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There was a time when life on Earth was almost wiped out. The Great Dying was the biggest extinction ever. It happened 250 million years ago and was largely caused by greenhouse gases in the atmosphere. As NPR's Christopher Joyce reports, scientists are beginning to see alarming similarities between the Great Dying and what's happening to our atmosphere now.
CHRISTOPHER JOYCE, BYLINE: You can learn about the Great Dying at the new Deep Time exhibit at the Smithsonian's National Museum of Natural History. I get a backdoor visit via a giant freight elevator that's used to haul life-sized dinosaurs up to the new hall. Workers are assembling dioramas and video monitors. It's a few weeks before opening. Curator Scott Wing shows me the exhibit's crown jewel - the museum's first real Tyrannosaurus rex.
What an enormous head.
SCOTT WING: It's a pretty big body, too (laughter).
JOYCE: The Tyrannosaurus stands over a prone triceratops, its jaws clamped on its head. But I digress.
WING: Well, the truth is it really isn't a dinosaur hall.
JOYCE: Yes, there are plenty of dinosaurs in it.
WING: We like to say, come for the dinosaurs. Stay for everything else.
JOYCE: The theme is actually the interconnectedness of life through geologic time. Exhibits show, for example, how plants at the bottom of the food chain supported everything from insects to 20-ton apatosauruses. Wing likes that. He's a botanist.
WING: I'm a photosynthesis chauvinist (laughter). The whole ecosystem is based on photosynthesis.
JOYCE: And because life, from toadstools to tyrannosaurs, is connected, when something big happens to the Earth, the whole fabric can disintegrate. And that happened due to global warming. It's explained in the exhibit's Great Dying section.
WING: This is it. This is the big one.
JOYCE: The exhibit explains that an enormous volcanic field erupted in what is now Siberia. It spewed carbon dioxide and pollution into the atmosphere, possibly for millions of years. That warmed the planet, made the oceans acidic and robbed them of oxygen. There have been other mass extinctions like the one that wiped out the dinosaurs, but this one at the end of the Permian period was about what happens when too much carbon dioxide rises into the atmosphere.
WING: Those are lessons that we can learn from studying the past. And they're also those sort of processes that are being observed by Earth scientists today.
JOYCE: Earth scientists like Curtis Deutsch of the University of Washington, whose research helped inform the Smithsonian curators.
CURTIS DEUTSCH: The very same things that caused the Great Dying are happening right now in our ocean today as a result of human activities - not to the same degree but in the same direction.
JOYCE: So Deutsch thought, why not recreate the hothouse of the Great Dying in a computer and see how present-day life would fare? He could crank up the heat and lower the oxygen and watch as parts of the ocean started to become deadly.
DEUTSCH: The first thing that happens is that you start to see a local loss of species as they begin to move in response to the climate heating up.
JOYCE: But some parts of the planet were more forgiving.
DEUTSCH: And we discovered something that was kind of surprising and new, I think. And that is that extinction was very strong everywhere, but it was even stronger near the cold parts of Earth in the - near the polar oceans than it was in the warmer, tropical oceans.
JOYCE: It makes sense, he says. Animals that live near the equator can migrate toward the poles to find cooler water. But those that already live in cold, oxygen-rich waters near the poles have very little room to run. Deutsch says the experiment is a window on the future, even the present. Marine species are already migrating.
DEUTSCH: We see responses of marine species to those changes today that look like what we think happened at the end of the Permian.
JOYCE: And that, says the Smithsonian's Scott Wing, is what visitors should take away from the new exhibit.
WING: We're so powerful, we are basically a geological force now as well as a human force.
JOYCE: A force that's changing the conditions for life on the planet.
Christopher Joyce, NPR News.
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