I've read this entire thread so far.
The most insightful thing in it was:
Geoengineering could bring the temperature down but not in the same way we are raising it. Our goal is not to bring the temperature down. Our goal is to keep things like they were. An Earth with less incoming radiation, more co2, and the same temperature is still a completely different Earth.
The geoengineering fixes in question, are unlikely to work.
Take converting CO2 back to fuel.
Think of all the air you need to push through your reactor to do that. And then all the energy needed to convert that CO2 into fuel. And then add the fact that if you convert it into fuel rather than burying it you're releasing the CO2 right back into the atmosphere.
So even if the process is carbon neutral, with current technology setting up the infrastructure certainly isn't. This technology would be viable in a fantasy land with ample zero-carbon energy production, but it's not going to magically save us in the next 10-20 years.
Take throwing salt into the atmosphere:
There is the problem that even if the temperature is reduced, CO2 stays the same. The climate can still be different despite the temperature being the same.
Then there is the global conflict such geoengineering could spark. What if the temperature can only be reduced if Russia's or The United State's crops have to fail for one year?
Where is the clear proof that this actually works as intended? Then there is the simple fact that you're throwing more water in with the salt particles, water vapor is a greenhouse gas.
The take ocean greening
The article itself debunks it and points to another article:
http://news.bbc.co.uk/2/hi/7959570.stmI'd also like to add that iron ore isn't free and that it would probably sink to the bottom, requiring us to keep adding it to the ocean for eternity.
I believe that we'll totally wreck this planet's ecosystems and climate. The glaciers will melt, the sea levels will rise, millions will lose their homes, incomes and food stability. But we'll probably survive it. We'll just be living in a different planet earth.
And one day, the history books will have a chapter on the time we could have saved millions of species of animals and plants, and prevented human suffering equivalent to many world wars, but instead we chose to drive gas guzzlers, build tanks and bombs and destroy ourselves in the process.