“What nonsense! Does anybody realize that the polar bear population has increased from 5,000 in 1972 to 25,000 today! To be put on a threatened or endangered list, shouldn’t the numbers be declining???”

This, from blog reader Vince, was a recurring theme among the hundreds of responses to yesterday’s decision to list the polar bear as a threatened species under the U.S. Endangered Species Act.

I’d seen this number cited before, but I’d never seen any attribution as to its source. After some web research, conversations with polar bear researchers, and some help from a longtime journalist who specializes in animal/wildlife stories, here’s what we could find.

The number has some basis in fact, but is misleading: If polar bears have built in numbers since the 1970’s, it probably had a lot more to do with hunting bans than any aspect of global warming.

Polar Bear habitat covers five nations: The U.S. (Alaska), Russia, Canada, Denmark (Greenland), and Norway (the Spitsbergen and Jan Mayen Islands). Those five nations, along with the International Union for the Conservation of Nature, took a stab at guesstimating worldwide polar bear populations in the early 1970’s. For example, based on observer reports from Arctic villages, ships, and other sources, U.S. researchers came up with an estimate of 18,000 polar bears throughout the Arctic. The Canadian Wildlife Service set the number at 20,000. The Soviet Union submitted the low bid, estimating a worldwide population of 5,000 animals. In late 1973, the five polar bear nations signed the International Agreement on the Conservation of Polar Bears, and agreed to go with the lower Soviet estimates in order to wrap up a wildlife agreement that was unheard-of during the Cold War years.

Whichever of these estimates may have been closer to the real number is still unclear. It’s generally believed that polar bear populations did grow after the treaty was signed — but it had nothing to do with the Arctic climate: The Treaty also set restrictions on trophy hunting for the big bears — outlawing the then-common, controversial practice of hunting polar bears by helicopter. The U.S. had already banned all but some native subsistence hunting the previous year, through the US Marine Mammal Protection Act.

But there’s another revealing number from that year: Merritt Clifton, the editor of Animal People , dug through online newspaper archives and discovered this tidbit: Canada was the last Arctic nation to curtail large-scale hunting of polar bears. According to a 1973 United Press International story, Canada’s Northwest Territories allowed a quota of 422 bears to be killed that year.

So let’s do the math: If the 5,000 number were correct, they authorized the killing of nearly 10% of the world’s polar bear population — In just one part of Canada’s polar bear habitat, and in just one year. It’s very difficult to accept that a global population of only 5,000 could have sustained that rate of loss.

More recent polar bear research suggests that any growth in worldwide population has likely stopped, and that the bears themselves are generally thinner and give birth to fewer young. Here’s the key USGS paper on the bears’ status in the U.S. part of their habitat. The current estimates for global polar bear population is between 22,000 and 25,000 — numbers too big to risk any immediate extinction. But the overwhelming amount of research on polar bear health and future prospects says they’re in for a rough ride in the next fifty years.

One credentialed, dissenting scientist is Dr. Mitchell Taylor, a researcher who did much of his work on behalf of Canada’s Nunavut Territory. Taylor has acknowledged that climate change is impacting polar bears, but he does not see a great risk of collapse of the species. The recently-retired Taylor has researched bear populations in the Davis Strait, between Canada and Greenland. Taylor is due to publish his results later in the year, and in newspaper interviews, he has said that bears in the region are healthy in both size and number. Critics point out that Nunavut, Dr. Taylor’s longtime employers, have a huge stake in what remains of the legal polar bear trophy-hunting business, estimated to be a $2 million business for impoverished Nunavut communities. Yesterday’s US decision to declare the bears as “threatened” will dry up a longstanding loophole: U.S. trophy hunters were barred from killing bears in the U.S. (Alaska), but prior to the ruling, could still obtain permits to hunt polar bears in Canada and import the trophies.

-Peter Dykstra, Executive Producer, CNN Science Tech & Weather

U.S. Interior Secretary Dirk Kempthorne announced that the polar bear will receive protection as a “threatened” species under the U. S. Endangered Species Act. Conservation groups had petitioned the U.S. to give protection to the mammals — citing a rapid decline in Arctic sea ice, and U.S. government studies predicting a rapid decline for the bear population due to loss of habitat. The government was under federal court order to rule on the bears’ status by tomorrow.

CNN.com will have full details soon.

-Peter Dykstra, Executive Producer, CNN Science & Technology

The world’s oldest living tree has been found in Sweden, along with remnants of several other generations of it. A ripe 9,550 years old, this special spruce tree in Fulu Mountain, Dalarna, has profound implications for climate change.

The tree is single-stemmed and stands 5 meters — about 16.4 feet – tall. Researchers at Umeå University found decaying wood remnants in the soil that date back 375, 5,660, 9,000 and 9550 years, representing generations of the same genetic individual.

For thousands of years, the spruce appeared in a shrub formation called krummholz. But with warming in the last century, the tree changed its growth and became the single-stem spruce seen in this photo.

“The fact that we can see this spruce as a tree today is a consequence of recent climate warming since about 1915,” said Leif Kullman, Professor of Physical Geography at Umeå University.

Kullman and colleagues study how tree lines, or the edges of tree habitats, respond to climate change. They have shown that trees of different species have advanced into the alpine tundra by more than 650 feet during the past century, Kullman said, suggesting that there is less tundra area than there has been for 7,000 years.

“As we see it, that is the most interesting aspect of this and similar trees,” he said. “That this may also be the oldest tree in the world is more of a curiosity from a scientific point of view.”

The tree has been named Old Tjikko after Kullman’s late dog.

–Elizabeth Landau, Associate Producer, CNN.com

Climate change discussions often focus on carbon dioxide, but another major culprit gets unleashed every time a truck drives on diesel fuel.

