Dinosaurs became extinct 66 million years ago primarily because sulphuric acid clouds had led to frigid conditions, a new study has found. According to scientists at Potsdam Institute for Climate Impact Research in Germany, the sulphuric acid clouds were formed after an asteroid impact blocked sunlight for years. “The big chill following the impact of the asteroid that formed the Chicxulub crater in Mexico is a turning point in Earth’s history,” said Julia Brugger, lead author of the study that was published in the Geophysical Research Letters journal.

The scientists, who reconstructed the apocalyptic world, said that the annual mean temperature dropped by around 26°C globally. In tropical regions, temperatures fell from 27°C to 5°C. After the asteroid’s impact, the annual average temperature was below freezing point for about three years.

The frozen condition further led to mixing of the oceans, which affected marine ecosystems. “While the cooler water masses sank into the depths, warmer water from deeper ocean layers rose to the surface, carrying nutrients that likely led to massive blooms of algae that further produced toxic substances, thus affecting life on the coasts,” read the study.

The new study negates earlier theories that highlighted the impact of dust ejection. “The long-term cooling caused by the sulphate aerosols was much more important for the mass extinction than the dust that stays in the atmosphere for only a relatively short time. It was also more important than local events like the extreme heat close to the impact, wildfires or tsunamis,” said lead researcher Georg Feulner.