[hatsunearu]

wouldn't large scale usage of a device like this essentially increase the planetary albedo and help fight climate change? especially if you just skip the "environmental heat transfer" part

[alex_h]

There's some numbers here for what it would take.

https://www.cell.com/joule/pdf/S2542-4351(19)30354-X.pdf

Basically we need 1W/m^2 of cooling for the earth, so if you could get a radiative cooling device with 100W/m^2 you'd need to cover about 1% of Earth's area

[hatsunearu]

I assume the actual radiative power is greater than the cooling capability, since cooling power = radiative power - heat intake from atmosphere - heat intake from sun

so the math works out even better than it seems...?

[davidjytang]

Let's say human inhabit roughly 10% of Earth surface. If we cover all rooftops in the world, that ought to make some effect yeah?

[coolradmab]

Short answer not really https://what-if.xkcd.com/84/

[Tade0]

This makes me think: Earth's energy imbalance is around 0.5W/m2, while such a paint sends how much, 40W/m2 through the transparency window?

So we'd only have to paint 1/80 of the Earth. That's ~6.4mln km2, or 2/3 the area of the USA. Still a lot, but not impossible.

I'm sure paint manufacturing scales better than li-ion batteries, and those more than doubled in production volume over the last decade.

[IgorPartola]

All that would do is offset things so that we can pollute more. Not to mention the CO2 and other emissions from such a project. And it would ruin a huge amount of space because of course this would run into “not in my neighborhood”. It’s far better to fix the problem than to paint over it.

[david-gpu]

Interesting, but even if we solved the temperature problem, we would still have the issue of the acidification of the oceans due to excess CO2. In the end we must remove CO2 from the atmosphere one way or another.

[wolfram74]

That's more a "we haven't made enough paint to cover a large fraction of the planet" argument than a "what would the thermal ramifications of such an act be" argument. Which I was excited to read about, but alas.

[samatman]

For an interesting toy model related to this, check out Lovelock's Daisyworld simulation:

https://en.wikipedia.org/wiki/Daisyworld

The argument (and the related Gaia hypothesis) has some important and subtle connections to the facts of climate change. Though even if it's correct, and the biosphere will tend to naturally reassert homeostasis, there's no guarantee we'll enjoy living through it.

[jschwartzi]

You would need a really big roller with a lot of knap too. Although I suppose you could paint most of the midwest and avoid the mountains with a flatter roller.