Asteroid That Killed Dinosaurs Caused Global Warming For 1,000 Centuries

A massive asteroid struck Earth 66 million years ago and triggered a series of sporadic events that wiped out nearly three fourth of life living on the planet, including non-avian dinosaurs. It has long been believed the event, popularly known as the Chicxulub impact, proved catastrophic for all of life in ways more than one, but if the latest study is anything to go by, the impact had a much broader and long-lasting effect on global temperatures.

In the past, scientists have posited the immediate aftermath of the impact resulted in a period of what has been called a “global winter.” Dust and aerosols blocked sunlight and led to a massive decline in global temperatures for a few years. But, that was just the beginning.

As the asteroid crashed into rocks rich in carbonates and triggered massive wildfires around the globe, there was an extensive surge in the carbon dioxide levels prevailing in the atmosphere. So, as the dust and haze cleared and sunlight started reaching the surface of Earth, the greenhouse gas got into action and raised global temperatures. The idea of rising temperatures has also been around for a long time, but the latest work by scientists from the University of Missouri gives us a clearer picture.

According to the group, the surge in CO2 levels was so much that local seawater temperatures rose by five degrees Celsius for 100,000 years.

"Anything that's not killed by the thermal heat pulse likely had to deal with years of very little, if any, vegetation and anything that survived that then had to survive 100,000 years of quite substantial greenhouse conditions," Ken MacLeod, a University of Missouri researcher and co-author of the latest study told the Washington Post.

MacLeod and colleagues got this estimate after sampling rocks from an outcropping in Tunisia called El Kef, which was then known as the Tethys Sea, New Scientist reported. The layers of Earth at the site gave a clear picture of the time before, during and after the impact, and the researchers extracted remnants of marine life — tiny fish teeth, bones, and scales — from the post-impact sediments. These fragments, nearly as small as a grain of sand, were hard to find but contained calcium apatite — a material that is commonly found in human bones and teeth and stores chemical signs of oxygen.

So, they analyzed the ratio of oxygen isotopes. The changes witnessed in the abundance of these isotopes helped them understand the dramatic alterations in temperatures in the wake of the impact. Though the findings indicated temperatures only for that particular location — the group is working to test their technique at other locations — it does imply a worrisome situation for earthlings because climate's response to CO2 emission could be quicker and more devastating than we've estimated.

“The cascading implication of our finding is that carbon dioxide loading would have occurred for just maybe a decade [or two] and the greenhouse warming persisted for 100,000 years," stud MacLeod added. "Even if we go back to 1850 levels of CO2 emissions today, we're locked into 100,000 years of the Earth responding to the CO2 we've already put in."

The study, titled "Postimpact earliest Paleogene warming shown by fish debris oxygen isotopes (El Kef, Tunisia)," was published May 24 in Science Magazine.