Absorption of radiation
The uptake of radiation by a solid body, liquid or gas.
The absorbed energy may be transferred or re-emitted.
Adiabatic Process
A thermodynamic change of state of a system such that no
heat or mass is transferred across the boundaries of the
system. In an adiabatic process, expansion always results in
cooling, and compression in warming.
Aerosol
Particulate matter, solid or liquid, larger than a
molecule but small enough to remain suspended in the
atmosphere. Natural sources include salt particles from sea
spray, dust and clay particles as a result of weathering of
rocks, both of which are carried upward by the wind. Aerosols
can also originate as a result of human activities and are
often considered pollutants. Aerosols are important in the
atmosphere as nuclei for the condensation of water droplets
and ice crystals, as participants in various chemical cycles,
and as absorbers and scatters of solar radiation, thereby
influencing the radiation budget of the Earth's climate
system.
Albedo
The fraction of the total solar radiation incident on a
body that is reflected by it. Albedo can be expressed as
either a percentage or a fraction of 1. Snow covered areas
have a high albedo (up to about 0.9 or 90%) due to their
white color, while vegetation has a low albedo (generally
about 0.1 or 10%) due to the dark color and light absorbed
for photosynthesis. Clouds have an intermediate albedo and
are the most important contributor to the Earth's albedo. The
Earth's aggregate albedo is approximately 0.3.
Alliance of Small Island States (AOSIS)
The group of Pacific and Caribbean nations who call for
relatively fast action by developed nations to reduce
greenhouse gas emissions. The AOSIS countries are concerned
by the effects of rising sea levels and increased storm
activity predicted to accompany global warming. Its plan is
to hold Annex I Parties to a 20 percent reduction in carbon
dioxide emissions by the year 2005.
Annex I Parties
Industrialized countries that, as parties to the
Framework Convention on Climate Change, have pledged to
reduce their greenhouse gas emissions by the year 2000 to
1990 levels. Annex I Parties consist of countries belonging
to the Organization for Economic Cooperation and Development
(OECD) and countries designated as
Economies-in-Transition.
Antarctic "Ozone Hole"
Refers to the seasonal depletion of stratospheric ozone
in a large area over Antarctica.
Anthropogenic
Human made. In the context of greenhouse gases, emissions
that are produced as the result of human activities.
Aromatic
Applied to a group of hydrocarbons and their derivatives
characterized by the presence of the benzene ring.
Atmosphere
The mixture of gases surrounding the Earth. The Earth's
atmosphere consists of about 79.1% nitrogen (by volume),
20.9% oxygen, 0.036% carbon dioxide and trace amounts of
other gases. The atmosphere can be divided into a number of
layers according to its mixing or chemical characteristics,
generally determined by its thermal properties (temperature).
The layer nearest the Earth is the troposphere, which reaches
up to an altitude of about 8 km (about 5 miles) in the polar
regions and up to 17 km (nearly 11 miles) above the equator.
The stratosphere, which reaches to an altitude of about 50 km
(31 miles) lies atop the troposphere. The mesosphere which
extends up to 80-90 km is atop the stratosphere, and finally,
the thermosphere, or ionosphere, gradually diminishes and
forms a fuzzy border with outer space. There is relatively
little mixing of gases between layers.
