Emissions trading market in pollution-licenses is more widely applicable than the market in emission-licenses. The international community began the long process towards building effective international and domestic measures to tackle GHG emissions (carbon dioxide, methane, nitrous oxide, hydroflurocarbons, perfluorocarbons, sulphur hexafluoride) in response to the increasing assertions that global warming is happening due to man-made emissions and the uncertainty over its likely consequences. That process began in Rio in 1992, when 160 countries agreed the UN Framework Convention on Climate Change (UNFCCC). The UNFCCC is, as its title suggests, simply a framework; the necessary detail was left to be settled by the
Sulfur hexafluoride the gas's large molar mass. Unlike helium, which has a molar mass of about 4 grams/mol and gives the voice a childish and a "chipmunk like" quality, has a molar mass of about 146 g/mol, and the speed of sound through the gas is about 134 m/s at room temperature, giving the voice a "demonic" quality when is inhaled. For comparison, the molar mass of air, which is about 80% nitrogen and 20% oxygen, is approximately 30 g/mol which leads to a speed of sound of 343 m/s. Sulfur hexafluoride has an anesthetic potency slightly lower than nitrous oxide. Sulfur