Yumans have yet to see global warming impact

The global warming debate may not mean much to Yumans, who have long been accustomed to triple-digit summer temperatures.

Yuma nurseries, farmers, and others whose livelihoods depend on a nurturing climate say they have yet to see a negative impact, and records from the National Weather Service show little noticeable change in Yuma County's average highs over the past half-century.

But Randy Cerveney, an Arizona State University meteorology professor, says mornings in Yuma County and around Arizona are warmer than they were a century ago and that has resulted in fewer crop freezes than were recorded in the 1950s.

Global warming is a phenomenon climatologists agree is occurring, but its consequences are still debated.

Climate systems are complex and the science of understanding them is constantly being revised, said Cerveney.

A problem with determining whether global warming is occurring is that the NWS records only date back 120 years. Over that time natural weather cycles have been noted. When weather records were first charted in the 1880s, the climate was emerging from what was called a "little ice age," Cerveney said.

During the last 100 years scientists have tracked 20-year cycles of dryness or wetness. The question is, how much is because of natural cycles and how much owes to global warming? Both are going on at the same time, Cerveney said.

"Back in the 1970s we had a spate of cold temperatures and many climatologists thought we were entering a new ice age," Cerveney said.

As industry developed since the 1880s there has been an increase in carbon dioxide emissions into the air. That doesn't allow the heat of the earth to escape into space. It's akin to putting a blanket over the earth, Cerveney said. A lot of the gases that trap the heat are the result of human activity, he added.

"Some scientists say warming is because of both human activity and natural cycles but its outcome is not likely to be catastrophic, and I include myself in this group," Cerveney said.

Despite uncertainty, it is known that overnight temperatures are not as low as they have been in the past and it is also more damp than it has been previously, Cerveney noted.

John Curtis, owner of Highway Nursery and Landscaping, sells a variety of plants as well as citrus and shade trees. Curtis has run the business for the last 15 years, and for nearly three decades before that he helped work on a family citrus farm. Curtis said he has noticed no practical changes in temperature.

"I kind of get the impression from Mother Nature she just hits us - with no game plan," Curtis said.

"We are constantly altering our sales to our current situation," he noted. "I'm not sure if global warming is affecting me in Yuma, but I might have a different opinion about the global caps."

After 34 years of growing lemons and minneolas on the mesa and in the Yuma Valley, Mark Kuechel, owner of Kuechel Farms, said he has not noticed any affects of global warming. In fact, he said, it was just a year ago that a frost of 13 degrees and 40 mph winds ruined his citrus crop.

"It basically knocked us in the dirt," Kuechel said. "We started (this year) with just trees. Hardly any leaves on them - and what was on them was brown."

Kurt Nolte, Yuma County director of the University of Arizona's Cooperative Extension, acknowledges the implications of climate change but stressed other variables affecting farming are of greater concern.

"My personal view is global warming is not as critical as other areas impacting food production," Nolte said. "Other agricultural aspects are more critical- labor shortages, food safety, and urbanization."

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William Roller can be reached at

wroller@yumasun.com or 539-6858.