Just how much the state's snowpack shrank is stirring up heated debate among the region's climate scientists.

Share story

The number is eye-popping, and it was repeated so often it became gospel.

The snowpack in the Cascades, it was said, shrank by 50 percent in the last half-century. It’s been presented as glaring evidence of the cost exacted by global warming the drying up of a vital water source.

That statistic has been repeated in a government report, on environmental-advocacy Web sites and in media coverage. Seattle Mayor Greg Nickels recently mentioned it in a guest column in The Seattle Times.

Here’s the problem: The number is dead wrong.

The debunking of this statistic, and the question of just how much the state’s snowpack shrank, is stirring up a heated debate among the region’s climate scientists.

On Monday, it escalated further when University of Washington researcher and State Climatologist Philip Mote stripped a colleague of his title as associate state climatologist, triggering concerns that scientific dissent is being quashed. Losing the title doesn’t affect the man’s employment at the UW.

The affair might be dismissed as a tempest in an ivory-tower teapot. But it comes at a time when the science of climate change is getting more attention from policy-makers and the public.

Heated debate over global warming

University of Washington scientists are in a tense dispute over what has happened to snowpack in the Cascade Mountains, considered a critical potential effect of global warming.

The arguments and who’s behind them:

50 percent decrease since 1950: Widely used as recently as this year, now dismissed by scientists on all sides as a major overstatement.

35 percent decrease since the mid-1940s: Offered by Washington State Climatologist and UW climate scientist Philip Mote.

30 percent decrease since 1945: Professor Dennis Hartmann, chair of the Atmospheric Sciences Department, after a meeting with the different sides and consultations with other scientists.

10 to 15 percent decrease since the mid-1940s: Professor Cliff Mass, in association with meteorologist Mark Albright

It illustrates the challenge of teasing apart how global climate change affects a small region like the Northwest. It shows how a single statistic can take on a life of its own in this politically charged debate, batted around from politicians’ speeches to newspapers (including information from a Seattle official in a May 2006 story in The Seattle Times).

And it reflects the pressures and scrutiny surrounding politicians’ use of science as global warming gains more attention. Recently, some scientists have been criticizing claims in the Oscar-winning climate-change documentary “An Inconvenient Truth,” which stars Al Gore.

Shrinking, sure, but …

The debate in Seattle started with Mark Albright, a part-time UW meteorologist and, until this week, the associate state climatologist.

After reading Nickels’ February essay in The Times, Albright sent an e-mail to colleagues saying he didn’t see evidence that snowpack was steadily shrinking, much less by 50 percent.

A back-and-forth ensued, involving Albright, co-worker and meteorologist Cliff Mass, and several scientists with the UW’s Climate Impacts Group, a federally funded team of researchers that plays a prominent role analyzing climate change in the Northwest.

All quickly agreed that the 50 percent number was wrong. It may have originally come from an editing error in a 2004 report issued by an Oregon panel of scientists.

“No one believes in this 50 percent number anymore,” Mass said.

The mistake doesn’t discredit projections that the state’s snowpack will shrink in the future due to climate change, Mass and Mote agree. But Mass said it underscores the uncertainty around predicting what will happen. And it leaves people like Nickels vulnerable to attack from people questioning the importance of climate change.

“To allow him [Nickels] to be out there with numbers that are unsupportable, it’s setting him up to walk the plank,” Mass said.

Todd Myers, a critic of Nickels’ global-warming strategy and director of the local free-market policy group the Center for Environmental Policy, said this shows the danger of science getting distorted for political goals.

“If you have people who are campaigners in one direction or the other, you’re going to get data out there that’s used incorrectly,” Myers said.

Which is it?

So what is the right number?

That’s where things have gotten testy.

On one side, Mass, who is working with Albright, said they see only a small downward trend in Cascade Mountain snowpacks, perhaps 10 to 15 percent since the 1940s. The measurement can be exaggerated by starting during a time of high snowfall, in 1950, and ending at a time of low snowfall in the mid-1990s, Mass said. But snowfall has increased again in recent years, and there is little overall change in snowpack in the past 30 years, Mass said.

Mass stressed that he is not one of the small number of scientists disputing that humans are causing the planet to heat up.

Albright, in an e-mail, said the evidence doesn’t support claims of a dramatically shrinking snowpack. But he didn’t answer questions on his disagreements with Mote.

Mote, meanwhile, questioned the methods Albright and Mass are using to analyze data, mostly gathered from weather stations in the mountains that track snowfall. Mote, a member of the Climate Impacts Group who rose to prominence partly due to his work documenting shrinking snowpack around the West, said the decline is more like 35 percent.

In late February, professor Dennis Hartmann, chair of the UW Atmospheric Sciences Department, stepped in to referee. After a meeting with the researchers, Hartmann issued a statement saying that snowpack appears to have dropped 30 percent, and that warming in the future will likely affect snowpack, particularly at lower elevations.

“Gag-order approach”?

Since then, the debate has gotten more heated.

Mote, upset that Albright was broadly distributing e-mails about the issue, last week told Albright that he would have to let Mote preview any e-mails before sending them out, if he was tying his work to the state climatologist’s office.

Mote’s position as the state climatologist is a volunteer job that doesn’t carry any official recognition or rules. Mote agreed to do the job several years ago, and his colleagues accepted it. The office collects and disseminates climate information and advises the state on climate-related issues.

When Albright refused Mote’s ultimatum, Mote barred him from associating himself with the state climatologist’s office.

Mote said Albright was sending out messages showing just his side of the story, and airing an analysis that hadn’t gone through proper quality checks. As a representative of the climatologist’s office, there needed to be standards, he said.

“I’m not trying to squelch debate by any means,” Mote said.

But Mass said Albright was doing nothing wrong — simply airing his analysis and seeking feedback as he researched further.

“In all my years of doing science, I’ve never seen this sort of gag-order approach to doing science,” he said.

Meanwhile, Nickels’ office has switched to using the 30 percent figure announced by Hartmann, the department chair.

“Obviously we’re going to use whatever number the scientists at UW say is accurate,” Nickels spokesman Marty McOmber said.

Warren Cornwall: 206-464-2311 or wcornwall@seattletimes.com