The rate at which carbon emissions warmed Earth’s climate almost 56 million years ago resembles modern, human-caused global warming much more than previously believed, but involved two pulses of carbon to the atmosphere, University of Utah researchers and their colleagues found.
The findings mean the so-called Paleocene-Eocene thermal maximum, or PETM, can provide clues to the future of modern climate change. The good news: Earth and most species survived. The bad news: It took millennia to recover from the episode, when temperatures rose by 5 to 8 degrees Celsius (9 to 15 degrees Fahrenheit).
The rate at which carbon emissions warmed Earth’s climate almost 56 million years ago resembles modern, human-caused global warming much more than previously believed, but involved two pulses of carbon to the atmosphere, University of Utah researchers and their colleagues found.
The findings mean the so-called Paleocene-Eocene thermal maximum, or PETM, can provide clues to the future of modern climate change. The good news: Earth and most species survived. The bad news: It took millennia to recover from the episode, when temperatures rose by 5 to 8 degrees Celsius (9 to 15 degrees Fahrenheit).
“There is a positive note in that the world persisted, it did not go down in flames, it has a way of self-correcting and righting itself,” says University of Utah geochemist Gabe Bowen, lead author of the study published today in the journal Nature Geoscience. “However, in this event it took almost 200,000 years before things got back to normal.”
Bowen and colleagues report that carbonate or limestone nodules in Wyoming sediment cores show the global warming episode 55.5 million to 55.3 million years ago involved the average annual release of a minimum of 0.9 petagrams (1.98 trillion pounds) of carbon to the atmosphere, and probably much more over shorter periods.
That is “within an order of magnitude of, and may have approached, the 9.5 petagrams [20.9 trillion pounds] per year associated with modern anthropogenic carbon emissions,” the researchers wrote. Since 1900, human burning of fossil fuels emitted an average of 3 petagrams per year – even closer to the rate 55.5 million years ago.
Each pulse of carbon emissions lasted no more than 1,500 years. Previous conflicting evidence indicated the carbon release lasted anywhere from less than a year to tens of thousands of years. The new research shows atmospheric carbon levels returned to normal within a few thousand years after the first pulse, probably as carbon dissolved in the ocean. It took up to 200,000 years for conditions to normalize after the second pulse.
Saber Tooth Tiger image via Shutterstock.
Read more at University of Utah news.
