Extreme weather is likely on tap for West

Friday, Sept. 23, 2005 | 10:04 a.m.

The climate globally is changing, mostly getting hotter, and the bad news for the West is that the "worst and first" impacts are already here, scientists reported Thursday at a Las Vegas conference.

A parade of researchers presented evidence that they believe shows that not only is global warming due to the burning of fossil fuels a reality, but that the impact of the process has huge variations over even neighboring regions.

For the West, water agencies will have to deal with more extreme weather events such as floods and droughts, potentially drier summers and wetter winters,

The results came as climatologists met with managers from regional water agencies in an effort to bridge an information gap.

Using increasingly sophisticated climate models, researchers are trying to understand what will happen to temperature and precipitation. The water managers can use that information to better serve their populations, especially in the arid West.

"It gives us a real opportunity for water managers to catch up to where the climatologists are," said Kay Brothers, deputy general manager of the Southern Nevada Water Authority, which co-sponsored the conference, "Urban Water Supplies and Climate Change in the West," Desert Research Institute and the Natural Resources Defense Council, an environmental advocacy organization.

"The more we know about the future, the better off we are," Brothers said.

A poll by one scientist of the 50 or so people at the conference found that not one disputed that human activity is profoundly altering the global climate. Marty Hoerling, a meteorologist with the National Oceanic and Atmospheric Administration, said that might not have been true just a few years ago.

"There is increasingly an embrace of the idea that the climate is changing," Hoerling said.

Hoerling presented slides that showed that while the world's climate has increased just a about a degree on average over the last 100 years, some parts of the world -- such as the American West -- have seen more significant increases.

Fort Collins, Colo., Hoerling said, has warmed five times more rapidly than the global average.

Bob Wilkinson, a researcher from the University of California, Santa Barbara, pegged the temperature increase over the coming decades in a range of 2.5 to 10.4 degrees Fahrenheit.

"The numbers are, if anything, changing upwards," he added.

Extreme floods or drought events that once would had a 2 percent chance of occurring in a given year, a "50-year event," will come on average every five years, he warned.

The major contributor to the process is carbon dioxide, a "greenhouse gas" coming from the burning of fossil fuels, he said. The amount of the gas in today's atmosphere is higher than it has been for millions of years, and it cannot be explained by any natural processes, he said.

"That is so far off the scale that there it undoubtedly human contribution to that, and some warming is going to come from that," Hoerling said. "Never has it warmed so rapidly. It is the rate at which things are changing which is so alarming."

He said the West has warmed faster than any other part of the United States and that all seasons have been affected.

Oceans are warming almost as fast as land, and that has important implications for the West, he said.

Hoerling's research shows a correlation between water temperatures in the Indian Ocean, halfway across the world, and temperatures and precipitation in the West.

Hoerling and other researchers believe that their models of climate change are accurate because they correspond to what they see actually happening around the world. The models also can be moved backwards in time, and again accurately predict what will happen.

Michael Dettinger, a researcher with the U.S. Geological Survey and Scripps Institution of Oceanography in La Jolla, Calif., said some impacts appear to be clear. There will be less snow in the mountains and less snow remaining on the ground in the spring to melt and contribute to rivers and streams.

This evidence is already piling up that the process is happening, Dettinger said.

"We will be dealing with these problems before most of us retire," he said.

"What you find is that somewhere around the year 2000 these projections start to leave the envelope of what you might see from natural variability. By about 2025, 2030 or so you simply don't see cooler than normal temperatures anymore. Now it's a completely different world."

One impact would be a 15 to 25 percent decline if the recharge of groundwater aquifers from slow-melting snowpacks in the mountains. Even in the most optimistic projects, Dettinger said, the mountains would lose 30 percent of the snowpack that was once customary.

The good news, perhaps, is that Dettinger and the other researchers said one variable looks to be more or less unchanged. While the periods and type of precipitation will likely shift, the amount is, according to most models, more or less unchanged for the West.

But "the models seem to agree: The variability of precipitation will increase. Extreme precipitation events will increase. Flood frequencies will increase."

"A few degrees warmers makes us all vulnerable to this. The Western U.S. tends to be the most vulnerable and gets there fast."

Kelly Redmond, deputy director of the Desert Research Institute's Western Regional Climate Center in Reno, said the issues are important to everyone with an interest in water issues.

"This issue of climate change has been bubbling up and slowly taking over our lives," Redmond said. And that's most clear in the Western United States, he said.

"The West is worst and first."

He said that water management is already challenged in the West because of scant, and in some cases shrinking, supplies coupled with population increases that continue to boom.

"Climate is not the only issue, and in some cases it is not the most important issue, but it is an important driver," Redmond said. "The West is really facing this issue first in the United States.

"It may be up to us as a group," he told the scientists and water management officials, "to figure out where to go with this."

One of those officials from Las Vegas who will have to consider the impact of climate change is Ken Albright, resources director for the Southern Nevada Water Authority. Albright said there is no solid modeling that shows what will happen to stream flows on the Colorado River due to the global and regional warming, but it is an important issue of concern.

The Colorado River, which begins with snowmelt in the mountains of Wyoming and Colorado, provides 90 percent of the Las Vegas' drinking water, although the Water Authority is trying to diversify its resource portfolio with groundwater from rural Nevada.

The Water Authority and water officials from six other basin states of the river have been meeting to discuss how the river should be managed. The officials are using the "normal" runoff for now, but they could use better models of what will be happening, Albright said.