Doesn't that mean we're facing unintended consequences whether we do something or we don't?
(I'm not saying that this has to be the solution -- after all, there may be some consequences we determine beforehand that put it out of the running. But worrying about the dangers of a megascale geoengineering project just because it is a megascale geoengineering project, would seem to require our current path to be a known status quo, rather than just another megascale geoengineering project.)
I was just looking for smaller scale iron spreading projects, and apparently this was already done, with mostly positive effects, wikipedia seems to have good info: https://en.wikipedia.org/wiki/Iron_fertilization
There is also fertilization from natural sources of iron and other minerals that we can observe - the sands of Sahara that fly to the Atlantic and the Amazon basin, some vulcanic eruptions had high iron content, etc.
I suppose slowly increasing the scale of iron fertilization experiments could be a good direction.
But you don't understand. If we do a large scale climate control project:
1) we will make some things worse (just like returning to pre-industrial climate would). From roads in France, life in Eastern Europe/Russia, destruction of trade through the "Northwest passage", ... Some 100's of people will freeze to death in Brussels, London and Paris and most of Western Europe every winter once again if climate return to pre-industrial levels.
I wonder if the few thousand I-needed-heat-so-got-a-fire-I-fucked-it-up-and-got-carbon-monoxide-poisoning deaths will return too. On the one hand we don't use coal anymore. On the other hand with enough stupidity (and leaving something bad on top of it) you can still get even an electric heater to give you carbon monoxide poisoning.
2) it's a project done by someone. So someone will have responsibility. Whoever actually acts will be vilified endlessly for the inevitable negative consequences. Such as those people freezing to death.
3) it will have unforeseen consequences. In other words: despite climate "proof" implying models are complete ... they aren't. There will be big surprises.
4) Nature is good and great and Gaia will save us! We are killing people's belief in nature and/or God by fixing problems by interfering in Nature on a large scale. They will fight any and all attempts to interfere at all just for that reason.
5) it won't stop most of the changes underway. We are in an interglacial. Temperature is rising, just way too fast. But it should be rising. Getting CO2 to pre-industrial levels leaves most or all of the changes we've already seen intact. In a practical example, that means every cubic meter a glacier loses is gone until the next ice age. Ice sheets will grow back more, but not to the levels 100 years ago. Pre-industrial climate generally won't make them grow back.
6) what's to stop some countries from using Climate change as a weapon if they control climate change infrastructure?
So it doesn't really matter that we know of many ways to influence and take control of the climate, and that it's becoming ever clearer we want to do so. The problems are political, even psychological, not scientific (although more research into it would help with more options)
The method of pilot projects that are then scaled up is very mature, well understood, and universally applied. It works, way, way, way better than thinking hard.
While there is some truth in your statement, a lot of unintended consequences only show up after considerable time and at scale, and then only if you know where to look.
The original steam engines standing in as a pilot project didn‘t do much to the atmosphere. Billions of combustion engines did.
The great insect apocalypse went almost unnoticed until two decades in and an order of magnitude of change.
Some things are nonlinear (that's kind of what "second order" means). With a pilot project, it's easy to observe things that are O(n), but not so easy to observe things that are O(n^2).
So sure, do a pilot project. Let's make sure that even the first-order stuff works the way we expect. But also think hard about second-order effects. And even after that, continually watch for un-thought-of second-order effects emerging as (and after) you roll it out.
It's not just that it's a megascale project, it's that it's a potentially unstoppable megascale project.
Starting a potentially unstoppable chemical chain reaction to stop another unstoppable chemical chain reaction just seems a bit... dumb to me, you know?
If we're going to be doing megascale engineering to mitigate our past mistakes with greenhouse gasses we should look towards using something like space-based lenses or mirrors to lower the amount of energy that the Earth receives. We can always turn them off if we decide that we want to.
Space-based mirrors are about the worst imaginable idea. Stratospheric sulfur is almost as bad.
Neither one gets any acid out of the oceans, and instead allows their acidity to continue rising until the entire ocean ecosystem collapses. Then, billions go hungry.
Meanwhile, the moment these shading projects hiccup, e.g. from mass starvation induced global thermonuclear war, temperatures skyrocket to where they would have been, but much more quickly. And then of course there is the starvation and war.
What "unstoppable chemical chain reaction" are you imagining? The exact moment you stop spreading olivine powder, the chemical reaction process stops dead.
Why do billions go hungry? Serious question. Do billions really get the majority of their calories from seafood? I’m probably biased since I won’t eat any seafood, so I’m having a hard time imagining that many people subsisting off of it.
Yes, in many poor coastal areas ( like in Africa and Asia, but not only; many European coastal cities also fall into this) fishing is a main source of employment and calories for the population. Even if you replace the calorie intake, you can't easily replace the employment, so they can't pay for that new food.
There's no meaningful amount of employment in Europe from fishing.
European fishing is done with mega trawlers operated by tiny crews.
It's just a political football generally used by nationalists to further their agenda.
You could ban industrial fishing in the UK or France or Spain and it would have no effect on their economies, just personal tragedy for a few thousand.
For example in the UK, out of 66,000,000 people a tiny 12,000 are professional fishers.
Food production already uses essentially all arable land on the globe. Changing environmental conditions are expected to significantly reduce the amount of arable land fit for agricultural use.
(I'm not saying that this has to be the solution -- after all, there may be some consequences we determine beforehand that put it out of the running. But worrying about the dangers of a megascale geoengineering project just because it is a megascale geoengineering project, would seem to require our current path to be a known status quo, rather than just another megascale geoengineering project.)