Glossary of  Frequently Used Terms


Albedo is the fraction of incoming solar radiation (sunlight) that is reflected back into space. Albedo values range from 0 to 1, and because they are expressed as fractions, they have no units. Objects that are very dark in color absorb most of the incoming radiation (causing them to heat up) and have a low albedo, while objects that are very light in color reflect most of the incoming radiation and have a higher albedo.


An anomaly is the departure from the average over a certain period of time. For example, a positive temperature anomaly indicates that the observed temperature is warmer than the climate averaged over a period of time, while a negative anomaly indicates that the observed temperature is cooler than the average climate.


A biome is a major ecological community that extends over a large geographic area, characterized by an abundant type of vegetation. The organisms of a biome are adapted to the climate conditions associated with the region.


Climate is the long-term patterns of weather. This is often measured as the average of weather of a 30-year period (see 'Climate Normal' below). For example, the annual temperature averaged over the past 30 years in Durham, NH was 8°C.

Climate Normal

Climate normal is the average of a climate variable (temperature, precipitation, etc.) over a 30-year period.


An ecosystem in a community plus its physical surroundings.

Emission Scenario

Emission scenarios characterize the heat-trapping gasses that we expect to find in the atmosphere based on different scenarios describing future trends in human population growth, energy use, economic development, and technology use. For more information on specific emission scenarios see information from the World Meteorological Organization.

Global Climate Model

Global Climate Models (GCMs) are complex mathematical representations of the physical processes occurring throughout the Earth's land-ocean-atmosphere system. They generate predictions extending 100 years into the future.


MODIS stands for MODerate-resolution Imaging Spectroradiometer. It is a scientific instrument (aboard the Terra and Aqua satellites) launched by NASA that captures data in 36 spectral bands. It images the entire Earth every 1 to 2 days. For more information, see


NDVI stands for Normalized Difference Vegetation Index. It measures the greenness of an area, and is calculated using a combination of red and infrared bands. It is often measured by Earth observing satellites with instruments such as MODIS (see above). For more information on NDVI, see NASA's Measuring Vegetation website.

Vegetation Index

Vegetation Indices are mathematical combinations of surface reflectance (measured from the reflectance of the vegetation), and are designed to highlight a certain property of the vegetation. An example of a vegetation index is NDVI (see above).


Weather is the mix of events (precipitation, humidity, temperature, etc.) that happen over a short period of time (minutes to months) in a specific location. For example, the temperature on June 12th, 2012 in Durham, NH was 18.9°C.

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