So what I’m reading is that these gas absorb the light from the sun and keeps it trapped on the earth.
What I don’t get is how is it letting the light and heat in from the sun in, but not the light and heat reflected from the Earth out? If it’s a barrier, shouldn’t it block both ways? If it’s not a barrier, how is it trapping the heat?
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Its like in a car. When light goes thru the glass heats up the surface inside , but the glass is air tight so the heat cant escape.
It’s not letting heat in, only visible light (mostly). That gets converted into infrared light (heat) by the ground, which cannot pass back through the greenhouse gases because of their properties.
Ask yourself what happens to a car parked in the sun with its windows up? Answer: the interior heats up. Why? Because the car windows let in the sunlight but do not let out the resultant heat (that the sunlight converts into when it hits the interior of the car). What happens if the windows are rolled down? Answer: the interior cools down. Why? Because the resultant heat is now able to escape. The earth’s atmosphere acts similarly to the glass windows in a car.
It isn’t one way. The other side of the equation is global dimming.
There was big news (big science news) last month about the reduction in Sulphur Dioxide and how that may affect climate change. Sulphur Dioxide affected the atmosphere by seeding clouds that reflected light away from the earth. Now we’ve stopped emissions, we get to wait and see how much of an effect it will have.
Global dimming will never be enough to counter global warming, but it is enough to make climate change more difficult to predict.
https://www.washingtonpost.com/business/energy/2023/03/27/climate-change-how-cleaning-up-pollution-may-heat-the-planet/dd7496b0-ccdc-11ed-8907-156f0390d081_story.html
https://www.carbonbrief.org/analysis-how-low-sulphur-shipping-rules-are-affecting-global-warming/
The sun is really hot, about 6000 degrees. The light from the sun looks white. The earth is currently much cooler, about 60 degrees. The light (EM radiation) from the earth looks much ‘redder’, so red that you cannot see much of it. The gasses in the atmosphere allow most of the white sunlight to pass, whereas those same gasses absorb proportionately more of the redder light energy and that causes heating. The crazy thing is that you can get into a runaway situation. With enough water vapor in the atmosphere, there can be no balance between incoming and outgoing energy at current earth surface temperatures, as the water vapor absorbs too much. Only when the earth gets really hot, too hot for life to exist, will it radiate colors sufficiently ‘blue’ to readily escape the atmosphere. That’s when we become Venus 2.0.
It’s like a car sitting in the sunshine all day with the windows rolled up. The windows let the sunlight in but don’t let the heat out.
The difference is in the wavelength. CO2 and other greenhouse gasses block infrared light, ie heat, but not so much visible light. Unlike Sun, Earth doesn’t radiate visible light, only infrared light.
Light has frequency when coming in, hitting the earth and warming it. Earth then emits Light with much lower frequency. The one with the higher moves through greenhouse gases when coming in, the one with the lower gets trapped in. Like it got all the motivation and focus when coming in, and when going out it does not. Like In a swamp.
LIGHT comes in and heats things up (radiation). HEAT can’t get back out because the greenhouse gases act as a blanket between a warm earth surface and cold space.
Followup ELI5: Why can’t we open the atmosphere and “vent” some of this heat out? I know holes in the ozone are bad, but would it let the heat out?
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