By mid-century scientists predict declining Arctic sea ice levels will lead to the loss of nearly two-thirds of the world's polar bear population, according to a series of U.S. Geological Survey reports produced in September 2007.
However, the Department of Interior remains months overdue on making its final decision on whether polar bears should be considered a threatened species under the Endangered Species Act.
According to Center for Biological Diversity - the group that first led the Endangered Species Act petition for polar bears in 2005 - the failure of the federal government to meet the Endangered Species Act deadline is against the law.
Just last month, the CBD, along with environmental advocacy groups Greenpeace and the Natural Resources Defense Council sued the Bush administration for its failure to make a decision regarding the classification of the polar bear by the late-January 2008 deadline set by law.
If polar bears are eventually listed under the Endangered Species Act, it will mark the first time a species is considered threatened explicitly by global warming.
Climate physicist and UW-Madison professor Eric DeWeaver was one of 16 researchers on the international team involved in producing the USGS reports. DeWeaver said his expertise in climate models and his interest in interdisciplinary research drove him to become part of the International Polar Bear Science Team.
DeWeaver shared his findings and insights into the pending federal decision with The Daily Cardinal.
The Daily Cardinal: What was your task as part of the International Polar Bear Science Team?
Eric DeWeaver: I compared climate model simulations of 20th century Arctic sea ice to 20th century observations to see which models have the most accurate present-day sea ice simulations. We used a subset of most accurate models to capture the likely range of outcomes for future sea ice loss due to global warming
DC: How do climate models work?
DeWeaver: The Earth receives energy from the sun, which is absorbed and exchanged between its land surfaces, oceans, atmosphere and sea ice '¦ CO2 affects the transfer of energy from the Earth to outer space that keeps the planet cool. Models attempt to simulate the energy exchange between atmosphere, land surfaces and sea ice through mathematical equations based on the laws of physics. When climate models are used to inform policy decisions it's important we use the most credible models and also acknowledge the degree of uncertainty in the model simulations.
DC: Would you consider the uncertainty of climate models to be a limitation?
DeWeaver: Science never fills in the gaps completely. We are not soothsayers. We do not read tea leaves. We use science to make projections. Some people assume you can plug information into a model, turn a crank and it'll tell you the future exactly. This is not the case. What models give you is a range of possible environmental outcomes.
The only way to eliminate all uncertainty is to eliminate all uncertainty in our understanding of the physical processes and their representation in computer models, which is not realistic. Just like you will probably never get a perfect weather forecast, climate models cannot be perfect.
It would be a bad idea to base all of our understanding of global warming on models by themselves; we must also look at observations. How do we know the Earth is warming? We can see the changes around us.
DC: What did the sea ice models you used in your study predict for the future of Arctic ice?
DeWeaver: Four out of 10 credible models show an 80 percent reduction in September sea ice by 2050; by the end of the century, seven out of 10 models show no September sea ice.
DC: What do rapidly declining levels of September sea ice mean for polar bears?
Deweaver: The life of a polar bear is 'feast-and-fast.' Polar bear mothers go into maternal dens in November, give birth and nurse two cubs to between 25 to 30 pounds and don't eat again until April. As a result, the late summer is crucial for polar bears to store food.
With September sea ice rapidly declining the polar bears will have reduced time for hunting. The question becomes how much food deprivation can a mother polar bear withstand?
One group tracking the weight and survival of polar bears for the past five years found in the last two years, when sea ice in the study area went away for more than 125 days per year, polar bear survival rates were poor.
Based upon the models and habitat information on polar bears, our research predicts that two-thirds of the present polar bear population will be gone by mid-century; by the end of the century, polar bears will likely be reduced to a remnant population living in the Canadian Arctic.
DC: Do you think there's anything that can be done to save the polar bears?
DeWeaver: I don't think we've reached the tipping point. If people try to mitigate CO2 emissions, then I believe we could save the polar bear habitat. Any strategy to control will take time to implement and global warming has inertia, but I don't think it's too late.
DC: If all scientific evidence suggests polar bears are in trouble, why is the federal government delaying making a decision about classifying them as a threatened species?
DeWeaver: I don't know, but a decision has to be made. While there have been delays at every stage of the process, the good news is scientists are being listened to and appear to be informing the political process.
Some policy makers want to use uncertainty as a fig leaf for inaction. However, any policy decision ever made despite some level of uncertainty. We have to be leery of the doublestandard.
DC: What's the most important message you want to get across to readers of The Daily Cardinal regarding the pending federal decision about polar bears?
DeWeaver: Pay attention to what the government is about to say on this issue. The listing will have an impact on other animals and other listings and will show how the government is thinking about these issues. These are important questions and they are going to come up over and over again '¦ there's a lot to think about.
