Geothermal Energy: The natural heat energy of the Earth. Also called Earth energy.

Global Warming: An overall increase in the Earth’s temperature, which may be caused by reduced numbers of trees and increased levels of carbon dioxide and other greenhouse gases. See Greenhouse Effect.

Grassland: Large areas of land that are flat, grow different kinds of grasses and other plants and get less than 100 cm of precipitation each year. They also do not have many trees. Some grasslands are called Prairies.

Greenbelt: A large area where recreational parks, farmland and natural land surrounding communities are protected against building.

Greenhouse Effect: The warming of the Earth's surface. Gases (See Greenhouse Gases), trap heat between surface of the Earth and the atmosphere. See Atmosphere.

Greenhouse Gas(es): Gases that suck up the energy coming from the Earth and send most of it back to the Earth. They are apart of "the Greenhouse Effect." Examples: Carbon dioxide, Nitrous oxide, Methane, water vapour, CFCs (Chlorofluorocarbons).