(I'm warning you now, my english is bad and my explanation are usually a bit confuse)
CO2 concentration as been increasing exponencialy since industrial era and CO2 is one of the gases responsible for greenhouse effect.
Stronger greenhouse effect leads to higher atmosphere temperature, wich can have more water vapor (the biggest responsible for greenhouse effect). So, +CO2 -> +temperature -> +H20 -> + temperature...
Equator is much more heated than poles by increasing of the atmosphere temperature. This will increase the flux of energy from the equator to the poles aka haddley circulation. Haddley circulation makes the air rise in the equator (forming clouds and rain) and fall at latitudes of 30º (forming desert regions). The strengthening of this circulation result in a wider tropical belt (region where the air rises) leading desert regions to stay above latitudes of 30º.
Another transporter of energy from the equator to the poles are the hurricanes that with strenghening of the poleward circulation are much more likely to appear.
Basically this is just a climate change and i believe that we do not need to get much alarmed, our country might be flooded by the sea level rise (I'm watching you nederlands) or be devastated by desertification (like the mediterranean countries). But this will happen gradually and a lot of things may change before, even without the man having to do anything.
ps: honestly i didn't read the OP, i'm just exposing my knowledgement into the discusion.
