It’s relatively easy for scientists to see the signature of droughts and other climate events in the prehistoric past by digging into underground or seafloor sediments, or drilling into ancient ice. In order to say exactly when these events happened, though, you need a reliable natural dating method, and even the best of these is flawed.
However, one of the most familiar of these timelines, known as radiocarbon dating, just got a lot more precise. According to a paper published in the journal Science, measurements from the bottom of Japan’s Lake Suigetsu have allowed scientists to improve the technique dramatically.
Now, thanks to those lake sediments, scientists can narrow that range down to just 10 years or less -- but only if the sample is between 11,000 and 53,000 years old. Younger and there hasn't been enough breakdown in the radioactive carbon. Older, and the lake's sediments don't go back that far.
This impressive achievement comes thanks to Lake Suigetsu’s calm waters, and also from the lucky fact that the plant matter that drifts into the water and sinks to the bottom is light-colored in winter and dark in summer. The result: alternating layers under the lake bottom that make it easy to identify every year, one after the other, going well back into the last Ice Age.