Chapter 21.1

• Climate is an area’s long-term pattern of weather
• The two main characteristics of climate are Temperature and Precipitation
• Other characteristics are the number of days and hours of sunlight; direction, speed and steadiness of the wind; and occurrence of severe weather

• Annual Temperature range is the difference between the average temperature of the warmest month and the average temperature of the coldest month
• Average Temperature can be misleading.
– e.g. Average temperature for Beijing, China, and Valdivia, Chile are the same. However,
Beijing goes to extremes from –4°C to 26°C while Valdivia ranges from 7°C to 16°C.

• Average Precipitation can also be misleading, one place may get all its rain during a few months (Bombay, India) and another over the entire year (Mobile,
Alabama)

• Latitude – generally colder toward poles with little precipitation
• Elevation – higher the cooler and drier
• Nearby Water – Temperature range small mild climate if downwind more moisture
• Ocean Currents – warm currents warm nearby coasts
• Topography – leeward side warmer than windward, windward side may be wetter, can act as a barrier to air masses.

• Prevailing Winds – blow from a hot or cold region, blow from water or land
• Vegetation – will effect insulation, releases water vapor
• Some climate controls are more important than others depending on location.
– e.g. London, England is pretty far north, however the warm ocean currents keep its climate mild.

Chapter 21.2

• Very cold in winter with little or no daylight
• The sun strikes at such a low angle in summer it provides little solar energy
• Much of the light is reflected back to space by snow and ice
• Tundra are located in Polar Climates, they are very cold with little precipitation
• Ice caps are another sub climate in polar climates

• Occur in regions that lose more water due to evaporation than it receives from rain
• Dry climates often exist on leeward sides of mountain ranges and where air sinks in the horse latitude
• Semi-arid climates are not as dry as deserts and are often home to dense grasses. (Great Plains of the US)

• Hot year round – near the equator…ITCZ
• Two sub climates…Tropical wet & Tropical wet and dry – wet summers, dry winters.

• Mild winter – There are 3 types
– Humid subtropical – SE U.S. – Hot muggy summer, mild winters
– Marine west coast – west coast of Canada and
NW U.S. – cool summers, mild winters
– Mediterranean – west coast of SW U.S. & the
Mediterranean Sea – dry summers – wet winters with mild temperatures

• Severe winters – snow often covers ground in winter but summers are warm – subclimates humid continental and the subarctic
– Humid continental – found in the interior of continents and on eastern coasts including the N U.S. east of the great plains – winters very cold and summers very warm
– Subarctic – near poles – short summers
• Highlands – mountainous regions in which multiple climates exist

Chapter 21.3

• Global mean temperature during the last
Ice Age was only 5°C cooler than today’s global mean temperature
• If an increase in cloud or ice cover causes more sunlight to be reflected out to space,
Earth may cool

– Earth’s Motion – shape of its orbit, tilt of its axis varies between 22.1° to 24.5° in a
41,000 year period
•
These changes affect sun intensity which may allow ice to grow on surface
– Plate tectonics – moving of the continents
• e.g. Greenland is thought to once have a warmer climate
(close to equator) because of tropic fossils found in
Greenland

– Sunspots – the more sunspots the more energy given off by the sun
– Volcanoes – increase dust, clouds and CO
2
– may add to warming the atmosphere like what happened during the cretaceous period.

• Due to deforestation and fossil fuel burning CO
2 in the atmosphere has increased since the 1800’s
– Computer models not accurate because of all the variables

• Scientists use sea floor sediments, glacier samples and tree rings to study the past climates