A collection of airborne solid or liquid particles, with a
typical size between 0.01 and 10 micrometers (µm) and
residing in the atmosphere for at least several hours. Aerosols
may be of either natural or anthropogenic origin. Aerosols
may influence climate in two ways: directly through scattering
and absorbing radiation, and indirectly through acting as
condensation nuclei for cloud formation or modifying the optical
properties and lifetime of clouds.
The gaseous envelope surrounding the Earth. The dry atmosphere
consists almost entirely of nitrogen (78.1% volume mixing
ratio) and oxygen (20.9% volume mixing ratio), together with
a number of trace gases, such as argon (0.93% volume mixing
ratio), helium, radiatively active greenhouse gases such as
carbon dioxide (0.035% volume mixing ratio), and ozone. In
addition the atmosphere contains water vapor, whose amount
is highly variable but typically 1% volume mixing ratio. The
atmosphere also contains clouds and aerosols.
The numbers and relative abundances of different genes (genetic
species, and ecosystems (communities) in a particular area.
The part of the Earth system comprising all ecosystems and
living organisms, in the atmosphere, on land (terrestrial
biosphere) or in the oceans (marine biosphere), including
derived dead organic matter, such as litter, soil organic
matter and oceanic detritus.
Climate change refers to any change in climate over time,
whether due to natural variability or as a result of human
activity. This usage differs from that in the United Nations
Framework Convention on Climate Change (UNFCCC), which defi
nes “climate change” as: “a change of climate
which is attributed directly or indirectly to human activity
that alters the composition of the global atmosphere and which
is in addition to natural climate variability observed over
comparable time periods”.
The process by which an amount of greenhouse gas emissions
equal to that
caused by a certain activity, e.g., a flight, is reduced,
or offset, elsewhere.
Carbon Dioxide (CO2)
A naturally occurring gas, and also a by-product of burning
fossil fuels and biomass, as well as land-use changes and
other industrial processes. It is the principal anthropogenic
greenhouse gas that affects the Earth's radiative balance.
It is the reference gas against which other greenhouse gases
are measured and therefore has a Global Warming Potential
Any natural unit or entity including living and non-living
parts that interact to produce a stable system through cyclic
exchange of materials.
The release of a substance (usually a gas when referring to
the subject of climate change) into the atmosphere.
El Niño – Southern Oscillation (ENSO) refers
to widespread 2-7 year oscillations in atmospheric pressure,
ocean temperatures and rainfall associated with El Niño
(the warming of the oceans in the equatorial eastern and central
Pacific) and its opposite, La Niña. Over much of Australia,
La Niña brings above average rain, and El Niño
brings drought. A common measure of ENSO is the Southern Oscillation
Index (SOI) which is the normalised mean sea level pressure
difference between Tahiti and Darwin. The SOI is positive
during La Niña events and negative during El Niño
Global warming is an average increase in the temperature of
the atmosphere near the Earth's surface and in the troposphere,
which can contribute to changes in global climate patterns.
Global warming can occur from a variety of causes, both natural
and human induced. In common usage, "global warming"
often refers to the warming that can occur as a result of
increased emissions of greenhouse gases from human activities.
The natural greenhouse effect is the process where gases in
the lower atmosphere such as carbon dioxide, methane and water
vapour are warmed by radiation released by the Earth’s
surface after it has been warmed by solar energy. These gases
then radiate heat back towards the ground—adding to
the heat the ground receives from the Sun. Without the natural
greenhouse effect the surface of the planet would be about
33 °C colder on average.
Greenhouse Gas (GHG)
Any gas that absorbs infrared radiation in the atmosphere.
Greenhouse gases include, but are not limited to, water vapor,
carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O),
chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs),
ozone (O3 ), hydrofluorocarbons (HFCs), perfluorocarbons (PFCs),
and sulfur hexafluoride (SF6).
A greenhouse gas produced through processes including decomposition
of landfill waste in the absence of oxygen, digestion in animals
such as cattle, production of coal, natural gas and oil, and
rice growing. Atmospheric methane concentrations have increased
by 151% since the Industrial Revolution.
An anthropogenic intervention to reduce the output or enhance
the sinks of
Nitrogen Oxides (NOx)
Gases consisting of one molecule of nitrogen and varying numbers
of oxygen molecules. Nitrogen oxides are produced in the emissions
of vehicle exhausts and from power stations. In the atmosphere,
nitrogen oxides can contribute to formation of photochemical
ozone (smog), can impair visibility, and have health consequences;
they are thus considered pollutants.
The layer of ozone that begins approximately 15 km above Earth
and thins to an almost negligible amount at about 50 km, shields
the Earth from harmful ultraviolet radiation from the sun.
The highest natural concentration of ozone (approximately
10 parts per million by volume) occurs in the stratosphere
at approximately 25 km above Earth. The stratospheric ozone
concentration changes throughout the year as stratospheric
circulation changes with the seasons. Natural events such
as volcanoes and solar flares can produce changes in ozone
concentration, but man-made changes are of the greatest concern.
Region of the atmosphere between the troposphere and mesosphere,
having a lower boundary of approximately 8 km at the poles
to 15 km at the equator and an upper boundary of approximately
50 km. Depending upon latitude and season, the temperature
in the lower stratosphere can increase, be isothermal, or
even decrease with altitude, but the temperature in the upper
stratosphere generally increases with height due to absorption
of solar radiation by ozone.
The lowest part of the atmosphere from the surface to about
10 km in altitude in mid-latitudes (ranging from 9 km in high
latitudes to 16 km in the tropics on average) where clouds
and "weather" phenomena occur. In the troposphere
temperatures generally decrease with height.