Researcher: Unprecedented global warming killed off 95 percent of the Earth’s species

December 31, 2012

Researcher: Unprecedented global warming killed off 95 percent of the Earth’s species

A massive extinction gets a second look.

Extreme global warming seems to have been the cause of the largest mass extinction the planet has ever seen, according to LiveScience.com.

After examining a variety of fossil evidence, researcher Paul Wignall, a geologist at the University of Leeds in England, said his research shows climate change may have been responsible for the massive extinction.

“We may have found the hottest time the world has ever had,” said Wignall.

The mass extinction at the end of what scientists call the Permian Era (some 250 million years ago) was the largest extinction in Earth’s history, killing off 95 percent of the planet’s species. In addition to rising temperatures, numerous volcanic eruptions—including a catastrophic eruption in Siberia that spanned 2.7 million square miles (7 million square kilometers), roughly the size of Australia—depleted the Earth’s important protective ozone layer, allowing the temperature to climb unchecked.

Mr. Wignall says the post-Permian Era is known as “the dead zone.” Elaborating, he says, “It’s this 5 million year period where there’s no recovery, where there is a very low diversity of life.”

Scientists are not yet sure what temperature extremes the Earth experienced during this period. However, fossil evidence dating from 253 to 254 million years ago, shortly before and after this period, reveal incredibly high sea surface temperatures as high as 100 degrees F (38 degrees C).  For comparison, modern day sea surface temperatures hover around 77 to 86 degrees F (25 to 30 degrees C).

“Photosynthesis starts to shut down at about 35 degrees C [95 degrees F], and plants often start dying at temperatures above 40 degrees C [104 degrees F],” Mr. Wignall said. “This would explain why there’s not much fossil record of plants at the end-Permian— for instance, there are no peat swamps forming, no coal-forming whatsoever. This was a huge, devastating extinction.”

In order to determine the rate at which temperatures rose during the period of extreme global warming, scientists examined oxygen isotopes in the shells of marine life. “[Sea creatures] tend to use lighter isotopes of oxygen under warmer conditions,” said Mr. Wignall. “You can still see this today when looking at modern day sea creatures. The ratios of oxygen isotopes in their shells are entirely controlled by temperature.”

Researchers focused on sea creatures known as conodonts, eel-like animals with elaborate mouthparts, from the Nanpanjiang Basin in southern China. Different varieties of conodonts shed light on the temperatures at various depths during the end-Permian Era.

“We had to go through several tons of rock to look at tiny conodont fossils,” said Mr. Wignall. “People always thought the end-Permian extinctions were related to temperature increases, but they never measured the temperature then in much detail before, since it involves a lot of hard work looking at these microfossils.”

The results of this tedium were rewarding, providing scientists with the evidence they needed to prove the world’s hottest temperatures to date. Thankfully, Mr. Wignall thinks we might yet avoid a similar fate, saying, “we’re not going to get anywhere near the level seen after the end-Permian,” Wignall said. “We need to worry about global warming, but it’s not going to get to this stage.”


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