Generally speaking these schemes aren't science, they are engineering. Science itself can't really be irresponsible, but you can use the results of science irresponsibly. For example, the Haber process can be used to make explosives or fertilzer, but science itself isn't really irresponsible, it's a way of enabling us to understand the world around us and the universe. Science allows us to understand what is causing global warming and ways to prevent it. Economics, or for most part simple accounting, shows us the most practical, cost effective methods (which are almost always simply reducing CO2 and methane emissions).

Most grand engineering schemes to stop climate change are impractical. Many are just silly. Seeding parts of the ocean to promote plankton growth is not and may be cost effective. A considerable amount of responsible study has been done to try to ensure that no unexpected unwanted results will occur as a result of it. While we can't be completely certain nothing untoward will happen, it's a matter of taking a small risk to mitigate a certain danger.