Warming Will Exacerbate Global Water Conflicts

San Luis Reservoir in California, which is down 186 feet from normal levels (David Paul Morris - Getty Images)

FRESNO, Calif. -- Steve Johnson scans the hot, translucent sky. He wants to make rain -- needs to make rain for the parched farms and desperate hydro companies in this California valley. But first, he must have clouds. The listless sky offers no hint of clouds.

Inside a darkened room near the Fresno airport, Johnson's colleagues study an array of radar screens. If a promising thunderstorm appears, Johnson will send his pilots into it in sturdy but ice-battered single-engine planes, burning flares of silver iodide to try to coax rain from the clouds.

This year, there have been few promising clouds, to the dismay of the farmers, ranchers and power companies who hire Johnson's cloud seeders.

"We can increase the rainfall by 10 percent. But Mother Nature has to cooperate. Ten percent of zero is zero," says Johnson, a meteorologist and director of Atmospherics Inc.

A few miles south of Fresno, Steve Arthur is looking the other way for water. His company is working around the clock drilling wells to irrigate fields in California's 400-mile-long Central Valley, one of the most productive food-growing areas in the world.

"People are really starting to panic for water," said Arthur, whose father started drilling wells in 1959. They must drill ever deeper to tap the sinking water table. "Eventually, the water will be so deep the farmers won't be able to afford to pump it," he said. "There's only so much water to go around."

As global warming heats the planet, there will be more desperate measures. The climate will be wetter in some places, drier in others. Changing weather patterns will leave millions of people without dependable supplies of water for drinking, irrigation and power, a growing stack of studies conclude.

At Stanford University, 170 miles away, Stephen Schneider, editor of the journal Climatic Change and a lead author for the authoritative Intergovernmental Panel on Climate Change (IPCC), pours himself a cup of tea and says the future is clear.

"As the air gets warmer, there will be more water in the atmosphere. That's settled science," he said. But where, and when, it comes down is the big uncertainty.

"You are going to intensify the hydrologic cycle. Where the atmosphere is configured to have high pressure and droughts, global warming will mean long, dry periods. Where the atmosphere is configured to be wet, you will get more rain, more gully washers.

"Global warming will intensify drought," he says. "And it will intensify floods."

According to the IPCC, that means a drying out of areas such as southern Europe, the Mideast, North Africa, South Australia, Patagonia and the U.S. Southwest.