Honestly, if they choose this option, they surely will run a bunch of simulations before it, unlike the current path, when they are just randomly substracting gases from the atmosphere.

Well, they "randomly subtracted" a gas that they were previously "randomly adding". In fact, even "subtracted" is wrong - they randomly stopped adding a gas that they had been randomly adding.

They did not run a bunch of simulations before randomly adding the gas.

In addition to the likely high costs and predictable negative side-effects, one could extrapolate from the article title that climate engineering could also have unpredictable negative effects.

Making big changes to a complex system that we do not fully understand seems very dangerous to me.