Earth Can’t Keep Up with Modern Carbon Emissions
Scientists say long before mankind began burning fossil fuels, there was an eons-long balance between carbon dioxide emissions and Earth’s ability to absorb them. But now the planet is having trouble keeping up.
A report in the journal Nature Geoscience, is based on ancient Antarctic ice bubbles that contain air samples going back 610,000 years.
For the last 25 years, climate scientists have suggested that our planet’s temperature and the level of carbon dioxide in the atmosphere have been regulated by some sort of natural mechanism. This is pointed to as the cause for recent climate change by those skeptical of human influence on global warming.
This research may be the first observable evidence for this natural mechanism.
Richard Zeebe, a co-author of the report, said this mechanism, known as "feedback," has been thrown out of whack by a steep rise in carbon dioxide emissions from the burning of coal and petroleum for the last 200 years or so.
"These feedbacks operate so slowly that they will not help us in terms of climate change that we’re going to see in the next several hundred years," Zeebe said. "Right now we have put the system entirely out of equilibrium."
Long ago, excess carbon dioxide came mostly from volcanoes, which spewed a fraction of the chemical compared to what human industry does now, but it still had to be addressed.
“This antique excess carbon dioxide “” a powerful greenhouse gas “” was removed from the atmosphere through the weathering of mountains, which take in the chemical. In the end, it was washed downhill into oceans and buried in deep sea sediments,” said Zeebe.
For his study, Zeebe analyzed carbon dioxide that had been captured in Antarctic ice and figured out how much carbon dioxide was in the atmosphere at various points in time. He and his co-author determined that it waxed and waned along with the world’s temperature.
"When the carbon dioxide was low, the temperature was low, and we had an ice age," he said.
The planet’s mean temperature has been going slowly down for about 600,000 years since Earth’s temperature fell during ice ages and rose during so-called interglacial periods between them.
“The average change in the amount of atmospheric carbon dioxide over the last 600,000 years has been just 22 parts per million by volume, which means that 22 molecules of carbon dioxide were added to, or removed from, every million molecules of air,” Zeebe said.
Since the beginning of the widespread human use of fossil fuels in the Industrial Revolution in the 18th century, the amount of carbon dioxide in the atmosphere has risen by 100 parts per million.
“That means human activities are putting carbon dioxide into the atmosphere about 14,000 times as fast as natural processes do,” Zeebe said.
And it appears to be getting worse: the U.S. government reported last week that in 2007 alone, atmospheric carbon dioxide increased by 2.4 parts per million.
Zeebe said the natural mechanism will eventually absorb the excess carbon dioxide, but not for hundreds of thousands of years.
"This is a time period that we can hardly imagine," he said. "They are way too slow to help us to restore the balance that we have now basically distorted in a very short period of time."
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