Atmosphere & Climate Change Section #2: The Ozone Shield

Ozone Layer an area in the stratosphere where ozone is highly concentrated ozone is a molecule made of three oxygen atoms this layer absorbs most of the UV light from the sun UV light is harmful to organisms & damages the genetic material in living cells

Chemicals that Deplete the Ozone CFCs (chlorofluorocarbons) man made “miracle” chemical nonpoisonous & nonflammable they do not corrode metals popular as coolants in refrigerators & air conditioners used in making plastic foams used as a propellant in spray cans

CFCs chemically stable at Earth’s surface because they do not combine with other chemicals or break down substances but up in the stratosphere, CFC molecules break apart & begin to destroy the protective ozone

Problems with CFCs scientists began to worry about the impact of CFCs in the atmosphere in the 1970s each CFC molecule that breaks up releases one to four chlorine atoms that remain in in the stratosphere for many years a single chlorine atom can destroy 100,000 ozone molecules

CFCs Destroying the Ozone

CFCs Destroying the Ozone

CFCs Destroying the Ozone

The Ozone Hole first news of a hole in the ozone layer came out in 1985 from scientists studying the ozone layer over the South Pole data revealed that the ozone layer over the poles had thinned by 50 to 98 percent during the spring

Satellite Images of the Ozone Hole Growing Over 2 Decades

How Does the Ozone Hole Form? clouds do not normally form in the stratosphere because it is so dry there however, during the polar winter, when temperatures drop below -80°C, high altitude clouds called POLAR STRATOSPHERIC CLOUDS begin to form because condensation can occur outside of the polar region, it is too warm in the stratosphere for clouds to form

How Does the Ozone Hole Form? on the surface of these polar stratospheric clouds, the products of CFCs are converted to molecular chlorine when sunlight returns in the spring, these chlorine molecules split into two chlorine atoms by UV radiation where they rapidly begin destroying ozone thin spots & holes can last for several months

Effects on Humans as the amount of ozone in the stratosphere decreases, more UV light is able to pass through the atmosphere where it reaches Earth’s surface UV light damages DNA & makes the body more susceptible to skin cancer

More UV radiation can penetrate at the poles where the ozone holes is located.

Effects on Plants UV light can kill phytoplankton at the ocean’s surface loss of phytoplankton disrupts the ocean’s food chains & reduces fish harvests reduction of phytoplankton also means more CO2 is left in the atmosphere which is a greenhouse gas

Effects on Plants UV light can also damage land plants by interfering with photosynthesis this damage could impact crops & create a lower yield during harvesting this will disrupt the food chains of many organisms, & humans too

Effects on Animals UV light can damage amphibians like toads & salamanders normal UV levels kill many eggs of amphibians that lack shells & are laid in the shallow water of ponds & streams at higher levels, UV light can kill more eggs putting the amphibian population at risk

Protecting the Ozone Layer in 1987, soon after the first news of the holes in the ozone layer, a group of nations met in Canada to take action against ozone depletion called the Montreal Protocol, these nations agreed to sharply limit their production of CFCs

Protecting the Ozone Layer in 1992, developed countries met again & agreed to eliminate most CFCs by 1995 the U.S. pledged to ban all substances that pose a significant danger to the ozone layer by 2000

Protecting the Ozone Layer chemical companies have developed CFC replacements that can be used in aerosol cans & in air conditioners decline in developed countries is profound due to the overwhelming collaborative efforts from so many involved countries

World CFCs Production

Why are Holes in the Ozone Layer Still a Problem? CFC molecules remain active in the stratosphere for 60 to 120 years even though production has stopped, CFCs that were released 30 years ago are still actively destroying ozone today it will be many years until the ozone layer completely recovers