Au contraire, climate change will not pose an existential risk within the next 30 years. The chance of that happening is pretty much nil and no one serious argues otherwise. Even in 100 years, there could be much suffering and dislocations, but it still most likely won't be an existential risk to all of humanity.
There is a non-negligible possibility that AGI will be invented in 30 years. Many AI experts agree on that. A number of experts also believe that its invention could be highly beneficial or catastrophic, depending on its form and our preparation.
With cost-benefit analysis based on the best knowledge we have weighed by probabilities, it is clear that AGI risks are more substantial and worth at least as much investment as climate change. The current funding for AI Safety Research is not even 1/10th, perhaps less than 1/100th, of climate change funding. Inaction is also an action.
If you do not trust intelligent domain experts, and also intelligent non-experts with almost no conflict of interests like Bill Gates and Stephen Hawking, then please let us know which source(s) of knowledge we should rely on instead.
Note: I believe we should fund both. A certain but slow train wreck and an uncertain but even more catastrophic and possibly speedier train wreck are both worth preventing.