this post was submitted on 06 Dec 2024
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Discussion of climate, how it is changing, activism around that, the politics, and the energy systems change we need in order to stabilize things.

As a starting point, the burning of fossil fuels, and to a lesser extent deforestation and release of methane are responsible for the warming in recent decades: Graph of temperature as observed with significant warming, and simulated without added greenhouse gases and other anthropogentic changes, which shows no significant warming

How much each change to the atmosphere has warmed the world: IPCC AR6 Figure 2 - Thee bar charts: first chart: how much each gas has warmed the world. About 1C of total warming. Second chart: about 1.5C of total warming from well-mixed greenhouse gases, offset by 0.4C of cooling from aerosols and negligible influence from changes to solar output, volcanoes, and internal variability. Third chart: about 1.25C of warming from CO2, 0.5C from methane, and a bunch more in small quantities from other gases. About 0.5C of cooling with large error bars from SO2.

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Weatherwatch: why cooling white roofs cause neighbours to swelter | Climate crisis (www.theguardian.com)
submitted 2 weeks ago by sabreW4K3@lazysoci.al to c/climate@slrpnk.net
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[–] ShaunaTheDead@fedia.io 32 points 2 weeks ago (3 children)

The important thing is that the high albedo material has to convert incoming light into a particular wavelength of infrared light that is not absorbed by the atmosphere and so it flies straight out into space. If it's just white (high albedo) but doesn't convert light into the right wavelengths of infrared light, then yes, it will warm the surrounding areas because a lot of the light it's reflecting will get reflected off the atmosphere back down somewhere else.

Wikipedia has a thorough article on it: https://en.wikipedia.org/wiki/Radiative_cooling

Here's a video by a channel called NighthawkInLight: https://youtu.be/KDRnEm-B3AI?t=78

And here is a 2 part series by TechIngredients: https://www.youtube.com/watch?v=5zW9_ztTiw8 https://www.youtube.com/watch?v=dNs_kNilSjk

[–] Womble@lemmy.world 11 points 2 weeks ago* (last edited 2 weeks ago) (1 children)

Things appear white because they are reflecting a lot of light in the visible wavelengths you can see, to which the atmosphere is unsurprisingly transparent. Things that are black on the other hand absorb the light, heat up and re-emit at their thermal temperature which in the terrestrial range of 0-100 degrees peaks in the far infrared which the atmosphere is not (as) transparent to.

The linked study is talking about a boundary effect between the cooler area of high albedo (because painting things white does reduce the energy absorbed and reflects a good chunk of that back into space) and the warmer area of normal albedo. Its modelling how that change between different temperature areas affects air circulation and cloud cover, not that the reflected light is warming up other areas.

[–] mindbleach@sh.itjust.works 0 points 2 weeks ago* (last edited 2 weeks ago) (1 children)

to which the atmosphere is unsurprisingly transparent.

The sky is blue specifically because that's wrong.

[–] bane_killgrind@slrpnk.net 1 points 2 weeks ago (1 children)

so it's blue because specifically that wavelength of light is scattered, not the rest of it. it's not reflection, it's refraction.

[–] mindbleach@sh.itjust.works 0 points 2 weeks ago (1 children)

You are within sight of a blue LED. Does that monochromatic blue look like the blue of the sky? No. Because Rayleigh scattering diffuses higher wavelengths more, not exclusively.

Even a deep red sunset scatters enough light to overwhelm the stars.

Cooling paint emits light deep enough in the infrared that this effect becomes negligible. It proportional to frequency, to the fourth power.

[–] bane_killgrind@slrpnk.net 1 points 2 weeks ago (1 children)

The sky is not emitting light, it is refracting light, like a prism. A blue LED is emitting light at different wavelengths than the blue of the sky.

[–] mindbleach@sh.itjust.works 1 points 2 weeks ago (1 children)

... no shit.

Like a prism, it affects all wavelengths. If it was "specifically that wavelength," "not the rest of it," it would be monochromatic. Like an LED. But it's not. Rayleigh scattering diffuses any near-visible photons, at a rate proportional to their frequency, squared, squared.

That's why cooling paint works differently than merely reflecting light. Even red light can scatter in the air and warm up the environment. Red scatters less than blue... but infrared scatters less than anything visible.

[–] bane_killgrind@slrpnk.net 1 points 2 weeks ago

Alright, I'm trying to say that "mostly transparent" is a fine way to describe it.

[–] fraksken@infosec.pub 2 points 2 weeks ago

I was thinking of lining my roof with tinfoil. Would that be a better option or would that just make it worse?

[–] jmiller@lemm.ee 1 points 2 weeks ago

NighthawkInLight has lots of great stuff, but his subambient temperature paint videos are the best.

[–] Oestradiolo@lemmy.blahaj.zone -1 points 2 weeks ago

Chuckle. Taking bets for what the humans will actually learn from this based on their actions.

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