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Thu, July 18

Government planners must prepare for climate change, panelists warn

Joanna Dodder/The Daily Courier<p>
Climate change experts forecast that flows in Arizona rivers such as the Upper Verde (pictured here) could drop 20-40 percent by the end of the century.

Joanna Dodder/The Daily Courier<p> Climate change experts forecast that flows in Arizona rivers such as the Upper Verde (pictured here) could drop 20-40 percent by the end of the century.

Panelists at an Arizona Planning Association conference in Prescott Valley Thursday warned members to start planning now for climate change.

"We know it's coming, even if we flat-lined our emissions tomorrow," said David Schaller, sustainable development administrator for Tucson's Office of Conservation and Sustainable Development. "Inaction is not an option."

Yet resistance to the facts still exists, he said. Some people are "treating it as some sort of continuing debate," but "climate science is conclusive."

Scientists are "quite certain" that carbon dioxide and other gasses are "increasing at an incredible rate" since the start of the 20th century, said Gregg Garfin, director of science translation and outreach at the University of Arizona's Institute of the Environment.

The International Panel on Climate Change (IPCC) concluded it is 90 percent likely that carbon emissions from humans are causing most of the global warming since the 20th century, he said. The IPCC consists of prominent scientists working under the scrutiny of 113 governments.

Computer models can't produce any scenarios in which carbon dioxide emissions could be increasing this much without human sources, he said.

IPCC computer models project temperatures in the Southwest will increase 5-8 degrees by 2100, depending on population and emissions growth. They forecast serious water supply shortages.

"This is a very robust result and in accordance with what we've already observed," Garfin said.

Arizona temperatures already have increased an average of 2.5 degrees since 1976, according to information compiled by the University of Arizona's Southwest Climate Change Network (southwestclimatechange.org).

This warming is exacerbating the 10-year drought and making it more severe than natural droughts of the past several centuries, according to a June report from the U.S. government's Global Change Research Program (www.globalchange.gov) that was the result of a consensus of 13 agencies. Winter and spring storm tracks already are shifting to the north away from Arizona. Results include record-sized wildfires and the die-off of piñon trees throughout 4,600 square miles of the Four Corners area.

Climate models project that precipitation across much of Arizona will drop five percent by the end of the century, according to the Southwest Climate Change Network. At the same time, because of the warming trend, streamflows could drop 20-40 percent.

Precipitation is more complex to predict than temperature, added the Southwest Climate Change Network. For example, the warming air also could produce more intense storms. In short, the weather will feature more extreme swings - extreme drought and heat as well as extreme storms.

Tucson has registered its 10th straight year of above-normal temperatures and eighth straight year of below-normal precipitation, Schaller noted. The city has set up a Climate Change Advisory Commission that is likely to lead to the addition of climate change elements to the city's drought and emergency preparation plans.

Under all climate change scenarios, the City of Phoenix will need more water, said Ray Quay, assistant director of the city's water department. Under the worst-case scenario, it would have only one-third of its current surface water supplies.

He advised governments to identify the worst-case scenario and plan for it, while using conserved water to help existing customers instead of for future growth.

By the mid-century, urban areas will have more heat, more flooding and less water, he said.

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