The whole water vapor thing has the nice effect that it should be reasonably reversable, and if it works might buy us a little time.
Time to do what? That seems to be reasonably straight forward at this point, the problem is the political will and the costs involved.
- Step 1. Build Gen 3+ PWR Reactors to replace all coal power stations currently in service. These are commercial designs that can be built today on a technology that we have 50+ years experience with in a commercial capacity, not some pie-in-the-sky Gen 4 tech that hasn't really succeeded past the research reactor phase
- Step 2. Build devices to concentrate and remove CO2 from seawater. We have already built research devices that can do this using a series of membranes to concentrate the dissolved CO2 and then using available industrial filters to remove the CO2 from the water. Can this be done on a large enough scale? that is a current research topic, but worth pursuing as the seas are already doing a fine job of removing the CO2 from the atmosphere where the warming effect is, rather than fixing the atmosphere and releasing all the stored CO2 in the ocean again.
- Step 3. Encourage cattle farmers to change their habits to increase grass growth. There's plenty of available desert in Australia, and no shortage of livestock there either, no doubt there are other suitable continents as well.
- Step 4. Subsidise electric cars and do a cash-for-guzzlers scheme to reduce inefficient cars on our roads
There are likely other little things we can do that will all add up, but that would make a fairly big dent right there.