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The average air conditioning unit in American homes releases about two tons of carbon dioxide each year. About two thirds of American homes have air conditioners, meaning that about 100 million tons of carbon dioxide are released in total. 

A/C has mainly been an American and Western luxury good until recently. About 5 percent of India's 1.25 billion people had A/C unit in 2011. The numbers are also on the rise in Mexico and China. As the prices drop and the demand grows in developing countries, a new estimate suggests that 700 million air conditioners are expected to be installed by 2030, and 1.6 billion by 2050.

How will that effect greenhouse gas emissions? It's like several new countries popping up around the world. 

Energy policy leaders are meeting today at the 7th Clean Energy Ministerial to discus how to lessen the climate impact from air conditioning.  Durwood Zaelke is there now. He's president of the Institute for Governance and Sustainable Development.