PBS News Hour

JOHN YANG

It's one of the great environmental success stories of our time. Scientists say that a 35-year-old agreement has resulted in the steady and promising recovery of the earth's ozone layer. Located in the stratosphere about 10 to 25 miles above the earth's surface, the ozone layer is a critical protective shield protecting the -- blocking rather the sun's harmful ultraviolet radiation. William Brangham has more.

WILLIAM BRANGHAM

Back in 1987, after scientists discovered a dangerous thinning of the ozone layer, 198 countries signed the Montreal Protocol, which largely phased out the use of substances that damaged fat protective barrier like chemicals used in aerosols or refrigeration. Now, 35 years later, a recent assessment by the UN shows it is steadily recovering. In fact, much of the ozone layer is on pace for nearly full recovery by the year 2040. Joining us now is Dr. Paul A. Newman. He's chief scientist for Earth Sciences at NASA's Goddard Space Flight Center and co-chair of the assessment panel that documented the ozone's recovery. Before we talk about the recovery can you just remind us why we care about the ozone layer what benefits it provides to us humans and life down here on Earth? PAUL A. NEWMAN, Co-Chair,

Panel To The Montreal Protocol

Sure. Ozone is three atoms of oxygen and most of it is located many miles above our heads. It screens harmful solar ultraviolet radiation. Ultraviolet radiation can break the bonds of biologically active molecules that can lead to things like skin cancer and cataracts. A healthy ozone layer is necessary for life on Earth.

WILLIAM BRANGHAM

And so were we seeing some of those impacts as the ozone thinned over the years?

PAUL NEWMAN

We saw a pretty good well, actually a very strong depletion of ozone over Antarctica. Over the rest of the year's surface we saw thinning of a few percent which is not a terribly big deal because the Montreal Protocol captured the problem with ozone depletion and they acted to curtail the production and consumption of chlorofluorocarbons and other ozone depleting substances. So the problem over most of the year didn't get too bad.

WILLIAM BRANGHAM

There has been this steady evidence that it looks like the protocol worked as intended and now this most recent report that you were a part of. It's really tremendous news. I wonder what is the reaction you've been hearing in the scientific community?

PAUL NEWMAN

I think the scientific community has been pretty aware of the progress of things. But to see it all comprehensively to know that emissions of ozone depleting substances are declining to know that levels of these ozone depleting substances are going down we see methane, CO2, N2O that continue to go up but ozone depleting substances are going down. And now we see the increase of ozone in the southern Midlatitudes and the tropics in the northern Midlatitude. This is good news for the scientific community and for the Earth as a whole.

WILLIAM BRANGHAM

Well, how rare it is we get to say that in this world today. What kind of tangible impacts? You mentioned some of them that it might be a reduction in skin cancer. Are there other tangible impacts for a repaired ozone layer for us?

PAUL NEWMAN

Sure. Besides the health effects for humans. Crop yields. Crops are damaged by UV radiation. Materials are actually degraded by UV radiation. Plants, other phytoplankton, for example are affected by UV radiation. So this is overall a very good story for life at the Earth's surface. As you might know, we use UV to sterilize, for example, medical instruments. Getting UV down here at the surface is not a good thing and to see the ozone recovering is a very nice thing to know about.

WILLIAM BRANGHAM

Is that all good news in this report or is there anything in there that is troubling to you?

PAUL NEWMAN

There's a number of things we continue to worry about. We need to continue to monitor the ozone layer. There are new technologies coming on, for example, new supersonic aircraft. One would hope that they could be designed and flown in an ozone friendly manner. There's also more rocket launches that are going on. They deposit material into the stratosphere. We're worried about the potential impacts of large numbers of rocket launches and actually the satellites, as they reenter the Earth's atmosphere, what do they do to the ozone layer. So we worry about these things. We also worry about rogue production of ozone depleting substances. In fact, that happened in the last few years with Chlorofluorocarbon 11. But the Chinese government acted to curtail that and it's come back down to a more normal level. So we worry about it, we monitor it, and hopefully countries continue to abide by the Montreal Protocol.

WILLIAM BRANGHAM

My understanding is that targeting these particular chemicals was in somewhat easier because there were safer alternatives available for industry. The other big emissions that we're trying to stop, obviously, is carbon and methane, as you were describing, which drive climate change. Targeting those emissions obviously is a much steeper climb for humanity, right?

PAUL NEWMAN

It very much is a steep climb. People have gas stoves, they have automobiles burning fuels. We have power plants burning coal. These are all CO2 of carbon dioxide producers And solving the problem of carbon emissions will be very difficult. That doesn't mean it can't be done. Every nation on the earth has signed on to the Montreal protocol in all the political differences, national differences, every nation has identified the ozone layer as something that needs to be watched and preserved. They've all signed on to the Montreal protocol. I'm actually optimistic that something will be done eventually about climate and we will cure this environmental problem.

WILLIAM BRANGHAM

All right, Dr. Paul Newman at NASA's Goddard Space Flight Center. Thank you so much for being here.

PAUL NEWMAN

Thank you for having me.