Overview of the California climate change scenarios project

In response to an Executive Order by California Governor Schwarzenegger, an evaluation of the implications to California of possible climate changes was undertaken using a scenario-based approach. The "Scenarios Project" investigated projected impacts of climate change on six sectors in the California region. The investigation considered the early, middle and later portions of the twenty-first century, guided by a set of IPCC Fourth Assessment global climate model runs forced by higher and lower greenhouse gas emission scenarios. Each of these climate simulations produce substantial impacts in California that would require adaptations from present practices or status. The most severe impacts could be avoided, however, if emissions can be held near the lower end of global greenhouse gas emissions scenarios. It is increasingly apparent that the rising atmospheric concentration of greenhouse gases (GHGs), resulting from human activities, is changing the climate in ways that pose serious risks to California's health, economy, and environment. Furthermore, the more GHGs accumulate in the Earth's atmosphere, the more the climate is likely to change and the greater the risks that Earth's system processes and society will face (IPCC 2007). If actions are not taken soon, substantial impacts are likely to happen sooner and grow to larger magnitudes.