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Greenhouse Glossary
Aerosols. Particles of 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 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 in this case are often considered pollutants. They can act
as condensation points for hail, snow, and for water droplets that form clouds.
Albedo. The ratio of reflected to incoming light; 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 total average albedo is approximately 0.3.
Anthropogenic. Derived from human activities. For example: burning fossil fuels is a source of
anthropogenic CO2.
Atmosphere. The mixture of gases surrounding the Earth. The Earth's atmosphere consists of about
78% nitrogen (by volume), 21% oxygen, 0.04% carbon dioxide, and trace amounts of other gases. Gas
concentrations are often expressed in parts per million or billion (or, ppm or ppb). For example CO2 in
the atmosphere recently reached 400 ppm.
Biomass. Organic non-fossil material of biological origin. For example, trees and other plants are
biomass.
Biomass Energy. Energy produced by combusting renewable biomass materials such as wood. The
carbon dioxide emitted from burning biomass will not increase total atmospheric carbon dioxide if this
consumption is done on a sustainable basis (For example, if we burn as much wood as the Earth grows,
that would be sustainable and not raise CO2 levels.) Biomass energy is often suggested as a partial
replacement for fossil fuel burning which has large greenhouse gas emissions.
Biosphere. The region on land, in the oceans, and in the atmosphere inhabited by living organisms.
Carbon Dioxide (CO2). The greenhouse gas whose concentration is being affected directly by human
activities. The major source of CO2 emissions is fossil fuel burning. CO2 emissions are also a product
of forest clearing, biomass burning, and non-energy production processes such as cement production.
Atmospheric concentrations of CO2 have been increasing since the industrial revolution from about
275 parts per million (ppm) to about 400 ppm today.
Carbon Sequestration. The uptake and storage of carbon. Trees and plants, for example, absorb
carbon dioxide, release the oxygen and store the carbon. Fossil fuels were at one time biomass and
continue to store the carbon until burned. Some have proposed sequestering carbon dioxide
underground.
Chlorofluorocarbons (CFC’s) and related compounds. This family of anthropogenic compounds
includes chlorofluorocarbons, bromofluorcarbons, methyl chloroform, carbon tetrachloride, methyl
bromide, and hydrochlorofluorcarbons (remember those reactive halogens?). These compounds have
been shown to deplete stratospheric ozone, and therefore are typically referred to as ozone depleting
substances. Most all of these are also powerful greenhouse gases. The most ozone-depleting of these
compounds are being phased out under the Montreal Protocol. Most greenhouse gases do not destroy
ozone – but CFC’s do. Repeat: Most greenhouse gases do not destroy ozone – but CFC’s do.
Climate is the average weather (usually taken over a 30-year time period) for a particular region and
time period. Climate is not the same as weather, but rather, it is the average pattern of weather for a
particular region. Weather describes the short-term state of the atmosphere. Climatic elements include
precipitation, temperature, humidity, sunshine, wind velocity, phenomena such as fog, frost, and
hailstorms, and other measures of the weather. Please see “weather”, below.
Climate Change (also referred to as 'global climate change'). The term 'climate change' is
sometimes used to refer to all forms of climatic inconsistency, but because the Earth's climate is never
constant, the term is more properly used to imply a significant change from one climatic condition to
another. In some cases, 'climate change' has been used the same as the term, 'global warming';
scientists however, tend to use the term in the wider sense to also include natural changes in climate.
Climate Modeling. The simulation of the climate using computer-based models.
Deforestation. Those practices or processes that result in the change of forested lands to non-forest
uses. This is often cited as one of the major causes of the enhanced greenhouse effect for two reasons:
1) the burning or decomposition of the wood releases carbon dioxide; and 2) trees that once removed
carbon dioxide from the atmosphere in the process of photosynthesis are no longer present and
contributing to carbon storage.
Desertification. The progressive destruction or degradation of existing vegetative cover to form desert.
This can occur due to overgrazing, deforestation, drought, and the burning of extensive areas. Once
formed, deserts can only support a sparse range of vegetation. Climatic effects associated with this
phenomenon include increased albedo, reduced atmospheric humidity, and greater atmospheric dust
(aerosols).
Electromagnetic Radiation. Energy emitted in the form of electromagnetic waves. It has differing
characteristics depending upon the wavelength and frequency. Because the radiation from the Sun is
relatively energetic, its energy has a shorter wavelength than the heat leaving earth. Visible light has a
longer wavelength than Infrared light.
Feedback Mechanisms. A mechanism that connects one aspect of a system to another. The
connection can be either amplifying (positive feedback) or moderating (negative feedback). Please
remember that positive feedbacks increase the warming. Negative feedbacks can slow the warming.
Fossil Fuel. A general term for combustible geologic deposits of carbon in reduced (organic) form and
of biological origin, including coal, oil (and it’s products like gasoline), and natural gas. A major
concern is that they emit carbon dioxide into the atmosphere when burnt, thus significantly
contributing to the enhanced greenhouse effect.
Global Warming. An increase in the near surface temperature of the Earth. Global warming has
occurred in the distant past as the result of natural influences, but the term is most often used to refer to
the warming predicted to occur as a result of increased emissions of greenhouse gases. Scientists
generally agree that the Earth's surface has warmed by a bit more than 1 degree Fahrenheit in the past
150 years. The Intergovernmental Panel on Climate Change (IPCC) concluded that increased
concentrations of greenhouse gases are causing an increase in the Earth's surface temperature.
