Sustainable automotive air conditioning is the subject of a debate – also known as the Cool War – about the next-generation refrigerant in car air conditioning. An advocacy group, The Alliance for CO2 Solutions, supports the uptake of carbon dioxide (CO2) as a refrigerant in passenger cars, and the chemical industry is developing new chemical blends. The Alliance propositions the car industry to replace more unsustainable chemical substances with the natural refrigerant like carbon dioxide (CO2, R744/ R-744) in car cooling and heating. They claim that this would lead to 10% fewer emissions from new cars, potentially reducing global greenhouse gas emissions by 1%. If CO2 technology is applied in other sectors, such as commercial and industrial refrigeration, heat pumps for water heating etc., they claim it may save up to 3% of the world's greenhouse gases. Opponents of the advocacy group claim that CO2 refrigeration technology is not cost-efficient nor safe, and support the development of new chemical refrigerant blends instead. Background A debate had emanated from the decision of the European Union to phase out the current high global warming refrigerant HFC-134a in car air conditioning from January 2011 onwards. To comply with the legislation, carmakers have to decide on new refrigerants as they typically need 3 to 4 years to develop and introduce a new car platform including the new air conditioning system. Arguments Arguments for CO2 The Alliance for CO2 Solutions and its supporters agree that the refrigerant CO2 is: More environmentally friendly with the lowest global warming potential (GWP) of all currently used and proposed refrigerants. CO2 does not deplete the ozone layer. Because the carbon dioxide used in car air conditioning is a recycled industrial waste product, it is an environmentally neutral solution. The Alliance claims that using a CO2-based air conditioning system will reduce total car emissions by 10%, thereby sparing the planet 1% of total greenhouse gases. More technically ready because CO2 models have been developed and tested in all climates, being now ready for mass production. They are faster to heat and cool a car, and show superior performance in over 90% of all driving conditions. More cost-efficient because as a refrigerant itself, CO2 is cheap and worldwide available. The servicing of CO2 systems will be less costly and less complicated than that of present systems. For the consumer, the total cost of ownership is lowest with CO2 as it will