Ancient farming practices led to a rise in the atmospheric emission of the heat-trapping gases carbon dioxide and methane — a rise that has continued since and has profoundly changed Earth’s climate, a study has claimed.
The findings, led by researchers from the University of Wisconsin-Madison, showed that ancient farmers cleared land to plant wheat and maize, potatoes and squash, flooded fields to grow rice and raised livestock, but unknowingly, altered the climate of the Earth.
Without this human influence, by the start of the Industrial Revolution, the planet would have likely been headed for another ice age, the researchers said.
“Had it not been for early agriculture, Earth’s climate would be significantly cooler today,” said lead author Stephen Vavrus, from the varsity.
“The ancient roots of farming produced enough carbon dioxide and methane to influence the environment,” he added.
The study, published in the journal Scientific Reports, is based on a sophisticated climate model that compared the current geologic time period — called as the Holocene — to a similar period 800,000 years ago.
The results showed that the earlier period, called MIS19, was already 2.3 degrees Fahrenheit (1.3 degrees Celsius) cooler globally than the equivalent time in the Holocene, around the year 1850.
This effect would have been more pronounced in the Arctic, where the model shows temperatures were 9-to-11 degrees Fahrenheit colder, the team explained.
Using climate reconstructions based on ice core data, the model also showed that while MIS19 and the Holocene began with similar carbon dioxide and methane concentrations, MIS19 saw an overall steady drop in both greenhouse gases while the Holocene reversed direction 5,000 years ago, hitting peak concentrations of both gases by 1850.
The glaciers have long served as Earth’s predominant source of freshwater.
But, climate scientists now agree that the next glaciation period is put on hold for the long, foreseeable future, “because even if we stopped putting carbon dioxide into the atmosphere, what we have now would linger”, said co-author William Ruddiman, paleoclimatologist at the University of Virginia.
“The phenomenal fact is, we have maybe stopped the major cycle of Earth’s climate and we are stuck in a warmer and warmer and warmer interglacial,” he stated.