Scientists using a new and highly precise dating technique have concluded that the late Cretaceous asteroid strike in Mexico's Yucatan Peninsula coincided almost exactly with the extinction of the dinosaurs — give-or-take a few tens of thousands of years. While it's clear that other factors were contributing to the rapidly deteriorating environmental conditions, it's now obvious that the asteroid was the final coup-de-grace for the dinosaurs.
Indeed, all was not well on Earth when the asteroid struck. Volcanoes in India were wreaking havoc to the planet's ecosystems, and earlier asteroid strikes may have contributed to an already fragile environment. Other research shows that Earth experienced six abrupt temperature shifts of two degrees or more in mean temperatures in the one million years before the impact. In one instance, the temperature swung 6-8 degrees.