reply to post by TWILITE22
You're referring to what's in the vernacular called "acid rain". Unfortunate choice of terms, because of the mental image....any simple chemistry
study will show it's merely a way to describe the pH balance of the rain water, as affected by (mostly) man-made pollutants.
In fact, the MAJORITY of such pollutants are sourced from industrial activities, like factories, on the ground --- when they get into the atmospheric
"water cycle"...either from being belched out in smokestacks, into the air....or, discharged into waterways, and then taken up by evaporative
"Acid rain" was first coined, as a term, back in the 1970s....but, the effects of industrial pollution had been seen for centuries prior....
Read at Wiki
The corrosive effect of polluted, acidic city air on limestone and marble was noted in the 17th century by John Evelyn, who remarked
upon the Arundel marbles "miserably neglected, & scattredup & downe about the Gardens & other places of Arundell-house, & how exceedingly the
corrosive aire of London impaired them". Since the Industrial Revolution, emissions of sulfur dioxide and nitrogen oxides to the atmosphere have
increased. In 1852, Robert Angus Smith was the first to show the relationship between acid rain and atmospheric pollution in Manchester,
England. Though acidic rain was discovered in 1852, it was not until the late 1960s that scientists began widely observing and studying the
phenomenon. The term "acid rain" was generated in 1972.
, and may Google for other examples of articles.
Jet airplanes spew exhaust the entire time the engines are operating, of course. Even on the ground, at the gate, when engines shut down, the APU
(Auxiliary Power Unit) is often running, for long periods. It is nothing other than a jet-fuel-burning turbine powerplant, to run certain accessories
like electrics and pneumatics, when engines are off. (Many airlines try to curb their use...not because of pollution, but because of the high cost of
Jet fuel. Electricity can be supplied when at the gates, either by the poser cords built in to most Jet-ways....or, by stand-alone GPUs [Ground Power
Units] that...well, they burn DIESEL fuel in their engines, so again, with the pollution.....)
Still, when you compare the millions and millions of cars, trucks and thousands of railroad locomotives, and ships at see, on lakes, rivers...and gas
lawnmowers, weed-whackers (
), leaf blowers, and such --- airplanes account for a SMALL minority of contribution, overall, to air pollution from
vehicles and petrochemical-burning machines.
THEN....don't forget the factories! Coal burning power-plants! The list is long......
An article in USAToday, from 2006...."Global Warming" and "Carbon Footprint" were trigger words, so this article talks that up a bit:
Now, aviation is believed to be less a factor in the Earth's warming than power plants or vehicular traffic. But its emissions are considerable.
On a New York-to-Denver flight, a commercial jet would generate 840 to 1,660 pounds of carbon dioxide per passenger. That's about what an SUV
generates in a month.
Edit here -- thought I'd better add, when people look at that article, and see the Boeing 737 photo that is "Landing in Brazil"....that is
condensation forming off the trailing edges of the flaps...areas of low pressure, and very high relative humidity (even down low, it IS Brazil, after
all) and you sometimes see such examples. Water condensing from vapor, into visible moisture. Doesn't usually last long.)
Article goes on to predict "dire" consequences by....(drumroll)....2050
!!! Based on expected increases in air travel. Still, in that
same forty years, I expect a great deal of effort, and improving technology, to cut emissions, in cars, trucks, airplanes...etc.
says, contrails can have an impact on climate....but, there is no way to "turn them off", nor to "turn them on". ONLY
alternative is to fly at low altitudes...and THAT is not a viable option.
Fuel burn rates increase significantly, at lower altitudes. Costs more, reduces range capabilities, etc.
edit on 18 October 2010 by weedwhacker because: Note