Here's what I'd do if I were the king of SA: build a lot of solar (maybe 100 GW, like Mukesh Ambani in India), desalinate lots and lots of water and plant billions of trees. Saudi Arabia has about half a billion acres of desert. If you reforest only 10% of that with about 400 trees per acre (below average density, one tree per each 10'x10' square), you end up with 20 billion trees, or 2% of the global aim of one trillion trees to get us to carbon neutral. If you increase the area you reforest, and the density of the trees, it's not unthinkable you can reach 20% of the goal.<p>Sure, it's not as glitzy as a 1km tall tower, or a 100km long city, but humanity will appreciate this more.
An interesting podcast on the topic:<p><a href="https://podcasts.apple.com/gb/podcast/streetsweeper/id1564302864?i=1000518212248" rel="nofollow">https://podcasts.apple.com/gb/podcast/streetsweeper/id156430...</a><p><a href="https://podcasts.apple.com/gb/podcast/streetsweeper/id1564302864?i=1000518211708" rel="nofollow">https://podcasts.apple.com/gb/podcast/streetsweeper/id156430...</a>