Hotter, drier years in store for LV, study says

Friday, Sept. 23, 2005 | 10:21 a.m.

Las Vegas hit its highest average temperature in recorded history in the summer of 2005, but expect more of the same over the next, say, several hundred thousand years.

And it won't just be hotter. It will be drier too, climatologists are warning.

That's bad news for Las Vegas and the West, which is already dealing with dwindling water supplies to sustain a growing population. The weather report has long-term implications for public policy issues ranging from Yucca Mountain to regional water use.

The Rocky Mountain Climate Organization, a Louisville, Colo.-based nonprofit group that includes government agencies, businesses, farmers and ranchers and environmental groups in the West, released a study Wednesday that said temperatures are already rising and mountain snow packs are shrinking, and that the impacts will be greater in the West.

By the end of the century, temperatures could go up 3 to 10 degrees compared to 1990.

For the Colorado River basin, snow packs could shrink by 24 percent over the next 35 years, and by 30 percent by 2069, the organization's report said.

Snow packs in the Rocky Mountains are the critical source of water to the Colorado River, which supplies 90 percent of Las Vegas' supply. The river also is a key component of the supply for 23 million Californians and a huge agricultural industry in California and Arizona.

The report from the Colorado coalition came out the same day that a scientist reported similar conclusions in Las Vegas to an advisory committee to the Nuclear Regulatory Commission.

Matthew Huber, a climatologist with Purdue University's Climate Change Research Center in Indiana, told the five-member Advisory Committee on Nuclear Waste that multiple and increasingly detailed models of the long-term pattern indicates that the Southwest will be hotter.

Both the Rocky Mountain Climate Organization and Huber said the basis of the unpleasantly sunny projections is human-caused climate change from the burning of fossil fuels, or in popular terms, global warming.

While some observers continue to insist that global warming because of human activity is an unproven theory, a growing consensus of scientists believe the phenomenon is real and weather patterns over the last two decades match the theoretical expectations.

The models show that not all parts of the world will heat up equally. While the ice sheets over the North and South poles will disappear, the West and the desert Southwest could be disproportionately affected.

"It's going to be a lot hotter here," Huber said.

The advisory committee is charged with advising the Nuclear Regulatory Commission on the licensing of the Yucca Mountain nuclear waste dump proposed for 90 miles northwest of Las Vegas. The committee is holding three days of meetings in Las Vegas this week, which included Huber's presentation.

Those who were looking for climate change to threaten the federal effort to put a radioactive waste dump in Nevada did not get a boost from Huber. While some parts of the West will likely experience more rain, especially with summer monsoons, models show that those monsoons are not likely to fall on Yucca Mountain, he said.

The models are not cut-and-dried, Huber said. One possible outcome of global climate change could be "a permanent El Nino," the periodic concentration of warmer-than-usual water in the equatorial eastern Pacific Ocean.

"That could lead to a substantial increase in precipitation, although nothing that has not been considered in these reports," Huber said, referring to analyses prepared by the Nuclear Regulatory Commission and other government agencies on the Yucca Mountain issue.

A worst-case scenario, at least from the perspective of the 80,000 tons of high-level radioactive waste potentially buried in Yucca Mountain, would be a Southwest that is turned into a subtropical rainforest. The last time the Southwest had such a climate was about 54 million years ago during the early Eocene period, Huber said.

The critical element that will impact future climate for hundreds of thousands of years will be the amount of carbon dioxide in the air produced by burning fossil fuels, he said. The gas builds up in the atmosphere and through the "greenhouse effect" warms the planet. Shrinking ice packs and dwindling winter snow cover further accelerate the warming process, he said.

The carbon dioxide buildup is working in unison with the Earth's orbital mechanics to make for a hotter world, he said. Those who were looking for a global cooling because of the orbital mechanics are going to be disappointed.

A new ice age, or period of glaciation, will not happen for at least 500,000 years or so, he said. Huber said those looking for some way to reverse the process will probably be disappointed.

"There are no known negative feedbacks in the system," he said of global warming.

Huber said the models that are being produced, and which back up the warnings of global warning, are not just matching what would be expected, but the same models can be extrapolated to past climate events. They work then, too, indicating that the science is valid.

"At a very basic level, we understand climate and what causes it to change," he said.

Huber said the Energy Department has failed to include new, detailed climate models as it has planned the Yucca Mountain dump.

Abe Van Luik, an Energy Department senior policy advisor on the Yucca project, disputed Huber's statement. He said that not only had the agency considered global climate change in preparation of the environmental impact statement for the project, but that the agency had included a much wetter environment.

"It is in the EIS," Van Luik said.

However, Van Luik told the advisory committee that the Energy Department also may want to look at the new models in more detail as it moves forward with its effort to win licensing approval from the Nuclear Regulatory Commission.

The issue of climate change will stay on the public-policy agency for Las Vegas this week. The Southern Nevada Water Authority, the Desert Research Institute and the Natural Resources Defense Council, a national environmental group, are sponsoring a meeting today and Friday to consider "Urban Water Supplies and Climate Change in the West."

J.C. Davis, a Water Authority spokesman, said the studies by the Rocky Mountains group and other scientists are not definitive.

"While it (climate change in the West) is an important issue, there certainly is not consensus in the scientific community over what this data means," Davis said. "We're not endorsing or disputing what the findings are, but we can't at this point accept that any particular numbers are accurate."

The possible impact to water flows in the Colorado River cannot be ignored, however. Davis said the issue has helped push the Water Authority's efforts both to conserve the existing supplies of the resource and to seek new supplies from wells and rivers in rural Nevada.

"We've been looking to reduce our reliance on the Colorado (River) for a while because of the legal and physical constraints on our allocation," Davis said. "But if in fact there is a climate change that has an impact on flows in the Colorado, that is something that is going to affect the lone city on the river."

Las Vegas, the only major city on the 1,500 mile river basin, receives an annual allocation of 300,000 acre-feet. California takes 4.4 million acre-feet from the river annually to contribute to the supply for 23 million people.

Water agencies using the river are increasingly concerned that five years of drought, rather than being an anomaly, is closer to what will be the new normal for the Colorado River basin.

Nevada, California and five other states are now in negotiations to recommend ways to share cuts if the river continues to be hit by drought. Already, Lake Powell and Lake Mead together have about half of the supply that the reservoirs held less than a decade ago.

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