Uncertainty spells extinction for polar bears, unless we accept it*September 8, 2007 at 6:42 am | Posted in Arctic, Climate change, Extinction, Habitat destruction, Habitat loss, Habitats, Model uncertainties, Polar, Polar bears, Reports, Sea ice decline, Threatened, Uncertainties, USGS | 4 Comments
* Uncertainty, I mean. If we accept uncertainty and get on with taking climate-beneficial action—despite uncertainty—using the best informed judgement we can muster, then perhaps Arctic habitats have a chance of persisting, even though they are certain to deteriorate in our lifetimes. There is still time turn the situation around if we make significant and rapid cuts in our greenhouse gas emissions from now on.
So, here I am, checking up on the projected demise of polar bears due to habitat loss, after watching another Attenborough programme with the kids which mentioned that the continued home-melt of the polar bear spells extinction for these amazing creatures sometime in the next century. This is not news, it is just something worth checking, we thought. Little did we know that, somewhere across the Atlantic, there was a miserable little-trumpeted announcement while we were sleeping last night. (By twenty-four hours later, the news had travelled far and wide.)
Suddenly, I came across some new news on the United States Geological Survey (USGS) website on this page entitled:
You may be forgiven, kids, for thinking that USGS has actually found a new polar bear. Far from it.
This recent PDF document on Climate Model Uncertainty takes the lead at the top of that page:
Newly-released USGS information from 9 recent studies presents relationships of polar bears to present and future sea ice environments.
Despite having no date on the front cover, this refers to nine reports (of which this is one) completed between February and August 2007. So, that, in my interpretation dates this as pretty recent!
Uncertainty in Climate Model Projections of Arctic Sea Ice Decline: An Evaluation Relevant to Polar Bears
By Eric DeWeaver
This report describes uncertainties in climate model simulations of Arctic sea ice decline, and proposes a selection criterion for models to be used in projecting polar bear (Ursus maritimus) habitat loss. Uncertainties in model construction are discussed first, both for climate models in general and for their sea ice component models. A key point in the discussion is that the inherent climate sensitivity of sea ice leads inevitably to uncertainty in simulations of sea ice decline. The ability of climate models to simulate gross properties of Arctic ice cover, including the annual mean, seasonal cycle, and recent trends, is then assessed, followed by a review of model projections of 21st Century decline. The proposed selection criterion selects models with less than 20% error in their simulations of present-day September sea ice extent, where extent is defined as the area of the Arctic with at least 50% ice cover. Of the 10 models satisfying this criterion, all lose at least 30% of their September ice extent, and 4 lose over 80% of their September ice by the middle of the 21st Century (years 2045 to 2055). By the end of the 21st Century (years 2090 to 2099), seven of the models are essentially ice free in September.
The U.S. Fish and Wildlife Service (USFWS) proposed listing the polar bear as a threatened species under the Endangered Species Act in January 2007. To help inform their final decision, they requested that the U.S. Geological Survey (USGS) conduct additional analyses about polar bear populations and their sea ice habitats. Between February and August 2007, USGS and collaborators developed nine reports targeting specific questions considered especially informative to the final decision. This is one of the nine reports. This report addresses climate model projections of Arctic sea ice decline, focusing on factors contributing to uncertainty in those projections.
This report has two goals. First, I describe the kinds of uncertainty inherent in climate models, particularly those uncertainties that directly affect the reliability of their projection of future Arctic sea ice conditions. The purpose of this description is to provide background helpful to polar bear scientists and managers, because an understanding of the future for polar bears necessarily requires an understanding of projections of sea ice. Second, I propose a criterion for selecting a subset of the available climate models for use in projections of future polar bear habitat.
Among the Concluding Remarks:
The close association between uncertainty and climate sensitivity suggests that future climate projections will always be expressed in terms of a range of outcomes. Uncertainty does not arise because the models are bad, but because the climate system is sensitive. The most dramatic forms of climate change, sea ice decline in particular, will always be the most difficult to simulate.
Perhaps the most important lesson from the extensive history of climate projections is that uncertainty, both in model construction and from internal variability, is an essential ingredient of the climate change problem. We anticipate that future generations of climate model projections will continue to produce a substantial range of estimates of the pace of sea ice loss. As with present models, the best guidance from these models will come from selective subsets, using the ensemble mean as the best estimate and the ensemble spread to cover the probable range of outcomes. The recent climateprediction.net study by Knutti et al. (2006, see section 1.3 above) suggests that it is difficult to assign an upper bound to the global temperature increase which could occur due to increased CO2. In that case, the range of estimates of Arctic sea ice decline examined here may also be too conservative.
