Abrupt Climate Change(14)

A shift in climate (e.g.. temperature or precipitation) that occurs faster than the rate of change in the mechanism causing the change. The shift between glacial and interglacial stages. the shift between warm and cool periods during the last glacial time (Dansgaard-Oeschger cycles). and the Arctic oscillation are all considered abrupt climate changes. The shift in climate can occur over months to thousands of years and can occur in the absence of any known external cause.


The process in which radiant energy is retained by a substance. A further process always results from absorption. that is. the irreversible conversion of the absorbed radiation into some other form of energy within and according to the nature of the absorbing medium. The absorbing medium itself may emit radiation. but only after energy conversion has occurred.

Advanced Very High Resolution Radiometer (AVHRR)(1)

A five-channel scanning instrument that quantitatively measures electromagnetic radiation. flown on NOAA environmental satellites. AVHRR remotely determines cloud cover and surface temperature. Visible and infrared detectors observe vegetation. clouds. lakes. shorelines. snow. and ice.


Particles of liquid or solid dispersed as a suspension in gas.


The percentage of solar radiation that is reflected relative to the total incoming radiation.


The deviation of a measurable unit. (e.g.. temperature or precipitation) in a given region over a specified period from the long-term average. often the thirty-year mean. for the same region.


Made by people or resulting from human activities.

Arctic Oscillation (AO)(6)

The Arctic Oscillation is a pattern in which atmospheric pressure at polar and middle latitudes fluctuates between negative and positive phases. The negative phase brings higher-than-normal pressure over the polar region and lower-than-normal pressure at about 45 degrees north latitude. The negative phase allows cold air to plunge into the Midwestern United States and western Europe. and storms bring rain to the Mediterranean. The positive phase brings the opposite conditions. steering ocean storms farther north and bringing wetter weather to Alaska. Scotland and Scandinavia and drier conditions to areas such as California. Spain and the Middle East. In recent years research has shown. the Arctic Oscillation has been mostly in its positive phase. Some researchers argue that the North Atlantic Oscillation is in fact part of the AO.


Lacking moisture. especially having insufficient rainfall to support trees or woody plants.


The whole mass of gases surrounding the earth or other celestial bodies. Today's atmosphere is made up primarily of nitrogen (78%). free oxygen (21%) and greenhouse gases which can capture solar radiation- water vapor. which ranges from less than 1% in arid regions to over 3% in moist areas. carbon dioxide (0.035%) and methane (0.00018%). In the past the composition of the Earth's atmosphere has varied.

Atmospheric Circulation Model(3)

A mathematical model for quantitatively describing. simulating. and analyzing the structure of the circulation in the atmosphere and the underlying causes. Sometimes referred to as Atmospheric General Circulation Models or AGCMs (See GCMs).

Biogeochemical Cycle(4)

Natural processes that recycle nutrients in various chemical forms from the environment. to organisms. and then back to the environment. Examples are the carbon. oxygen. nitrogen. phosphorus. and hydrologic cycles.


Part of the Earth system in which life can exist. between the outer portion of the geosphere and the inner portion of the atmosphere.

Calcium carbonate (CaCO3)(2)

A molecule consisting of calcium. carbon and oxygen that are secreted by corals. forming their skeleton; it also secreted by mollusks (clams. oysters. etc.). forming their protective shells.

Calcium concentrations(2)

Concentration (units mass/mass) of the calcium ion (Ca+). often found in layers of ice. and derived from atmospheric transport of dust.

Carbon cycle(1)

All parts (reservoirs) and fluxes of carbon. The cycle is usually thought of as four main reservoirs of carbon interconnected by pathways of exchange. The reservoirs are the atmosphere. terrestrial biosphere (usually includes freshwater systems). oceans. and sediments (includes fossil fuels). The annual movements of carbon. the carbon exchanges between reservoirs. occur because of various chemical. physical. geological. and biological processes. The ocean contains the largest pool of carbon near the surface of the Earth. but most of that pool is not involved with rapid exchange with the atmosphere.

