Olivine weathering addresses both: https://projectvesta.org/
I think Bill Gates has an opinion that we underestimate technological capabilities available for dealing with climate crisis.
Suppose we reduce solar power reaching the planet by 1%. Biosphere will get 1% reduction. How much temperature decrease we'll get and how soon?
Even with undesirable consequences another tool may be valuable to help us get where we want.
> Solar geoengineering isn’t only technically feasible, it’s a bargain. Next to the trillions in costs from unmitigated climate change, and even the expense of cutting CO₂, solar geoengineering costs practically nothing. If anything, it’s too cheap. A program that releases SO₂ to decrease average temperatures by about 0.1C would cost less than $5 billion per year. This should prompt the world to prepare for its inevitability. Dozens of countries have both the capacity and possible motivation. The operative word is “when,” not “if.”
Ignoring the unwanted environmental side effects of pumping SO2 into the atmosphere, one thing this article does not mention is that the results of geo engineering will be non uniform. Just like global warming will causes non uniform temperature & climate change over the globe, similarly geoengineering approaches will have non uniform results -- some regions will be relative winners and some regions will be relative losers -- getting a larger share of the unwanted consequences of geo engineering with few or no corresponding benefits.
The results of any climate change plan are not going to be uniform.
But more seriously. Sunlight that hits the planet(and isn't reflected back out) is a different variable than solar heat that stays in the atmosphere. Our carbon levels are increasing the second variable. Trying to counteract that by lowering the first seems like it would have tons of unintended consequences.
Solar heat that stays in the atmosphere originates from the sunlight that hits the planet and does get reflected.
A better, but more expensive idea is to build a giant sunshade at Earth-Sun Lagrange 1, a gravitationally stable point well beyond the Moon's orbit. It could be constructed with raw materials from the Moon and near-Earth asteroids, and the logistical capacity is within the design goals of SpaceX's Starship fleet.
It's expensive, and it's a giant band-aid until planetary CO2 removal is feasible. But building it would make humanity a truly interplanetary species, and benefit all of humanity for about the same cost as a city on Mars.
Re "band-aid" -- I agree -- all solutions of this form that aim to partially mitigate one unwanted consequences of rising CO2 without addressing other consequences or halting the rise of CO2 are unlikely to result in a stable solution & instead just buy time.
As to expense, it's an opportunity for the space industry to contribute to solving the #1 problem on Earth. The Starship fleet is being built anyway.
As a fringe benefit, if made of thin-film photovoltaics a sunshade could generate ~300TW of electricity. Compare that to current terrestrial consumption of 17TW. It creates enough energy and in-space manufacturing capacity to unlock the solar system.
It's much harder to undo terraforming attempts.
Issac Arthur's podcasts are great to listen to for this sort of thing.
One reddit discussion on the concept:
At worst we are back in time where plankton and trees began absorbing the CO2 and turning it into oil and gas. In other words, nature will survive because such a state is well within the planet's capabilities. What am I missing?
I worry if people get in a panic about global warming there could be similar rash actions that might be worse than the problem.
Mass panic feedback loops are definitely a threat we should now be aware of.
(Edit. Of course global warming is a big problem and this could be a good solution.)
The less toxic atmosphere of a terrestrial-based Type 1 civilization would still require planetary cooling mechanisms.
Ocean acidification continues increasing, soon eliminating the base of the marine food chain, and the main source of protein for much of the world's human population.
To be useful, a geoengineering program should increase bio-uptake of CO2 in the oceans, driving up the pH. This was tried in a small experiment scattering iron-containing dust, but the results were strangely confiscated and suppressed, and implausible consequences published instead. I would like to know more about the whole event, but it is hard to find out anything.
The Atlantic ocean gets a big periodic influx of iron dust from winds off the Sahara, but the Pacific doesn't.
- Question over who holds the dial (Russia's ok with some warming, India not so much) can easily lead to nuclear war.
- Just telling people "we're considering pumping atmosphere with a gas that causes acid rains in order to cool the planet" makes them reevaluate how serious of a problem climate change is.
So now life is imitates the movies (I need more popcorn!!)
Biospheres are complex, potentially chaotic, systems.
Consider a much-less complex, less-likely chaotic, system: a company. You reduce revenues 1%. As a result, do all other line items fall by 1%? Of course not. For some businesses, if you reduce revenues by even 10% fast enough, it kills the beast.
see: Mercury vs Neptune
Of course by then we've mastered FTL so no need.
We can block the sun out or shoot ourselves to Mars, but apparently can't pass a law on the consumption of oil
Geoengineering requires no other change on anyone's part. Except for the funding (which could fit into any government budget with little notice), nothing changes for most people.
Perhaps the United States and other rich countries could subsidize Peru and friends. The political cost for that will be very high.
But look, we flattened the curve!