Global atmosphere issues
Ozone depletion
The ozone layer is continually being formed by photochemical reactions between oxygen molecules and ultraviolet radiation and breaking down as part of a natural cycle. However, the balance of this cycle has been disturbed by increased emissions of substances that enhance the breakdown of ozone, in particular chlorofluorocarbons (CFCs), a group of compounds that were used in a variety of industrial and domestic applications, such as refrigeration and as propellants in aerosol spray cans.
This depletion of the ozone layer allows more of the ultraviolet radiation, mainly the more harmful wavelengths (UV-B at wavelengths of ~280—315 nm) to reach the Earth's surface. This is causing potentially significant impacts on human health (for example, skin cancer), the health of terrestrial and marine ecosystems, agricultural productivity and the durability of materials as shown in the image below.
This depletion of stratospheric ozone has been mainly observed in the Antarctic where there has been a significant change in the atmospheric circulation pattern, resulting in a cooling of the stratosphere leading to a greater destruction of ozone. This is commonly referred to as a 'hole in the ozone layer'. The depletion of stratospheric ozone has important implications for the Australian regional climate, and for human health, agriculture and biodiversity.
Legislation has been introduced to reduce and manage the emission of ozone depleting substances to allow the atmosphere to return to its natural state over time.
Global warming and climate change
In addition to the ozone depleting substances, other chemical compounds are emitted to the atmosphere as a result of natural and human activities. These compounds have been implicated as being partly, if not wholly, responsible for a global warming trend, resulting from the alteration of the composition of the atmosphere.
The Earth's climate is maintained at a relatively consistent and stable temperature by what is known as the 'greenhouse effect' where the atmosphere acts as a form of blanket keeping it warm. Heat from the suns radiation is released from the surface of the Earth and is trapped and redirected back to the surface keeping temperatures relatively warm and conducive to life. This is shown in the image below.
However, changes to the composition of the atmosphere from human activities have resulted in changes to the global climate. Emissions of the most significant greenhouse gas, carbon dioxide (CO2), have greatly increased since the industrial revolution, chiefly from the combustion of fossil fuels. As a result the concentration in the atmosphere continues to rise. The consequence of this is an 'enhanced greenhouse effect' where the temperature is no longer stable but rises, bringing increasing problems of drought, unstable weather patterns, melting of polar and glacial ice, and sea-level rise.
Last updated 14 February 2011