November 8, 2007

Sciencedude: CSUF says Southern California climate getting drier

Gary Robbins

Southern California’s climate has gotten progressively drier over the past 10,000 years and will become even more arid in the future, says a new study co-authored by Cal State Fullerton paleoclimatologist Matthew Kirby.

Kirby and his collaborators base their finding on analysis of sediment beneath the floor of Lake Elsinore, the largest natural lake in Southern California.

“The level of organic matter in the sediment has been rising, which indicates that the lake level has generally been falling over the past 10,000 years,” says Kirby. “The amount of nitrogen and carbonate in the core samples also show increases over the same time interval.

“From that, we infer that Lake Elsinore is probably smaller today, and maybe shallower, than it was 10,000 years ago.

“Simply put, in small, shallow evaporative lakes like Lake Elsinore, a decline in lake level (such as that caused by less precipitation) concentrates nutrients, increasing organic matter productivity and also enhancing the chemical precipitation of carbonate.”

The study was recently published in the Journal of Paleolimnolgy and was co-authored by researchers from USC, UC Riverside and the University of Pittsburgh.

Kirby says the drying trend “doesn’t disprove global warming. What it means is that we already live in a dry climate that’s expected to get drier, and that could pose problems. Southern California is an over-populated region that is water poor. As the region gets drier, we’re going to face tough issues on water use.”