THE OZONE LAYER

What is it?Where is it?

Why is it important to life on Earth?

How are we as humans affecting it?

Kushagra RohatgiBSc.BEd(sem-2)

What is the ozone layer?

The ozone layer is a layer of gas consisting of O3 molecules, called ozone it is also known as tri-oxygen, that forms when free Oxygen molecules bond to O2 molecules.

What is the ozone layer? a gas composed of

three atoms of oxygen

bluish gas that is harmful to breathe.

Nearly 90% of the Earth's ozone is in the stratosphere and is referred to as the ozone layer.

Ozone absorbs a band of ultraviolet radiation called UVB

Ozone

Ozone is a molecule consisting of oxygen atoms.

Ozone gas can be created or destroyed by the sun’s Ultraviolet rays as shown in the picture to the right.

Where is the ozone layer?

The ozone layer is a protective layer of gas molecules located within the stratosphere.

Ozone gas also exists in the troposphere and at ground level, but most is located within the stratospheric layer shown to the right.

Why is it important to life on Earth? On a daily basis, the sun radiates its energy

toward Earth. One form of this energy is Ultraviolet radiation, also known as UV rays.

UV rays are relatively high energy waves that provide Earth with the warmth it needs to support life as we know it.

Ultra-Violet Radiation

UV rays penetrate the Earth’s atmosphere at 3 slightly different wavelengths called UV-A, UV-B, and UV-C rays.

So, why is the ozone layer important to life on Earth?

The stratospheric ozone layer completely stops the penetration of UV-C rays and eliminates most of the UV-B rays.

Therefore, the ozone layer protects life on Earth from the harmful effects of solar radiation on a daily basis.

So what might life be like without the ozone layer?

Since 1928, Chlorofluorocarbons have been produced, originally as nonflammable refrigerants for use in refrigerators, and eventually for use in fire extinguishers, dry cleaning agents, pesticides, degreasers, adhesives, and as propellants for aerosol products.

As these CFCs have been released into the atmosphere, the level of ozone in the stratosphere has decreased.

CFCs have an estimated lifespan of more than 100 years.

How are we as humans affecting the ozone layer?

CFCs HCFCs Haloalkanes Methyl bromide Carbon tetra chloride Methyl chloroform

Ozone depleting substances

CFCs and Ozone

So what about the hole in the ozone layer?

October 1979

October 2007

Ozone hole is defined as the area having less than 220DU of ozone in the above column(“i.e., between ground and space)

DU is the unit of measurement of columnar density of the trace of gas in earth’s atmosphere

Since the 1970’s the ozone hole has been increasing in size over the Antarctic.

For the first time, in September of 2000, the ozone hole became so large it actually left populated areas of southern Chile fully exposed to the effects of the Sun’s UV rays.

The Ozone Hole

Chile’s Ozone Hole

Why ozone hole is only over Antarctica?

Ozone-depleting substances are present throughout the stratospheric ozone layer because they are transported great distances by atmospheric air motions. “The Antarctic ozone hole” occurs because of the special atmospheric and chemical conditions that exist there and nowhere else on the globe. The very low winter temperatures in the Antarctic stratosphere cause polar stratospheric clouds (PSCs) to form. Special reactions that occur on PSCs, combined with the relative isolation of polar stratospheric air, allow chlorine and bromine reactions to produce the ozone hole in Antarctic springtime. refer: why ozone hole is only over the antartica.pdf

As ozone levels in the stratosphere are depleted, more solar radiation penetrates the Earth’s atmosphere.

This affect results in an increase in solar radiation reaching the Earth’s surface adding to an increase in surface temperature.

In turn, global warming actually results in a warming of the troposphere, but a cooling of the stratosphere, hindering the ozone layer’s natural chemistry for repairs.

How does ozone depletion affect global warming and ultimately climate change?

After the discovery of ozone depletion in the late 1970’s, many countries agreed that something must be done worldwide to stop the production of man-made, ozone harmful products.

The world started promoting and adopting products that are ozone friendly. today we can see that refrigerators and air conditioners are now coming with coolant made up of hydrocarbon and not CFCs. Also in the aerosol sprays we can find written as ozone safe, ozone friendly etc.

So what are we doing about it?

So what are we doing about it? The latest reports confirm that it has

led to the phasing out of about 95% of the consumption of ozone-depleting substances (ODS) listed in the agreement. In turn, this has led to the prospect of the ozone layer recovering by 2050 to 2075.

Furthermore, the phasing out of ozone-depleting substances has helped to fight climate change since many of these chemicals are also powerful greenhouse gases. So also helping to control green house effect.

THANK YOU

•Links and sources•http://www.theozonehole.com/•http://www.cfcs.co.in/ •http://en.wikipedia.org/wiki/Ozone_depletion•https://www.youtube.com/•https://www.google.co.in/•http://news.nationalgeographic.com/news/2010/05/100505-science-environment-ozone-hole-25-years/

•http://www.esrl.noaa.gov/csd/assessments/ozone/2010/twentyquestions/Q10.pdf

17/03/2015