Thursday, July 17, 2003 | 11:14 a.m.
Hot enough for you? You ain't seen nothing yet.
A group of 125 scientists throughout the West is predicting that Nevada and the Rocky Mountain states will get 4 to 14 degrees hotter over the next 100 years. The scientists, in their report released Wednesday, studied historical records and used sophisticated computer models that seem to validate theories that rising carbon dioxide levels in the atmosphere are changing the climate, a pattern known as global warming.
"Recorded temperatures since the middle of the 19th century show an abrupt rise, exceeding levels seen in the preceding 1,000 years," said Fred Wagner, Utah State University researcher and principal investigator for the nine-state Rocky Mountain/Great Basin region. "That pattern is continuing."
The study, "Preparing for a Changing Climate: The Potential Consequences of Climate Variability and Change," predicts large-scale impacts on the natural and human habitats throughout the region due to the climate swing.
Wagner said the best models available today show considerable variation, but they all suggest temperature increases throughout the West. The worst-case scenario, at least for Nevadans dreading the summer heat, has temperatures rising 14 degrees.
The good news is that the models also show increased precipitation, especially over the Rocky Mountains. That region has been going through four years of exceptional drought, a situation that is especially worrisome for Las Vegas because it is the source of the Colorado River that feeds Lake Mead.
Local officials have passed water-use restrictions and higher rates throughout Clark County in response to the drought, which is threatening the lake's water supplies. Lake Mead provides about 90 percent of the county's water supply.
Wagner said the data and long-range predictions on temperature change are much more solid than those for precipitation.
"We're more confident in the temperature rise than the precip rise," he said. And if the models are wrong on increased precipitation for the Southwest and Rocky Mountains, that combined with the hotter temperatures would be very bad for Las Vegas and other arid areas in the region.
"If we just get the temperature rise, then we're going to be hurting," Wagner said.
"The main concern is water. All the water in the Intermountain West is now appropriated," he said, referring both to groundwater and Colorado River water. "You know that predictions for population growth in the Intermountain West is going to double, so the demand is going to double."
According to the study, if drought patterns persist and spring runoff continues to decline, the Colorado, Rio Grande, Columbia, Missouri, Platte and Arkansas rivers could have distinctly reduced flows, leaving the region vulnerable to extreme water shortages.
Water in the West is allocated on a first-come, first-served basis. Junior rights holders could come up empty in coming years. The shortage is exacerbated by groundwater that's being polluted and mined faster than it's being recharged, higher temperatures leading to massive evaporation in existing dams, and increasing demands by urban users, the report states.
Society may see the return of water disputes like those of the historical West, Wagner said.
"If the massive natural and human-made hydrology systems that sustain municipalities, farms and ecosystems were to see significant changes, there would be serious social, economic and ecological impacts,' he said.
Wagner said the hotter temperatures mean faster, greater evaporation, more demand for irrigation and more demand for water in the urban areas. He also forecasts that the calls for greater diversion from agricultural uses -- which still consume 80 percent of Colorado River water -- to urban uses will grow.
Like other parts of the 240-page study, the forecast is being already realized. The call for switching from agriculture to urban use is already coming from local officials struggling to deal with the falling levels in Lake Mead. Those officials are privately, and sometimes publicly, furious that Southern California farmers continue to use old-fashioned and inefficient flood irrigation methods to grow thousands of acres of heavily water-dependent crops such as alfalfa -- and those farmers have priority over Las Vegas and other cities.
The study also notes that the models used are borne out by other factors. Glaciers are already shrinking in Montana's Glacier National Park, and will disappear completely by 2070 if the models are correct.
Wagner warned that like all models, the predictions in the study are just that -- predictions. Reality could bring very different results.
But one observer who has been a skeptic of some of theories of global warming said the study, one of 14 produced on regional levels for the entire United States, is solid.
Kelly Redmond, regional climatologist for the West for the Desert Research Institute, the research arm of the Nevada university and college system, said he believes what the thermometers are telling him.
"When we look at the records of the West over the last 30 to 40 years, the West is warming up," Redmond said. "Temperatures, snow melt, the blooming of lilacs -- all point to the fact that especially winter and spring seem to be getting warmer. This is consistent with that."
Redmond said he suspects that the actual warming over the next century will be close to the middle of the 4-to-14 degree rise predicted in the study.
Redmond echoed Wagner on the studies' prognostication on moisture.
"Precipitation turns out to be, just like in day-to-day weather forecasts, to be harder to forecast than temperatures," he said.
Some people will put the federally funded study to work. Kim Zikmund, a hydrologist and manager of the watershed division of the Southern Nevada Water Authority, said the study will be another tool in the arsenal that scientists and the technicians at her agency use to predict long-term water use trends.
"It is one more element of any equation when we need to do our long-term water resources planning for 20, 40, 60 years from now," Zikmund said. "We're very interested in any studies that might impact our community."
The study results aren't a surprise, she said.
"That's pretty typical of the other studies we've seen, maybe a little bit on the higher side than we've seen," Zikmund said. But there are still a lot of uncertainties that could affect the water authority's planning, particularly when the greater precipitation -- if it occurs -- happens.
Zikmund said greater summertime precipitation isn't very helpful for the Colorado River. The bulk of the water filling Lake Mead comes from snowpack in the Rockies.
"We'd like it to snow," she said.
Local meteorologists said the work is interesting, but people shouldn't look for the evidence supporting the study in day-to-day weather.
"It's hot here in Las Vegas every summer,"' said Charlie Schlott, a meteorologist with the National Weather Service. "We've been above normal so far, but that's not unusual."
Long range studies such as this one "are very speculative," Schlott said, and Wagner agreed.
"Models are always uncertain," Wagner said. "They are always simulations. That is the best of what the climatologists say in advance."
But Wagner said even the short-term evidence seems to back up the study's conclusions. He noted that this year has been, so far, exceptionally warm.
"Most of the hottest years on record were in the '90s, and we've got a sizzler right now."
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