Carbon dioxide surface, warming the surface and the lower atmosphere. Less energy reaches the upper atmosphere, which is therefore cooler because of this absorption. Increases in atmospheric concentrations of and other long-lived greenhouse gases such as methane, nitrous oxide and ozone have correspondingly strengthened their absorption and emission of infrared radiation, causing the rise in average global temperature since the mid-20th century. Carbon dioxide is of greatest concern because it exerts a larger overall warming influence than all of these other gases combined and because it has a long atmospheric lifetime (hundreds to thousands of years). Not only do increasing carbon dioxide
Sulfur hexafluoride circuit breaker Sulfur hexafluoride circuit breaker Sulfur hexafluoride circuit breakers protect electrical power stations and distribution systems by interrupting electric currents, when tripped by a protective relay. Instead of oil, air, or a vacuum, a sulfur hexafluoride circuit breaker uses sulfur hexafluoride (SF) gas to cool and quench the arc on opening a circuit. Advantages over other media include lower operating noise and no emission of hot gases, and relatively low maintenance. Developed in the 1950s and onward, SF circuit breakers are widely used in electrical grids at transmission voltages up to 800 kV, as generator circuit breakers, and in distribution systems