Global Warming Effects Around the World

Napa Valley, CA, USA

Top Impact

Temperature (Air)

Other Impacts

People (Food)

Ecosystems (Land)

Grape harvesting in Napa Valley, California

The Napa Valley, which plays a key role in California's $60 billion wine industry, may become less suitable for growing premium wine grapes as our climate changes. High temperatures can cause premature ripening and reduce grape quality. 1

Key Facts

With mild winters, little chance of frost, and warm, dry summers, the Napa Valley is a showpiece of wine production in California, the state that accounts for more than 90 percent of U.S. wine exports.2 However, global warming may make the Napa Valley less suitable for premium wine production5—which could also have a major impact on tourism in the region.

  • The total area within the continental United States suitable for premium wine growing could be reduced as much as 81 percent by the end of this century under a high-emissions scenario, primarily due to an increase in extremely hot summer days (>95° F or 35° C).3
  • According to projections, premium wine grapes could only be grown in a thin strip of land along the coast of California, while the climate becomes more favorable in coastal Oregon and Washington.3
  • Warm nights have boosted growth of high-quality wine grapes in California,4 but further warming is not likely to be as beneficial.5


California, well known for a wide variety of agricultural products, has earned international acclaim for its wine production. The state's 2,972 wineries, from Napa Valley in the north to Temecula Valley in the south, accounted for more than 90 percent of U.S. wine exports in 2009.2 Wine generates more than $61 billion annually for California's economy.2

The ideal climate for premium wine production features little risk of severe frost damage in the spring, followed by sufficient—but not extreme—heat during the growing season.3 A delicate balance of these factors is needed to produce the highest-quality wines.3

Warmer nights have boosted growth of high-quality wine grapes in the Napa Valley and other parts of California.4 However, further warming may not be as beneficial.5 Wine grapes are already close to their climate thresholds in California, so even minor warming is likely to cause lower yields, quality, or both.6,3

What the Future Holds

In order to map the possible effects of climate change on the future of the wine industry throughout the United States, a scenario based on continuing high increases in heat-trapping emissions7 was applied to climate simulations.3 This study indicated that, over the next century, the area suitable for premium wine grape production is likely to shrink and shift.3 According to the higher emissions projections, premium wine grapes could only be grown in a thin strip of land along the coast of California, with premium wine-producing regions shifting northward to coastal Oregon and Washington.3

The premium wine-growing area in the United States risks changing in three key ways: 1) northern and higher-altitude regions are likely to become more suitable for wine production due to a longer growing season with higher average temperatures; 2) high-quality wine production is likely to end in the south-central and southwestern United States due to an increase in extremely hot days (>95°F or 35°C) during the growing and ripening seasons; and 3) a decrease in the number of cold days—often by more than three weeks—during winter in the Northeast and spring in the Rocky Mountains may make these regions more suitable for premium wine grape production.3

The study also showed that the total area within the continental United States suitable for premium wine growing could be reduced as much as 81 percent by the end of this century, and is likely to be cut in half, primarily due to the increase in extremely hot summer days.3 Overall, temperature extremes may have a much more pronounced effect on plant biology and agriculture than rising mean temperatures.3

Wine growers are now faced with the costs of adapting to a warming climate. Possible future advances in genetics, breeding, and vineyard adaptation may help mitigate some of the adverse affects of climate change. Heat-resistant vine stocks, for example, may be developed through breeding programs.3 But the problems facing California's agricultural sector are compounded by the prospect of drought, such as those experienced in 2007 and 2008. Indeed, one of the most significant challenges facing California in the coming century is adapting its water management systems to climate change.8



  1. Photograph courtesy of Indexstock.
  2. The Wine Institute. 2010. A signature California industry: California wine brochure. San Francisco. Online at files/ EIR%20Flyer%202008.pdf. Accessed March 23, 2010.
  3. White, M.A., N.S. Diffenbaugh, G.V. Jones, J.S. Pal, and F. Giorgi. 2006. Extreme heat reduces and shifts United States premium wine production in the 21st century. Proceedings of the National Academy of Sciences 103:11217-11222.
  4. Nemani, R.R., M.A. White, D.R. Cayan, G.V. Jones, S.W. Running, J.C. Coughlan, and D.L. Peterson. 2001. Asymmetric warming over coastal California and its impact on the premium wine industry. Climate Research 19:25-34.
  5. Field, C.B., L.D. Mortsch, M. Brklacich, D.L. Forbes, P. Kovacs, J.A. Patz, S.W. Running, and M.J. Scott. 2007. North America. In: Climate change 2007: Impacts, adaptation and vulnerability. Contribution of Working Group II to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, edited by M.L. Parry, O.F. Canziani, J.P. Palutikof, P.J. van der Linden, and C.E. Hanson. Cambridge University Press, 617-652.
  6. Hayhoe, K., D. Cayan, C. Field, P. Frumhoff, E. Maurer, N. Miller, S. Moser, S. Schneider, K. Cahill, E. Cleland, L. Dale, R. Drapek, R.M. Hanemann, L. Kalkstein, J. Lenihan, C. Lunch, R. Neilson, S. Sheridan, and J. Verville. 2004. Emissions pathways, climate change, and impacts on California. Proceedings of the National Academy of Sciences 101:12422-12427.
  7. The Intergovernmental Panel on Climate Change emissions scenario referred to in this hot spot is the high-emissions path known as A2.
  8. California Department of Water Resources. 2009. California's drought. State of California. Online at drought. Accessed January 28, 2009.
Climate Hot Spots
Australia & New Zealand
Latin America
North America
Polar Regions
Small Islands
Key to top impacts color code