Asteroid Strike

Science Daily: Dino-killing asteroid could have thrust Earth into two years of darkness - Light-absorbing soot in the atmosphere had the potential to block photosynthesis

summary - Tremendous amounts of soot, lofted into the air from global wildfires following a massive asteroid strike 66 million years ago, would have plunged Earth into darkness for nearly two years, new research finds. This would have shut down photosynthesis, drastically cooled the planet, and contributed to the mass extinction that marked the end of the age of dinosaurs.