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Earth NASA Space Science

Thermosphere Contraction Puzzles Scientists 200

Posted by Soulskill
from the chicken-little-knows-what's-up dept.
The thermosphere layer of earth's atmosphere begins 80 to 90 kilometers above the surface and extends several hundred kilometers into the sky; it is the home to numerous satellites and the International Space Station. It is known that the thermosphere occasionally cools and contracts, but a recent study of satellite orbital decay (due to light atmospheric drag) found that the contraction during 2008 and 2009 was significantly more severe than expected, leaving researchers at a loss for how to explain it. From Space.com: "This type of collapse is not rare, but its magnitude shocked scientists. 'This is the biggest contraction of the thermosphere in at least 43 years,' said John Emmert of the Naval Research Lab, lead author of a paper announcing the finding in the June 19 issue of the journal Geophysical Research Letters. 'It's a Space Age record.' The collapse occurred during a period of relative solar inactivity — called a solar minimum from 2008 to 2009. These minimums are known to cool and contract the thermosphere, however, the recent collapse was two to three times greater than low solar activity could explain."
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Thermosphere Contraction Puzzles Scientists

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  • Re:Great (Score:5, Informative)

    by bunratty (545641) on Saturday July 17, 2010 @01:04PM (#32937580)

    Think of insulation. Insulation can keep heat in, and it can also keep heat out. Insulation will keep your house warm in the winter, and also cool in the summer. It's not that hard to understand, is it?

    Although CO2 may be causing cooling high in the troposphere, it's keeping the surface of the Earth warm. So far, 2010 is the warmest year on record [usatoday.com], with Arctic [nsidc.org] and Antarctic [nasa.gov] ice continuing to melt, despite low solar activity.

  • Re:Great (Score:2, Informative)

    by siride (974284) on Saturday July 17, 2010 @01:10PM (#32937608)
    The ice always melts during the summer. But it is melting faster than "normal". Thankfully, in July, the ice loss is now behind 2007 instead of being miles ahead of it like it was in June.
  • Re:actually it's (Score:4, Informative)

    by Bigjeff5 (1143585) on Saturday July 17, 2010 @01:36PM (#32937748)

    Actually it's likely related to global warming, since CO2 emits light at a different wavelength than it absorbs it, it sometimes causes the thermosphere (and other layers) to cool and contract by the time the light gets to the outer layers. There are climate models that predict this.

    The problem with that is the CO2 levels have been gradually rising over the years - the 2008-2009 cycle did not have significantly more CO2 in the atmosphere than did previous cycles, yet there is a massive difference thermosphere compression.

    If CO2 were the cause you would still expect to see a gradual increase in thermosphere compression year to year - the current 16 year cycle would simply have a higher rate of compression on average than the previous solar cycles.

    That's not what was observed. What was observed was a massive compression in a single year - far greater than the previously useful solar models predicted. CO2 can definitely be part of the cause, but it cannot explain the huge difference between 2007-2008 and 2008-2009. They should only differ by the difference in solar activity, as CO2 levels are essentially the same.

  • by RobinEggs (1453925) on Saturday July 17, 2010 @01:47PM (#32937800)

    CO2 is denser than air so naturally the atmosphere compacts under gravity as the density increases.

    Utterly incorrect. CO2 levels rising dramatically doesn't mean the percentage composition of CO2 in the atmosphere has changed by a large number. The atmosphere is still less than .5% CO2 today; even if it had started at 0% CO2, adding .5% concentration of something only half again as heavy (or dense, if you prefer; not that dense and heavy are synonyms but either way my point stands) as the vast majority of the atmosphere would not logically explain "the biggest contraction of the thermosphere in at least 43 years" without some serious synergy compounding the effect of that minimal impact on atmospheric density.

    Furthermore, a given swath of the atmosphere is all roughly the same density; it's not like there's this big fat pocket of air that weighs 0.1 g/L and this other pocket a mile away at the same altitude that weighs 0.19 g/L. Diffusion dictates that CO2 could change the density of the air only as much as it changes the average density of the entire atmosphere (at a given altitude) once completely diffused into all the other stuff. You could jack the atmosphere up to 10% CO2, 20 times what it's ever been in the last billion years, and I doubt you could explain these contractions with simply density arguments.

    Also, TFA mentions CO2 - not in any conjunction whatsoever with your insane reason for mentioning it, but it does mention CO2 - and says "Even when we take CO2 into account using our best understanding of how it operates as a coolant, we cannot fully explain the thermosphere's collapse." Note that they're talking about CO2 cooling the upper atmosphere, not about density.

    Whoever marked the parent as informative is a moron.

    Definitely, and there's at least 4 of them apparently. 4 people who felt compelled to tell us this was good information but couldn't remember anything about 101 level chemistry. How the fuck did they pretend to know it was good information if they can't see through something that stupid?

  • by phoenix321 (734987) * on Saturday July 17, 2010 @02:30PM (#32938040)

    We had 8 months of winter in Europe, with record snow down to Spain and temperatures lower than they were in the last 30 years. Were constantly reminded that it was a seasonal event, weather, that had nothing to do with climate.

