Ch 21 climate

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21.1 Factors the Affect Climate

• Latitude – as latitude increases, the intensity of solar energy decreases

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Elevation – the higher the elevation, the colder the climate

• Air temperature decreases with elevation by an average of about 6.5 oC every 1000 meters.

• Increasing altitude has the same affect on climate as increasing latitude

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• Topography – the windward side of a mountain has more precipitation than the leeward (sheltered) side.

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Water Bodies • Large bodies of water such as lakes

and oceans have an important effect on the temperature of an area because the temperature of the water body influences the temperature of the air above it.

• Places downwind of a large body of water have cooler summers and milder winters than inland.

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• Atmospheric Circulation - global pressure zones creates areas of precipitation (lows) and dry areas (highs)

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• Vegetation

• Vegetation influences how much of the sun’s energy is absorbed and how quickly this energy is released. Areas with vegetation will be cooler and more humid than areas without vegetation.

• Deforestation dries the climate.

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• 21.2 World Climates

• Climates are classified by the temperature and precipitation.

• Climate determines the type of plants in an area and the type of plants determines the types of animals.

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• Humid Tropical Climates – border the equator

• No winters• Mean temperature of 18 oC• Rainfall can exceed 200 cm• Wet tropical forms the tropical rain forest

with high temperatures and high precipitation throughout the year

• Wet and dry tropical have high temperatures but periods of low precipitation.

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• Humid Mid-latitude with mild winters1. Humid subtropical climates – southeastern US

Summers- hot and humidWinters – relatively mild

2. Marine West Coast ClimatesMild winters and cool summers

3. Dry-summer subtropical climates – Mediterranean Climates

CaliforniaWet winters, dry summers

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• Humid Mid-Latitude With Severe Winters• 1. Humid Continental Climates –

winters are severe and summers quite long, upper mid-west

• 2. Subarctic climate– winters are long and bitterly cold, summers are warm and short, northern Canada

• Highest annual temperature range on Earth

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Dry Climates – annual precipitation not as great as evaporation

• Located near the Tropics of Caner and Capricorn due to sinking air (High pressure) areas

• Arid or desert• Semi-arid or steppe (marginal area and more

humid than desert)Polar Climates – mean temperature during the warmest

month is below 19 oC, the temperatures remain cool and very little precipitation

• Tundra – plants are low to the ground• Polar ice capHighland Climates – cooler and wetter than nearby areas at

lower elevations• South-facing slopes will be warmer than north-

facing slopes

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• 21.3 Climate Changes• Natural Processes that Change Climate• Volcanic eruptions – causes more solar

radiation to be reflected and cools the atmosphere

• El Nino causes parts of the eastern tropical Pacific to become warmer than usual.

Some areas will receive more rainfall and some areas will have drought.

• Solar activity – the formation of sunspots appears to correspond with warm periods in Europe and North America

• Tectonic Plate movements• Changes in the Earth’s orbit or tilt of the


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Human Impact on Climate Change

• The greenhouse effect is the natural warming of both Earth’s surface and the lower atmosphere.

• The greenhouse effect is important because it makes life on earth possible

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Global warming• As a result of increases in carbon dioxide levels,

as well as other greenhouse gases, global temperatures have increased.

• Warmer temperatures results in greater evaporation. More water vapor in the atmosphere results in more radiation absorbed.

• Climate patterns will change and as ice caps melt, global sea levels will rise.

• Global warming might cause a greater number of hurricanes, intense heat waves and droughts, changing vegetation patterns and more disease-causing insects

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