Carbon dioxide(1)

A minor but very important component of the atmosphere. carbon dioxide traps infrared radiation. Atmospheric CO2 has increased about 25 percent since the early 1800s. with an estimated increase of 10 percent since 1958 (burning fossil fuels is the leading cause of increased CO2. deforestation the second major cause). The increased amounts of CO2 in the atmosphere enhance the greenhouse effect. blocking heat from escaping into space and contributing to the warming of Earth's lower atmosphere.

Carbon sequestration(1)

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.


Temperature scale proposed by Swedish astronomer Anders Celsius in 1742. A mixture of ice and water is zero on the scale. boiling water is designated as 100 degrees. A degree is defined as one hundredth of the difference between the two reference points. resulting in the original term. 'centigrade' (100th part). To convert Celsius to Fahrenheit- multiply the Celsius temperature by 1.8 and add 32 degrees. F = 9/5 C + 32. To convert Fahrenheit to Celsius- subtract 32 degrees from the Fahrenheit temperature and divide the quantity by 1.8. C = (F -32) / 1.8.

Chlorofluorocarbons (CFCs)(3)

Manufactured substances used as coolants and computer-chip cleaners. When these products break down they destroy stratospheric ozone. creating the Antarctic Ozone Hole in the Southern Hemisphere spring (Northern Hemisphere fall). While no longer in use. their long lifetime will lead to a very slow removal from the atmosphere.


The flow. or movement. of a fluid (e.g.. water or air) in or through a given area or volume.

Climate Change(3)

A non-random change in climate that is measured over several decades or longer. For example. when less energy reaches the earth. temperature decreases and the area covered by snow increases. Consequently less energy is available at the surface. and temperature further decreases.

Climate Diagnostics Center (CDC)(3)

The mission of NOAA's Climate Diagnostics Center is to identify the nature and causes for climate variations on time scales ranging from a month to centuries.

Climate Model(3)

Mathematical model for quantitatively describing. simulating. and analyzing the interactions between the atmospheres and underlying surface (e.g.. ocean. land. and ice). OR A quantitative way of representing the interactions of the atmosphere. oceans. land surface. and ice. Models can range from relatively simple to quite comprehensive. Also see General Circulation Model.

Climate Outlook(3)

A climate outlook gives probabilities that conditions. averaged over a specified period. will be below normal. normal. or above normal.

Climate Prediction Center (CPC)(3)

A branch of the National Oceanographic and Atmospheric Agency (NOAA) whose mission is to assess and forecast the impacts of short-term climate variability. The CPC produces official U.S. climate forecasts.

Climate System(3)

The system consisting of the atmosphere (gases). hydrosphere (water). lithosphere (solid rocky part of the Earth). and biosphere (living) that determine the Earth�s climate.

Climate Variability(6)

The range of values the climate at a particular location can take over time. Example- Although the average September to December rainfall in Entebbe from 1902 to 1992 was 438mm. the actual amounts each year were somewhere in between 200mm and 1000mm. which is a large range of values.


The average of weather over at least a 30-year period. Note that the climate taken over different periods of time (30 years. 1000 years) may be different. The old saying is climate is what we expect and weather is what we get.

Climatic feedback mechanisms(2)

A feedback is an enhancement (positive feedback) or a damping (negative feedback) of an initial change. in this case in the climate system. For example. when less energy reaches the earth. temperature decreases and the area covered by snow increases. The albedo of the planet decreases. reflecting more energy towards the atmosphere. Consequently less energy is available at the surface. and temperature further decreases. The whole 'cycle' from the initial cooling to the further cooling is a feedback. It is a positive feedback in this example.

Climatological Outlook(3)

An outlook based upon climatological statistics for a region. abbreviated as CL on seasonal outlook maps. CL indicates that the climate outlook has an equal chance of being above normal. normal. or below normal.


(1) The description and scientific study of climate. (2) A quantitative description of climate showing the characteristic values of climate variables over a region.


An average that is calculated according to specific criteria. For example. one might want a composite for the rainfall at a given location for all years where the temperature was much above average.


