1. Climate and Climate Change
Chapter 21
Climate and Climate Change

2. Chapter 21.1

3. What is Climate?

4. Temperature and Precipitation
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

5. Average Temperature can be misleading.
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.

6. 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)

7. Climate Controls
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.

8. Vegetation – will effect insulation, releases water vapor
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.

9. Chapter 21.2

10. Climate Zones

11. Polar Climates 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

12. Dry Climates – cover 30% of Earth
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)

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

14. Most mid-latitude Climate – There are 2 of them, one with mild winters, the other with severe 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

15. Highlands – mountainous regions in which multiple climates exist
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

16. Chapter 21.3

17. Climate Change

18. Cause of Climate Change
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

19. There is thought to be 4 basic causes for climate change
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

20. Sunspots – the more sunspots the more energy given off by the sun
Volcanoes – increase dust, clouds and CO2 – may add to warming the atmosphere like what happened during the cretaceous period.

21. Human Effects on Climate
Due to deforestation and fossil fuel burning CO2 in the atmosphere has increased since the 1800’s
Computer models not accurate because of all the variables

22. Measuring Climate Change
Scientists use sea floor sediments, glacier samples and tree rings to study the past climates