Scientists from the British Antarctic Survey discovered something surprising while analyzing ice core samples taken from James Ross Island in Antarctica: levels of black carbon began to rise substantially around 700 years ago.
Black carbon, often known as soot, is a light-absorbing particle produced by combustion processes such as biomass combustion (forest fires) and, more recently, fossil fuel combustion.
An international group of scientists set out to figure out what had caused the rapid spike in black carbon trapped in Antarctic ice.
The researchers' findings, published in Nature this week, hint to an odd source: ancient Māori land-burning practices in New Zealand, which impacted the atmosphere across most of the Southern Hemisphere and exceeded other preindustrial emissions in the region during the past 2,000 years.
"The idea that humans at this time in history caused such a significant change in atmospheric black carbon through their land clearing activities is quite surprising," Joe McConnell, the study's lead author said.
Because current climate models use information from the climate's past to predict its future, the findings could help reshape how we understand the atmosphere and climate. This research suggests that human-caused fires may have a longer-term impact on the atmosphere, and possibly the climate, and at much larger scales than previously thought.
The findings also add to our understanding of when the Māori arrived in New Zealand, one of the last habitable regions on the planet to be colonized by people.
Māori arrival dates based on radiocarbon dates range from the 13th to 14th centuries, though ice core data allow for more exact dating, pinpointing the commencement of large-scale burning by early Māori in New Zealand to 1297, with a 30 year uncertainty.
Although it is commonly assumed that human impacts during preindustrial times were negligible when compared to background or natural burning, this study provides new evidence that emissions from human-related burning impacted the Earth's atmosphere and possibly its climate much earlier and at much larger scales than previously thought.
"It is clear that ice core records are very valuable for learning about past human impacts on the environment," McConnell said. "Even the most remote parts of Earth were not necessarily pristine in preindustrial times."
