Researchers say a spike in temperatures during an ice age 304 million years ago could inform what climate scientists are learning about rapidly changing conditions today.
University of Cincinnati Professor Thomas Algeo worked with a team of international researchers, including lead author Le Yao from the Nanjing Institute of Geology and Paleontology, to examine a period of rapid warming that occurred during the Late Paleozoic Ice Age, the second most recent ice age on Earth.
They found that a small spike in global sea surface temperatures led to a far bigger one fed by the release of methane into the atmosphere from melting permafrost. Global sea surface temperatures climbed by more than 7 degrees Celsius or 12 degrees Fahrenheit.
The study was published in the journal Proceedings of the National Academy of Sciences. It was supported with grants from Peking University and the National Natural Science Foundation of China.
Algeo noted that the change occurred over tens of thousands of years at a rate of about a tenth of a degree Celsius increase every 1,000 years. By comparison, researchers today have observed a nearly 1 degree Celsius increase of sea surface temperature in just the past 100 years.
Possibly triggered by volcanic activity and aided by a cyclical variation in the shape of Earth's orbit that influences the distribution of solar radiation, a modest release of carbon crossed a "climatic tipping point that led to massive carbon release and transient global warming."
Researchers said an increase in temperatures today could speed melting of permafrost, releasing trapped carbon that could create a positive feedback loop that contributes to more warming.
Rapid warming on Earth more typically happens under what scientists call "greenhouse conditions" when the atmosphere has high amounts of methane and carbon dioxide that trap heat.
Algeo said some people are surprised to learn that all of recorded human history has taken place in the midst of the most recent ice age. Its peak called a glacial maximum occurred about 20,000 years ago when woolly mammoths, cave bears and giant ground sloths roamed the Earth.
"We're technically in an ice age because there are two continent-scale ice masses in Greenland and Antarctica," he said. "What makes this warming event 304 million years ago unique is that it occurred during an ice age. That's what makes this event important as an analog for modern-day climate warming."
