Older farmers may have influenced climate change: study

Washington: Older farming practices may have increased heat-trapping gas emissions, such as carbon dioxide and methane, a trend that has continued since, according to one study.

Without this human influence, at the beginning of the industrial revolution, the planet would probably have moved to another ice age, according to the researchers.

Millennia ago, former farmers cleared land for planting wheat and corn, potatoes and squash. They flooded fields to grow rice and started raising livestock. Without knowing it, they may have fundamentally altered the climate of the Earth.

"Without early agriculture, the Earth's climate would be significantly cooler today," said Stephen Vavrus, a researcher at the University of Wisconsin-Madison in the United States.

"The ancient roots of agriculture produced enough carbon dioxide and methane to influence the environment," said Vavrus, lead author of the study published in the journal Scientific Reports.
The results are based on a sophisticated climate model that compares our current geological period, called the Holocene, to a similar period 800,000 years ago.

They show that the previous period, called MIS19, was already 1.3 degrees Celsius colder overall than the Holocene equivalent time, around 1850.

This effect would have been more pronounced in the Arctic.

Using ice core-based climate reconstructions, the model also showed that MIS19 and the Holocene had similar concentrations of carbon dioxide and methane, but that both greenhouse gases had decreased overall. 5000 years ago. of the two gases in 1850.

Researchers deliberately cut the pattern at the beginning of the industrial revolution, when sources of greenhouse gas emissions had become much more numerous.

For most of Earth's history since 4.5 billion years, its climate has been largely determined by a natural phenomenon known as the Milankovitch cycles, periodic changes in the shape of Earth's orbit the way the Earth is wobbling and tilting on its axis.

Astronomers can calculate these cycles accurately and they can also be observed in geological and paleoecological records.

Cycles affect the distribution of sunlight on the planet, resulting in glacial periods or ice ages as well as warmer interglacial periods.

The last ice age ended about 12,000 years ago and the Earth has since been in the Holocene, an interglacial period. The Holocene and MIS19 share the same characteristics of the Milankovitch cycle.

All the other interglacial periods that scientists have studied, including MIS19, start with higher levels of carbon dioxide and methane, which are gradually decreasing over millennia, resulting in colder conditions on Earth.

In the end, conditions cool down to a point where glaciation begins.

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