Black carbon, a principle component of soot, contributes more to climate change than previously thought, new research shows. In fact, black carbon could have as much as 60 percent of the current global warming effect of carbon dioxide, scientists reported in the journal Nature Geoscience.

Diesel combustion in trucks, buses and cars emit a lot of black carbon. The particulate air pollution also commonly comes from burning firewood, indoor cooking, and biomass burning.

Using data from satellites, aircraft and surface instruments, the scientists found that the warming effect of black carbon amounts to 0.9 watts per meter squared. That’s at least two times greater than estimates put forth by the United Nations-sponsored Intergovernmental Panel on Climate Change (IPCC), the researchers said.

Besides making things look dirty, black carbon particles contribute to the retreat of glaciers and pose a public health risk, said V. Ramanathan, co-author of the study and atmospheric scientist at the Scripps Institution of Oceanography at the University of California, San Diego.

A major difference between black carbon and carbon dioxide is in their respective life spans, Ramanathan said. Carbon dioxide molecules can stay in the atmosphere for more than 100 years after being released, whereas black carbon only stays up there for about 10 days.

Black carbon pollution is a problem worldwide, the scientists said. China and India are responsible for between 25 and 35 percent of black carbon in the global atmosphere, mostly from burning wood and cow dung for cooking and using coal for heating. Countries that extensively use diesel fuel for transportation are also responsible for a lot of black carbon pollution.

While policy action should be taken to reduce black carbon emissions, it would be a “catastrophic mistake” to think that’s enough, without also addressing the problem of carbon dioxide emissions, Ramanathan said. “We have to do both,” he said.

–Elizabeth Landau, Associate Producer, CNN.com

Want to know exactly where in the U.S. the biggest belches of fossil-fuel carbon dioxide are emitted? Researchers at Purdue University have just released a map that shows you, in more detail than ever before.

Source: Purdue University

The Purdue scientists say their system, called Vulcan, is more accurate than earlier inventories of CO2 sources, because it’s based on actual emissions of greenhouse gases, as measured by the EPA and other agencies, rather than estimates.

Another reason it’s more accurate, they say, is because it uses data collected every hour at local levels, rather than monthly on a state-by-state basis. The data are broken down into areas as small as 6 miles across.

Vulcan takes into account carbon dioxide from all sources that burn fossil fuels like gasoline or coal: vehicles, factories, home heating, power plants.

The Purdue researchers say when they combined a huge amount of data into a format that’s easy to grasp, they got some surprises.

“For example, we’ve been attributing too many emissions to the northeastern United States, and it’s looking like the southeastern U.S. is a much larger source than we had estimated previously,” says Kevin Gurney, the leader of the project, in a written statement.

At first glance, you may think that the CO2 emissions follow the roadways with amazing precision - for instance, along I-80 in northern Nevada. But that’s actually because the researchers built the map that way; all the emissions attributed to cars and trucks were shown hovering over the major roads.

Check out the little patch of clean air in upstate New York, close to the Vermont line: that’s the state’s 6-million acre Adirondack Park, created in 1892.

The Purdue researchers have also posted some videos from the Vulcan project on YouTube, including a cool animation of CO2 emissions over months, which are shown billowing off the map in a big brownish-purple cloud.

The researchers say because of the accuracy of the Vulcan tool, it could help policy-makers come up with more precisely targeted ways to battle greenhouse gas emissions.

And they say the project is not about assigning blame for greenhouse gases. “What Vulcan makes utterly clear is that CO2 emissions cannot be exclusively affixed to SUV drivers, manufacturers or large power producers; everybody is responsible,” Gurney says in the press release. “It’s not about politics. It’s about doing good science and solving the problem, and we can all be a part of that.”

The project included researchers from Purdue, Colorado State University and Lawrence Berkeley National Laboratory. It was funded by NASA and the Department of Energy.

–Kate King, Writer, cnn.com

A Meeting of Skeptics

Check out the Anderson Cooper 360 show tonight for Miles O’Brien’s report on the Heartland Institute’s 2008 International Conference on Climate Change. Judging just from the title, the meeting sounds official, maybe even boring…but it is in fact one of the largest gatherings of the year for global warming skeptics, doubters and dissenters.

Conference organizers bill it as the “first major international conference to focus on issues and questions not answered by advocates of the theory of man-made global warming.”

And they go on to say:

“The global warming debate that the public and policymakers usually see is one-sided, dominated by government scientists and government organizations agenda-driven to find data that suggest a human impact on climate and to call for immediate government action, if only to fund their own continued research, but often to achieve political agendas entirely unrelated to the science of climate change. There is another side, but in recent years it has been denied a platform from which to speak.”

They’ll get a platform tonight…but expect Miles to ask some tough questions…about the Heartland Institute’s ties to the oil and gas industry, about the overwhelming scientific consensus supporting the human link to climate change expressed last year by the blue ribbon Intergovernmental Panel on Climate Change (IPCC), and about just who in this debate might be trying to advance an agenda.

Heartland raised some eyebrows by offering “fellowships” to cover travel and lodging costs for legislators attending the conference. The conference literature says that no energy company funds are paying for the conference, but the list of sponsoring organizations include many groups who receive direct support from Exxon/Mobil and other oil and coal entities.

The conference agenda includes several credentialed scientists, and a few who are members of the IPCC. Those few are in the ironic, if not uncomfortable position of sharing a slice of the Nobel Peace Prize with Al Gore – who to many at this conference is the arch-villain of climate change. Others are political advocates from groups like the Competitive Enterprise Institute. And the political opposites of those groups are keeping their powder dry. Desmogblog.com, a website which describes itself as unmasking the motives of global warming skeptics, has labeled the conference a “Denial-a-palooza.”

–Kate Tobin and Peter Dykstra, CNN Science & Technology