The United Nations Intergovernmental Panel on Climate Change (IPCC) estimates that human activities have caused approximately 1.0 °C of global warming above pre-industrial levels, and are likely to cause a 1.5 °C increase between 2030 and 2052 if warming continues at the current rate. Impacts from global warming are already apparent. Unless we act to quickly reverse course, these trends will persist for centuries and will continue to cause further long-term changes to the environment, such as sea level rise, changing precipitation patterns, more acidic oceans, and increasing frequency and intensity of extreme weather events as reported in Chapter 1. Chapter 2 provides information on USDA efforts to identify and address potential vulnerabilities of U.S. agriculture, forestry, and food systems to projected climate change.