So if we drastically lowered emissions and irrigated and grew plants on as much available land as possible it would both provide a cooling effect and draw down huge amounts of CO2.
We're supposed to be carbon neutral by 2050 but we are heading in the wrong direction fast. At this point I rather have nuclear war to reset everything.
If we can keep it under around 3C we may avoid that fate. This book will explain. https://itunes.apple.com/WebObjects/MZStore.woa/wa/viewBook?id=1435723767
If we see several degrees C of temperature rise then civilization would collapse with the eventual extinction of any remnant populations on a planet to hot to adapt to.