Napa Valley, Calif. -- Climate change may have wine makers over a barrel. A new study suggests it may drastically affect some of the world's great wine-producing regions. The study, from Stanford University, says vineyards in California could shrink by 50 percent over the next 30 years. California wine is currently a $16.5 billion industry. Other famous regions could be affected, as well.As CBS News Correspondent John Blackstone points out, the vineyards of California's sunny Napa Valley are known for their top-quality cabernets and chardonnays. Which may explain why the people who make wine there, such as Michael Honig,