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Commercial Aviation Creating Ice Haze and “Accidental Geoengineering”

If the recent clear sky “brightening” trend were due to cleaner air and fewer aerosols alone, it should be accompanied by an increase in direct downwelling shortwave radiation, one part of solar radiation reaching the surface directly from the Sun. That didn’t happen, Long reported during the American Geophysical Union fall meeting in San Francisco.

Instead, Long and his colleagues found that at the continental United States sites they analyzed, direct downwelling shortwave radiation remained roughly steady between 1995 and 2007, under cloud-free skies. Rather, it was the diffuse shortwave radiation that increased. That simply couldn’t happen if fewer aerosols alone were the reason behind the brightening. If anything, fewer aerosols should mean less diffuse shortwave radiation, because particles in the atmosphere can bounce light around and back to space.

So the scientists dug deeper, and in a provocative new analysis, not yet published, Long suggests that a high-altitude “ice haze,” created by water and other emissions from aircraft, is responsible. “I’m talking about a sub-visual contrail-generated haze of ice, which we do not classify as a cloud but gives blue sky more of a whitish tint.” Long said.

The finding—if verified—could mean that we are in essence already conducting a geoengineering experiment on the atmosphere, adding ice particles that change the way solar radiation reaches Earth’s surface. Understanding the overall impact of those changes on warming or cooling at the surface will take more research, Long said. [1]

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Related Timeline Entries



"Accidental Geoengineering?" Cooperative Institute for Research in Environmental Sciences (CIRES), NOAA Earth System Research Laboratory (2015). •
Long, Charles N., et al. "Evidence of Clear-Sky Daylight Whitening: Are We Already Conducting Geoengineering?" NOAA ESRL Global Monitoring Annual Conference, Cooperative Institute for Research in Environmental Sciences (CIRES), University of Colorado, Boulder, CO (2015).
Long, Charles N., et al. "Significant decadal brightening of downwelling shortwave in the continental United States." Journal of Geophysical Research: Atmospheres 114.D10 (2009).
Zielinski, Sarah. "Airplane Contrails May Be Creating Accidental Geoengineering." Smithsonian Magazine (2015).
Amos, Jonathan. "Jet traffic linked to ice haze." Smithsonian Magazine (2015).
"Explaining geoengineering to normal people." Ken Caldeira’s Geoengineering Group (2015).
Kärcher, Bernd. "Formation and radiative forcing of contrail cirrus." Nature Communications 9.1 (2018): 1-17.
"Obituary of Charles Nelson Long." Koch Funeral Home (November 21, 2019).

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