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Narrator: There’s a new class of chemical compounds

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impacting the Earth's ozone layer and raising concerns among some scientists,

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but a new NASA analysis indicates

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stratospheric ozone could actually be impacted more by

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climate change and the continued release of already-banned chemicals.

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The Earth’s ozone hole is showing signs of recovery,

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decades after the landmark agreement called the Montreal Protocol

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that banned many chemical compounds harmful to the ozone layer.

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Liang: So we know the Montreal Protocol was a huge success.

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This was signed in the late 1980s when scientists and policy makers

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from around the world gathered together to try to save the ozone layer.

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Strahan: The chemicals they regulated persist in the atmosphere

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for many decades, they thinned the ozone layer and created a seasonal hole over Antarctica.

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They basically take away part of our planet’s natural sunscreen,

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and that increases the risk of skin cancer and damage to plants.

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Narrator:Scientists have projected the ozone hole could disappear almost completely

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by about 2075, but several factors could delay that recovery.

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Liang: There are some industrial compounds that were not banned

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by the Montreal Protocol, but as they enter the atmosphere, they will also

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hurt the ozone layer.

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Strahan: But the unregulated compounds have a short lifespan in the atmosphere

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than the chlorofluorocarbons that were originally banned, so they have a short-lived impact on ozone,

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and we don’t think they’ll delay recovery by more than a few years.

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Liang: We projected by 2050 more than

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half of ozone-destroying compounds in the atmosphere will come from

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long-lived substances banned by the Protocol.

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Narrator:Because these compounds stay in the air for such a long time compared to the

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unregulated short-lived compounds, they will have a disproportionate and lingering

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impact on ozone, so any non-compliance with the Protocol

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can have significant consequences.

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Strahan: And the really big uncertainty in ozone-layer recovery is climate change.

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There are many naturally produced ozone-depleting substances that are emitted by the oceans,

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and as the oceans continue to warm due to climate change,

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those emissions will increase, and that will further delay ozone recovery.

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Narrator:Scientists want to better understand how climate change will affect ozone recovery.

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Liang: This is a hard problem.

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As a scientific community we need to work on this major issue.

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We now have a powerful new tool to simulate atmosphere and its interaction

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with land and ocean, to study this issue. And that’s what we’re going to do.

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