Climate and Climate Change Chapter 21 Climate and Climate Change

Chapter 21.1

What is Climate?

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

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.

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)

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.

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.

Chapter 21.2

Climate Zones

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

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)

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

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

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

Chapter 21.3

Climate Change

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

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

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.

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

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