El Niño and La Niña, the periodic shifts in Pacific Ocean temperatures, affect weather around the globe, and many scientists have speculated that a warming planet will make those fluctuations more volatile, bringing more intense drought or extreme rainfall to various regions.
Now, scientists have used tree-ring data from the American Southwest to reconstruct a 1,100-year history of the cycle that backs up that assertion. The researchers found a 50-90-year cycle of waxing and waning El Niño intensity that shows that, when the earth warms, the climate acts up.
“Our work revealed that the towering trees on the mountain slopes of the U.S. Southwest and the colorful corals in the tropical Pacific both listen to the music of El Niño, which shows its signature in their yearly growth rings,” explains Jinbao Li, the paper’s lead author and a former PhD student at Lamont-Doherty Earth Observatory.
The research, published May 6 in Nature Climate Change, will improve scientists’ ability to predict future climate and the effects of global warming, the scientists say.
The temperature of the eastern tropical Pacific fluctuates between relative warm (El Niño) and relatively cold (La Niña) every 2 to 8 years, based on well-known instrumental records from the recent past. This is coupled with shifts in air surface pressure in the western Pacific – the Southern Oscillation. The patterns have a strong impact on the climate in many regions of the world, including the American Southwest: Warmer sea surface waters lead to relatively wetter winters there, while the cooler La Niña leads to drier ones.