The Weather Notebook: Younger Dryas

Younger Dryas
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Dave Thurlow, Host

Scientists used to think that climate took hundreds, even thousands of years to change. Now we know better. Hi, I'm Dave Thurlow from the Mount Washington Observatory and this is The Weather Notebook.


Ice Core

By looking at layers of snow and ice in glacial ice cores, and the gases trapped inside, we can analyze thousands of years of climate change. And, these snapshots of climate history shows us how quickly climate can change.

An example of an extremely quick climate change came during a period of time known as the Younger Dryas, which happened right after the last ice age ended, about 12,000 years ago. The Younger Dryas itself lasted about 1,000 years. What we didn't know until recently was just how quickly the Younger Dryas started and stopped. In a period of less than 50 years, the climate from the eastern US and Canada to much of Europe went from climate conditions much like today's, to frigid readings more like the Ice Age, at least a ten degree Farenheit change. That's how it stayed for a thousand years - and then the climate flipped back to normal in as little as 20 years.

As the Ice Age glaciers dissolved across North America, their meltwater poured into the Atlantic. Some researchers think this meltwater pinched off the warm Gulf Stream, allowing the water to cool down dramatically in the northern Atlantic Ocean. Could this happen in our lifetime? Well, it could, and ironically it could because of global warming. If global warming causes heavier rain, and more water is being dumped into the North Atlantic, it could flip the climate switch just like that and changes hot or cold would occur around the world in a climatological blink of an eye.

The weather Notebook is funded by Subaru and the National Science Foundation.