How will changes in global climate influence California?

California is the leading dairy state in the United States, producing 21% of the nation’s milk supply. The state’s highest concentration of dairies is in the San Joaquin Valley, a region that violates federal limits for ozone and particulate matter in the air. Volatile organic compounds and greenhouse-gas emissions from dairies contribute to regional air-quality challenges and also play a role in climate change. We used an environmentally controlled chamber to monitor greenhouse-gas emissions from dairy cattle over a 24-hour period, and we measured the emissions from waste slurry using a simulated dairy waste lagoon. This research helps to quantify emissions from dairies in California and suggests possible approaches for their mitigation. Important consequences of observed and future global warming are as diverse as decreases in winter chilling, necessary for many fruit and nut crops, more extreme air pollution episodes, and more frequent coastal flooding. Most important are past and future reductions in winter snow pack, which enhance the likelihood of winter flooding, and reduce water available from reservoirs for irrigation and other uses in late spring and summer.