This episode of The Daily looks at how air conditioning has become both our answer to a warming planet and a major obstacle to actually tackling it. When Willis Carrier invented the first version of air conditioning in 1902 (to control the moisture content of printed documents), it suddenly made places like Las Vegas, Dallas and Houston, which had previously been almost uninhabitable, attractive places to live (often requiring an additional artificial water supply). Because energy was cheap, buildings could be inefficient: glass instead of stone, air conditioning instead of windows, and less clever architectural features like window awnings. Many people now live in these "greenhouses", which are not only very vulnerable to power outages, but also contribute to 30 per cent of greenhouse gases in the United States.