Computer simulations of the effects of the asteroid impact that reshaped life on Earth 66 million years ago have revealed that dust was responsible for the extinction of the dinosaurs.
The catastrophic impact of what is now known as Chicxulub on the Yucatán Peninsula, Mexico, wiped out 75% of species on Earth, including non-avian dinosaurs. But the precise nature of the fatal hit has kept scientists busy for decades.
The Belgian scientists wrote in the journal Nature Geoscience that the “precise killing mechanisms” resulting from the impact are still not well understood, and that little attention has been paid to the role potentially played by the trillions of tons of dust generated by this violent event.
Soot, sulfur and dust, swirling in the atmosphere for years, have the ability to block sunlight and contribute to a global winter, with devastating effects on animals and plants.
To delve deeper into the role of different factors, scientists ran paleoclimate simulations that took into account measurements of fine particles extracted from a site in North Dakota, where a layer of dust from the Chicxulub impact settled.
According to simulations, dust of the size found in Dakota could remain in the atmosphere for up to 15 years after it exploded into the sky. By blocking sunlight, up to 2,000 billion tons of it would have stopped photosynthesis for about two years and cooled the planet by up to 15 degrees Celsius.
The dust, created from crushed granite and other rocks at the impact site, "most likely triggered the recent mass extinction event by disrupting photosynthetic activity," said Jim Burke Senel, study researcher at the Royal Belgian Observatory in Brussels.
Philippe Claes, a geologist and planetary scientist at the Free University of Brussels and co-author of the study, added that silicate dust emerged from the simulations as “the most efficient barrier to photosynthesis. It makes the atmosphere opaque to sunlight, which hinders the photosynthesis of plants.”
According to computer models, it could take up to two years for photosynthesis to resume.
Steve Brusatte, a professor of paleontology and evolution at the University of Edinburgh, who was not involved in the study, described the asteroid that killed the dinosaurs as "horrific."
He said: “It was the largest asteroid to hit the Earth in the last half a billion years, and it exploded with more force than a billion nuclear bombs combined. But this is not what killed the dinosaurs and 75% of other species that have already become extinct. What really led to their destruction is what happened after that.” "The dust resulting from the asteroid impact moved into the atmosphere and blocked out the sun. The Earth became dark and cold for a few years. The asteroid did not kill all the dinosaurs at once, but it was a more subtle killer, which led to a depletion that resulted in the death of three out of every four species."
The “safe” threshold for global warming will be crossed soon!
A study said that global carbon emissions are on track to exceed safe limits by 2030, which means we have only 6 years to change course and reduce greenhouse gas emissions.
A new estimate of our remaining “carbon budget,” the amount of carbon dioxide we could produce while keeping global temperatures below a dangerous threshold, suggests that as of January, if we emit more than 276 gigatonnes (250 gigatonnes) of carbon dioxide, we will reach temperatures 1.5°C (2.7°F) above pre-industrial levels. The researchers found that if emissions continue at the current rate, we will exceed this threshold before the end of the decade, according to a study published on Monday, October 30, in the journal Nature Climate Change.
“Our findings confirm what we already know: we are not doing enough to keep temperature rise below 1.5 degrees Celsius,” the study’s lead author Robin Lambole, a researcher at the Center for Environmental Policy at Imperial College London, said in a statement. "Bigger than ever before, the window to keep temperatures rising to safe levels is closing quickly."
In 2015, 196 world leaders signed the Paris Agreement, a legally binding climate change treaty that aims to keep the average global temperature below 2 degrees Celsius (3.6 Fahrenheit) above pre-industrial levels. The agreement stressed that limiting global warming to 1.5 degrees Celsius would help prevent the worst effects of climate change.
Earlier this year, a United Nations report warned that temperatures may soon periodically exceed the 1.5 degree Celsius threshold, but the new study indicates that temperatures will rise in the long term.