And we all know what happened to them...
Carbon emissions are still rising, and they will likely continue to rise in the future. To look back in Earth’s climate history — before the 1850s when the earliest measurements began — scientists investigate air bubbles trapped in ice cores. And amazingly, ice cores have expanded the climate record to nearly a million years.
But to look back even further, over millions of years, researchers examine the chemical and biological signatures in deep-sea sediments. It is in these sediments that researchers discovered something rather startling.
Examining sediments cores collected from the New Jersey coast aboard the ocean drillship JOIDES and re-evaluating the carbon-13 and oxygen-18 isotope records, which indicate atmospheric carbon and global temperatures, respectively, researchers found that humans are responsible for releasing carbon about 10 times faster than during any time in the past 66 million years — since the age of the dinosaurs!
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At that time, the excess carbon resulted in a 5 degree Celsius (9 degree Fahrenheit) temperature increase, along with droughts, insect plagues and extinctions according to National Geographic.
“In studying one of the most dramatic episodes of global change since the dinosaurs, the researchers show that we are currently in uncharted territory in the rate carbon is being released into the atmosphere and oceans,” Candace Major, program director in the National Science Foundation (NSF) Division of Ocean Sciences, said in a press release.
The research paper, published in the journal Nature Geoscience, explains how geoscientist Richard Zeebe of the University of Hawaii at Manoa and colleagues Andy Ridgwell, of the University of Bristol and University of California, and James Zachos, of the University of California, developed a new method to determine the duration of the onset of an important past climate event — the Paleocene-Eocene Thermal Maximum (PETM), which occurred 56 million years ago.
“As far as we know, the PETM had the largest carbon release during the past 66 million years,” Zeebe said in the release.
It is hard to know exactly what the levels of CO2 were in the atmosphere 10 million years before PETM — the age of the dinosaurs — because geological records get worse the further back they go. However, it is possible that the 9.6 km-wide (6-mile-wide) asteroid that slammed into Earth’s surface resulted in CO2 emissions similar to what we see today.
The researchers calculated how fast carbon was being released during PETM and how fast Earth’s surface warmed. They determined that the maximum sustained carbon release rate was less than four billion metric tons of CO2 per year or about one-tenth the current rate. In 2014, carbon emission rates reached a record high of 37 billion metric tons.
“Because our carbon release rate is unprecedented over such a long time period in Earth's history, it also means that we have effectively entered a 'no-analogue' state,” said Zeebe in the release. “This represents a big challenge for projecting future climate change because we have no good comparison from the past.”
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Most climate transitions in the past were relatively smooth and slow, so there is no guarantee for the future, said the scientists. “If you kick a system very fast, it usually responds differently than if you nudge it slowly but steadily,” Zeebe explained in the release. “It is likely that future disruptions of ecosystems will exceed the relatively limited extinctions observed at the PETM.”
According to Zeebe, the results of the PETM suggest that the consequences of our insatiable burning of fossil fuels will have much longer-lasting effects. “Everyone is focused on what happens by 2100, but that's only two generations from today. It's very clear that over a longer time scale there will be much bigger changes.”
The researchers are continuing their work with PETM to study other aspects of environmental and climatic change. For example, they are looking into how severe ocean acidification was during that time and its effect on organisms in the ocean.
The hope is that the results will provide some insights about what to expect in the future as Earth continues to warm.
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