The physical process by which water vapor in the atmosphere changes to liquid in the form of dew. fog or cloud; the opposite of evaporation.


Transfer of heat by fluid motion between two areas with different temperatures. In meteorology. the rising and descending air motion caused by heat. Atmospheric convection is almost always turbulent and is the dominant vertical transport process over tropical oceans and during sunny days over continents. The terms 'convection' and 'thunderstorms' are often use interchangeably. although thunderstorms are only one form of convection. In the ocean. convection is prominent in regions of high heat loss to the atmosphere and is the main mechanism for deep-water formation.

Cooling Degree Days(3)

A form of degree-day used to estimate energy requirements for air conditioning or refrigeration.

Coral bleaching(2)

An environmental stress indicator for coral. if conditions for corals are not optimum. the corals will expel the algae that live among the living polyps. therefore giving the colony a bleached appearance.

Coupled Model(3)

In the context of climate modeling this usually refers to a numerical model which simulates both atmospheric and oceanic motions and temperatures and which takes into account the effects of each component on the other. (also referred to as coupled atmosphere-ocean model)


In general use the term cyclone is applied to any storm. especially violent. small-scale circulations such as tornados. waterspouts. and dust devils. In meteorology. the term refers to a type of atmospheric disturbance centered on a low-pressure center that often results in stormy weather. In common practice the term cyclone. and low. are used interchangeably and are frequently referred to as storms. In the Northern Hemisphere the air rapidly circulates counterclockwise and in the Southern Hemisphere clockwise. Tropical cyclones with sustained winds above 73 miles per hour are known as hurricanes in the North Atlantic Ocean. Caribbean Sea. Gulf of Mexico and the Eastern North Pacific (east of the date line) and cyclones in the Indian Ocean. They are known as typhoons in other areas or the world. Both mid-latitude and tropical storms serve an important function in transferring warmth away from the tropics to the poles.

Data set(1)

A logically meaningful grouping or collection of similar or related data. Data having mostly similar characteristics (source or class of source. processing level and algorithms. etc.)


A collection of facts. concepts or instructions in a formalized manner suitable for communication or processing by human beings or by computer.


A consecutive ten-year period.


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 (aerosol) loading.

Dew Point(3)

The point at which the air at a certain temperature contains all the moisture possible without precipitation occurring. When the dew point is 65�F. one begins to feel the humidity. The higher the temperature associated with the dew point. the more uncomfortable one feels.

Dobson Unit(3)

Unit used to measure the abundance of ozone in the atmosphere. One Dobson unit is the equivalent of 2.69 x 1016 molecules of ozone/cm2.

Doppler radar(3)

Radar that measures speed and direction of a moving object. such as water or ice particles. birds. and insects.


The process of accumulation and sinking of warm surface waters along a coastline. A change of air flow of the atmosphere can result in the sinking or downwelling of warm surface water. The resulting reduced nutrient supply near the surface affects the ocean productivity and meteorological conditions of the coastal regions in the downwelling area.

Drought Assessments(3)

At the end of each month. CPC issues a long-term seasonal drought assessment. On Thursdays of each week. the CPC together with NOAA National Climatic Data Center. the United States Department of Agriculture. and the National Drought Mitigation Center in Lincoln. Nebraska. issues a weekly drought assessment called the United States Drought Monitor. These assessments review national drought conditions and indicate potential impacts for various economic sectors. such as agriculture and forestry.


Drought is a deficiency of moisture that results in adverse impacts on people. animals. or vegetation over a sizeable area. NOAA together with its partners provides short- and long-term Drought Assessments.

Earth Radiation Budget Experiment (ERBE)(1)

An experiment to obtain data to study the average radiation budget of the Earth and determine the energy transport gradient from the equator to the poles. Three satellites were flown in different orbits to obtain the data- the Earth Radiation Budget Satellite. ERBS (launched in October 1984). NOAA-9 (launched in December 1984). and NOAA-10 (launched in September 1986).
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Americans’ health, security and economic wellbeing are tied to climate and weather. Every day, we see communities grappling with environmental challenges due to unusual or extreme events related to climate and weather.