Ancient human activity affected the atmosphere more than thought

Madrid, October 6 (European press) –

Human activities affected Earth’s atmosphere and climate earlier and on a larger scale than previously known, according to a new study published in the journal. ‘nature tempered’.

An international team led by Dr. Joe McConnell of the Desert Research Institute (DRI) used data from Antarctic ice cores to trace a 700-year rise in black carbon to an unexpected source: ancient carbon-burning practices. Maori lands in New Zealand, carried out on a large scale impact on the atmosphere in much of the Southern Hemisphere It has exceeded other pre-industrial emissions in the region over the past 2,000 years.

Several years ago, while analyzing ice core samples from James Ross Island in Antarctica, scientists Joe McConnell and Nathan Chilman of the British Institute for Research and Surveys and Robert Mulvaney of the British Antarctic Survey noticed something unusual, such as A significant increase in black carbon levels began around 1300 and continues to this day.

Black carbon, known as soot, is a light-absorbing molecule that comes from combustion sources such as the burning of biomass (such as forest fires), and more recently the combustion of fossil fuels. Together with an international team of scientists from the United Kingdom, Austria, Norway, Germany, Australia, Argentina and the United States, McConnell, Chilman and Mulvaney set out to discover the origin of the unexpected increase in black carbon trapped in Antarctic ice. They found that the sources are the ancient land burning practices of Maori in New Zealand.

“The idea that humans, at this point in history, have caused such a significant change in atmospheric black carbon through their purification activities is very surprising,” he said. It’s a statement McConnell, the hydrology research professor at the DRI who designed and led the study. We used to think that if we went back a few hundred years, we’d encounter an indigenous and pre-industrial world, but this study shows that Humans have been affecting the environment over the Southern Ocean and the Antarctic Peninsula for at least 700 years.”

To determine the origin of black carbon, the study team analyzed a series of six ice cores collected from James Ross Island and mainland Antarctica using the unique DRI continuous ice analysis system. The method used to analyze black carbon in ice was first developed at McConnell’s laboratory in 2007.

While the James Ross Island ice core showed a marked increase in black carbon beginning in the 13th century AD, tripling over the next 700 years and peaking during the 16th and 17th centuries, black carbon levels at sites on the mainland were Antarctica during the same time period. Relatively stable.

Dr Andreas Stoll of the University of Vienna led atmospheric simulation models of black carbon transport and deposition in the Southern Hemisphere that supported the findings. “From our models and the sedimentation pattern over Antarctica seen in the ice, it is clear that Patagonia, Tasmania and New Zealand The most likely source points were an increase in black carbon emissions from about 1,300Stoll says.

After consulting palefire records for each of the three regions, one viable possibility was: New Zealand, where coal records showed a significant increase in fire activity from about 1300 onwards. This date also coincided with the arrival, settlement and burning of much of New Zealand’s forested areas by the Maori people.

This is a surprising conclusion, the authors acknowledge, given New Zealand’s relatively small area and the distance (more than 7,000 km) smoke traveled to reach the ice core site of James Ross Island.

“Compared to natural burning in places like the Amazon, South Africa or Australia, the Māori burning in New Zealand is not expected to have a significant impact, but it does have a significant impact on the Antarctic Ocean and the Antarctic Peninsula.” Chilman, Postdoctoral Fellow at DRI – The ability to use ice core records to show influences on atmospheric chemistry that reached the entire Southern Ocean, And to be able to attribute that to the arrival of Maori and settlement of New Zealand 700 years ago was truly amazing.”

The authors note that the study’s conclusions are important for several reasons. First, the findings have important implications for our understanding of Earth’s atmosphere and climate. Modern climate models rely on accurate information about the past’s climate to make predictions for the future, especially about the emissions and concentrations of light-absorbing black carbon that correlate with the Earth’s radiative balance.

Although it is often assumed that human influence during pre-industrial periods was negligible compared to background or natural combustion, this study provides new evidence that Emissions from human-related combustion have affected the Earth’s atmosphereYou will likely be in your climate much earlier, and at much larger scales than you could have imagined.

Second, the radioactive precipitation from biomass burning is rich in micronutrients, such as iron. Phytoplankton growth across much of the Southern Ocean is nutrient-limited, thus increasing radioactive precipitation from Maori burning It may have led to centuries of overgrowth of phytoplankton in large areas of the Southern Hemisphere.

Third, the findings improve what is known about the timing of the arrival of Maori to New Zealand, one of the last habitable places on Earth to be colonized by humans. Radiocarbon-based Maori arrival dates vary between the thirteenth and fourteenth centuries, but the most accurate dating allowed by glacial core records places the beginning of large-scale burning by early Maori in New Zealand in 1297, With an uncertainty of 30 years.

“From this study and other previous work by our team, such as the one on 2,000-year Arctic lead pollution in ancient Rome, it becomes clear that ice-sampling records are of great value for understanding human impact on the environment in the past,” McConnell points out. Even the most remote parts of the Earth were not necessarily pure in pre-industrial times.”