That's wishful thinking. Humanity was not sure how to solve x, until it was solved. It happened all the time. For example, Gödel or Einstein work were major breakthrough, and we didn't wait AGI to solve this.
I'm not saying AGI is useless. On the contrary, I think it could be extremely useful. But we need to act very quickly to limit the negative consequences of climate change. Waiting for an hypothetical AGI would be foolish.
Taking off my devil's advocate hat (horns?)... I agree. Even if we use that logic to punt some problems to AGI -- e.g. solve near-light speed travel, or space-based solar power -- we cannot afford to sit idly by while climate change destroys the planet.