If they have a "fixing climate change" solution, they go to one of the dozens of incubators and funds and government innovation grant programmes that specialise

If they have a "fixing climate change" solution, they go to one of the dozens of incubators and funds and government innovation grant programmes that specialise in funding climate change-related innovation, both practical and moonshot If their ideas involve space travel, their funding options are probably restricted to NASA (or ESA or the local equivalent) who will expect there to be a consortium of partners with legitimate relevant experience involved.