Figure out a way to breed whales - lots of them... 1 whale = thousands of trees... though the real cause is they help increase phytoplankton... if we could make boats that somehow release the same stuff the "whale pump" does while they travel, perhaps we could raise phytoplankton numbers... or some other mechanism to do the same...
1. Deal with it being not only hotter, but also there being enough CO2 in the air to significantly reduce human intellect
2. Kill 97% of humans (or whatever percentage, as that’s not what the headline actually means)
3. Geo-engineering to deal with the heat, but keeping all the cognitive impact of the CO2
4. Invent something to suck CO2 out of the air so cheaply that it can be cracked into the carbon-rich fuels people want to burn for a lower cost than just digging it out of the ground