New research on the health of the ozone layer has been called “the most significant environmental success story of the 20th century,” by Michael Newchurch, an atmospheric chemist at the University of Alabama at Huntsville, according to the Christian Science Monitor.

And while Newchurch was not a part of the new study, he joined many other scientists in crediting human action as the one of the reasons for the closing of the hole in the stratosphere above Antarctica.

The ozone layer acts as sort of a sunscreen for the planet, blocking harmful ultraviolet (UV) rays from reaching the planet’s surface, with radiation that damage cells of all living organisms.

Lead author on the study that was just published in the journal Science, Susan Solomon, said “There would actually be no life on the planet’s surface if we didn’t have an ozone layer.”  Solomon is an atmospheric chemist at the Massachusetts Institute of Technology.

Scientists were worried back in 1985 when the discovery of the hole in the layer was first noted.  Researchers at the time estimated there was only about half as much ozone over their station in Antarctica than there had been decades earlier.

They found the certain chemicals reacted with atmospheric clouds and damaged the layer of ozone.  So, 1n 1987, an international treaty was signed, called the Montreal Protocol, to end the use of production of some chemicals that were causing the issue, notably chlorofluorocarbons (CFCs), commonly used in refrigerants and propellants.

Solomon said they scientists did not expect to see a rapid improvement in the hole in the ozone layer, because these CFC molecules stay in the atmosphere for quite a long time.

“Even though we have stopped producing them, what’s already there from your grandmother’s refrigerator that she got rid of in the 1970s or the hairspray that you put on in 1972, some of it is still left,” according to Solomon.

But, the new research is finding the hole has shrunk by as much as 1.5 million square miles during the month of September since the year 2000, an area about half the size of the US.  They also noted the hole opens up more slowly than in years past.

Paul Newman, chief scientist for atmospheric sciences at NASA’s Goddard Space Flight Center, who was not part of the study, said he was hesitant to give all the credit to human intervention, since there were mismatches between the study’s models and what is actually happening.

“Nature always seems to be throwing us curve balls when it comes to figuring out if things are getting better,” according to Newman.  But, he adds, if nothing had been done, approximately two-thirds of the ozone layer would have been depleted by 2065 across the globe.

Solomon adds, “It’s wonderful to see that this most untouched part of our planet that we actually did touch in a very unusual way by creating the ozone hole is going back to its original state.”