Dinosaur Era Had 5 Times Today's CO2
Dinosaurs
that roamed the Earth 250 million years ago knew a world with five
times more carbon dioxide than is present on Earth today, researchers
say, and new techniques for estimating the amount of carbon dioxide on
prehistoric Earth may help scientists predict how Earth's climate may
change in…
Dinosaur Era Had 5 Times Today's CO2
By Katia Moskvitch, Live Science Contributor
March 25, 2014 5:21 PM
A group of Boy Scouts examines the skeleton of the Jurassic dinosaur Stegosaurus at the Smithsonian.
The findings are detailed in a recent paper published in the journal Proceedings of the National Academy of Sciences.
During the Jurassic
Period, dinosaurs — ranging from the plant-eating Diplodocus and
Brachiosaurus to the meat-craving Ceratosaurus and Megalosaurus — ruled
the world. During this time, the Earth's interior was not standing
still; rather, the supercontinent Pangaea had started to split into two
smaller landmasses, called Laurasia and Gondwana.
These tectonic movements made the oceans close up and the tectonic plates
sink into the Earth. This process, called subduction,led to volcanism
at the surface, with rocks constantly melting and emitting CO2 into the
atmosphere. Huge amounts of this greenhouse gas made the climate during
the Jurassic Period extremely humid and warm, said geoscientist Douwe
van der Meer, lead author of the study and a researcher at Utrecht
University in the Netherlands. [Weather vs. Climate: Test Yourself]
Scientists have known for some time that a large amount of volcanic
activity results in more CO2 than is present on Earth today, but with
previous methods, it had been tricky to come up with a reliable
estimate.Looking deep inside
Van der Meer's team used a cutting-edge imaging technique called seismic tomography to reconstruct 250 million years of volcanic CO2 emissions.
To do so, the researchers analyzed earthquake waves traveling through Earth, to image the structure of the Earth's interior.
"This method is comparable to CT scans used in hospitals to image inside bodies," van der Meer said. "With sufficient earthquake wave travel times, one can create a velocity model of the Earth. Faster regions are more dense, colder material plates that sunk into the Earth."
The aim has been to demonstrate how variations in plate tectonics have led to variations in CO2 emissions from volcanoes 250 million years ago.
And the
deeper the imaging equipment goes, the farther back in time scientists
can see — as far back as 250 million years, said van der Meer.
"Essentially, we can see the breakup of the supercontinent Pangaea, and the opening and closing of oceans," he said.
In other words, the scans depicted the interior of the Earth, enabling
the researchers to "see" the tectonic plates that have sunk into the
planet over the past 250 million years.
The researchers then quantified the plates that have sunk into the deep
Earth, and their calculations showed that the Earth produced twice as
much CO2 as there is today.
The scientists then inserted this number into a comprehensive, commonly
used paleoclimate model, to calculate how all the volcanic CO2
emissions at the time would have added up. Because there was also less
CO2 being removed from the atmosphere by vegetation and by weathering
rocks than today, total atmospheric CO2 levels were probably five times
higher than at the present, the researchers said.
The findings suggest much higher CO2 levels than had been estimated in
previous studies conducted in the 1980s and 1990s. That research had
been based on indirect data from sea-level variations. Since then,
scientists' understanding of Earth has improved significantly, and
researchers already had begun to suspect that the old estimates were
imperfect.
"They were
fundamentally flawed in hindsight," said van der Meer. "Especially in
the Jurassic Period, major differences were seen between the old and the
new estimates."
"The higher CO2 levels [must] have [had] significant effects on the planet's climate, and its flora and fauna," he said.
And, in general, the concept of plate tectonics through time is crucial
for a variety of geological processes, said van der Meer. "The rate of
spreading plates dictates the height of mountains, the amount and
location of ores, sea level and the magnetic field of the planet," he
said. "For the first time, we have quantified in this study the link
between plate tectonics and volcanic CO2 emissions — a major step
forward in understanding and predicting the behavior of the Earth, and
its consequences." [History's Biggest Earthquakes]
Future climate change
"The new estimates of CO2 emissions are crucial for determining the
relationship between CO2 and climate," said climate researcher Appy
Sluijs, also of Utrecht University and a co-author of the study. "Our
new information from the deep Earth is independent of, and confirms
existing data on, atmospheric CO2 levels as determined from fossils."
One of the researchers' goals is to understand the strong link between
climate and volcanic CO2 emissions, and apply it to future
climate-change predictions.
"As this study researched how much CO2 was emitted through time, we are
now able to zoom into the most interesting time intervals," Sluijs said.
"This will eventually lead to long-term predictions of future climate change."
"We are now producing more CO2 than all volcanoes on Earth," van der
Meer added. "We will affect climate in ways that are unprecedented and
unnatural. The question is how much climate will change. We can now
answer this for the past and apply [it] to the future by extrapolation."
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