Global environmental change, particularly climate change, is rapidly emerging as the defining environmental issue of the 21st century. Climate change will bring widespread impacts to California, as well as the possibility of novel opportunities for innovation and global leadership to reduce its magnitude and adapt to new challenges. California has exceptional natural resources, high levels of biological and societal diversity, and a strong and vibrant economy. The environment, history, and economy of California are strongly linked to climate, and how climatic conditions vary in space and time. We are also intimately connected to the rest of the world through physical, biological and social connections (e.g., climate dynamics, invasive species, economic markets, etc.). California has a long history as a leader in environmental policy and industrial innovation in the face of new challenges. Understanding the impacts of climate change in California, and the opportunities and barriers to respond and both reduce the rate of change and the magnitude of its impacts, is essential–as citizens and voters–and serves as a microcosm of the challenges faced globally.