BENTON CITY - Tom Judkins Jr.'s grape-growing experience began with just a few backyard vines when he was 16 years old.
Some 40-odd years later, his 100-acre nursery produces more than 3 million grape vine cuttings in the lower Yakima Valley.
The tender plants have fed a boom in Washington's wine industry, which now boasts 500 wineries and 31,000 acres of wine grapes.
Judkins admits he's wondered when that growth will slow. "Five years ago, I kept saying, 'Is this peak going to happen?' And each year, I keep seeing more and more interest," he said.
That peak still could be a ways off. As the region prepares for the possibility of warmer temperatures and reduced snowpack resulting from climate change, more growers could be moved to plant a crop that requires less water while meeting consumers' thirst for fine wine.
And while wine grapes aren't Washington's biggest or most valuable crop, they might be emblematic of how changes in climate could have both positive and negative effects on Washington's $6.4 billion agriculture industry.
Debate continues about causes and possible effects of climate change, or even if it really exists. But scientists at the University of Washington's Climate Impacts Group for years have studied what global warming could mean for the state: a half-degree temperature increase each decade, on average; an earlier onset of warmer temperatures each spring; a decline in snowpack, particularly at low and middle elevations, with more rainfall in the winter instead.
The potential effects on agriculture vary.
Warmer temperatures can stress livestock, reducing production in dairy herds, as well as burn fruit and other crops. Bugs and diseases that survive if temperatures don't drop enough in the winter become a growing concern, particularly for organic growers who don't use pesticides.
At the same time, elevated levels of carbon dioxide generally increase sizes and yields of some crops.
More rainfall in the winter raises the potential for flooding west of the Cascades. Less snowpack or an earlier thaw means less water for irrigation in the dry eastern half of the state during the summer and early fall.
Some projections also show a decline in precipitation in general, which could hurt dryland crops that already receive little moisture.
But longer growing seasons could allow growers to plant new crops and varieties that flourish under different conditions.
It's a complex kaleidoscope determined not just by the effects of warming on Washington state - both the benefits and detriments - but also the effect on other regions that compete for agricultural markets.
Central to the debate is water. West of the Cascades, only 58,434 acres are in irrigated agriculture. East of the mountains, it's a different story, where some 1.6 million acres produce a cornucopia of crops - tree fruits, hops, grain and vegetable fields, hay and alfalfa feed for livestock.
According to a 2005 study by researchers at Pacific Northwest National Laboratory, the likelihood of severe drought conditions in the Yakima Valley increases to one out of every two years by the middle of the century as the region warms.
That concerns Mario Mosso, a 41-year-old fruit grower in Wapato, who saw his water supply halved during the 2005 drought.
Apples, apricots, peaches and pears didn't develop as they should and his trees yielded
20 percent less fruit, cutting his income in half.
"I recognize that water is not going to be there forever and there's changes that we'll have to make," Mosso said, pointing to a sprinkler system he'd like to replace with more a more efficient, and more expensive, drip system. "This year's a good year for water. Next year, who knows?"
Further complicating matters is the arid West's long-standing rule on water rights: first in time, first in right, which doesn't consider which crops require less water or which growers manage the water best.
Tedd Wildman, a wine grape grower on the Wahluke Slope near Mattawa, is a junior water rights holder. Each of the past two years, he was notified that his water might be rationed to provide a full supply to farmers with more senior rights. It never was.
Growers have become more efficient in how they manage water. However, while most are watchful of any signs of global warming, few manage their crops to protect themselves from it daily, Wildman said.
"It's so much conjecture at this point. Not that I'm a climate change doubter - I think there's enough evidence of global warming around the globe," Wildman said. "I just think we're too young of an industry to know the effects to be able to manage for them."
Assuming that Washington's water supply doesn't dry up, the state should be in a good position to compete globally in agricultural markets, said Thomas Wahl, director of Washington State University's IMPACT Center, the international marketing program for agricultural commodities and trade.
Of course, agricultural markets also depend on what's happening elsewhere in the world. For example, growers in China have been shifting their production to higher altitude to produce better apples, he said.
Wine grape growers in Spain have been doing the same thing. In Australia, citrus trees are being replaced with wine grapes to conserve water.
Some reports have even questioned the viability of California's wine crops amid warming temperatures.