Robinson Meyer in The Atlantic:
It took, at most, several seconds. An enormous hunk of rock, roughly the size of Manhattan, came whirling out of the vastness of space. It pierced Earth’s thin atmosphere, ignited as it fell, and slammed into the crust, opening a crater 20 miles deep in modern-day Mexico’s Yucatan Peninsula. Of course, it killed the non-avian dinosaurs: How could it not? By its end, the cataclysm wiped out 75 percent of all species that dwelled on Earth. In the last quarter century, we have gotten used to seeing images of that catastrophe: of the hellfire that rained down to Earth, igniting massive forest fires; of the years-long “impact winter” that dimmed the sun and chilled the Earth. But less well-known is what followed that winter. Scientists believe that the asteroid, which struck Earth roughly 66 million years ago, eventually triggered a lengthy period of ferocious global warming. Upon impact, it vaporized solid limestone into gas, and it incinerated enormous swaths of forest. This unleashed so much heat-trapping carbon dioxide into the atmosphere so quickly that, across all of Earth’s history, its rate of increase seems to be rivaled only by recent carbon pollution from factories, cars, planes, and modern industry.
A study published Thursday in Science finds new evidence of that warming while setting it in a dreadful context. It may have taken seconds for the asteroid to chew a 20-mile-deep hole in Earth. But, its authors say, it took roughly 100,000 years for Earth’s climate to return to normal. The research argues that Earth’s average temperature was elevated by 5 degrees Celsius for the 100 millennia that followed the impact. Notably, it supports this assertion not just with computer models, but with direct, observed evidence from the time period. By analyzing the bones of fish that lived in modern-day Tunisia before, during, and after the impact, scientists were able to detect a planet-sweltering warming signal.