    After a mere 3 weeks of summer, with record hot temperatures, the media is already reviving the global warming mantra.

    I was modded into oblivion when I half-jokingly asserted that record lows are weather and record highs are climate change, but now we see exactly that.

    8 mo. of the harshest winter for 30 years = press says "weather".
    4 we. of the hottest summer for 30 years = press says "global warming, doom, hellfire".

    I have no problem with either explanation, but it sure should be consistent.

  • Banking analogy (Score:5, Informative)

    by mangu (126918) on Saturday July 17, 2010 @03:05PM (#32938236)

    We had 8 months of winter in Europe, with record snow down to Spain and temperatures lower than they were in the last 30 years

    Interestingly, global warming does cause colder winters. The cause of those colder winters is the melting of the ice caps.

    More heat in the atmosphere means more energy, which causes stronger winds and quicker circulation. Cold air from the north pole travel faster to Europe and therefore has less time to warm in the way.

    Those colder winters are more than balanced by hotter summers, we are spending away our ice reserves. It's like when you spend more than you earn. Your having more money to spend does not mean you're getting richer.

  • by Vintermann (400722) on Saturday July 17, 2010 @03:07PM (#32938240) Homepage

    We had 8 months of winter in Europe,

    No, we had not. When you say something like that I wonder if you're living in Europe at all - or maybe you're counting on your readers to not be in Europe?

    Winter in Europe, December to February, were below the average for the period 1951-1980 (the standard reference period). But already in spring, March to May, it was back above it.

    Another issue: the amount of snowfall depends primarily on water vapor in the atmosphere. As long as there's freezing temperatures, more moisture means more snow. More cold below zero degrees celsius does not cause more snow. A very basic prediction of climate modeling is that water vapor in the atmosphere will increase as temperature increases. So record cold might be unexpected from a climate science perspective; record snowfall would not.

  • Re:Great (Score:3, Informative)

    by camperdave (969942) on Saturday July 17, 2010 @03:56PM (#32938498) Journal
    There's all sorts of materials that do that. Thorium, radium, polonium, plutonium, uranium. All of these materials induce a temperature gradient without an external energy input. That's why they're used as power sources in RTGs and nuclear reactors. See, there's this equation; perhap's you've heard of it: e=mc^2. What it means is that mass can be traded for energy. That's what radioactive isotopes do. They trade the odd subatomic particle off as energy. The law of conservation of energy was superseded by the law of conservation of mass and energy. It is not true that "If one thing gets hotter, another thing must get cooler."
  • Re:Banking analogy (Score:5, Informative)

    by Arlet (29997) on Saturday July 17, 2010 @04:08PM (#32938578)

    Actually, the Antarctic ice cap is losing volume, even though it is gaining surface area. The Arctic ice cap is losing both volume and area. Greenland ice is also losing volume.

  • BZZZT, Wrong!!! (Score:5, Informative)

    by mangu (126918) on Saturday July 17, 2010 @04:49PM (#32938844)

    the ice caps are not melting. One is in a decline (the Arctic) and one is growing (Antarctic)

    I wonder by which definition you say the Arctic ice cap is in "decline", but not melting?

    The Antarctic ice sheet is shrinking, not growing. It's losing volume [edf.org], which is the only significant definition of size when one considers climate issues. It's losing volume the only way a polar ice cap can lose volume, by melting. But, of course, you'll never know this if you have only one news source [foxnews.com].

    Warmer oceans cause increased water evaporation, which then precipitates as snow or rain. Considering that a large part of Antarctica is still well below freezing point, it's only natural that *some* regions of Antarctica have had more snowfall caused by global warming. Yes, global warming does cause both more snowfall and colder winters. Which is more than offset by hotter summers and increased ice melting.

  • by SETIGuy (33768) on Saturday July 17, 2010 @10:00PM (#32940478) Homepage

    The temperature of the thermosphere has nothing to do with the temperature of the climate. We're talking about the part of the atmosphere where the international space station orbits. The rules there are very different from the lower atmosphere (as are the temperatures (up to a few thousand C depending upon where you are). The temperatures are controlled by the absorption and emission of radiation (and, of course, conservation of energy).

    The radiation absorbed by these tenuous gasses is in the extreme ultraviolet and soft x-ray. We've been monitoring the solar EUV and SXR output for quite a while. When they are high the thermosphere heats up and expands. Satellites in low orbit experience a lot of drag and end up in lower orbits. Because of the extended solar minimum EUV and SXR are way down, but they haven't changed enough to explain the entire temperature difference. So the remainder of the difference has to be in the emission of radiation in the thermosphere. There's a series of linked partial differential equations involved, so I won't do the actual math. But the easiest way to cool the thermosphere is to add higher amounts of species that have a lot of cooling transitions.

