When the Montreal Protocol was signalize in 1987 the major fear were CFC ( CFCs ) , and the Protocol order the production of most of these must be cut back to 25 % of 1986 levels by 1994 , with production end two class later . Other particle , considered less life-threatening , were given farseeing meter - lines .
Carbon tetrachloride , CCl4 , was give its own department . Its habit in refrigeration and lava lamps was banned . However , CCl4is still used inscientific instrumentsand to make other , less prejudicial refrigerant .
Nevertheless , the quantity of CCl4 in the atmosphere were expected to be dropping , along with all the other chemical substance mostly banish for more than 20 year . Instead , NASA has found signs worldwide emissions remain at 39,000 tonnes a year , 30 % of their pre - treaty level .
" We are not supposed to be seeing this at all , " says Dr Qing Liang of the Goddard Space Flight Center . " It is now apparent there are either unidentified industrial outflow , large emissions from contaminated sites , or unknown CCl4sources . "
The good news is that the Protocol has been so successful withmost of the other chemicalsit targeted that the overall trend is down , leading to a slow restoration of the ozone level . Nevertheless , in 2008 11 % of the chlorine ripping the ozone layer asunder come from CCl4 , and that percentage will rise unless the source can be found and stopped .
Although persistent in the atmosphere CCl4is finally put down by radiation and chemical reaction . For some time atmospheric scientists debated whether it was being removed more slowly than models suggest , or still being emitted . However , inGeophysical Research LettersLiang and her colleagues used the difference in concentrations between the cerebral hemisphere to demo that both are the guinea pig . CCl4stays in the ambiance 40 % longer than was thought , as well as being pass off at pace we can not account for .
Goddard ’s Dr Paul Newman warns against complacence . " citizenry think the emissions of ozone - depleting substances have arrest because of the Montreal Protocol , " he say . " Unfortunately , there is still a major source of CCl4out in the world . "
Ozone depletion isdamaging marine lifein the Southern Ocean and create lethalskin Cancer the Crab in ChileIt is also a contribute factor tolocal climate change around Antarctica . CCl4also has1400 timesthe atmospheric warming issue , molecule for molecule , of C dioxide .
