Lesser Greenhouse Gases

Wheat Crop

The destruction of these crops for use in sectors other than food supply contributed to the World Food Crisis 2007-2008

Courtesy of stock.xchng

Wheat Crop
Courtesy of stock.xchng

Wheat Crop

The destruction of these crops for use in sectors other than food supply contributed to the World Food Crisis 2007-2008

Courtesy of stock.xchng

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Ozone

Ground level ozone is also an important greenhouse gas but it has a very short atmospheric lifetime of about one week. Ozone also causes damage to human health, crops and ecosystems. Actions to reduce ground level ozone levels are being taken under actions on air quality. These are primarily designed to address the more immediate impact of ozone and other standard air pollutants but will have some positive effects for climate change.

Similarly actions being taken under the Montreal Protocol to the Vienna Convention to address stratospheric ozone depletion by CFCs will have some positive effects for climate change since these actions reduce the emissions of ozone depleting substances, which are also greenhouse gases.

Camac Aqueduct, Co. Laois

Camac Aqueduct, Co. Laois

Copyright Michael Neill

Camac Aqueduct, Co. Laois
Copyright Michael Neill

Camac Aqueduct, Co. Laois

Camac Aqueduct, Co. Laois

Copyright Michael Neill

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Water Vapour

Water vapour is an important component of the atmosphere. It is also a short lifetime greenhouse gas. The amount of water vapour that the atmosphere can hold is largely determined by its temperature. As temperatures increase the amount of water vapour that the atmosphere can hold increases. Climate scientists see this as important positive feedback, which amplifies the warming caused by long lived greenhouse gases. It also influences rainfall characteristics as the increased levels of water vapour can result in more intense rainfall. More generally this is referred to as an intensified hydrological cycle. However, other factors such as aerosols also play important roles in the hydrological cycle.

Aerosols and Global Dimming

Aerosols are largely invisible microscopic particles that are an integral part of the atmosphere. They can be examined using powerful microscopes. Aerosol particles are a complex mixture of salts, soot and organic materials. They absorb water vapour from the atmosphere and give rise to hazes and smogs. Also, as air rises high up in the atmosphere and cools, these aerosols become centres for condensation of cloud drops and cloud formation. Therefore, aerosols have a key role in the water cycle.

Aerosols influence climate in a number of ways. They can reflect sunlight back to space before it causes warming and can influence the characteristic of clouds and their lifetimes. These influences all have a cooling effect and are enhanced by human emissions of pollution such as sulphur dioxide (SO₂), nitrogen oxides (NOX) and ammonia (NH₃). The effect is sometimes called global dimming. Aerosols have short atmospheric lifetimes, typically from days to weeks.

Volcanoes

Large volcanic eruptions inject a massive amount of aerosol material into the upper atmosphere. Such eruptions can result in significant global cooling for 1 to 2 years until these aerosols are removed from the atmosphere. These events are very sporadic and do not have a long term impact on climate.

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