Does the Earth accumulate the energy it receives from the Sun, or does it reflect all of it back into space?

Question

I understand that the sun gives energy primarily in the form of sunlight, which contains various wavelengths of electromagnetic radiation. If the earth absorbs some of the energy, does the earth’s “total energy” accumulate?

In: Planetary Science

Answer 1

there was a veritasium video about this that i would love to link to you, but somehow i’m not finding it.

no, the earth doesn’t accumulate energy from the sun. all the energy that the sun provides is eventually radiated back into space. if that wasn’t the case, than you can imagine that the earth would gradually become hotter and hotter, and by now would have probably evaporated.

this doesn’t mean that all the energy is reflected immediatly. as someone else said, some is reflected, and some is absorbed, the ratio betweeen those being the albedo. earth’s albedo is around 0.3, so it absorves around 70% of the light that hits it. but the energy that this light carries is then radiated away, in the form of infrared radiation, back into space.

it’s what happens between the absorbion of the energy from the sun by the earth and it being radiated back into space that is interesting. this is the energy that plants use, by converting water and CO2, into their mass, that later animals eat, that later die and are decomposed by microbes, and so on. it is also the energy that powers our climate, driving winds, creating rain, etc. what the sun provides to the earth, rather than just “energy”, as that would mean that the earth would get ever-increasing hotter, is “usable energy”, or in other words, entropy.

if you imagine the earth as a closed system, with the same amount of energy as the earth currently has, being provided from the sun, eventually all this energy would spread evenly, and there wouldn’t be no source to power anything (powering something means having energy flow through it; having a source of energy means that somewhere the energy is more concentrated, so it may flow somewhere, powering it). what the sun does is provide a source of concentrated energy, that then is able to flow around the earth, powering our climate and the biosphere.