[stouset]

If we find a cheap new way to generate orders of magnitude more energy, we'll use orders of magnitude more energy.

And you're right. We're only a bit over two hundred years away at 2.3% annualized growth in energy use from noticeably raising Earth's surface temperatures just from a thermodynamic perspective. And that's completely ignoring the effects of greenhouse gases.

[saiya-jin]

You and parent project this in some theoretical universe where these effects would be ignored. Why on earth do you think so? With semi-unlimited energy at our palms, we can do serious geoengineering. We can put these furnaces into high orbits, or moon and beam down just raw output energy with lasers. Or whatever, even the sky isn't a proverbial limit.

[stouset]

Unlimited energy doesn't free us from the consequences of thermodynamics. Geoengineering doesn't help us. Where we generate the energy doesn't change anything if it's used here on this planet.

There are literal physical limits here that can't just be handwaved away by space magic. Higher energy use in a finite spherical volume fundamentally results in increased temperatures when your only way of getting rid of that heat is radiation (and not convection or conduction). And we can't just beam that heat away with space magic either thanks to entropy.

Thermodynamics gives us no tools to deal with this problem outside of increasing the spherical volume of Earth (and therefore its surface area).

[root_axis]

Fusion isn't magic, more energy doesn't suddenly obviate the burden of practical engineering constraints, we won't be "geoengineering" our way out of climate change for the foreseeable future.

[willis936]

A world where energy consumption increases by a factor of 10,000 is a far fetched fantasy. If we're starting with such premises, should they not be followed?

[stouset]

A world where energy consumption increases by a factor of 10,000 would already be a world where the surface is lava thanks to basic thermodynamics. Earth can only radiate so much heat into space, and its ability to do so will not outpace energy production for much longer.

A world where energy consumption increases fiftyfold is a century and a half away and would be brushing up against the point where we are noticeably increasing the equilibrium temperature of Earth sans any greenhouse gases. Hitting the thermodynamic limits of Earth's ability to radiate heat into space isn't a far-fetched fantasy, it's terrifyingly close.

[willis936]

This is very wrong. Humans produce about 30 TW of heat. The sun imparts 10 trillion times this amount. If we increased our production by 10,000 then we need to put a small umbrella in space to slightly dim the sun the smallest amount to maintain power balance.

[stouset]

Feel free to do the math yourself. You’ll forgive me for trusting in the calculations of UCSD professor of physics Tom Murphy, who’s written about this extensively.

Edit: Also, your numbers are quite simply incorrect. The 70% of sunlight that doesn’t bounce back into space is about 35,000TW, far from the hundreds of trillions of terawatts you claim. At 2.3% energy growth for the next 275 years, we’ll be adding 7,000TW to this number. That is easily enough to noticeably increase Earth’s equilibrium temperature, and far less than this will be necessary to do so given greenhouse gases which reduce our ability to radiate heat into space.

https://dothemath.ucsd.edu/2011/07/galactic-scale-energy/