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> And why is it that modifying such a small part of the atmosphere (0.04%) can cause such a huge problem? There's a lot of energy going by, and greenhouse gasses grab a slice of it that is otherwise poorly grabbed. Perhaps picture a small cabin, with a big hot stove, and a window open to bitter arctic night. Without the window, you soon bake. Without the stove, you soon freeze. You tweak the window's openness to change room temperature. Keeping or killing your house plants as you prefer. The window is a patchwork, some patches overlapping, some not. The part of the window along the ceiling matters a lot, as much heat is trying to escape there. Tweak a patch over an otherwise open hole there, and it matters. Earth is doing a BBQ roll, hanging between white hot Sun, and black cryo space. The atmosphere fluffs out during the day, and contracts at night. Lunar day is 120-ish C. If aliens umbrellaed the Earth, then vacuum would come down to ground, the atmosphere become some meters of oxygen nitrogen snow. That's a large flow of energy going by. Atmospheric water absorbs, and emits back, a lot of heat - deserts get cold at night. Different molecules have different absorption spectra. CO2 absorbs well at some frequencies water doesn't. Including in thermal infrared, where ground is radiating heat to space. As an aside, Stanford has a fun project for more efficient refrigeration. A material engineered to preferentially emit heat, thermal infrared, at frequencies less well absorbed by the atmosphere. The "holes". So just sitting on a roof, it's cooler than the roof, because it can better "see" space than the roof can. |