So now I am hoping we get an Administration that can get over the uncertainty of uncertainty and lead the battle to combat climate change despite uncertainty. We cannot completely eliminate uncertainty, so let’s quit adding more studies into degrees of uncertainty of this and degrees of uncertainty of that, and accept that we live in an uncertain world, and we have to do what’s best. Even if we could be wrong.
There is a Press Release, published yesterday, another nice Friday afternoon release, on this very topic:
Future Retreat of Arctic Sea Ice Will Lower Polar Bear Populations and Limit Their Distribution
Released: 9/7/2007 2:48:28 PM
U.S. Department of the Interior, U.S. Geological Survey
Office of Communication
119 National Center
Reston, VA 20192
Future reduction of sea ice in the Arctic could result in a loss of 2/3 of the world’s polar bear population within 50 years according to a series of studies released today by the U.S. Geological Survey.
Last December, Secretary of the Interior Dirk Kempthorne announced that the U.S. Fish and Wildlife Service (Service) was proposing to list the polar bear as a threatened species under the Endangered Species Act. In January 2008, following a one-year review period, the Service is expected to make a recommendation to Secretary Kempthorne on whether or not to list the polar bear as threatened. To assist the Service in making that recommendation, Secretary Kempthorne requested USGS leadership in studies to inform the Service’s deliberations on polar bear status. This information summarizes and integrates the results from a series of studies on polar bear populations, range-wide habitats and changing sea ice conditions in the Arctic.
In making the announcement last December, Secretary Kempthorne said: “I am directing the U.S. Fish and Wildlife Service and the U.S. Geological Survey to aggressively work with the public and the scientific community over the next year to broaden our understanding of what is happening with the species. This information will be vital to the ultimate decision on whether the species should be listed.”
Specifically the USGS has improved knowledge on the status of three polar bear sub-populations, projected numbers of polar bears into the future in relation to sea ice and integrated the information into a range-wide assessment of polar bear status under scenarios of future climate change.
The newly-released USGS information, presented to the Service in the form of nine administrative reports to be open for public comment, will now be considered within the context of the Fish and Wildlife Service’s one-year review. The Service will analyze it and other information provided by scientists, government agencies and the public in order to arrive at an informed and scientifically justifiable decision. That decision is due in January.
The team investigating the future of polar bears and their habitat included scientists from the USGS, other American and Canadian government agencies, academia and the private sector.
“This team has done a tremendous job in furthering polar bear science through the use of long-term observational measurements on polar bears, their habitats, and many other factors integrated into a range of new and traditional models,” said Mark Myers, Director of the U.S. Geological Survey.
During a six-month period of intensive analysis of both existing and new data, the team documented the direct relationship between the presence of Arctic sea ice and the survival and health of polar bears. Polar bears depend on sea ice as a platform to hunt seals, their primary food. But sea ice is decreasing throughout their Arctic range due to climate change. Models used by the USGS team project a 42 percent loss of optimal polar bear habitat from the Polar Basin during summer, a vital hunting and breeding period, by mid-century.
In addition to forecasts, declines in habitat have been recorded throughout the Polar Basin over the past 20 years of observations. To project future sea ice conditions, USGS scientists used 10 general circulation models that best approximated observed trends in sea-ice loss and could be expected to do the best job of simulating future conditions. Scientists characterize their conclusions as conservative because even the best available models are believed to underestimate the actual decline in Arctic sea ice.
The reports are available to the public at Polar Bear Finding Web page.
Update: And here, well caught by Defenders of Wildlife, is a response to that late-breaking, bury-it-late-on-a-summer-Friday-afternoon news:
WASHINGTON, Sept. 7 /PRNewswire-USNewswire/ — The following is a statement by Rodger Schlickeisen, president of Defenders of Wildlife, in reaction to the USGS studies confirming the threats to the polar bear due to global warming.
“The results of the scientific studies released by USGS today provide very sobering information on the fate of the polar bear. The government’s top scientists have painted a bleak picture: there will be no polar bears in Alaska within the next 50 years due to a drastic decline in Arctic sea ice by mid-century.
“We should remember that polar bears are not the only animals that rely on Arctic sea ice. Therefore, we can expect that not only will polar bears be in jeopardy, but so too will the walrus, ivory gull, spectacled eider, and ringed, bearded and harp seal, to name just a few.
“There should be no question now that the polar bear should be listed as a threatened species. The Bush administration has to face the reality that global warming is real, with real and devastating consequences for wildlife and people.”
Defenders of Wildlife is dedicated to the protection of all native animals and plants in their natural communities. With more than 900,000 members and activists, Defenders of Wildlife is a leading advocate for innovative solutions to safeguard our wildlife heritage for generations to come. For more information, visit http://www.defenders.org.