From record temperatures to proliferating wildfires and rising seas, climate change poses an immediate and escalating threat to California’s environment, public health, and economic vitality. Recent climate-related events – such as the devastating 2017 wildfires and the record-setting 2012-16 drought – have highlighted the challenges that confront the state as its climate continues to evolve. California has been a pioneer in addressing climate change. This report helps support policy decisions and facilitates communication about climate change by providing, in a single document, indicators characterizing its multiple aspects in California. Indicators are scientifically-based measurements that track trends in various aspects of climate change. Many indicators reveal discernable evidence that climate change is occurring in California and is having significant, measurable impacts in the state. The report’s 36 indicators are grouped into four categories, as listed below. The report discusses what these indicators show, why they are important, and the factors that may be influencing them.

• Human-influenced (anthropogenic) drivers of climate change, such as greenhouse gasemissions
• Changes in the state’s climate
• Impacts of climate change on physical systems, such as oceans, lakes and snowpack
• Impacts of climate change on biological systems – humans, vegetation and wildlife