Between about 55.5 and 52 million years ago, Earth experienced a series of sudden and extreme global warming events (hyperthermals) superimposed on a long-term warming trend. The first and largest of these events, the Palaeocene–Eocene Thermal Maximum (PETM), is characterized by a massive input of carbon, ocean acidification and an increase in global temperature of about 5 °C [9°F] within a few thousand years.
So begins an article in the journal Nature that offers an unsettling explanation for one of the great climate mysteries: What caused the PETM?
The article’s title gives away the answer: “Past extreme warming events linked to massive carbon release from thawing permafrost” (subs. req’d).
The lead author, climate scientist Rob DeConto, explains in a news release:
“The standard hypothesis has been that the source of carbon was in the ocean, in the form of frozen methane gas in ocean-floor sediments,” DeConto says. “We are instead ascribing the carbon source to the continents, in polar latitudes where permafrost can store massive amounts of carbon that can be released as CO2 when the permafrost thaws.”
The new view is supported by calculations estimating interactions of variables such as greenhouse gas levels, changes in the Earth’s tilt and orbit, ancient distributions of vegetation, and carbon stored in rocks and in frozen soil.
While the amounts of carbon involved in the ancient soil-thaw scenarios was likely much greater than today, implications of the study appear dire for the long-term future as polar permafrost carbon deposits have begun to thaw due to burning fossil-fuels, DeConto adds. “Similar dynamics are at play today. Global warming is degrading permafrost in the north polar regions, thawing frozen organic matter, which will decay to release CO2 and methane into the atmosphere. This will only exacerbate future warming in a positive feedback loop.”
Indeed, the recent scientific literature suggests that the permafrost is poised to be a major amplifying feedback if we are self-destructive enough to ignore yet another dire warning and stay anywhere near our current path of unrestricted carbon pollution:
- Nature: Climate Experts Warn Thawing Permafrost Could Cause 2.5 Times the Warming of Deforestation!
- NSIDC: Thawing permafrost feedback will turn Arctic from carbon sink to source in the 2020s, releasing 100 billion tons of carbon by 2100
A 2010 study found our oceans are acidifying 10 times faster today than 55 million years ago when a mass extinction of marine species occurred.
In short, whatever we do, we don’t want to duplicate the conditions of the PETM. But, tragically, we are. Indeed, a 2011 study that found humans are releasing carbon to the atmosphere 10 times faster now than during the PETM. “Rather than the 20,000 years of the PETM which is long enough for ecological systems to adapt, carbon is now being released into the atmosphere at a rate 10 times faster,” one of the authors of that study explained. “It is possible that this is faster than ecosystems can adapt.”
Here’s more on this important new study: