Scott Wing had spent more than a decade in the wastelands of Wyoming's Bighorn Basin, most of them thirsty, sunburnt and on hands and knees, digging through the muck endlessly. But he had never found anything like the fossil he held in his hand now – an exquisitely preserved leaf, embossed on beige rock. Wing gave a jubilant laugh as he spotted a second and then a third fossil. Each leaf was different from the others. Everyone was completely new to him.
And then he started to cry.
That was exactly what he was looking for. As these strange fossils formed 56 million years ago, the planet was warming faster and more dramatically than ever in its history except for the present.
He recently reported in his office at the Smithsonian National Museum of Natural History, Wing He recalled the uneasy reaction of the field assistant with whom he had wandered. Understandably, the young man looked nervous that his supervisor shed tears over a handful of stones.
"I said," You just have to realize that I've searched for it … since you were a kid. I'm unreasonably happy right now, but I'm not crazy, "chuckled Wing," so this was the first really good plant fossil from PETM. It was definitely a moment I will not forget. "
The PETM is the Paleocene Eocene Maximum ̵
If the story repeats itself, the consequences for modern life could be similarly long – so Wing is so determined to understand this age-old climate catastrophe. "] For me, it does not scare me," said Wing. It makes me feel responsible. I feel that we need to be better informed. "
The first important evidence for PETM was discovered in the early 1990s by scientists who pioneered the transition from the Paleocene, the epoch after the extinction of dinosaurs to the Eocene, to modern mammalian orders.
The boundary line between these two epochs had something weird in it: its ratio of carbon isotopes – different shapes of the same element – was distorted, and further research showed that something between 4 trillion and 7 trillion tons of carbon – the approximate equivalent of the total current reserve Fossil Fuels – flooded the atmosphere at that time, it came from the decomposed remains of old algae and plants, so it contained a larger amount of carbon 12 – the isotope preferred for photosynthesis.
This "spike" in carbon 12 served as a marker for the PETM and allowed researchers to exit to track the effects of this sudden climate shift in rocks and fossils around the world.
This week, Wing and his colleagues from the Smithsonian have gathered 17 experts to a symposium on ancient climate. Over the course of two days, they will try to reconstruct a timeline of the Earth's temperature and atmospheric carbon content, since complex life began about half a billion years ago.
"Science has finally brought us to a point where we have an idea of what the consequences of the things we do are," said Wing. "Now the question is, can we use that knowledge in something approaching a wise path?"
Back to the PETM, lime deposits dissolved at the bottom of the ocean as carbon dioxide made seawater more acidic. Fossils of tiny, deep-sea creatures showed signs of hypoxia – a sign that the water was getting warmer. Throughout the ocean, living things have adapted to the changed environment or they have become extinct.
On land, mammals became smaller and smaller. Ancient ancestors of horses, tiny at first, shrank by 30 percent on the size of domestic cats. Abigail Carroll, a paleoclimatologist at the University of New Hampshire, said that this was probably an adaptation to the warmer weather: smaller bodies are easier to keep cool.
The weather also became wilder. Geologists have discovered huge rocks that have traveled long distances due to heavy flooding – something that happens when dry periods are followed by extreme rains.
And then there are the plants in Wings collection in the National Museum of Natural History. Before PETM, fossils suggest, Wyoming looked more like Florida – a lush, subtropical forest shaded by stately sycamore trees, silvery birches, and waving palms.
But as the world warmed, the Bighorn Basin changed. The fossils from this period belong to plants that typically grow in hot, dry locations even further south – spindly plants and relatives of poinsettia and sumac. These plants must have migrated north after the change of weather and have followed their preferred environment to ever higher latitudes.
Obviously followed by a flock of greedy herbivores. Many of Wings fossils are riddled with bite marks left by insects that are more numerous and diverse than those that preceded them.
The source of all this chaos remains uncertain. Some have suggested that the flood of carbon that has triggered the PETM comes from volcanic eruptions or even a comet impact. The most popular theory, however, is that solids stored in seabed sediments are released from methane as the temperature and chemistry of the ocean change. Methane is a powerful greenhouse gas that is short-lived but harder than carbon dioxide. As global warming sets in, rising temperatures could have triggered the release of even more methane and released additional carbon sources – forest fires, changing ocean currents, soil microbes that exhale greenhouse gases – in a chain reaction that changed the planet. 19659002] Scientists today are familiar with many of the phenomena observed during PETM – so familiar "it's almost scary," said Wing. People who burn fossil fuels have produced the same kind of carbon isotope spike researchers find in 55 million year old rocks. The ocean has become about 30 percent more acidic and loses oxygen – changes that already trigger dying. The world has experienced dramatic weather extremes – deadly heat waves, heavy storms, devastating droughts. In response to these shifts, plants and animals emerge at unusual times in new places. There is even evidence that some species, such as birds called red knots, are becoming smaller due to the warmer climates.
Yet the past is an imperfect predictor of what could happen if the modern world continues to warm. For one, the Earth was much hotter on the eve of PETM than it is today. With the poles unfrozen and sea levels high, the old creatures did not have to worry about the effects of the melting ice, as we do today.
And the speed with which we change the climate surpasses everything in the geological record. The carbon spike that triggered PETM unfolded over 5,000 years. At our current pace, people will achieve a similar increase within a few centuries.
"On all important ways, it is now more dangerous than it was then," said Wing.
But for scientists who are trying to predict our future risk, PETM is an invaluable reference. Jeff Kiehl, senior scientist at the National Center for Atmospheric Research, uses the research of Wing and others to test models of the interaction of carbon and climate.
"We have no data for the future, but we have data from the past," said Kiehl. "This is where Scott's work … played a crucial role."
Data from the PETM and other periods of global warming can be used to answer the questions of modern climate researchers: How much will the earth heat up if it is atmospheric? Carbon doubles? What will happen to the water of the world then? How long will it take for things to return to normal?