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A fiery past sheds new light on the future of global climate change

May 31, 2021

By Paul Homewood

 

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Centuries-old smoke particles preserved in the ice reveal a fiery past in the Southern Hemisphere and shed new light on the future impacts of global climate change, according to new research published in Science Advances.

"Up till now, the magnitude of past fire activity, and thus the amount of smoke in the preindustrial atmosphere, has not been well characterized," said Pengfei Liu, a former graduate student and postdoctoral fellow at the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) and first author of the paper. "These results have importance for understanding the evolution of climate change from the 1750s until today, and for predicting future climate."

One of the biggest uncertainties when it comes to predicting the future impacts of climate change is how fast surface temperatures will rise in response to increases in greenhouse gases. Predicting these temperatures is complicated since it involves the calculation of competing warming and cooling effects in the atmosphere. Greenhouse gases trap heat and warm the planet’s surface while aerosol particles in the atmosphere from volcanoes, fires and other combustion cool the planet by blocking sunlight or seeding cloud cover. Understanding how sensitive surface temperature is to each of these effects and how they interact is critical to predicting the future impact of climate change.

Many of today’s climate models rely on past levels of greenhouse gasses and aerosols to validate their predictions for the future. But there’s a problem: While pre-industrial levels of greenhouse gasses are well documented, the amount of smoke aerosols in the preindustrial atmosphere is not.

To model smoke in the pre-industrial Southern Hemisphere, the research team looked to Antarctica, where the ice trapped smoke particles emitted from fires in Australia, Africa and South America. Ice core scientists and co-authors of the study, Joseph McConnell and Nathan Chellman from the Desert Research Institute in Nevada, measured soot, a key component of smoke, deposited in an array of 14 ice cores from across the continent, many provided by international collaborators.

"Soot deposited in glacier 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 less fire took place in the preindustrial era, the ice cores suggested a much fierier past, at least in the Southern Hemisphere," said Loretta Mickley, Senior Research Fellow in Chemistry-Climate Interactions at SEAS and senior author of the paper.

To account for these levels of smoke, the researchers ran computer simulations that account for both wildfires and the burning practices of indigenous people.

"The computer simulations of fire show that the atmosphere of 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 greater than previous studies suggested. Most of this was caused by widespread and regular burning practiced by indigenous peoples in the pre-colonial period," said Jed Kaplan, Associate Professor at the University of Hong Kong and co-author of the study.

This result agrees with the ice core records that also show that soot was abundant before the start of the industrial era and has remained relatively constant through the 20th century. The modelling suggests that as land use changes decreased fire activity, emissions from industry increased.

What does this finding mean for future surface temperatures?

By underestimating the cooling effect of smoke particles in the pre-industrial world, climate models might have over-estimated the warming effect of carbon dioxide and other greenhouse gasses in order to account for the observed increases in surface temperatures.

"Climate scientists have known that the most recent generation of climate models have been over-estimating surface temperature sensitivity to greenhouse gasses, but we haven’t known why or by how much," said Liu. "This research offers a possible explanation."

"Clearly the world is warming but the key question is how fast will it warm as greenhouse gas emissions continue to rise. This research allows us to refine our predictions moving forward," said Mickley.

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https://www.eurekalert.org/pub_releases/2021-05/hjap-afp052621.php

 

In my opinion, nobody has come forward with a proper explanation of the Little Ice Age, which HH Lamb reckoned started as early as the 13thC. In all probability, a number of factors contributed. I therefore cannot get too excited about this latest research.

But what is significant is its finding that fire activity was actually much greater in the past than the 20thC. This of course ties in with historical knowledge about aboriginal burning practices; that is controlled burns used to prevent over forestation and clear the land for agriculture and wildlife.

Captain Cook notably described Australia as “.The Continent of Smoke”, and early explorers such as Tasman were used to seeing smoke billowing into the sky for days at a time. This destroys claims that recent wildfire activity there are the result of global warming.

