A fiery previous sheds new gentle on the way forward for international local weather change – Watts Up With That?
[Interesting conclusion which I’ve bolded for emphasis. Perhaps the beginning of the climb down~cr]
Ice core samples show significant smoke aerosols in the pre-industrial southern hemisphere
HARVARD JOHN A. PAULSON SCHOOL OF TECHNOLOGY AND APPLIED SCIENCES
Research news
Centuries-old smoke particles preserved in the ice reveal a fiery past in the southern hemisphere and shed new light on the future effects of global climate change. This is evident from new research published in Science Advances.
“Until now, the level of past fire activity, and therefore the amount of smoke in the pre-industrial atmosphere, has not been well characterized,” said Pengfei Liu, a former PhD and postdoctoral fellow at Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) and First author of the paper. “These results are important to understand the evolution of climate change from the 1750s to today and to predict future climate.”
One of the biggest uncertainties in predicting the future effects of climate change is how quickly surface temperatures will rise in response to increases in greenhouse gases. Predicting these temperatures is complicated because competing warming and cooling effects are calculated in the atmosphere. Greenhouse gases store heat and warm the planet’s surface, while aerosol particles in the atmosphere from volcanoes, fires, and other burns cool the planet by blocking sunlight or covering clouds. Understanding how sensitive surface temperature is to each of these effects and how they interact is critical to predicting the future effects of climate change.
Many of today’s climate models rely on previous greenhouse gas and aerosol levels to validate their predictions for the future. But there is a problem: while pre-industrial greenhouse gas levels are well documented, the amount of smoke aerosols in the pre-industrial atmosphere is not that high.
To model smoke in the pre-industrial southern hemisphere, the research team looked to Antarctica, where the ice trapped smoke particles that were released from fires in Australia, Africa and South America. Ice core scientists and co-authors on the study, Joseph McConnell and Nathan Chellman of the Desert Research Institute in Nevada, measured soot, a key component of smoke, deposited in a number of 14 ice cores across the continent, many of them from international ones Providers were provided employees.
“Soot deposited in glacial ice directly reflects past atmospheric concentrations, so well-dated ice cores provide the most reliable long-term records,” said McConnell.
What they found was unexpected.
“While most studies have assumed that fewer fires occurred in the pre-industrial era, ice cores suggest a much more fiery past, at least in the southern hemisphere,” said Loretta Mickley, senior research fellow on chemistry-climate interactions at SEAS and senior author of the paper.
To account for this smoke development, the researchers performed computer simulations that take into account both forest fires and the burning practices of the indigenous people.
“The computer simulations of the fire show that the atmosphere in the southern hemisphere could have been very smoky in the century before the industrial revolution. Soot concentrations in the atmosphere were up to four times higher than suggested in previous studies. Most of this was caused by widespread and regular burning practiced by indigenous peoples in the pre-colonial era, ”said Jed Kaplan, associate professor at the University of Hong Kong and co-author of the study.
This finding is consistent with the records on the ice core, which also show that soot was abundant before the industrial age began and remained relatively constant until the 20th century. The modeling suggests that industrial emissions increased when land use changes decreased fire activity.
What does this finding mean for future surface temperatures?
By underestimating the cooling effect of smoke particles in the pre-industrial world, climate models may have overestimated the warming effect of carbon dioxide and other greenhouse gases to account for the observed increase in surface temperatures.
“Climatologists knew that the latest generation of climate models overestimated the sensitivity of surface temperature to greenhouse gases, but we don’t know why or by how much,” Liu said. “This research offers one possible explanation.”
“Of course the world is warming up, but the real question is how quickly will it warm up if greenhouse gas emissions continue to rise. This research allows us to refine our predictions for the future, ”Mickley said.
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The research was co-authored by Yang Li, Monica Arienzo, John Kodros, Jeffrey Pierce, Michael Sigl, Johannes Freitag, Robert Mulvaney, and Mark Curran.
It was funded by the Directorate of Geosciences of the National Science Foundation under grants AGS-1702814 and 1702830 with additional support from 0538416, 0538427 and 0839093.
From EurekAlert!
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