<P> Reductions of up to 70 percent in the ozone column observed in the austral ( southern hemispheric ) spring over Antarctica and first reported in 1985 ( Farman et al . ) are continuing . Antarctic total column ozone in September and October have continued to be 40 -- 50 percent lower than pre-ozone - hole values since the 1990s . A gradual trend toward `` healing '' was reported in 2016 . In 2017 , NASA announced that the ozone hole was the weakest since 1988 because of warm stratospheric conditions . It is expected to recover around 2070 . </P>
where was it first discovered that the earth 's ozone layer was being depleted
in the austral ( southern hemispheric ) spring over Antarctica