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The hot past sheds new light on the future of global climate change.



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Hundreds of years of smoke particles preserved in ice reveal a warming past in the Southern Hemisphere and shed new light on the future impacts of global climate change, according to new research. published in Scientific breakthrough.

“Until now, the scale of the fires in the past and the amount of smoke in the pre-industrial atmosphere It doesn̵

7;t have very good characteristics,” said Pengfei Liu, a former graduate and postdoctoral student at Harvard University’s John A. Paulson. Engineering and Applied Sciences (SEAS) and the first author of the paper. “These results are important for understanding the evolution of climate change from the 1750s to the present. and for predicting future weather conditions.”

One of the biggest uncertainties in predicting future impacts of climate change is how quickly surface temperatures will rise in response to increases in greenhouse gases. Predicting these temperatures is complicated. Because it requires calculating the effects of global warming and cooling competing in the atmosphere. Greenhouse gases trap heat and warm the Earth’s surface. while aerosol particles in the atmosphere from volcanoes, fires and other combustion Cool the world by blocking sunlight or creating cloud cover. Understanding how surface temperature is susceptible to these effects and how they interact is crucial to predicting future impacts of climate change.

Many current climate models rely on past levels of greenhouse gases and aerosols to validate future forecasts. But there is a problem: although pre-industrial greenhouse gas levels are well documented. But the amount of aerosol in the pre-industrial atmosphere is not so.

To model smoke in the pre-industrial southern hemisphere. The research team studied in Antarctica. The ice smoke particles captured from fires in Australia, Africa and South America. Ice core scientists and co-authors of the study Joseph McConnell and Nathan Chellman from the Nevada Desert Research Institute measured soot, a key component of smoke. which are deposited in 14 ice cores from across the continent. collaborator

“The soot deposits in glacier ice directly reflect past atmospheric concentrations,” McConnell said. Therefore, aged ice cores are the most reliable long-term statistical data.

What they found was unexpected.

Loretta Mickley, SEAS senior researcher in the Chemical and Climate Interactions and senior author of the study, said: “While most studies assume that fires were less common in the pre-industrial era, But the ice core points to a much hotter past. At least in the southern hemisphere.” Paper.

to describe these smoke levels. The researchers used computer simulations that looked at both wildfires and indigenous burning.

“Computer simulations of fire show that the Southern Hemisphere’s atmosphere may have been very smoky in the centuries before the Industrial Revolution. Soot concentrations in the atmosphere were four times higher than previous studies. Most of them are due to widespread spread. and frequent burning by pre-colonial indigenous peoples,” said Jade Kaplan, an associate professor at the University of Hong Kong and a co-author of the study.

This result is consistent with ice core records showing that soot was abundant before the start of the industrial age and remained relatively stable throughout the 20th century. Industrial emissions are also increasing.

What do these findings mean for future surface temperatures?

Climate models may underestimate the warming effects of carbon dioxide and other greenhouse gases by underestimating the cooling effect of smoke particles in a pre-industrial world. to determine the observed increase in surface temperature

“Climate scientists know that the latest climate models overestimate the sensitivity of surface temperature to greenhouse gases,” Liu said. But we don’t know why or how much.” “This research has a possible explanation.”

“Clearly the world is warming. But the key question is how quickly the world will warm as greenhouse gas emissions continue to rise. This research allows us to further refine our forecasts,” Migley said.


Reducing air pollution can increase global warming without reducing greenhouse gas emissions.


More information:
“Better estimates of pre-industrial biomass combustion reduced the scale of aerosol-forced climate in the Southern Hemisphere.” Scientific breakthrough (2021). Advances.sciencemag.org/lookup … 1126/sciadv.eabc1379

Provided by the Harvard John A. Paulson School of Engineering and Applied Sciences.



reference: A hot past sheds new light on the future of global climate change (2021, 28 May). Retrieved 29 May 2021 from https://phys.org/news/2021-05. -fiery-future-global-climate.html

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