This an amazing opportunity to develop our capabilities and deliver real value to earth at the same time. Geo-engineering on this scale is not without its risks but the pay off could be huge. We could buy time to lower our carbon emissions without huge economic impacts.
If we get lunar mining up and running that opens up a world of space based resources at far cheaper than anything we could launch from earth. With a mass driver and solar power we could avoid the need for propellants for launch.
Once you have an economic reason to be up there getting there will become much cheaper. That will enable a new wave of scientific exploration.
With more or less the same tech, we can make Venus inhabitable. Would take a long time to cool and a lot more sunshade to cover the Sun, but once we start making them on the Moon and dispatch them with a magnetic rail launcher, it becomes a lot easier.
A similar technology could shield Mars from solar radiation and reduce exposure at the surface (at least from the Sun). If we could make it into a lensing system, we could focus protons or Alpha particles from the Sun into a small region of the planetary disc and slowly re-add hydrogen back into the planet’s atmosphere.
> There are two main types of geoengineering. The first is removing carbon from the environment to restore pre-Industrial levels. While carbon removal is necessary, it will take over a century to remove and sequester the carbon already present in the atmosphere and oceans.
We're on an engineering (among other things) forum, and it's surprising that technological solutions to the global climate problem aren't discussed enough. This statement illustrates another problem - "space" technologists assume that carbon cleaning would take "over a century", while some "carbon-cleaning" technologists assume space-related solutions will take too long. And in this thread there's also an opinion that, since we don't know much about global cooling, we should redouble our efforts elsewhere.
On the other hands, we seem to need all of that. We try political solutions, and they work - too bad so far, even though they do show some progress. We start talking about technological approaches - like, take a billionaire and a tech program, make an analysis (it's a sticky part) and then actually try to do something (aerosols? ocean seeding? pulverized minerals which react with CO2? space shadow? direct carbon capture from atmosphere?). We shouldn't tie our hands to the point of inaction, because inaction is also costly. And yes, we need more traditional approaches too - pressure on politicians, economical means of stick and carrot to get the intended results, green energy approaches - but in addition, not instead, since so far we're badly lagging.
While the cheapest CO2 sequestration sinks are limited in capacity, there seems to be enough alternatives that could be scaled up to virtually any required capacity.
Furthermore, direct air capture doesn’t appear to require anything else that isn’t abundant - and the absorption materials and catalysts can be recycled indefinitely.
I’m not sure I’ll live to see it but my belief is that in the latter half of the 21st century we’ll see direct air capture deployed on a truly astonishing scale.
Sure but looking at the energy requirements of those systems it doesn't really start to make sense to deploy before you've seriously decorbanised your energy supply, which comes back to OP's remark. Why discuss these types of systems when we should be focusing on decorbanisation?
> Why discuss these types of systems when we should be focusing on decorbanisation?
We should, but we don't do enough of that. So let's put efforts where they bring results - even if they'd theoretically bring more results elsewhere, in practice they don't.
In reality we do try to prevent atmosphere pollution from happening, we just don't do enough of it. Some others of us, who're not involved in this process may have better chances with other, less efficient for now but still useful approaches.
It's annoying that there seems to be rather promising technological approaches, which don't even require a lot of political will - and yet we don't seem to see them applied at a needed scale, or getting there.
A close approach seems to be taken by Terraform Industries - in a sense of scale. Just like Elon Musk repeats that SpaceX doesn't build rockets as much as it buildы a proper rocket industry, Casey Handmer at https://caseyhandmer.wordpress.com/2023/04/11/climate-tech-c... demonstrates good attention to scale. A BOTE calculations showed that if we have a billion m^3/s of air cleaned from CO2, we'd reduce CO2 in atmosphere twice as fast as we're adding CO2 there. A unit which handles 1 m3/s - given rather simple goal - doesn't look too expensive, and Earth already has a billion personal automobiles, so technically speaking we should be able to have some progress.
We need to pay enough attention to the urgency of the situation, the solutions should really scale.
The paper glosses over the technical design of the solar shield spacecraft. I'd like to understand how they will maintain their attitude given how huge they are. Would gyros be enough to counteract radiation pressure?
