Air-Conditioning

Why? I’m in Orlando right now – but it’s the same in Dubai or Singapore – and I’m wearing a jacket. I need to take it off when I’m outdoors because of the baking (or steaming) heat but I need it to go indoors because of the ferocious air-con. How does that work? What is the contribution to global-warming made by systems chilling air to a level which requires people to wear extra clothes indoors?