[istjohn]

A global cooling system is easily conceivable. The ISS uses radiators to dissipate heat into outer space. We could do the same. We could concentrate heat with heat pumps and pump hot steam, molten salt, or plasma up a space elevator and radiate the heat away.

Edit: The link points out that in 1,400 years we'd be using energy at the rate produced by the sun and in 2,500 years at the rate of the entire Milky Way. Even if we solved the heat radiation problem, it seems unlikely we'd be able to obtain fuel for our fusion reactors at a sufficient rate given the speed of light and the density of matter in the universe.

[amluto]

There’s no free lunch.

The sun radiates heat like a blackbody sphere with the surface area of the sun and a surface temperature of 5600K or so.

If the Earth were to have a fancy heat pump that radiated the same amount of heat into space, it would need the radiating area times the effective temperature to the fourth power equal to that of the sun. The real killer problem is that your heat pump is subject to the Carnot efficiency of pumping heat to that same temperature.

By the most straightforward Second Law calculation, entropy transferred to hot side >= entropy removed from cold side. So Q_hot / T_hot >= Q_cold / T_cold. Q_cold is the heat removed from the pleasant ~300K place where the humans are. At 5600K on the hot side, 18.6 times as much heat needs to be radiated out, so for every bit of useful work done on Earth, at least 17.6 times as much energy is consumed in cooling. If you want the radiator to be only half the surface area of the sun, multiply that by about 16.

What future humans really need is a Dyson sphere with absolutely enormous radiating area. :)

[anon____]

Well then maybe we should do this at night, i.e. always on the dark side of the Earth, not the one that's facing the Sun. Basically passing through the radiation that reaches us.

[pyinstallwoes]

Like space itself

[naikrovek]

we can (and do) radiate heat into space already. there's a specific infrared wavelength that passes out of our atmosphere unimpeded.

building things which receive sunlight but which emit IR at this wavelength would have a cooling effect, though I don't know to what scale.

no need to pump anything up to space, lol. just put hot stuff inside vessels which are painted with a material which radiates heat at this specific wavelength.

[AstralStorm]

Uh, paint doesn't radiate heat not does it convert IR frequencies. (except for very unusual, usually fluorescent materials) It reflects incident IR.

[naikrovek]

not normal paint, no.

thanks for nitpicking; always appreciated

[bmitc]

> A global cooling system is easily conceivable.

That sounds like a line from Dr. Strangelove by the titular character with ol' Bucky following up with "Mr. President, we should not allow a heat pump gap!".