Climate tech doesn't fit the YC model (and tech VC model in general) at all. Projects are too unpredictable and hard to judge. They need many orders of magnitude greater investment to get started than a seed fund can provide. And tech VCs can't really contribute any business expertise in the area.
It's a lot easier to fund a hundred B2B SaaS apps and wait for a handful of them to return 1000x in 5 years.