Sounds simple but it would be hard to get an accurate test. I mean, it's not a basic kitchen experiment, is it? And why is it that modifying such a small part of the atmosphere (0.04%) can cause such a huge problem?
> 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.
> And why is it that modifying such a small part of the atmosphere (0.04%) can cause such a huge problem?
The modification is invisible to you, but not invisible to the photons which are supposed to leave the atmosphere and cool off the earth a bit. It it were visible to you, it would look like this:
Regarding the photons of thermal frequencies leaving the Earth atmosphere, or remaining there, the simplest you can imagine is a blanket: if it's cold outside the blanket keeps the heat not leaving the area under the blanket, keeping you warm. Here, the CO2 is actually a "one-way" blanket, it doesn't block the incoming radiation:
The heat coming from Sun has other frequencies as it comes than the photons blocked that would cool off the Earth.
The key is: CO2 is an ink-black "blanket" for exactly a part of the radiation that cools off the Earth. It's not too big, but big enough to make in sum that 0.8 C degree change since 1880. Or to produce even more warming in the coming years as we burn always more and we haven't managed to change that.
A little more precise:
"Energy arrives from the sun in the form of visible light and ultraviolet radiation. The Earth then emits some of this energy as infrared radiation. Greenhouse gases in the atmosphere 'capture' some of this heat, then re-emit it in all directions - including back to the Earth's surface."
(There's of course infrared radiation coming from the Sun, but the one making problem is the radiation from the Earth)
It doesn't. The atmosphere is not a closed system as upper limit varies. The global temperature strongly correlates to the sun's activity and our distance from it, and nearly not at all to anything else, other than cataclysmic events such as huge volcanoes, asteroid strikes, etc.
Not true. Very short term effects correlate to solar exposure, where CO2 effects have a built-in long-term filtering that stretches out the response time, averaging out shorter fluctuations.
Temperature is increasing not because of increased insolation, but because of increased retention.
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.