MANOA, Hawaii, May 6 (UPI) -- Tree rings in the American Southwest provide clues to future El Nino and La Nina cycles in a changing climate, scientists say.

The rings, going back 1,100 years, correlate closely with 150 years of ocean surface temperature records in the tropical Pacific, finds a study led by Jinbao Li of the International Pacific Research Center at the University of Hawaii at Manoa and published Friday in the journal Nature Climate Change.


During El Ninos, a warmer eastern Pacific increases winter precipitation in the Southwest, producing wider tree rings. The cold-water La Nina causes drought and narrower rings.

The tree rings show El Nino's intensity has ranged widely from decades of strong events and decades of little activity.

Cores from lake sediments in the Galapagos Islands, Yucatan and the Pacific Northwest indicate swings between warm and cool phases in the east-central tropical Pacific lasting from 50 to 90 years.

During warm phases, El Nino and La Nina events were more intense, while during cool phases, they strayed little from the long-term average.