Living the Scientific Life (Scientist, Interrupted)

Computer simulation of the Earth’s annual average surface temperatures in degrees Celsius 251 million years ago, at the Permo-Triassic (PT) boundary. Approximately 96% of marine species and 70% of terrestrial vertebrate species became extinct at the PT boundary, creating niches that the dinosaurs then occupied as the dominant animal group during the next geological age.

Image: National Center for Atmospheric Research (NCAR) in Boulder, Colorado.


A computer simulation of the Earth’s climate 250 million years ago suggests that increased carbon dioxide levels led to global warming that triggered the so-called “Great Dying”. The Great Dying was the largest mass extinction event on earth. It occurred approximately 251 million years ago and marks the boundary between the Permian and Triassic geologic periods, commonly known as the PT boundary. In less than one million years, approximately 96% of all marine species and 70% of all terrestrial animal species, paving the way for the dinosaurs’ eventual rise as the dominant animal group.

The massive PT extinction event has mystified scientists for decades and many potential explanations have been proposed, including an impact event with an extraterrestrial rock, plate tectonics and glaciation, extreme volcanic activity, a supernova, the sudden release of frozen methane hydrate from the ocean beds to trigger a greenhouse effect, or some combination of these factors.

This new research, published this week in the peer-reviewed journal, Geology, adds support to the hypothesis that increased carbon dioxide levels, which cause global warming, were the ultimate culprit. These new data show that extensive volcanism over the course of hundreds of thousands of years released large amounts of carbon dioxide and sulphur dioxide into the air, causing Earth’s temperatures to rise from 10 to 30 degrees Celsius higher than today, write the scientists.

“The implication of our study is that elevated CO2 is sufficient to lead to inhospitable conditions for marine life and excessively high temperatures over land would contribute to the demise of terrestrial life,” wrote Jeffrey Kiehl and his colleagues in their Geology paper. Kiehl and his colleagues are research scientists at the National Center for Atmospheric Research (NCAR) in Boulder, Colorado.

During the Permian-Triassic boundary, most of the continents were united into one large landmass, known as Pangaea (right). This is where the largest surface temperature increases were noted by the researchers (see image at top)

To carry out this work, the NCAR team used a research tool known as the Community Climate System Model (CSSM) which looks at the combined effects of atmospheric temperatures, ocean temperatures and currents. Their research showed that global temperatures rose so much that the oceans warmed to a depth of about 3,000 meters (10,000 feet), particularly in the higher latitudes. The increased oceanic temperatures interfered with circulation that carries colder water, rich in oxygen and nutrients, into oceanic depths. As a result, the earth’s oceans became depleted of oxygen and were unable to support marine life.

Sources:

BBC News, story, quotes.

Extinction by Douglas H. Erwin (2006).

Comments

  1. #1 PiGuy
    November 3, 2006

    Another implication might be (wait for it) …

    that the global warming we see today is part of a natural cycle and that humans may not be able to impact it by switching to hydrogen cells.

    I don’t believe that there is any evidence of Euskelosaurus taking the family out for a spin in the old hoopty.

  2. #2 Jim
    November 3, 2006

    PiGuy, perhaps you missed the cause of the Permian temperature increase: the release of Carbon dioxide from volcanic activity.
    There are not any major natural sources of CO2 which have suddenly begun to release more greenhouse gases in the last few centuries (volcanic or otherwise). Rather, the only significant new source of greenhouse gases in the last 200 years is burning fossil fuels. And the increase in this anthropogenic CO2 correlates closely with the increase in global temperature. Perhaps that is the evidence you are seeking?
    The only good news from the report is that the temperature change associated with that mass extinction was 10C to 30C. The present anthropogenic increase is only modeled at 3-5C.

    Jim

  3. #3 Daniel Collins
    November 3, 2006

    Sephton et al. (2005) suggest the collapse in the marine ecosystems resulted from excess nutrient loading following the collapse of terrestrial ecosystems and associated erosion.

  4. #4 llewelly
    November 3, 2006

    that the global warming we see today is part of a natural cycle and that humans may not be able to impact it by switching to hydrogen cells.
    I don’t believe that there is any evidence of Euskelosaurus taking the family out for a spin in the old hoopty.

    Already debunked.

    PiGuy, your line was invented by con men who care nothing for your future.

  5. #5 biosparite
    November 3, 2006

    Pi,
    A “natural cycle” implies a repetitious, circular process. The end-Permian event(s) are unprecedented in their ferocious effects on life during the Phanerozoic Eon and are potentially instructive for us to the extent the disaster was caused by high CO2 levels. Those who forget the past, PiGuy, are condemned to repeat it.

  6. #6 David Harmon
    November 4, 2006

    Welcome to Easter Island Earth….

  7. #7 jo_bobtwc
    November 16, 2006

    Am I the only one concerned about the fact that we don’t even have enough data to run an accurate simulation of climate a few hundred years ago let alone 250 million years ago. I’m going to go out on a limb and say that to trust the accuracy of this simulation would be sketchy at best.