It’s not just about Global Warming…

The Problem with the Ozone Layer

What is it?

• "The ozone layer" refers to the ozone within stratosphere, where over 90% of the earth's ozone resides.

• Ozone is an irritating, corrosive, colorless gas with a smell something like burning electrical wiring.

• Each molecule of ozone has three oxygen atoms (O3) and is produced when oxygen molecules (O2) are broken up by energetic electrons or high energy radiation.

What does it do?

• The ozone layer absorbs 97-99% of the sun's high frequency ultraviolet light, light which is potentially damaging to life on earth.

• Every 1% decrease in the earths ozone shield is projected to increase the amount of UV light exposure to the lower atmosphere by 2%.

What caused the hole?

• Human activities in the last several decades have produced chemicals, such as chlorofluorocarbons (CFCs), which have been released into the atmosphere and have contributed to the depletion of this important protective layer.

Links to Climate

• Ozone is also a greenhouse gas in the upper atmosphere and, therefore, plays a role in Earth's climate.

• Under normal conditions, the amount of stratospheric ozone depends on the amount of sunlight reaching a certain geographic area of the atmosphere. – Ozone typically "builds up" to higher values over the

poles during the winter and early spring in each hemisphere. Because this season is offset by 6 months in the Northern and Southern hemispheres, the effect is seen at the North and South poles roughly 6 months apart.

How fast is it expanding? • the "ozone hole" is where lower than normal levels of

ozone have been detected. • it is formed and destroyed by chemical reactions that

require light. • So the ozone hole is more intense when there is sunlight

over the south pole then where then is darkness. • Human activities have made the hole much more

intense, but as far as we know there was always a lower amount of ozone over the south pole (and to a lesser extent over the north pole too) before human activities altered the composition of the atmosphere.

• the ozone layer has also thinned in the temperate and tropical zones on Earth

An Anthropogenic Issue!

• The data showed conclusively that human-produced trace gases that contain chlorine and bromine were causing the ozone hole.

• The Global Monitoring Division of ESRL has monitored the yearly Antarctic ozone hole from the South Pole station and measuring total column ozone from a ground based Dobson spectrophotometer since 1963, and since 1986 by launching balloons.

Driven by Temperatures…

• View of the Antarctic Ozone hole

(July thru December)

The ozone hole “closes” up in winter but intensifies in the summer…

Arctic Ozone Hole

• http://earthobservatory.nasa.gov/Newsroom/NasaNews/ReleaseImages/20031210/07a_ozone2000.mpeg

• Not as pronounced as the Antarctic Ozone Hole, although does show up. (Blue regions indicate low ozone levels)

Arctic Ozone Problem?

• Significant depletion also occurs in the Arctic ozone layer during the late winter and spring period (January - April). However, the maximum depletion is generally less severe than that observed in the Antarctic, with no large and recurrent ozone hole taking place in the Arctic.

Why is a “hole” in the atmosphere an issue?

If there is a hole in the ozone layer then this means that more harmful ultra-violet rays get through than are good for us or many other life forms, plant or animal.

Too much ultra-violet light can result in:

• Eye damage such as cataracts

• Immune system damage

• Reduction in phytoplankton in the oceans that forms the basis of all marine food chains including those in Antarctica.

• Damage to the DNA in various life-forms So far this has been as observed  in Antarctic ice-fish that lack pigments to shield them from the ultra-violet light (they've never needed them before)

• Skin cancer

…ozone-depleting gases

• These gases contain chlorine and bromine atoms, which are known to be harmful to the ozone layer

– CFCs & hydrochlorofluorocarbons (HCFCs),• human-produced gases once used in almost all

refrigeration and air conditioning systems

– Methyl bromide, • Primarily used as an agricultural fumigant

– Nitrous Oxides, • oxidation of ammonia (NH3) – primarily from farming• Also a result of burning fossil fuels

Global warming and the ozone hole – is there a connection?

• The ozone hole is a completely different phenomenon to global warming, however there are links between them.  The ozone hole is caused by ozone depleting chemicals in the atmosphere, which have been produced by industry, for example CFCs. 

• One link is that CFCs are also 'greenhouse gasses'.  Enhanced global warming is a probable consequence of increasing amounts of 'greenhouse  gasses', such as carbon dioxide and methane, in the atmosphere. 

• Although the surface of the earth warms, higher up the atmosphere cools, thus increasing the area where stratospheric clouds can form.  This makes a larger area susceptible to ozone depletion and provides another link between the two issues.

Global warming and the ozone hole – is there a connection?