Greenhouse Effect. The effect produced as greenhouse gases allow incoming solar radiation to pass
through the Earth's atmosphere, but slow the outgoing infrared (heat) radiation from the surface and
lower atmosphere from escaping into outer space. This process occurs naturally and has kept the
Earth's temperature about 59 degrees F warmer than it would otherwise be. Most current life forms on
Earth could not exist without the natural greenhouse effect.
Greenhouse Gas. Any gas that absorbs infrared radiation in the atmosphere. Some greenhouse gases
include: water vapor, carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), ozone (O3), and
hydrofluorocarbons (HFCs).
Hydrocarbons. Substances containing primarily hydrogen and carbon. Fossil fuels like coal, methane,
gasoline, and oil are examples of hydrocarbons. They have high energy density and are useful in
transportation energy production. The release carbon dioxide and water (and other compounds) when
burned.
Infrared Radiation. The heat energy that is emitted from all solids, liquids, and gases. In the context
of the greenhouse issue, the term refers to the heat energy emitted by the Earth's surface and its
atmosphere. Greenhouse gases strongly absorb this radiation in the Earth's atmosphere, and reradiate
some back towards the surface, creating the greenhouse effect.
Insolation. The solar radiation striking Earth or another planet (or the rate of delivery of solar
radiation per unit of horizontal surface). The Equator gets much more insolation than the poles.
Methane. The simplest hydrocarbon CH4. A useful fossil fuel for cooking, heating, and electrical
generation. The US supply of methane has increased recently due to “fracking”. Methane is a powerful
greenhouse gas. The concentration of methane in the atmosphere has gone from about 700 ppb at the
time of the Industrial Revolution to close to 1800 ppb today.
Montreal Protocol - A treaty begun in the 1980’s that led to the elimination or reduction of the
making of many ozone depleting gases, like CFC’s. It seems to be working!
Mount Pinatubo. A volcano in the Philippine Islands that erupted in 1991. The eruption of Mount
Pinatubo ejected enough particulate and sulfate aerosol matter into the atmosphere to block some of
the incoming solar radiation from reaching Earth's atmosphere. This effectively cooled the planet from
1992 to 1994, masking the warming that had been occurring for most of the 1980s and 1990s.
Ocean Acidity. The pH scale measures acidity and varies from 0-14. Values under 7 are acidic, and
over 7 are basic. As CO2 dissolves into the ocean, it forms carbonic acid (the stuff in our lab that
turned the BTB solution from blue to green/yellow when you breathed into it.) As more CO2 gets put
in the air, more gets dissolved in the oceans. This has caused the average pH of the oceans to drop
from 8.179 (pre-industrial times) to 8.069 (today) – and likely below 8.0 within your lifetime.
Ozone (O3). Ozone consists of three atoms of oxygen bonded together in contrast to normal
atmospheric oxygen, which consists of two atoms of oxygen (O2). Ozone is an important greenhouse
gas found in both the stratosphere the troposphere. Up high it shields us from harmful UV radiation,
down low in cities, if there is too much, it’s a pollutant and contributes to smog and lung irritation.
Photosynthesis. The process by which green plants use light to make organic compounds from carbon
dioxide and water. In the process oxygen and water are released. Increased levels of carbon dioxide
can increase net photosynthesis in some plants. Plants create very important storage for carbon.
Pollutant. Strictly, too much of any substance in the wrong place or at the wrong time is a pollutant.
More specifically, atmospheric pollution may be defined as the presence of substances in the
atmosphere, resulting from man-made activities or from natural processes that cause adverse effects to
human health, property, and the environment.
Respiration. The process by which animals (and plants and anything living) use food (with oxygen) to
produce energy.
Sink. A reservoir that that takes up a something from another part of its cycle. For example, soil,
oceans, and trees tend to act as natural sinks for carbon (see ocean acidity above). The oceans are sinks
for heat, as well.
Solar Radiation. Energy from the Sun. Also referred to as short-wave radiation. Of importance to the
climate system, solar radiation includes ultra-violet radiation, visible radiation, and infrared radiation.
Water Vapor. The most common greenhouse gas, it is the water present in the atmosphere in gaseous
form. Water vapor is an important part of the natural greenhouse effect. While humans are not
significantly increasing its concentration, it contributes to the enhanced greenhouse effect because the
warming by greenhouse gases leads to a positive water vapor feedback (warmer air can hold more
water vapor, which can warm the earth since it is a greenhouse gas). In addition to its role as a natural
greenhouse gas, water vapor plays an important role in regulating the temperature of the planet because
clouds form excess water vapor.
Weather. Weather is the specific condition of the atmosphere at a particular place and time. It is
measured in terms of such things as wind, temperature, humidity, atmospheric pressure, cloudiness,
and precipitation. In most places, weather can change from hour-to-hour, day-to-day, and season-toseason. Climate is the average of weather over time and space. A simple way of remembering the
difference is that 'climate' is what you expect (e.g., cold winters) and 'weather' is what you get (e.g., a
blizzard) or, climate tells you what clothes to buy, but weather tells you what clothes to wear.