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Earth Science

Carbon Emissions 'Will Defer Ice Age' 347

Posted by Soulskill
from the not-cool dept.
Sven-Erik writes "Due to subtle variations in the Earth's orbit, researchers have calculated that the next Ice Age is due within 1,500 years. However, a new study suggests greenhouse gas emissions mean it will not happen that soon (abstract). 'Dr Skinner's group ... calculates that the atmospheric concentration of CO2 would have to fall below about 240 parts per million (ppm) before the glaciation could begin. The current level is around 390ppm. Other research groups have shown that even if emissions were shut off instantly, concentrations would remain elevated for at least 1,000 years, with enough heat stored in the oceans potentially to cause significant melting of polar ice and sea level rise.'"
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Carbon Emissions 'Will Defer Ice Age'

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  • by Nidi62 (1525137) on Monday January 09, 2012 @04:40PM (#38641670)
    And people said global warming deniers didn't care about future generations. They were trying to help them all along!
  • He did it! (Score:2, Funny)

    by KIFulgore (972701) on Monday January 09, 2012 @05:10PM (#38642094)
    One thing's for certain: whether coastal cities are under 20 feet of water or up to their asses in ice 2000 years from now, there will still be politicians pointing at each other over whose fault it is.
  • by alphatel (1450715) * on Monday January 09, 2012 @05:22PM (#38642274)
    The earth is just a computer. You need two. See Slartibartfast.
  • by DanielRavenNest (107550) on Tuesday January 10, 2012 @12:53AM (#38647450)

    No, I'm here. What did you want to know? Getting off the Earth? That's easy:

    * Orbital velocity is root (R(e) * g), where R(e) is the radius of the Earth (6378000 meters), and g is the surface gravity (9.80665 m/s^2). That works out to 7908 m/s
    * Kinetic Energy is 0.5 * m * v^2. Thus kinetic energy to reach orbit is 31.27 MJ/kg.
    * One kiloWatt-hour (kWh) is the common unit of electric energy. 1000 W * 3600 seconds = 3.6 MJ.
    * Therefore it takes 31.27 / 3.6 = 8.7 kWh/kg to get something into orbit.
    * Multiply by your local electric rate. Where I an now, that works out to $1/kg, about what potatoes cost at the local market.

    So getting off the Earth is cheap, if you use energy efficiently. You haven't been, though. You have been using about the least efficient method available: chemical rockets. The best rocket fuels only have a bit under half the energy needed to get to orbit (15 MJ/kg), and the engines are around 2/3 efficient, which leaves you at around 10 MJ/kg. So the fuel can't even get itself to orbit, much less anything else, like cargo. You end up using a lot of fuel to lift a smaller amount of fuel part way, then use that to push an even smaller amount a bit further, and finally that last bit pushes a very small cargo to orbit. For those who understand math, that is an exponential ratio of fuel to cargo, where the exponent is the ratio of mission velocity / rocket exhaust velocity. For chemical rockets, that works out to 2-3, depending on which fuel. So you use e (2.718...) raised to 2-3 power as much fuel as cargo that gets to orbit.

    The answer is quite obvious: use something else. Something that has better efficiency, so you are not slaughtered by the exponential. There are a number of choices. Which one you use depends on a number of "mission requirements": What are you launching, how often, how much up front development money you can spend, how much risk do you want to take, etc.

    OK, that takes care of getting out of *this* gravity well. What next?

    (1) Don't go right down another one. The Moon and Mars can wait till you build up some infrastructure. Use near Earth asteroids first, followed by other asteroids, including the ones orbiting Mars, as a source of building materials. You can use efficient electric thrusters as long as you are not diving down a gravity well.

    (2) Don't send humans first. Humans have all kinds of picky needs about temperature, pressure, food, radiation, etc. Robots, remote controlled, and automated equipment (which I will call just "robots" for brevity) are not as sensitive. Send robots first, have them build stuff up. Once you have enough stuff in place and can support the humans, then they can come.

All this wheeling and dealing around, why, it isn't for money, it's for fun. Money's just the way we keep score. -- Henry Tyroon

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