| A | B |
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| climate | The average, year-after-year conditions of temperature, precipitation, winds, and clouds in an area. |
| tropical zone | The area near the equator, between about 23.5° north latitude and 23.5° south latitude. |
| polar zone | The areas near both poles, from about 66.5° to 90° north and 66.5° to 90° south latitudes. |
| temperare zone | The area between the tropical and polar zones, from about 23.5° to 66.5° north and 23.5° to 66.5° south latitudes. |
| marine climate | The climate of some coastal regions, with relatively warm winters and cool summers. |
| continental climate | The climate of the centers of continents, with cold winters and warm or hot summers. |
| The main factors that affect precipitation are | prevailing winds and the presence of mountains. |
| windward | The side of mountains that faces the oncoming wind. |
| leeward | The downwind side of mountains. |
| microclimate | The climate characteristic of a small, specific area; it may be different from the climate of the surrounding area. |
| The seasons are caused by | the tilt of Earth’s axis as Earth travels around the sun. |
| Scientists classify climates according to two major factors: | temperature and precipitation. |
| rain forest | A forest in the tropical wet climate zone that gets plenty of rain all year. |
| savanna | A tropical grassland with scattered clumps of trees; found in the tropical wet-and-dry climate zone close to the equator. |
| desert | A region that receives less than 25 centimeters of rain a year. |
| steppe | A prairie or grassland found in the semiarid climate region. |
| humid subtropic | A wet and warm climate area on the edge of the tropics |
| subarctic | A climate zone that lies north of the humid continental climate zone, with short, cool summers and long, bitterly cold winters. |
| tundra | A polar climate region, found across northern Alaska, Canada, and Russia, with short, cool summers and bitterly cold winters. |
| permafrost | Permanently frozen soil found in the tundra climate region. |
| ice ages | Cold time periods in Earth’s history, during which glaciers covered large parts of the surface. |
| Possible explanations for major climate changes include | variations in the position of Earth relative to the sun, changes in the sun’s energy output, and the movement of continents. |
| sunspots | Dark, cooler regions on the surface of the sun. |
| greenhouse gases | Gases in the atmosphere that trap heat |
| gloabal warming | A gradual increase in the temperature of Earth’s atmosphere |
| Chemicals produced by humans have been damaging | the ozone layer. |
| chlorofluorocarbons | Chlorine compounds formerly used in air conditioners, refrigerators, and spray cans; also called CFCs. |
