Tue Nov 13, 2012, 11:44 AM
amborin (11,722 posts)
CO2 Emissions Reaching Upper Atmosphere, Potentially Imperiling Satellite Launches, etc.
Carbon Dioxide Emissions Reaching Upper Atmosphere, Canadian Space Satellite Finds
Not only is the Earth warming at the high-end of predicted models, but now human produced carbon dioxide emissions are accumulating in greater amounts in the upper reaches of the atmosphere, according to the results of a new study of data captured by a Canadian satellite.
What the scientists found from looking at the ACE’s data from 2004 through 2012 was troubling: Carbon dioxide levels in the upper atmosphere increased eight percent over the period, from 209 parts per million in 2004 to 225 parts per million in 2012.
.....At lower altitudes, carbon dioxide emissions make the Earth warmer by trapping sunlight.
But at higher altitudes, the reverse is true: In the mesosphere (between 31 miles and 55 miles up) and the thermosphere (above 55 miles up), carbon dioxide’s density is thinner and a less effective at trapping infrared radiation. In fact, CO2 at these altitudes is something of a heat sink, allowing infrared radiation to escape back out into space.
But this isn’t a good thing. On the contrary, the thinning, cooling trend at this level due to increasing CO2 is likely to have detrimental effects on human spacefaring activity, something of a bitter irony given that a satellite was the reason we know about the increased CO2 levels in the first place. .....
“The enhanced cooling produced by the increasing CO2 should result in a more contracted thermosphere, where many satellites, including the International Space Station, operate. The contraction of the thermosphere will reduce atmospheric drag on satellites and may have adverse consequences for the already unstable orbital debris environment, because it will slow the rate at which debris burn up in the atmosphere.” In other words, rather than trapping heat, the increased CO2 levels in the upper atmosphere is likely to result in longer-lasting debris, and thus, a greater proportion of debris over time as humans continue to launch objects into space.
...... Other scientists have previously warned that Earth is collectively approaching a “tipping point” when it comes to space junk, where one piece of space junk colliding into another could set off a chain reaction of cascading collisions that would make it prohibitively risky to launch anything else into space, a phenomena known as the “Kessler effect” or the “Kessler syndrome” after the scientist who first proposed it in 1978.
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CO2 Emissions Reaching Upper Atmosphere, Potentially Imperiling Satellite Launches, etc. (Original post)
Response to amborin (Original post)
Tue Nov 13, 2012, 07:31 PM
caraher (4,787 posts)
1. A better explanation
The writer's claim that the CO2 "is something of a heat sink" doesn't really make sense. (A heat sink would absorb or emit thermal energy without changing temperature appreciably.)
A better explanation is in NRL's news release:
CO2 occurs naturally throughout Earth's atmosphere and is the primary radiative cooling agent in the energy balance of the mesosphere (~50-90 km altitude) and thermosphere (>90 km). The same properties of CO2 that cause it to trap heat in the troposphere (<15 km) make it an efficient cooler at higher altitudes. The difference is that at high altitudes, the density of CO2 is too thin to recapture the infrared radiation (heat) that it emits. "In the upper atmosphere," explains Emmert, "thermal energy is transferred via collisions from other atmospheric constituents to CO2, which then emits the energy as heat that escapes to outer space."
Take "heat" in that last quote to mean "infrared radiation" and it now makes sense to me...