Researchers calculated that the heat trapped by the fine dust meant the dinosaurs received a dose of thermal radiation 17 times more than the amount that would be lethal to humans.
The intense heat was enough to ignite grass, pine needles, lichen and maybe even wood, causing widespread wildfires and turning Earth into a fiery oven from which only burrowing animals, and those in the sea, could escape.
“It probably looked more like hell,” said Prof Johnson. “The clouds would have blocked daylight so to any animal, like humans, that don’t see far into the infrared, the surface would have probably looked dark.”
Scientists knew that the impact had melted rocks and sent detritus showering down to Earth because spherules have been found in the gills of paddlefish, which probably died on the day the asteroid hit.
The spherules, about half the size of a grain of sugar, were made up of material of terrestrial origin – not from the asteroid itself, but almost certainly the deadly cloud that it created.
Dr Johnson looked at the physical properties of these particles and the dust cloud as a whole to determine how it would have handled heat.
She found the cloud layer was so impermeable that it trapped almost all of the heat from near the surface of the planet, the dust essentially acting like a lid on a pot, cooking Earth’s inhabitants on the surface.
The dust could have taken years, or even decades, to settle, and the particles themselves could have caused ongoing health problems for survivors.
The study was published in the Journal of Geophysical Research: Biogeosciences.