    One of the people quoted in TFA thinks it might be due to increased CO2. I have a hard time buying that. Because it's heavy, it's hard to get CO2 into the thermosphere. It would be tough to get an in situ measurement of CO2 and it's ionization products with any existing instrument

    As far as what this effect could do to the world. Well, it could screw up your AM reception. And it could screw up a prediction of a LEO satellite's orbit. (i.e. your sun synchronous polar orbit might not be as sun synchronous as you hoped.) But it's not going to kill dolphins or sea turtles, or cause earthquakes or polar shifts.

    I could do the required measurement with an FUV to NUV spectrometer for diffuse radiation on 2-axis coarse pointing gimbal. I'd need a satellite for a platform. But by the time I got it built and launched we'd be heading up toward solar max.

    Disclaimer, I do this for a living.

  • by TapeCutter (624760) * on Saturday July 17, 2010 @10:05PM (#32940502) Journal

    8 mo. of the harshest winter for 30 years = press says "weather". 4 we. of the hottest summer for 30 years = press says "global warming, doom, hellfire".

    I have no problem with either explanation, but it sure should be consistent.

    Your consistentcy problems are caused by looking to the press for an explaination rather than climate [realclimate.org] scientists [nature.com]. Climate is the long term statistics of weather and due to the signal to noise ratio it takes a couple of decades worth of data to observe a trend with high confidence. If you really do want a detailed and robust scientific explaination of what is causing the observed trend, then read the IPCC's WG1 report. Be warned the WG1 is heavy going but with the amount of layman-freindly explainations and commentry available directly from scientists and scientific institutions there really is no reason to allow the press to keep you ignorant and confused about the basics. If you don't know where to look then start with WP, it will give you a good run down of the science [wikipedia.org] and the anti-science [wikipedia.org]. If it's too much of a bother to read beyond the MSM then IMHO you should extend that apathy toward posting on the subject.

  • by Arlet (29997) on Saturday July 17, 2010 @10:30PM (#32940580)

    Except that the existing greenhouse effect is already 33 degrees C, of which about 1/3rd is due to CO2.

  • by TapeCutter (624760) * on Sunday July 18, 2010 @01:18AM (#32941084) Journal
    "Maybe I have made a simple math error, but from looking at data from the IPCC, the actual percentage of carbon dioxide in the atmosphere is about 0.0038 (380 parts per million)."

    That's correct.

    "I don't see much of a correlation there. The temperature increase is simply far too high."

    Instead of guessing, how about doing the math using Fourier's well established 1824 equation that he derived while he was inventing spectral analysis...

    RF=5.35ln(380/280) = 1.6 Watts/M^2.
    This translates to an equilibrium change of ~1.4degC given our current understanding of climate sensitivty [wikipedia.org]. Note that this is the lower bound of the 95% confidence interval, the upper bound is a lot less certain due to our incomplete understanding of feedbacks.

    Observations do not show the full 1.4C change, we have not reached the equibrium temprature yet due to the massive thermal inertia [wikipedia.org] of the oceans and ice caps. A more familiar and more rapid example of thermal inertia can be observed with the seasons, ie the warmest weather is at the end of summer not at the summer solstice.

    As for predictions of future warming here are some numbers to help you calculate your own. It's estimated that we have added half a trillion tons of CO2 to the atmosphere since the start of the industrial revolution and that we will double that figure in the next 40yrs. About 60% of what we have released so far has subsequently been absorbed by the ocean but that cannot continue indefinitely since the ocean will eventually turn to soda-pop (carbolic acid) and stop absorbing CO2.
  • Re:water (Score:3, Informative)

    by meringuoid (568297) on Sunday July 18, 2010 @12:11PM (#32943112)
    i have been saying this for quite some time but hasn't anyone paid attention to the fact that hydrocarbons produce more water than carbon dioxide?

    Our production of water vapour isn't all that big an issue. There's a given amount of water vapour that can exist in the air, which depends on local pressure and temperature. If for some reason there's too much around, it rains or forms dew. If there's too little around, water on the ground evaporates until equilibrium. There's already a huge amount of water available, so if the Earth's atmosphere was capable of taking up significantly more water vapour, it would have a source from which to take it, human industry or no. On the largest scale, then, we're not adding water vapour to the atmosphere, where it would affect the greenhouse effect very significantly; we're adding liquid water to the ocean, where it makes very little difference at all.

    Carbon dioxide on the other hand is a trace gas in the Earth's atmosphere. While the industrial output of water won't affect the ocean noticeably, our output of carbon dioxide has very definitely increased the concentration of that gas in the atmosphere. Will the plants not absorb it? Possibly; carbon dioxide is good for plant life. But the exchange is much slower here. Water rains out to the ocean in an hour or two, but a great tree takes decades to grow and absorb a comparable mass of carbon. And the proportions are very different. Estimates are that we've added something like 35% to the pre-industrial levels of carbon dioxide; that would be fine if the plant biomass increased by the same proportion, so that our additional carbon was locked up in the form of wood rather than loose in the air. 35% increase in plant biomass is a lot to ask. Especially when you're busy bulldozing rainforests for cattle grazing.

All life evolves by the differential survival of replicating entities. -- Dawkins

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