Pre-Industrial Polluters

A study published today in the journal Nature concludes that a 200-year period 2,000 years ago that included the heyday of the Roman Empire and Han Dynasty experienced a spike in greenhouse gases. The culprit was methane, released as forests were denuded for cropland and charcoal was burned for cooking and to smelt metals. Methane has 20 times the warming power of carbon dioxide. The study, based on ice core samples from Greenland, isolated naturally released methane -- such as from decomposition and forest fires -- from that of non-eco-savvy humans. 

While climate change skeptics might look at the information and add it to their long list of reasons to shrug off concern for climate change, during the Roman era the world’s population was a mere 300 million, and emissions then “were discernible but tiny compared with current levels caused by a population of 7 billion.” What’s most significant is that “the findings suggest that man’s footprint on the climate is larger than previously realized. Until now, it was assumed by scientists that human activity began increasing greenhouse gas levels only after the year 1750.”

“Between 100 BC and AD 1600,” the study's authors write, “human activity may have been responsible for roughly 20-30 percent of the total pyrogenic methane emissions.”

Image by iStock/andrearoad.

Reed McManus is a senior editor at Sierra. He has worked on the magazine since Ronald Reagan’s second term. For inspiration, he turns to cartoonist R. Crumb’s Mr. Natural, who famously noted: “Twas ever thus.”