstrup Image: Courtesy by Steven Amstrup
As a part of the US process to evaluate the proposed listing of the polar bear as a threatened species in 2007, the US Department of Interior commissioned nine reports from the USGS that were published in September 2007. These reports carried out comprehensive analyses on the basis of best available knowledge on polar bears and climate change. Based on output from GCMs (general circulation models) used by IPCC (International Panel of Climate Change), and their own long-term polar bear datasets, Amstrup and his collegues carried out modelling exercises that concluded polar bears will be dramatically reduced in distribution and number as a result of rapid and dramatic reduction of critical sea ice habitat upon which they depend for foraging. The findings in two of these reports were challenged in a report authored by J. Scott Armstrong and coworkers.  The Armstrong et al. paper was published in the journal Interfaces in summer of 2008  (Interfaces, 38(5):382-405, 2008.).  Armstrong and his colleagues also made numerous public statements denying the USGS results. Steven Amstrup and colleagues have now rebutted this challenge in an article published in the same journal (Interfaces).  Amstrup also included an easy to read tutorial on global warming and projections of climate models in the rebuttal.  Hence, readers are made clearly aware that the threat to polar bears is real, unless actions to reduce greenhouse gases are taken.
Further reading:
Original reports from USGS
Armstrongs audit
Steven Amstrups new rebuttal
Published Friday May 08 2009 by Dag Vongraven