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A new look at old smoke finds it has an important role in regulating the climate
Theo Stein

A new look at old smoke finds it has an important role in regulating the climate

Smoke emitted from wildfires and agricultural burning constitutes one of the largest sources of aerosol particles to Earth’s atmosphere. However, little is known about the importance of smoke on the climate system after it dissipates into remote areas of the planet.  

Four missions over the remote oceans

Four missions over the remote oceans

This map depicts the flight tracks for the four legs of the Atmospheric Tomography Mission from 2016-2018. Each flight track consists of 11 to 13 flights of the NASA DC-8. On each 10-hour flight, the DC-8 cycled from 500-feet elevation to nearly 40,000 feet, continuously sampling the atmosphere all the while. Credit: NOAA

A NOAA study published in Nature Geosciences takes a new look at this faint, old smoke and finds that it is just as important an influence on the climate as the thick plumes produced by active fires. 

The study, led by two CIRES researchers working for NOAA’s Chemical Sciences Laboratory, draws on data from NASA’s groundbreaking Atmospheric Tomography Mission (ATom), which sent NASA’s DC-8, packed with the state-of-the-art instrumentation, on four pole-to-pole flights over the middle of the Atlantic and Pacific oceans to search for short-lived pollutants in the most far-flung and unstudied parts of the atmosphere. 

Image
NASA’s DC-8 skims the surface of the Southern Ocean on October 14, 2017 on the third leg of the Atmospheric Tomography Mission. Even over the most remote oceans, scientists found dilute wildfire smoke. Credit: Sam Hall, NCAR

“We found that, although we were oftentimes thousands of kilometers from active fires, one-quarter of the aerosol particles in the remote lower atmosphere originated from a fire,” said lead author Gregory Schill, a CIRES scientist who works in NOAA’s Chemical Sciences Laboratory. “Even after smoke from wildfires and agricultural burns dissipates into the background atmosphere, it strongly influences particulate matter concentrations throughout the global atmosphere.”

Onboard the DC-8 was the NOAA Particle Analysis by Laser Mass Spectrometry or (PALMS) instrument, an instrument that is both highly sensitive and selective for detecting smoke particles. “What surprised us is that dilute smoke was detected almost everywhere, even over the remote southern ocean and Antarctica," said CIRES scientist Karl Froyd, the principal investigator for the PALMS instrument. 

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Karl Froyd, Principal Investigator of the NOAA Particle Analysis by Laser Mass Spectrometry instrument, is strapped in his workstation aboard the NASA DC-8 during the Atomic Tomography Mission. Measurements made by the PALMS instrument allowed the research team to document that dilute smoke was ubiquitous throughout the global atmosphere. Credit: Dan Murphy, NOAA

Globally, wildfires, agricultural burns and residential fires contribute roughly 37 million tons of smoke particles to the atmosphere every year. Biomass burning aerosol affects the Earth’s climate directly by blocking incoming sunshine from reaching the surface, and influencing clouds, which also intercept sunlight. Despite the key roles smoke plays in modulating climate, the abundance and distribution of smoke in the atmosphere has not been not well understood, especially after smoke plumes age, are diluted into the background atmosphere, and are removed by interaction with clouds and precipitation. In a future climate projected to be both drier and warmer, wildfires are expected to increase. 

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Sunset falls across the NASA DC-8 flying laboratory at its home base in Palmdale CA on January 26, 2017, prior to the second leg of the Atmospheric Tomography Mission. Credit: Sam Hall, NCAR

 Today’s global climate models rely heavily on satellite remote sensing to estimate the abundance of smoke aerosols, even though dilute smoke is sometimes too faint for satellites to detect. One of the primary goals of the four ATom research flights from 2016 to 2018 was to obtain accurate measurements of smoke and other short-lived climate-influencing pollution in the background atmosphere, then use these new data to calibrate satellite estimates and improve the skill of climate models in reproducing our current climate and predicting the impacts of climate change.

Schill and co-authors, who included scientists from NASA, the National Center for Atmospheric Research, the University of Maryland and the University of Vienna, found that one  prominent climate model, the Goddard Earth Observing Model, overestimated the amount of smoke aerosols by an average of more than 400 percent, largely due to underestimating removal by clouds and precipitation. 

After updating the model’s accounting for aerosol removal, the scientists estimate that although smoke in the background atmosphere is very dilute, it is so widespread that its impact on the Earth’s energy balance equals that of all the thick, fresh smoke plumes typically seen near fires.

NOAA scientist Dan Murphy, a co-author and the Chemical Science Laboratory’s Cloud & Aerosol Processes program leader, said the study provides important insights for a future that will be warmer, in many places drier, and severe droughts more common. 

“If we're going to look at climate effects from wildfires and biomass burning,” Murphy said, “we can't ignore the dilute smoke.”

For more information, contact Theo Stein, NOAA Communications, theo.stein@noaa.gov
 

 

 

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