Guest column: How dry, how long?

William Debuys Los Angeles Times

California, currently in the Great Drought, is a living diorama of how the future is going to look across much of the United States as climate change sets in.

Now, the large dark bruise spreading across the state on the U.S. Drought Monitor map is a preview of a bone-dry world to come.

Admittedly, recent summer rains have somewhat dulled the edge of this “exceptional” California drought, now in its fourth year. Full recovery however, would require about a foot of rain statewide between now and January. A veritable deluge for places like Fresno, which in good times get that much only in a full year.

To be clear, the current drought may not have been caused by climate change. After all, California has a long history of fierce droughts that arise from entirely natural causes, some of them lasting a decade or more. Even so, climate change remains a potent factor in the present disaster.

According to the state’s Climate Change Center, California is on average about 1.7 degrees hotter than a century ago, and its rate of warming is expected to triple in the century ahead.

The kicker is that hotter means much drier because as temperature creeps up, evaporation gallops. As a result, the droughts of the future will be effectively more destructive than those of the past.

Throughout the state, draconian cutbacks in water use are in force. Some agricultural districts are receiving 0 percent of the federally controlled irrigation water they received in past years, while state-controlled water deliveries are running about 15 percent of normal. A staggering 5,200 wildfires have burned across the state this year, and the fire season still has months to go.

Here is the unvarnished version as expressed in a paper that appeared in Science Advances in February: “The mean state of drought in the late 21st century over the Central Plains and Southwest will likely exceed even the most severe mega-drought periods of the Medieval era in both high and moderate emissions scenarios, representing an unprecedented fundamental shift with respect to the last millennium.”

Let’s unpack that. Principal author Benjamin Cook of NASA and his colleagues from Columbia and Cornell universities are saying that climate change will bring to the continent a “new normal” more brutally dry than even the multiple-decades-long droughts that caused the Native American societies of Chaco Canyon in New Mexico, and Mesa Verde in Colorado, to collapse. This, they add, will happen even if greenhouse gas emissions are significantly lowered soon.

If California points the way to dry times ahead, it also gives us a glimpse of how a responsible society can adjust to a warmer future. In general, the state’s individual consumers and water districts are meeting conservation goals, thanks to a range of innovations and sacrifices.

Perhaps most impressively, the state has adopted its own pioneering cap-and-trade program aimed at rolling back greenhouse gas emissions to 1990 levels. If they emit less, they can sell their extra permits in a state auction, creating incentives to cut carbon pollution.

Adaptation could soften some of the blows, and possibly, if we act soon enough and strongly enough, we may manage to cap the overall changes at some still livable level.

Eventually, California’s message will be heeded. Get ready.

William Debuys is an author for the Los Angeles Times.