Sự suy giảm Tầng ozone

Earth's sunscreen

• High in the atmosphere sits the ozone layer 臭氧层.
• It absorbs most of the sun's harmful ultraviolet 紫外线 rays.
• Without it, that UV would damage life on the surface.
• In the 20th century, we accidentally started destroying it.

The culprit: CFCs

• CFCs 氯氟烃 were chemicals used in fridges and spray cans.
• They seemed safe — stable, cheap, and non-toxic.
• But when they leak, they drift slowly up into the atmosphere.
• It takes years for them to reach the ozone layer.

The ozone hole over Antarctica (dark blue) on a NASA satellite map: this is where the ozone layer has thinned the most

How they destroy ozone

• High up, the sun's UV breaks a CFC apart.
• This frees a chlorine 氯 atom.
• The chlorine atom rips apart ozone molecules.
• Worse, it keeps going — one atom destroys thousands.

The ozone hole

• Over Antarctica, so much ozone was lost it became a "hole".
• A thinner layer lets more UV reach the ground.
• More UV means more skin cancer and eye damage.
• It also harms crops and the ocean's plankton.