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Comment by adrianN | Hacker News Reader

IMHO our only hope are technologies that actively remove carbon from the atmosphere, i.e. "unburn" the fossil fuels we used so far. Turning massive amounts of biomass into charcoal and burying it seems to be the most low-tech solution. That's even an energy positive process. But maybe we need faster methods to avoid catastrophe.

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This is pretty fast. From memory regrowing tropical forests can fix 20 tonnes of carbon per hectare per year. Most of these forests are slash-and-burned on a 30 to 50 year cycle that is carbon neutral, but a slash-and-char approach of about 30% of the forests would capture our total carbon output [0]. It would also have the nice side effect of providing local jobs to some of the poorest people in the world.

0. Research I did when I was an academic and never published. I really should get around to finishing it.

This sounds like a quick, easy and effective solution. Why is nobody doing this?

We don't have a global political consensus that we should be spending massive amounts of money to reduce global warming at all and, more importantly, who will be paying for that.

A few reasons, but the major one is the lack of money interested in actually doing something about pulling the CO2 out of the atmosphere.

I actually worked on a solution for the money problem too (I got a bit obsessed with doing something about climate change back in 2007). This I have written about if anyone is interested [0].

0. https://www.tillett.info/2015/12/13/preventing-global-climat...

Probably because there is no quarterly profit associated with it.

Because the people who have the money to do it have absolutely no immediate incentive to do it.

Is there money in it?

>Turning massive amounts of biomass into charcoal and burying it seems to be the most low-tech solution

If you've found a way to convince people to do that wouldn't it be easier to just not burn coal for energy? Or do you mean doing it at such a massive scale we reverse the net flow of coal from the ground to the atmosphere?

Not burning coal kills the job market for coal miners. Presidents have been elected on promises of keeping them employed. Burying more charcoal than the amount of coal we dig out creates jobs ("clean coal" can even be reused as a slogan!), and you can sell the energy you get from burning the wood gas.

There's not many coal miners, don't worry about that. 50000 in usa, just pay them all to not work.

Or pay them to be coal sequesterers.

Not sure if clever satire.

>Or do you mean doing it at such a massive scale we reverse the net flow of coal from the ground to the atmosphere?

We have no other choice. We either do that or it's possible that somebody is alive today who will see the collapse of human civilization.

There's always a choice. Even assuming that "We either do that or it's possible that somebody is alive today who will see the collapse of human civilization." is literally true (it's debatable - even the worst case scenarios stop at major population reduction, but quite a few areas would do no worse than the aftermath of a major war), choosing not to take major action and accept that the destruction will happen is not only possible, but actually very, very plausible for all kinds of political reasons. I'd be willing to bet with more than 50% odds that those who can do that will choose not to do actions like this and that plans like this won't actually be done.

There is no way that human civilization collapses because of climate warming.

Among all higher life forms (fish, reptiles, mammals and even most plants), humans with technology are the most robust.

Some billionaires waste even time and money for the colonization of dead spaces like Mars or the Moon.

You're assuming that we don't drive the entire ecosystem into the wall. The life forms with the highest chance of survival are bacteria, and maybe cockroaches and other insects, because of their fast reproduction rate and associated fast evolution.

Not burning coal is a critical first step, but at this point we already have enough CO2 in the atmosphere to cause serious damage, especially considering feedback effects.

Do you have any references for the process you describe? It sounds interesting.

It's not hard. You light a decent amount of wood and let in burn in an oxygen poor atmosphere, e.g. by covering it with sand. You get a bunch of charcoal, which you then bury. Charcoal is stable in the ground for a couple of millennia.

Who supplies the fuel though? It's not like charcoal forms at low temperatures...

Making charcoal is an exothermic process. You only need a little bit extra fuel to get it started.

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

It's called biochar. I don't have specific recommendations, but searching the term on Google and Amazon will turn up a lot of resources.

There is some interesting work being done that also restores topsoil:

https://www.youtube.com/watch?v=svNg5w7WY0k

What about mega structures...like super huge 'sun glasses' or shades that partially block sun rays from hitting earth so we can cool the planet that way? Maybe we just deal with 'near ice age' like weather for a couple years... we let the sun shine on farms only, block it for most other places forcing winter-like conditions year-round until the icecaps re-freeze...

Space-based reflectors on the scale of 600,000 square miles could cost about $800B if we could get transport costs down to $50/kg, it'd cost about $400 Trillion at the current cost.

It is probably cheaper to confer cities with huge geodesic domes with high reflectivity and deal with excess heat.

Ecosystems may have some trouble with it.

With the amount of energy it takes to bring anything to orbit, I suspect a ground based solution that just recaptures CO2 or regrows trees is going to be much more cost effective.

And where would we find the resources to build something like that? Let alone move it to orbit.

We're passed the point of no return... because the ice has melted, permafrost is about to unleash a feedback loop that will warm us even more. I'm not sure if we could remove all c02 from the atmosphere today, if that would have a net effect. -- We need to find a way to recool and rebuild the ice deposits we've lost at the north/south pole and refreeze all the permafrost -- that's the only real long-term solution... -- As for resources for something like this...no effing idea, it'll cost in the trillions... maybe Bezo's could get it done, or Elon ... If we could get space mining going we could mine the resources needed in space, and build it on the moon to make it easier to launch... We could also make it modular so we don't need to build it all at once but could build it in portions...

The melting arctic ice sheets cause an influx in cold freshwater in the north atlantic which works to slow the rate of thermohaline circulation, which is responsible for bringing warm sea water (energy) to the poles which accelerates melting. It's a big unknown what exactly will happen, but it's possible that the damages of climate change are less than projected if the thermohaline circulation slows sufficiently to bail out the world until it can start reducing carbon emissions cost effectively.

Or it could go the other way. No one is sure what happens if the major currents change. Northern Europe should probably get ready for a cold spell.

Bottom line, we need a space elevator.

It's not clear if a space elevator on earth is physically possible.

On tiny scales, carbon bonds have sufficient strength/weight ratio so that the elevator might support it's own weight, but there's not that much margin left. As the macrostructure likely requires a multiple of weight, to account for the fact that a kilometers-long string can't be manufactured perfect to the single atom, and that damage can and will occur (e.g. any radiation), etc, etc - according to our current knowledge of physics it might as well be that a sufficiently strong macroscale material for an Earth-sized space elevator cannot exist. Moon or Mars is a different issue, though.

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