El Nino getting naughty

HONOLULU —  Want to know how to figure out El Nino, a cyclic weather event that creates havoc and impacts the lives of millions of people?

Just ask the trees.

Scientists at the University of Hawaii and the University of California are saying they’ve learned how to look back into the history and future of El Nino. They say the trees are telling us that El Nino has been unusually active in the late 20th century. If the trend continues, there will be more floods and droughts.

An international team of scientists spearheaded by Jinbao Li and Shang-Ping Xie, while working at the International Pacific Research Center, UH Manoa, has compiled 2,222 tree-ring chronologies of the past seven centuries from both the tropics and mid-latitudes in both hemispheres.

They say the tree-ring records reflect El Nino-Southern Oscillation activity over the past seven centuries. Tree-rings have been shown to be very good proxies for temperature and rainfall measurements, according to the UH study.

Their work is published in the June 30 online issue of Nature Climate Change.

The inclusion of tropical tree-ring records enabled the team to generate an archive of ENSO activity of “unprecedented accuracy,” according to a press release.

These proxy records indicate that ENSO was unusually active in the late 20th century compared to the past seven centuries, implying that this climate phenomenon is responding to ongoing global warming.

“In the year after a large tropical volcanic eruption, our record shows that the east-central tropical Pacific is unusually cool, followed by unusual warming one year later,” lead author Li said.

He added that, “like greenhouse gases, volcanic aerosols perturb the Earth’s radiation balance. This supports the idea that the unusually high ENSO activity in the late 20th century is a footprint of global warming.”