A University professor of geological sciences is researching past occurrences of global warming to better understand the global warming taking place today.
Greg Retallack’s research, presented at the Geological Society of America’s annual conference in October, sprung from the common knowledge among geologists that there are certain places in the world where fossils are generally better preserved than others.
These “fossil bonanzas” are found in areas where there is a low oxygen content, because organisms that scavenge upon and promote the decay of dead animals require oxygen to survive.
Retallack discovered that fossils from certain time periods are more well preserved than others.
After compiling data on the ages of these well-preserved fossils, Retallack found that during the past 500 million years, there have been 41 periods where fossil preservation was exceptionally good.
Oxygen levels were low throughout the world during these periods.
Retallack said high levels of methane gas, introduced into the atmosphere either by igneous intrusion or the destabilization of deep sea sediments, were present in the atmosphere during these periods. When methane interacts with oxygen in the air, carbon dioxide forms.
Retallack said these periods of global warming contribute to the overall stability of the planet. When too much carbon is present in the air, it can change the oxygen that most animals need to breathe into carbon dioxide. Fossils, composed primarily of carbon, keep excess carbon underground.
While some species become extinct during periods of global warming, many species survive these periods, which is why there is still life on earth today, Retallack said.
However, global warming can cause difficulties for those experiencing it.
“Greenhouses can have a serious side,” Retallack said. “We have a record of greenhouses that have gotten wildly out of control.”
Research is currently in progress to determine the causes and length of global warming episodes, but some of the effects are already known. They include more stormy weather, increased weather variation between seasons, increased prevalence of fungal diseases, increased insect predation on plants and the depletion of soils.
Retallack said some of these effects are appearing today.
“It’s pretty clear now that we’re beyond the envelope,” Retallack said.
University geography professor Pat Bartlein, while not involved with Retallack’s recent study, also researches global warming.
He said in an e-mail that there are many signs of global warming today.
The last couple of decades have been the warmest to date, and the warming is unprecedented when compared with the last 1,000 years, Bartlein wrote.
“Most importantly, the pattern of temperature change is consistent with what we would predict as the response to the human-produced increase in greenhouse gases in the atmosphere,” Bartlein wrote.
Bartlein said the Earth is already on track for decades and probably centuries of increasingly warmer weather.
Current problems with coral reefs and wetlands are another sign that global warming is taking place, Retallack said.
“With many of these crises in the past, coral reefs and wetlands have really fared the worst,” Retallack said, explaining that organisms that don’t use lungs and muscular diaphragms to breathe are less equipped to handle air with a lower oxygen content than organisms that do.
Retallack said human activities such as using fossil fuels, tilling soil and burning forests for fuel are at least partly responsible for the current level of global warming.
Approximately 6.6 tons of greenhouse gases are emitted per person per year in the U.S., according to the U.S. Environmental Protection Agency Web site.
However, global warming has been occurring naturally since before humans existed and is not entirely caused by humans, Retallack said.
“Getting worried about (global warming) is like getting worried about an earthquake or asteroid,” Retallack said. “It’s not really something you can prepare for.”

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