Airplane Contrails May Be Creating Accidental Geoengineering
Dissipating haze from plane exhaust alters how sunlight reaches the Earth and may be unintentionally affecting our climate
If you go outside on a clear day and look up toward the sun—being careful to block out the bright disk with your thumb—you might see a hazy white region surrounding our star.
This haze is caused by airplanes, and it is gradually whitening blue skies, says Charles Long of NOAA’s Earth System Research Laboratory in Boulder, Colorado. “We might be actually conducting some unintentional geoengineering here,” Long said at a press conference this week at the American Geophysical Union Fall Meeting in San Francisco.
Geoengineering involves the manipulation of an environmental process in such a way, usually deliberate, that it affects the Earth’s climate. For instance, previous researchers have proposed combating global warming by intentionally seeding the atmosphere with small particles, or aerosols, to scatter some sunlight and reduce the amount of heat trapped by greenhouse gases.
Long and his colleagues don’t yet have enough data to know how much of an effect the icy haze left by airplanes may be having on the climate or whether it is contributing to warming or cooling. But its existence demonstrates yet another way that humans might be altering the climate system, Long says, and “you can see this with your own eyes.”
The discovery comes out of studies of how much sunlight reaches the Earth’s surface. This energy is not constant. From the 1950s to the 1980s, for instance, the sun seemed to slightly dim, then it started to brighten.
When scientists looked for a cause, they tried linking these changes to the sun’s variable output, said Martin Wild of the Institute for Atmospheric and Climate Science at ETH Zurich during the press conference. But they couldn’t find any correlations.
“If it’s not the sun, it must be the atmosphere” responsible for the change, he said. High levels of pollution in the mid-20th century sent massive amounts of aerosols into the atmosphere, where they blocked some of the sun’s energy. But when places like the United States and Europe began polluting less, the amount of aerosols decreased, and the sun appeared to slightly brighten.
Read more: http://www.smithsonianmag.com/scien...geoengineering-180957561/#WavlJGPdHh8JFrz4.99
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Dissipating haze from plane exhaust alters how sunlight reaches the Earth and may be unintentionally affecting our climate
If you go outside on a clear day and look up toward the sun—being careful to block out the bright disk with your thumb—you might see a hazy white region surrounding our star.
This haze is caused by airplanes, and it is gradually whitening blue skies, says Charles Long of NOAA’s Earth System Research Laboratory in Boulder, Colorado. “We might be actually conducting some unintentional geoengineering here,” Long said at a press conference this week at the American Geophysical Union Fall Meeting in San Francisco.
Geoengineering involves the manipulation of an environmental process in such a way, usually deliberate, that it affects the Earth’s climate. For instance, previous researchers have proposed combating global warming by intentionally seeding the atmosphere with small particles, or aerosols, to scatter some sunlight and reduce the amount of heat trapped by greenhouse gases.
Long and his colleagues don’t yet have enough data to know how much of an effect the icy haze left by airplanes may be having on the climate or whether it is contributing to warming or cooling. But its existence demonstrates yet another way that humans might be altering the climate system, Long says, and “you can see this with your own eyes.”
The discovery comes out of studies of how much sunlight reaches the Earth’s surface. This energy is not constant. From the 1950s to the 1980s, for instance, the sun seemed to slightly dim, then it started to brighten.
When scientists looked for a cause, they tried linking these changes to the sun’s variable output, said Martin Wild of the Institute for Atmospheric and Climate Science at ETH Zurich during the press conference. But they couldn’t find any correlations.
“If it’s not the sun, it must be the atmosphere” responsible for the change, he said. High levels of pollution in the mid-20th century sent massive amounts of aerosols into the atmosphere, where they blocked some of the sun’s energy. But when places like the United States and Europe began polluting less, the amount of aerosols decreased, and the sun appeared to slightly brighten.
Read more: http://www.smithsonianmag.com/scien...geoengineering-180957561/#WavlJGPdHh8JFrz4.99
Give the gift of Smithsonian magazine for only $12! http://bit.ly/1cGUiGv
Follow us: @SmithsonianMag on Twitter
