Originally Published: April 19, 2008 7:31 p.m.
PRESCOTT - Humans might have just a half-century to dramatically reduce their greenhouse gas emissions before climate change becomes irreversible, a science expert told a Prescott audience Wednesday.
Mike Crimmins, an assistant professor and climate science extension specialist at the University of Arizona, spoke to Prescott residents as part of the local events leading up to Earth Day.
Climate change already is occurring, Crimmins said.
The best science indicates that people must reduce their greenhouse gas emissions by about 80 percent in 50 years to avoid a 3.5-degree Fahrenheit increase in temperature that could lead to irreversible climate change, he said.
Crimmins based his talk on the latest climate change report from the Intergovernmental Panel on Climate Change (IPCC). Approximately 600 scientists from 40 countries produced it, and more than 620 experts and governments reviewed it.
"As the president has said, and this report makes clear, human activity is contributing to changes in our Earth's climate and that issue is no longer up for debate," U.S. Energy Secretary Samuel Bodman said at a news conference.
President Bush has called for a halt to the growth in greenhouse gasses by 2025, but he opposes any mandatory requirements to reach that goal.
"I think the science that stands is very solid," Crimmins said. "It's very difficult to get science better than this to make decisions with."
Crimmins said it's part of his job to get the word out about climate change and its impacts.
"That's a big issue in the science community right now - 'OK, we've done all the work, why isn't anybody listening?'" Crimmins related.
The Southwestern U.S. could be one of the biggest losers in the climate change forecast, Crimmins said. This region is likely to experience some of the highest temperature increases.
The IPCC forecasts an average annual increase of seven degrees Fahrenheit in Arizona by 2100 without action to reduce greenhouse gasses.
"It's a hot place already, and it's going to get hotter," he said.
Higher temperatures mean more evaporation and less natural water storage in the form of snow, he noted.
"I don't know if we can still think about water in the same way," he said.
The IPCC computer models also forecast drier winters in the Southwest, Crimmins noted. The latest local science is starting to show that species in the Verde River ecosystem are among those that especially depend on winter precipitation.
It's harder to tell how climate change will affect Arizona's summer precipitation because scientists don't have a good understanding of the monsoon, Crimmins said.
He noted that the planet will survive climate change, but the outlook isn't so good for humans.
"The planet is very dynamic and it's had many, many changes over time," Crimmins said after his presentation. "But it becomes irrelevant, because what we're talking about is maintaining a planet that is hospitable for human life."
Not surprisingly, Crimmins' presentation didn't exactly make the audience happy.
"I'm trying to cling to hope here," one woman said.
Crimmins said there is hope, and he noted that the IPCC report offers many ideas about how avoid disaster.
See the website www.ipcc.ch for details about the report and its suggestions.
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