Scientists Trace Human GHG Output Back To Roman & Han Empires Through Ice-Core Methane Data
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In their Oct. 3 study detailed in the journal Nature, the researchers found that methane production was high around 100 B.C., during the heyday of the Roman Empire, and waned around A.D. 200 as the empire faltered. The methane was released when Romans burned down forest to clear land for crops and expanding settlements, Sapart said. This time period also coincided with the peak of China's Han dynasty, which burned large amounts of wood to forge swords. Once the dynasty collapsed around A.D. 200, atmospheric methane levels dropped.
Methane production also spiked during Europe’s mini-ice age, around 1400, as people burned wood to stay toasty inside, she said. Across the time period the researchers studied, human activities such as growing food or keeping warm were responsible for 20 percent to 30 percent of the methane released from burning organic matter. Of course, the historical methane emissions were still small in comparison with modern levels.
The findings suggest that climate change predictions may need tweaking, Sapart said. Prediction models assume baseline, natural levels of methane emissions to forecast how human actions will change levels in the future. Previously, researchers thought natural events produced almost all of the methane prior to industrialization.
"The big goal of all this is to try to predict how greenhouse gas concentrations in the atmosphere are going to evolve in the future," Sapart said. "Already at this period humans were emitting greenhouse gases, especially methane, so we need to reconsider what are natural conditions.”
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http://news.yahoo.com/human-greenhouse-gas-emissions-traced-roman-times-192551162.html