Air-conditioning gases are regulated primarily though a 1987 treaty called the Montreal Protocol, created to protect the ozone layer. It has reduced damage to that vital shield, which blocks cancer-causing ultraviolet rays, by mandating the use of progressively more benign gases. The oldest CFC coolants, which are highly damaging to the ozone layer, have been largely eliminated from use; and the newest ones, used widely in industrialized nations, have little or no effect on it.But these gases have an impact the ozone treaty largely ignores. Pound for pound, they contribute to global warming thousands of times more than does carbon dioxide, the standard greenhouse gas.The leading scientists in the field have just calculated that if all the equipment entering the world market uses the newest gases currently employed in air-conditioners, up to 27 percent of all global warming will be attributable to those gases by 2050.
In Rising Use of Air-Conditioning, Hard Choices – NYTimes.com