Here's encouraging news about a reduced environmental risk: The ozone layer above our planet, a vital atmospheric shield against harmful ultraviolet sunlight, continues to slowly repair itself, a new United Nations (UN) study says. In 1987, leaders from around the world signed an agreement in Montreal to phase out chemicals that were creating a continent-sized hole in the ozone layer above Antarctica.

Ozone-depleting substances were widely used in refrigerators, air conditioners, electronics, firefighting, aerosols, medicine and agriculture. Ultraviolet radiation from the sun can cause skin cancer and eye damage, inhibit crop growth, affect fish and reduce the ability of plants to store planet-warming carbon dioxide. Without the absorbent layer in the stratosphere 10 to 30 miles above Earth, full-strength solar radiation would make it impossible for life to thrive here. Without ozone, the sun's intense UV rays would sterilize Earth's surface.

Ozone loss is most dramatic over the South Pole, scientists discovered in the 1980s. The hole size peaked in 2006 at an astonishing 10.6 million square miles. In a report last week to the UN, scientists meeting in Denver said the protective layer could recover across most of the globe by the 2040s, and by 2066 in Antarctica (site of the South Pole). UN official Meg Seki, an environmental scientist from Japan, calls the findings "fantastic news."

The turnaround shows that countries can unite to solve environmental problems and combat climate change, the UN report notes. By 2030, two million cases of skin cancer will be avoided because of the thickening ozone shield, the new study estimates. "The recovery of the ozone layer is on track," says David Fahey, director of the National Oceanic and Atmospheric Administration's Chemical Sciences Laboratory and a co-chairman of the UN assessment panel. "The peak destruction of the global ozone layer is behind us."

UN official says: "More than 99 percent of ozone-depleting substances have been phased out and the ozone layer is on a path to recovery." -- Meg Seki, executive secretary of the Ozone Secretariat

Expert says: "Ozone action sets a precedent for climate action. Our success in phasing out ozone-eating chemicals shows us what can and must be done — as a matter of urgency — to transition away from fossil fuels, reduce greenhouse gases and so limit temperature increase." – Professor Petteri Taalas of Finland, World Meteorological Organization secretary general

NASA scientist says: "Over time, steady progress is being made, and the hole is getting smaller. . . . Overall, we see it decreasing through the past two decades." -- Paul Newman, Earth sciences chief at the Goddard Space Flight Center (see video below)