上一片给地球盖了保温被。这片🌍蓝色星球向导掏出防晒霜：平流层里，还藏着一件地球的防晒衣。Last leaf we tucked a heat blanket around Earth. Now 🌍 Blue Planet Guide pulls out sunscreen: hidden in the stratosphere hangs Earth's own sunscreen coat.
第 1 步：防晒衣穿在平流层Step 1: The sunscreen coat hangs in the stratosphere
先跟向导穿上它——薄薄一层臭氧，怎么挡住毒辣的紫外线。Try it on with the guide — how does a whisper-thin layer of ozone block harsh ultraviolet light?
臭氧是三个氧原子抱成团（O₃），住在平流层里。它像防晒衣一样，吸掉大部分紫外线，只放温柔的阳光下来。没有它，人人出门都会被晒伤。Ozone is three oxygen atoms hugging together (O₃), living in the stratosphere. Like a sunscreen coat, it soaks up most ultraviolet light and lets only gentle sunshine through. Without it, everyone would get sunburned outside.
防晒衣这么好，怎么听说南极破了个大洞？If the coat is so good, why is there a giant hole over the South Pole?
第 2 步：南极上空的洞Step 2: The hole over the South Pole
元凶是氟利昂：旧冰箱空调里的它跑上天，一个氯原子能吃掉上万个臭氧分子。南极又冷又有极地云，破坏最狠，所以洞开在南极上空，每年南半球春季（9–11 月）最大。The villain is CFCs: drifting up from old fridges and air conditioners, one chlorine atom can eat tens of thousands of ozone molecules. The South Pole is extra cold with polar clouds, so destruction peaks there — the hole opens over Antarctica and grows biggest every southern spring (Sep–Nov).
洞破了怎么办？总不能看着防晒衣烂掉吧。The coat is torn — surely we did not just watch it rot?
第 3 步：全世界一起补衣服Step 3: The whole world mends the coat together
1987 年，各国签了《蒙特利尔议定书》，一起禁用氟利昂。这是环保史上最成功的一次补救：臭氧减少的曲线止跌回升，洞正在缩小，预计本世纪中叶补好。看天气预报里的紫外线指数，就是防晒衣的每日体检表。In 1987, countries signed the Montreal Protocol and banned CFCs together. It is the most successful rescue in green history: the ozone-decline curve bottomed out and turned up, the hole is shrinking, and the coat should be mended by mid-century. The UV index in your weather forecast is the coat's daily checkup report.
🎮 防晒实验室（30 秒）🎮 Your turn: sunscreen lab (30 seconds)
道理讲完了。先拖滑块调臭氧厚度，看紫外线怎么变；再点自动演示，看破坏与修复；最后接 4 道防晒工单。Theory done. First drag the slider to change ozone thickness and watch UV respond; press auto to replay the damage and the fix; then take 4 sunscreen jobs.
一句话记住它：臭氧是平流层里的防晒衣，南极春季洞最大，氟利昂是元凶，蒙特利尔议定书正在把它补好。Remember it in one line: ozone is the sunscreen coat in the stratosphere, the hole peaks over the South Pole each spring, CFCs are the villain, and the Montreal Protocol is mending it.
防晒衣：臭氧（O₃）住平流层，吸掉大部分紫外线The coat: ozone (O₃) lives in the stratosphere, soaking up most UV洞：氟利昂破坏，南极上空、南半球春季最大The hole: CFC damage, over the South Pole, biggest in southern spring修复：1987 蒙特利尔议定书，紫外线指数是体检表The fix: the 1987 Montreal Protocol; the UV index is the checkup report
内容参考 OpenStax 等公开教材，多来源核对 · AI 生成、人工审核 · 发现错误欢迎指正，帮这片叶子长得更好。Based on OpenStax and other open textbooks, cross-checked across sources · AI-generated, human-reviewed · Spotted a mistake? Tell us — help this leaf grow.
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