Historical clue formulations

• Absorber of UV light — 2026-04-08
• Layer wrapping Earth — 2025-11-19
• Global protection — 2024-07-21
• What offers worldwide protection? — 2024-02-07
• Stratosphere layer with a "hole" — 2023-10-16
• Kind of layer — 2022-11-10
• Vital part of the stratosphere's protective layer — 2022-05-16
• ___-friendly (ecolabel) — 2021-11-13
• Globe coverer — 2021-10-19
• ___ hole — 2021-04-11
• It's made of three oxygen atoms — 2019-10-29
• It's a gas — 2019-06-08
• Another name for O3 (as appropriate to 17-, 25-, 44- and 58-Across?) — 2018-12-31
• Layer of the upper atmosphere — 2018-03-19
• O3 — 2018-03-06
• ___ hole — 2017-12-29
• Absorber of UV rays — 2017-11-21
• Worry of stratospheric proportions — 2017-02-12
• A greenhouse gas — 2016-10-05
• Layer in global warming discussions — 2015-10-12
• Part of the atmosphere depleted by CFCs — 2015-06-01
• UV light blocker — 2015-04-26
• Layer in the stratosphere — 2015-04-07
• Form of 10-Down — 2014-10-22
• Triatomic oxygen molecule — 2014-04-13
• O-O-O — 2012-07-15
• Upper atmosphere layer — 2011-04-19
• Thunderstorm product — 2010-02-12
• Form of oxygen with a sharp odor — 2009-11-10
• Radiation reducer — 2009-07-19
• Ultraviolet blocker — 2009-04-19
• O3 — 2009-01-01
• Gas with a penetrating odor — 2008-12-19
• A high flier may fly in it — 2008-01-23
• Ultraviolet filter — 2007-09-16
• Gas in a layer — 2007-03-20
• Ultraviolet light filter — 2006-10-14
• Kind of layer protecting the earth — 2006-04-18
• O3 — 2005-12-26
• Atmosphere layer — 2005-03-21
• Gas in a layer — 2004-10-12
• Earth's ___ layer — 2004-06-22
• Thunderstorm residue — 2003-02-21
• Form of oxygen — 2001-12-05
• Thunderstorm product — 2001-09-15
• Ray blocker — 2001-04-29
• Ultraviolet ray blocker — 2001-01-15
• Odorous oxygen — 2000-12-05
• Kind of hole — 2000-12-02
• Layer with a hole in it — 2000-10-24