In fact the science points the other way. As Lamb knew years ago, Australia was a much wetter place when the world was warmer a few thousand years ago. It was this same epoch when the Sahara was also fertile. And there is a very good reason; a warmer world is a moister one:

 

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HH Lamb: Climate, History and the Modern World

9 Comments
  1. May 31, 2021 5:20 pm

    [[One of the biggest uncertainties when it comes to predicting the future impacts of climate change is how fast surface temperatures will rise in response to increases in greenhouse gases. Predicting these temperatures is complicated since it involves the calculation of competing warming and cooling effects in the atmosphere. Greenhouse gases trap heat and warm the planet’s surface while aerosol particles in the atmosphere from volcanoes, fires and other combustion cool the planet by blocking sunlight or seeding cloud cover. Understanding how sensitive surface temperature is to each of these effects and how they interact is critical to predicting the future impact of climate change.]]

    Telling lies like this should be some kind of global misdemeanor. There are no such things as greenhouse gases, and there can’t be because there is no place to “trap heat and warm the planet’s surface” in the face of the thermodynamic lapse rate of 18.8F/mi. temperature drop. If there were such a thing as greenhouse gas, it definitely can’t be atmospheric CO2, whose radiation absorption/emission wavelength has weak puny 15 micron photons that have a Planck radiation temperature of -80C, which can’t melt an ice cube.Yes, aerosols can block sunlight and cool the Earth, but there’s nothing humans can do to heat it hotter than the Sun does. The atmosphere just cools it, and can’t be turned into a second Sun in the sky by any means except talk.

    Meanwhile the global Marxist-run U.N. and its IPCC are turning the world into a madhouse in order to make the hordes of useful idiots they need to destroy the oil industry and soften the West up for a Marxist police state. Be grateful they still don’t completely control the Internet, and there’s still places to learn the sweet truth based on physics.

    https://www.quora.com/What-does-science-mean-in-the-following-question-Why-do-people-deny-the-science-of-climate-change/answer/TL-Winslow

    • Broadlands permalink
      May 31, 2021 5:43 pm

      Historyscoper: It’s the combination of CO2 and water vapor that is important for the greenhouse effect. Just look at Mars.

      “Climate scientists have known that the most recent generation of climate models have been over-estimating surface temperature sensitivity to greenhouse gasses, but we haven’t known why or by how much,”

      An admission that makes what policy-makers are recommending more than a bit awkward.

  2. Harry Passfield permalink
    May 31, 2021 7:23 pm

    No matter the belief, getting this into the curriculum for schools – especially junior schools, is an impossibility. I, personally, am leaving my notes and links to my young grandson in the hope that he may become a sceptic – and fight back (after all, it will be his life, not mine).

  3. ThinkingScientist permalink
    May 31, 2021 8:55 pm

    Sea level rise and glacial retreat indicate onset of modern warming as early as 1840. This directly contradicts CMIP5/6 forcing.

    I had the point about aerosols raised by someone (a warmist) when I gave my paper last week at Geol. Soc. They didn’t stop to think that more cooling aerosols back then would make the mismatch of climate model forcing worse.

  4. ThinkingScientist permalink
    May 31, 2021 8:57 pm

    The more I look at glacial data the more I am starting to think its the LIA that’s the anomaly in the last 2000 years, not the current warming

  5. Barrie Emmett permalink
    May 31, 2021 9:48 pm

    Fascinating, more knowledge to my elbow. Barrie

    Sent from my iPad

    >

  6. Gamecock permalink
    June 1, 2021 12:19 am

    Yawn. Perfectly normal.

    ‘On average, wildfires burn anywhere between 5 to 20 million hectares of boreal forest each year.’

    Up to 50 million acres a year. Naturally. Since time immemorial.

  7. June 1, 2021 12:09 pm

    When working on my PhD in botany my research area was the Gettysburg Basin in PA. While doing an historical analysis of the area’s vegetation, I came across an account of an expedition through that mid-PA region in the 1600’s

    According to the writer, it was possible to travel for more than a day in all directions by horseback without having to duck under trees. That was due to the extensive burning done by the Indians for land clearing, game increase and ease of war-party travel. The same was true throughout the southern Appalachians. The Iroquois also engaged in extensive farming and orchards in the vicinity of the Great Lakes. Burning was their method of forest clearing.

  8. Karl Smith permalink
    June 1, 2021 1:21 pm

    Western Australia water authority constantly blame climate change for water shortages. Is there any credibility to these claims that rainfall is reducing in WA.
    Thanks
    Karl Smith

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