California Set for Centuries of Drought; Pacific Ocean, Greenhouse Gases to Blame?

California has had a severely dry last few years -- and this could be the "new norm" for centuries. This extended drought is linked with the changes in the sea surface temperature of the Pacific Ocean, according to a study led by University of California Los Angeles (UCLA) professor Glen MacDonald.

The team's findings, published in Nature journal Scientific Reports, confirmed the connection in past climate warming, the Pacific Ocean's temperature shifts and long episodes of drought in California. They used data from the past 8,000 years, particularly studying the climate and water changes in the Sierra Nevada mountains and cross-referencing it against the history of Pacific through marine sediment.

Radiative forcing has historically caused the warming of the seas, which has resulted in an unparalleled extension of drought in the state, according to a report from UCLA. Now, greenhouse gases have also joined it in pushing the rise of the temperatures.

A History of Drought

"Radiative forcing in the past appears to have had catastrophic effects in extending droughts," MacDonald, an expert on drought and climate change, explained. "When you have arid periods that persist for 60 years, as we did in the 12th century, or for millennia, as we did from 6,000 to 1,000 B.C., that's not really a 'drought.' That aridity is the new normal."

These arid periods showed a clear pattern in the relationship; in the millenia-long California dry period from 6,000 to 1,000 B.C. there was a slight shift in the planet's orbit contributing to the increased amount of solar energy directed to the Northern Hemisphere. Later, in 950 to 1,250 A.D., there was a rise in radiative forcing and warming due to volcanic activity. In both cases, California was hot and dry, while the Pacific Ocean was in a La Niña-like state.

Future of California?

With the continuous increase in greenhouse gases, the drought-like conditions could settle in California for a longer period of time.

"In a century or so, we might see a retreat of forest lands, and an expansion of sagebrush, grasslands and deserts," MacDonald said. "We would expect temperatures to get higher, and rainfall and snowfall would decrease. Fire activity could increase, and lakes would get shallower, with some becoming marshy or drying up."