• Kyodo

  • SHARE

A research team in the United States said Tuesday they have found clear evidence that the ozone layer is on the way to recovery and that a worldwide reduction in ozone-depleting chemicals is having the desired effect.

The joint research effort by the U.S. National Aeronautics and Space Administration and the University of Alabama found that ozone depletion in the upper stratosphere has slowed since 1997, a decade after the Montreal Protocol was ratified in 1987 to phase out the production and consumption of cholorofluorocarbon (CFC) and other ozone-depleting substances.

“This is the beginning of a recovery of the ozone layer,” said Mike Newchurch, an associate professor at the university and the study’s lead scientist.

But he also cautioned, “Ozone is still decreasing, but just not as fast. We are still decades away from total ozone recovery.”

The fall in the rate of ozone depletion is consistent with the decline in the amount of man-made chorine and bromine-containing chemicals in the atmosphere, according to measurements taken from satellites, in the air and on the ground, the team said.

The depletion of the ozone layer, which protects the Earth’s surface from the sun’s ultraviolet rays, raised concern that skin cancer and cataracts in humans would increase, apart from harm being done to animals and plants. The thinning of the layer causes the ozone hole that occurs each spring over Antarctica.

The researchers analyzed data from satellites and international ground stations, including one in Tsukuba, Ibaraki Prefecture, between 1979 and early this year.

While the ozone layer in the upper stratosphere — between 35 km and 45 km above ground level — depleted by an average of 8 percent per decade between 1979 and 1996, the depletion pace fell to below four percent in a 10-year simulation from 1997, the team said.

However, it will take 40 to 60 years for the ozone layer to fully recover to its initial condition due to the lingering impact of CFCs and other harmful chemicals that have been emitted into the atmosphere.

In 2000, the ozone hole over Antarctica was the largest ever.