Academic journal article The Science Teacher

California Drought Could Persist for Centuries

Academic journal article The Science Teacher

California Drought Could Persist for Centuries

Article excerpt

Clues from prehistoric droughts and arid periods in California show that today's increasing greenhouse gas levels could lock the state into drought for centuries, according to a new study.

The study looked at how natural climatic forces contributed to centuries-long and even millennia-long periods of dryness in California during the past 10,000 years. These phenomena--sunpots, a slightly different Earth orbit, a decrease in volcanic activity--intermittently warmed the region through a process called radiative forcing and recently have been joined by a new force: greenhouse gases.

As long as warming forces like greenhouse gases are present, the resulting radiative forcing can extend droughtlike conditions more or less indefinitely, said researcher Glen MacDonald, an international authority on drought and climate change.

"Radiative forcing in the past appears to have had catastrophic effects in extending droughts," MacDonald said. "When you have arid periods that persist for 60 years, as we did in the 12 th 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."

Researchers tracked California's historic and prehistoric climate and water conditions by taking a sediment core in the Sierra Nevada Mountains. They pulled a 2-inch-wide, 10-footdeep cylinder of sediment from the bottom of Kirman Lake and analyzed it in third-of-an-inch sections, creating the most detailed and continuous paleoenvironmental record of California.

The team correlated their findings with other studies of California climate history, and for the first time, united all the studies and cross-referenced them with histories of the Pacific Ocean's temperature taken from marine sediment cores and other sources. …

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