What you need your counter ia radiation pressure gradients that would deform the shield. I’m assuming the craft rotates so that the centrifugal force keeps the shield flat and extended, so the craft itself would be a gyroscope on one axis. For average radiation pressure, the shield would need to be slightly closer to the Sun than the L1 point so that the pressure and the gravitational pull cancel each other out - you’ll still need at least two engines, one facing the Sun and other facing the Earth that would do orbit height adjustments. You may be able to get away with one if you shine lasers on the shield when you need to push it sunward.
At some point, we will probably want to actively manage Earth’s climate via space-based solar radiation management. We might also consider doing the same for Mars if we ever decide to settle on it.
However, we’re going to need to draw down CO2 over the course of this century regardless, and we can probably use stratospheric aerosol injection at a tiny fraction of the cost and for a decade or two if necessary during the process of drawdown.
As such, it doesn’t seem like this kind of space-based shelter is justifiable as a response to the warming we are currently dealing with.
Putting some kind of solar shield in L1 seems like a credible way to reduce energy input into the atmosphere. However, it creates a big “single point of failure”. And it’s difficult to believe we can build something of the size they propose (1.7 million sq km) in a timeframe that would make a significant difference to climate change without an Apollo or Manhattan-level of urgency.
The folks working on the L1 case (e.g. Robert Kennedy and his students in TN) estimate the shade would have to be approximately the size of Texas (about 700,000 km2, much smaller than you propose) and could be erected within 50 years.
Their plan is to make a lot of small devices rather than one large device. Just talking to the structure(s) is complex as there will be a huge noisy EM source right behind it.
Plants are going to get less sun and how would that impact the global ecology and economy? Would we need to grow more plants to make up the difference? Would this disrupt ecological balance in areas all over the earth? There’s a lot more to consider than just reducing global warming.
Putting aside "a space-based solar sunshade represents a technological leap forward and would be really cool" -- which I think speaks to me on an emotional level -- I do think this might be the single most powerful technological weapon we have to combat climate change.
My reasoning:
* people talk about going carbon neutral: great! But this isn't one problem, this is a thousand distinct problems. Our civilization is built on fossil fuels, and every manufacturing process, agricultural process, transportation process, etc, has to be re-invented to not be built on fossil fuels. Progress will never be as fast as we'd like on this front. We can and should push to get there (there is no good path but forward), but every new bit of news we hear out of Antarctica or Greenland should tell you that we need a longer runway.
* people talk about carbon sequestration: scaling up carbon sequestration is hard -- IMO, even with uncertainty, it feels a lot harder than blocking 1% of sunlight. There is a (semi)plausible technological path to the latter, at least. We will obviously have to keep exploring carbon sequestration in the hopes that a silver bullet emerges. But we can't count on nonexistent tech bailing us out. That's magical thinking, and one step above "thoughts and prayers". There has to be a plan in the mean time, and that plan needs to scale. We're probably going to need it.
* geoengineering with aerosols isn't just geo-engineering, it's essentially terraforming. That's a wing and a prayer, and at the scale we'd need to do it to have an impact we'd surely create some nasty unintentional consequences.
* Note: the above is an important risk calculation, because if you're ok with dumping a crapton of aerosols in the atmosphere -- as some people seem to be -- aren't we basically fine on climate already? Just do that indefinitely! Seems fine, right?
* if aerosol spam is not fine, your backup plan can only be something in space: you are here, at this pdf, at the solar sunshade. The sunshade has side effects, but they're much more palatable in my estimation -- the 1% of sunlight blocked will have the effect of making every day seem imperceptibly hazier (this was something I noticed during the 2017 solar eclipse at 50% of the sun being blocked -- seemed like a hazy day at that level of diminished sunlight. That was 50%. With the sunshade we're talking a 1% reduction to reduce the global temp by 2C.)
I don’t find it disgusting, but I can see that being a valid reaction to space-based solar radiation management (actually doing it, not the research). We probably know more about the consequences of inadvertent man-made global warming than deliberate man-made global cooling. To me that’s reason enough to just try our best using nuclear, solar, and fossil fuel substitution (electric vehicles, heat pump conversion,…) than this wild engineering project.
If we get lunar mining up and running that opens up a world of space based resources at far cheaper than anything we could launch from earth. With a mass driver and solar power we could avoid the need for propellants for launch.
Once you have an economic reason to be up there getting there will become much cheaper. That will enable a new wave of scientific exploration.