There are many reasons—rooted in culture, politics and economy—that California has become a leader in the fight against global warming.

One reason is increasingly obvious: The people who live there are being hit harder than ever by the costly effects of climate change.

"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," a comprehensive state climate change assessment issued Wednesday by the California Environmental Protection Agency says.

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The report notes that state emissions of greenhouse gases have been going down since 1990 when measured on a per capita basis or when compared to economic growth. But in absolute terms, the annual tonnage of carbon dioxide added to the atmosphere each year only began to decline about a decade ago.

The state is on track to meet its goal of cutting emissions to 1990 levels by 2020, but it may have a harder time hitting its 2030 target—a 40 percent reduction from 1990.

Cars: California's Achilles' Heel

The biggest challenge to meeting those goals is in the transportation sector.

The state has stringent emissions standards that rely heavily on the future adoption of electric vehicles, but those standards require a federal waiver, which the Trump administration is now threatening to revoke.

Fans of the California model say there's hope to avoid the worst effects of climate change if the state helps set a pattern for the whole world with landmark policies that promote electric cars, a wholesale shift to clean energy and an effective price on carbon pollution. If not, the damage will continue to build up.

"Humans have found ways of compensating for the changes that we are seeing in our environment at the moment, but that doesn't mean that, as these changes become larger, we'll be able to accommodate them so easily," said Philip Rasch, chief climate scientist at the Pacific Northwest National Laboratory, who was not involved in the report. "I am worried, and my suggestion to society is that it would be prudent to avoid putting ourselves into this situation as much as possible."

Daniel Swain, a climate scientist at UCLA, said the assessment offered a cohesive picture of just how much the climate has changed in recent years.

"We're now at a stage where these are no longer projections for the future, these are observational realities on the ground right now, and they are pretty striking numbers," he said.

The report's findings on environmental conditions in the state include:

Annual average air temperatures have increased since 1895, with the warmest four years on record occurring in the last four years.



Five of the state's years with severe to extreme drought since record keeping began in 1895 occurred between 2007 and 2016.



Some of the largest glaciers in the Sierra Nevada have lost between 50 to 85 percent of their surface area since 1903.



The area burned by wildfires each year has been increasing since 1950. Five of the largest fire years have occurred since 2006. The largest single recorded wildfire in the state, the Thomas Fire, which resulted in the filing of more than $1.8 billion in insurance claims, occurred in 2017.



Sea level has risen between 6 and 7 inches on average along the California coast since 1900.

Cities, State Policies Aim to Rein in Emissions

The report comes as eight cities and counties in California are suing oil and gas companies over the costs of climate change. The lawsuits allege that the companies knew for decades that the burning of fossil fuels was one of the biggest contributors to global warming but, instead of trying to reduce harm, the companies downplayed the risks of climate change.

The California Energy Commission voted Wednesday on another step to rein in emissions: It approved new energy standards that will require most new homes in the state to have solar panels starting in 2020.

Solar requirements such as these are critical for addressing climate change, not only in California, but globally, Swain said. "Anything that moves us in the direction of electrifying our transportation sector or actually making the electricity we are producing renewable, these are really important things to be doing, and we're not doing them fast enough."