Expert: AZ in climate-change bull’s-eye

posted Wednesday, February 18, 2009        

By Tony Davis, February 18, 2009, Arizona Daily Star

The state’s best-known climate-change expert presented harrowing forecasts for sharply higher temperatures and drier rivers and reservoirs before a legislative committee in Phoenix on Tuesday.
Jonathan Overpeck told the House Environment Committee that:

  • Temperatures could regularly hit the 130s in Phoenix by the second half of this century due to human-caused climate change. In Tucson, temperatures could periodically go into the 120s by that time, said the University of Arizona scientist in an interview shortly afterward.
  • A group of researchers meeting at a conference Overpeck attended this week in Seattle concluded that the most likely reduction in Colorado River flows from global warming and drought will be about 20 percent by 2050. A separate study, still under review for publication, will predict a 30 percent chance that Lake Mead and Lake Powell could go dry by 2050 if nothing is done about climate change, he said.

That’s far less severe than the prospect of a 2021 drying of those lakes that came from an earlier study from Scripps Institution of Oceanography researchers. But it’s still a significant threat. “It’s not if it will happen, it’s when it will happen,” Overpeck said.

  • Various reports indicate Arizona has the country’s fastest or second-fastest warming temperatures and predict that Arizona will warm up and dry faster than any other state.

He warned of an economic calamity if global warming isn’t curtailed. “Once the Central Arizona Project goes dry for one year, our state is dead; people won’t want to live here anymore.”
Larry Dozier, an official with the agency running CAP, said it is trying to avert such a crisis by planning to do cloud-seeding, remove water-sucking tamarisk trees from rivers and search for alternative water supplies.

“We’ve got to spend some money. It will take environmental clearances and political clearances, but if people want water at a rational, affordable price, you can have it,” said Dozier, CAP’s deputy general manager.

But Overpeck, director of UA’s Institute for Environment and Society, said Arizona has one of the country’s best opportunities to combat climate change because of its abundance of solar energy.
Two Republicans on the committee praised his talk but didn’t sign on to all of his solutions to reduce global warming.

The committee will consider legislation to pull Arizona out of a seven-state effort to limit greenhouse-gas emissions from power plants and other sources. Overpeck spoke against the legislation.

The bill targets the Western Climate Initiative, an effort pushed by former Gov. Janet Napolitano that has drawn criticism from many Republican legislators. They have tried unsuccessfully before to pull Arizona out of the agreement, partly on the grounds that Napolitano was wrong to sign the initiative without the Legislature’s backing.

Overpeck spoke the same day that a lobbying group for energy and other business interests released a study warning that the Western Climate Initiative will prolong the recession and will reduce global temperatures by only a tiny fraction of a degree even after a century.

The study, commissioned by the Western Business Roundtable, found the initiative’s greenhouse-gas cap-and-trade plan could “chase away tens of billions of dollars in high-technology investment from the West to other regions” and would “further stress the West’s already strained electricity grid, increasing the threat of potentially catastrophic power outages.”

The climate initiative calls for a system in each state that would limit greenhouse-gas emissions from utilities and other large sources of fossil fuels. Companies that produce fewer emissions than they are allowed to produce could trade those rights to companies producing more emissions than allowed.

Overpeck was a lead author for the 2007 report of the International Panel on Climate Change. It predicted average global temperature increases of more than six degrees Fahrenheit under the fastest growth rate in greenhouse-gas emissions that scientists at the time thought was possible.
Now, greenhouse-gas emissions are growing faster than the report predicted at the time, raising the prospect of dramatically higher Arizona temperatures by mid-century, according to Overpeck.
“Whether it is drought frequency, the increase in temperature or the decrease in soil moisture, we are in the bull’s-eye – the worst in the United States,” Overpeck said.

Overpeck is someone Rep. Lucy Mason, R-Prescott, said she wants to work with in developing policies “toward moving Arizona into the 21st century on renewable energy.” But Mason opposes the state being in the regional climate program, out of concern that having to follow a regional solution would hamper individual efforts made in Arizona to reduce emissions.

Overpeck’s presentation was “direct and to the point,” said Rep. Frank Pratt, R-Casa Grande.
But he said he has not made up his mind on the climate-initiative legislation and finds it hard to decide if global warming is human-caused.

Contact reporter Tony Davis at 806-7746 or

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