The El Nino weather pattern that can bring drought to Australia and rain to South America was “unusually active” at the end of the 20th century, possibly due to climate change, a University of Hawaii study found.
Researchers studied 2,222 tree-ring records as proxies for temperature and rainfall over the past 700 years, the university wrote in an online statement dated July 1. The records indicate the El Nino-Southern Oscillation weather phenomenon has been increasingly active in recent decades relative to the past seven centuries.
The drought associated with El Nino’s warm phase can cause smaller rice crops in Asia and cut wheat production in Australia, while the rains can cause flooding in South America and weaker cold ocean currents reduce anchovy catches off Peru. Accurately forecasting El Nino is challenging because it varies naturally over decades and centuries, the university said.
“If this trend of increasing ENSO activity continues, we expect to see more weather extremes such as floods and droughts,” Shang-Ping Xie, a meteorology professor at the University of Hawaii’s International Pacific Research Center and study co-author, was cited as saying in the statement.
The study found that in the year after a large tropical volcanic eruption, the east-central tropical Pacific is “unusually cool,” followed by warming a year later, the university wrote. Volcanic aerosols, like greenhouse gases, disturb the Earth’s radiation balance, it said.
“This supports the idea that the unusually high ENSO activity in the late 20th century is a footprint of global warming,” study lead author Jinbao Li was cited as saying.
The results from the study may help improve the accuracy of climate models and predictions for future El Nino activity, according to Li.
Editors: John Deane, Sharon Lindores
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