What was the new idea given out by scientists about earth 500 years ago?
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Answer:
When it opens next month, the revamped fossil hall of the Smithsonian Institution's National Museum of Natural History in Washington, D.C., will be more than a vault of dinosaur bones. It will show how Earth's climate has shifted over the eons, driving radical changes in life, and how, in the modern age, one form of life—humans—is, in turn, transforming the climate.
To tell that story, Scott Wing and Brian Huber, a paleobotanist and paleontologist, respectively, at the museum, wanted to chart swings in Earth's average surface temperature over the past 500 million years or so. The two researchers also thought a temperature curve could counter climate contrarians' claim that global warming is no concern because Earth was much hotter millions of years ago. Wing and Huber wanted to show the reality of ancient temperature extremes—and how rapid shifts between them have led to mass extinctions. Abrupt climate changes, Wing says, "have catastrophic side effects that are really hard to adapt to."
But actually making the chart was unexpectedly challenging—and triggered a major effort to reconstruct the record. Although far from complete, the research is already showing that some ancient climates were even more extreme than was thought.
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Ancient glaciations are easy enough to trace, as are hothouse periods when palms grew near the poles. But otherwise little is certain, especially early in the Phanerozoic, which spans the past 541 million years. Paleoclimate scientists study their own slices of time and use their own specialized temperature proxies—leaf shape, say, or growth bands in fossilized corals—which often conflict. "We don't talk to each other all that much," says Dana Royer, a paleoclimatologist at Wesleyan University in Middletown, Connecticut. So at a meeting last year, Wing and Huber assembled a loose-knit collaboration, dubbed Phantastic, dedicated to putting together a rigorous record. "Most people came away quite inspired to do something about this," says Dan Lunt, a paleoclimate modeler at the University of Bristol in the United Kingdom.
The value of a deep-time temperature curve extends beyond the exhibit. Similar curves exist for atmospheric carbon dioxide (CO2). Combine the two and you can see how much warming CO2 caused in the past, says Jessica Tierney, a paleoclimatologist at the University of Arizona in Tucson. Because the latest climate models seem to forecast more warming than earlier ones, "using paleoclimate to constrain the models is becoming much more important," she says. "We feel we have to step up."
Answer:
Ocean sediment
By extracting sediment cores from the ocean floor, it is possible to reconstruct the climate of the distant past. Fossilized plankton and other fossils provide information about what the temperature was like up to a million or so years ago.