Global warming jeopardises US wine-industry

The report's conclusions,  which appear online in the Proceedings of the National Academy of Sciences, could have multibillion-dollar implications for the U.S. wine industry.

Photo: Global warming jeopardises US wine-industry

California sales are $16.5 billion a year, and the United States is the world's fourth-largest grape producer, ABC reports.

In the last 50 years, the study says, average temperatures have warmed by about 1.6 degrees Fahrenheit in the main wine-producing regions of California, Oregon and Washington.

Virtually all climate scientists blame the rise on human-caused greenhouse gases released into the atmosphere from the burning of fossil fuels.

The paper indicates increasing weather problems for grapes in such areas as California's Napa and Sonoma valleys.

Grapes used in premium wines need a consistent climate. When temperatures top about 95 degrees, the vines have problems maintaining photosynthesis and the sugars in the grapes can break down, said Diffenbaugh, a co-author of the report.

Until now, climate studies centered only on the impact of average temperature increases on wine production and concluded that wine growers might, if anything, benefit from the temperature increases expected in coming decades.

The new study, funded by the National Science Foundation, the National Aeronautics and Space Administration and Purdue University, involved five months of supercomputer calculations. It is the first study in which researchers have been able to calculate the daily temperature swings from various climate-change scenarios in such detail.

The West Coast would experience one of the biggest changes in season, resulting in a significant alteration to the quality of its grape harvest. Suitable grape-growing areas in California would shrink to a narrow coastal band, the researchers said, while premium wine-grape areas would shift into the Pacific Northwest and New England, the AP reports.