There are different types of Freon. Originally R-12 Freon was used in car air conditioning prior to 1994, but it was found that when a car emits R-12 Freon, it depletes the ozone layer. R-13A Freon is used in auto AC in cars after 1994. R-13A has insignificant ozone layer depletion potential and somewhat lower global warming potential. However, studies show that the concentration of R-13A has doubled in Earth's atmosphere between 2001 and 2004, increasing the global warming potential significantly and acid rain negligibly. The European Union has banned the use of R-13A in cars and began phasing it out of cars since 2011. R-13A is anticipated to be completely phased out in 2017 in the EU. R-1234yf is the new Freon that is safer for the environment compared to R-13A, but only specific cars can use it. The US is planning to phase out R-13A by 2020.