Alex Knapp reviews new research on the extinction of the dinosaurs:

While an asteroid impact is obviously a devastating event, what’s interesting about this impact and the extinction of the dinosaurs is that it might not have happened – except that for a million years prior to the impact, the Earth’s climate had started to undergo some significant climate changes. That meant that the asteroid impact caused much more harm to the ecosystem than it otherwise might have during a more stable era.

“These precursory phenomena made the global ecosystem much more sensitive to even relatively small triggers, so that what otherwise might have been a fairly minor effect shifted the ecosystem into a new state,” [researcher Paul] Renne added in the release. “The impact was the coup de grace.”