Researchers analyzed radioisotopes in layers of fossilized volcanic ash. Decay of uranium to lead within tiny crystals enabled scientists to precisely pinpoint dates for certain events. They determined this event occurred 119.5 million years ago — coincident with evidence for massive volcanic eruptions — and lasted for 1.1 million years. Study results help scientists better understand links between atmospheric CO₂ levels, climate changes and conditions in the oceans.

On February 2, 1887, residents of Punxsutawney Pennsylvania consulted a large rodent regarding the arrival of spring, marking the first official celebration of Groundhog Day. Our ability to predict the timing of seasons hasn’t improved much since then, but a new study is set to make seasonal forecasting a lot more reliable.