Sobering New Climate Report for California

“An immediate and growing threat.”

That’s how California’s lead environmental agency — and the Governor’s office — describe climate change in the latest in a series of periodic reports on the subject.

The report cites “already discernible impacts of climate change” and attempts to pinpoint the main drivers — no pun intended. In California, nearly 40 percent of greenhouse gas emissions come from the transportation sector — trains, planes and automobiles, and the last in particular.

According to the report from the state Environmental Protection Agency, the annual average temperature in California has risen about 1.5 degrees (F) — but the state isn’t warming up uniformly. Parts of the Central Valley and Southern California are heating up faster; the hot are getting hotter. And a particularly insidious aspect of warming: overnight low temperatures are rising twice as fast as daytime highs. This has clear implications for agriculture, as many important cash crops, like stone fruits, need a certain amount of “chill time” to produce bountiful, quality fruit. Warmer nights put more pressure on the electric grid as air conditioners run longer, and also limit recovery time during hot spells, worsening the effects of heat waves.

And yes, those are increasing, the Cal/EPA report finds, and in some surprising places, such as the North Coast (bear in mind that what passes for a “heat wave” in Mendocino is a little different from the Mojave threshold).

The water picture is a little bit murkier, in that the report finds no clear change in the amount of precipitation that California is getting, but where and when that rain and snow falls is changing and proving to be just as important. For example, the Sacramento River — the main artery of California’s water system — has seen a nine percent drop in runoff coming into it over the past century. And the surface area of glaciers in the Sierra Nevada has receded anywhere from 20-to-70 percent in the same time frame.

The “good” news is that global warming emissions have tapered off in the state in recent years. The bad news is that’s largely due to slowing industrial activity in the recent recession. The long-term trend still has emissions rising overall but the state’s economy is becoming more carbon-efficient, so emissions per unit of industrial output are falling.

The Cal/EPA report is just the latest in a flurry of sobering climate reports to hit the streets in recent days. Federal climate watchers issued their State of the Climate report on August 6, with confirmation that 2012 was among the hottest years on record, among other cheery pronouncements. And the latest environmental scorecard for Lake Tahoe reveals gains in water clarity but mounting threats from climate change.

The steady drumbeat of climate data may be having an effect on public attitudes. In its most recent statewide poll, the California Public Policy Institute found that nearly 8-in-10 Californians consider warming at least a “somewhat serious” threat, and a record proportion favor immediate action to counter climate change impacts.