Total ozone over Antarctica on September 18 ( NASA )

EPA Administrator Lisa Jackson heaped praise on this landmark environmental treaty at an event celebrating the anniversary:

The Montreal Protocol has been called the most successful international environmental treaty ever – and with good reason. In the 25 years since it was first signed, the entire global community has committed to stop using and producing nearly 100 of the most ozone-damaging chemicals.

197 countries are signatories to the Protocol and scientists say the ozone layer - while thinner than decades ago - is showing early signs of healing.

Via NASA: “The images above show the Antarctic ozone hole on September 16 in the years 1979, 1987, 2006, and 2011.”

“The Antarctic hole is stabilizing and may be slowly recovering,” said NASA scientist Pawan Bhartia.

The motivation for restoring the ozone layer to its natural state is that depletion allows more of the sun’s damaging ultraviolet radiation to reach the Earth’s surface, increasing the risk of sunburn, skin cancer and eye damage.

“[The Montreal Protocol] is projected to ultimately prevent 295 million cases of non-melanoma skin cancer and more than 22 million cases of cataracts,” Jackson said.

NASA conducted an interesting experiment: What if the international community hadn’t undertaken the challenge of phasing out ozone depleting substances?

Via NASA: “These maps show computer model predictions of the state of the ozone layer in 2064 without (above left) and with (above right) the effects of international agreements to curb ozone-destroying chemicals in the 1980s and 90s.”

The year is 2065. Nearly two-thirds of Earth’s ozone is gone—not just over the poles, but everywhere. The infamous ozone hole over Antarctica, first discovered in the 1980s, is a year-round fixture, with a twin over the North Pole. The ultraviolet (UV) radiation falling on mid-latitude cities like Washington, D.C., is strong enough to cause sunburn in just five minutes. DNA-mutating UV radiation is up more than 500 percent, with likely harmful effects on plants, animals, and human skin cancer rates.

The Montreal Protocol may have saved the world from a skin blistering, cancer-plagued future.