Ice Age El Niño
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For many Americans, El Niño seemed to arrive out of nowhere three years ago. Suddenly every bit of weird weather seemed to have a connection to this warming of the tropical Pacific. Actually, El Niño's been studied for decades, even before it became a household word. What scientists are now finding is that El Niño itself goes back a lot further than even they suspected. A new study find evidence that El Niños were happening during the last ice age, which ended about 10,000 years ago. The new study was led by a graduate student at the University of Massachusetts.

Tammy Rittenour wasn't planning to study El Niño at first. Her goal was to look at the deposits left behind by glaciers as they melted into Lake Hitchcock. This ancient lake once filled the Connecticut River valley between New Hampshire and Vermont. Rittenour and her colleagues took a soil sample about 100 feet deep from the old lakebed and looked at each year's deposits. Each summer, water melted from the glaciers and left a band of thick sediment on the lake bottom. A band of thinner sediment was left as the lake froze over each winter.

As she studied the sediments, Rittenour found something unexpected. The sediment layers changed on a cycle that ran every two to five years. That's about how often El Niño occurs. The main difference was that the El Niño effects seemed to get weaker over the period that Rittenour studied, from about 17,000 to 13,000 years ago. It now seems possible that El Niños go through phases where they tend to be stronger than at other times. One big question is whether climate change due to greenhouse gases might push El Niño into a different mode. That's something the record from Lake Hitchcock can't tell us--but at least it can help point toward some possible answers.