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Comment by endisneigh | Hacker News Reader

Would nuclear fusion open up new avenues to reverse climate change?

If it proves to be cheap enough, yes. We could eliminate all fossil fuel use, and use electricity to remove carbon dioxide from the atmosphere.

And if it's too cheap, waste heat from all the electricity we'll be using will heat up the earth again.

But if we're using this clean energy and the levels of green house gases is lowered then the excess heat will simply leave the planet. Total non-issue.

It depends on price. If it proves to be more expensive then fusion, no. However if it's much cheaper than wind, we could use it to pull CO2 directly out of the air on a massive scale. One might imagine a sort of lo-fi global thermostat, an interesting and somewhat scary thought.

We do that on a small scale: https://en.wikipedia.org/wiki/Carbon_dioxide_removal#Direct_... - "a pilot plant in British Columbia, Canada that has been in use since 2015[51] and is able to extract about a tonne of CO2 a day.". CO2 is in the atmosphere at 400 parts per million, i.e. to get 400Kg of CO2 out you need to suck 1,000,000Kg of air through (at minimum, assuming you can get every single CO2 molecule out), which sounds like a lot of matter to move and a power-hungry approach.

The world emits about 37 billion tons of CO2 per year which is 33.5 billion Kg, so we need 90 million of those pilot plants to remove a year of CO2 in 365 days of operation, at a cost of $0.3T to $0.6T per year.

It would, but would likely be too late for most of the impacts of climate change

No, because climate change is made up of dynamic, layered, cyclical activity and influenced by volcanism (and stratospheric SO2 injections in particular), solar activity, cosmic rays, aerosol emission from humans, forests, and volcanoes, geothermal influence on sea temps (ENSO, AMO, PDO, etc), geomagnetic activity, orbital cycles, axial precession, albedo, and cloud cover.

What does it mean to even "reverse" a non-linear dynamic system that is unpredictable in its thrashing as an exponential function of time? Reverse it to what? The 1960-1990 average and hold it there? Good luck.

... yes, it could, because the excess energy could be used to capture carbon. All combustion is an exchange of electrons; providing electromotive force can reverse the reaction.

You can just plant trees to capture carbon. But of course, the ~400ppm carbon in the atmosphere is still far below natural levels that have occurred in history (as high as 7000 ppm). I'm not even convinced that removing carbon using heavy machinery is a good idea, as it would presumably reverse the fertilization effect of CO2: https://www.nasa.gov/feature/goddard/2016/carbon-dioxide-fer...

Nuclear is promising for other reasons, namely that it's a virtually infinite source of energy with no downsides if we can master a technique for producing it without meltdown risk.

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