If we settle at about double the preindustrial CO2 level, we would need to block about 8% of the solar radiation [0]. You could do that eg with floating structures of ultra-thin translucent sheets that reduce light intensity in their shadow. To maximize effectiveness you can put them in a sun-synchronous orbit, so it casts it shadow always at high noon [1].

However this solves only the warming itself, it does nothing about things like ocean acidification.

0: https://www.newscientist.com/article/dn11993-solar-shield-co...

1: https://en.wikipedia.org/wiki/Sun-synchronous_orbit

Sounds a bit dystopian to me. Want to shut down protests? Just block out the sun - no daylight for you!

The word 'dystopian' rings a bell quite often when it comes to so-called 'climate change' saving methods...

It sounds even more dystopian if we do nothing at all.

I agree. Shutting down protests by making it dark doesn't even work? OTOH, letting most of the people on the planet starve to death seems actually bad.

Actually, humans doing nothing would be the best thing for the environment

Industrial energy consumption feedback loops will occur in any system we attempt to build to curb the issue

Any machines, chemicals, processes, vehicles, etc, that need producing to “improve things” will all come along with chewing up resources at scale to provide the industrial pipeline

The only scientifically acceptable path is LESS industrial scale economic activity: https://www.bbc.com/future/article/20210312-covid-19-paused-...

I'm not sure what "doing nothing" would look like if we don't mean "continue on our current path".

The entire set of Western values as cemented by the Cold War seems incompatible with "less economic activity". And even if we somehow shake consumerism, modern agriculture is essential to feeding more than 1B humans and requires a significant amount of industrial scale economic activity.

The majority of the time "buy/make this thing to reduce climate change" is a mere distraction. But there are a lot of resources that we can afford to spend, some of which are near-limitless if you consider predictable advances like asteroid mining. If we find ways to spend those resources to get us at least part way out of this mess, or to buy us time for societal change, then those are paths worth pursuing.

Look at the current political leaders and ask yourself is something--anything--is going to happen. It isn't going to happen.

Blocking the sun enough to black out a protest for any length of time kills us all. Most of the proposals are talking like, 1% of the sun. The whole sun for a few hours is way too much, and would do all kinds of bad things.

Besides, they already tear gas and mass arrest protests if the cops don’t like the protestors, that’s already pretty dystopian.

The "right" way to do it, is to put something big at the L1 Lagrange Point.

That is permanently between Earth and the sun, and you'd see it as a black dot at the center of the Sun.

Downside is it needs to be real big. 2000 km, according to this:

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

This paper discusses the concept: https://www.pnas.org/content/103/46/17184

I think they were targetting "stop warming" more than "1990 levels", but they estimated 20 million tons/a few million square kilometers.

Supposedly this will have a negative impact on crop yields. They are photosynthesis machines after all.

There are always trade offs.

This issue will NOT be solved without substantial costs.

Why not over say, mid ocean or mid-desert, in a fixed spot?

Orbital mechanics.

The efficient (and probably only viable) way to do this is a solar shade at lagrange point 1 (directly between the sun and earth). There's an unstable equillibrium point there were things can sit permanently with some (but minimal) station keeping. But you don't get to pick which part you're shading, you're always directly between the earth and the sun (or really the center of the earth-moon systems gravity, and the sun).

I see, thanks. I guess I was thinking of something that 'moved' with the earth, but that probably isn't realistic.

Could something be placed at such a point that then only blocked sun on the far north/south of the planet, near the poles?

Not directly. You could place something in an orbit where it only ever blocked sun at the poles I think, but it would spend the vast majority of its time not blocking sun at all.