Climate and Climate Climate and Climate ChangeChange

Chapter 21Chapter 21

Chapter 21.1Chapter 21.1

What is Climate?What is Climate?

Temperature and PrecipitatiTemperature and Precipitationon• Climate is an area’s long-term pattern Climate is an area’s long-term pattern

of weatherof weather• The two main characteristics of climate The two main characteristics of climate

are Temperature and Precipitationare Temperature and Precipitation• Other characteristics are the number of Other characteristics are the number of

days and hours of sunlight; direction, days and hours of sunlight; direction, speed and steadiness of the wind; and speed and steadiness of the wind; and occurrence of severe weatheroccurrence of severe weather

• Annual Temperature range is the difference Annual Temperature range is the difference between the average temperature of the between the average temperature of the warmest month and the average warmest month and the average temperature of the coldest monthtemperature of the coldest month

• Average Temperature can be misleading.Average Temperature can be misleading.– e.g. Average temperature for Beijing, China, e.g. Average temperature for Beijing, China,

and Valdivia, Chile are the same. However, and Valdivia, Chile are the same. However, Beijing goes to extremes from –4°C to 26°C Beijing goes to extremes from –4°C to 26°C while Valdivia ranges from 7°C to 16°C.while Valdivia ranges from 7°C to 16°C.

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

Climate ControlsClimate Controls• Latitude – generally colder toward poles with Latitude – generally colder toward poles with

little precipitationlittle precipitation

• Elevation – higher the cooler and drierElevation – higher the cooler and drier

• Nearby Water – Temperature range small Nearby Water – Temperature range small mild climate if downwind more moisturemild climate if downwind more moisture

• Ocean Currents – warm currents warm Ocean Currents – warm currents warm nearby coastsnearby coasts

• Topography – leeward side warmer than Topography – leeward side warmer than windward, windward side may be wetter, can windward, windward side may be wetter, can act as a barrier to air masses.act as a barrier to air masses.

• Prevailing Winds – blow from a hot or cold Prevailing Winds – blow from a hot or cold region, blow from water or landregion, blow from water or land

• Vegetation – will effect insulation, Vegetation – will effect insulation, releases water vaporreleases water vapor

• Some climate controls are more important Some climate controls are more important than others depending on location.than others depending on location.– e.g. London, England is pretty far north, e.g. London, England is pretty far north,

however the warm ocean currents keep its however the warm ocean currents keep its climate mild.climate mild.

Chapter 21.2Chapter 21.2

Climate ZonesClimate Zones

Polar ClimatesPolar Climates• Very cold in winter with little or no daylightVery cold in winter with little or no daylight

• The sun strikes at such a low angle in The sun strikes at such a low angle in summer it provides little solar energysummer it provides little solar energy

• Much of the light is reflected back to space Much of the light is reflected back to space by snow and iceby snow and ice

• Tundra are located in Polar Climates, they Tundra are located in Polar Climates, they are very cold with little precipitationare very cold with little precipitation

• Ice caps are another sub climate in polar Ice caps are another sub climate in polar climatesclimates

Dry Climates – cover 30% of Dry Climates – cover 30% of EarthEarth• Occur in regions that lose more water Occur in regions that lose more water

due to evaporation than it receives from due to evaporation than it receives from rainrain

• Dry climates often exist on leeward sides Dry climates often exist on leeward sides of mountain ranges and where air sinks of mountain ranges and where air sinks in the horse latitudein the horse latitude

• Semi-arid climates are not as dry as Semi-arid climates are not as dry as deserts and are often home to dense deserts and are often home to dense grasses. (Great Plains of the US)grasses. (Great Plains of the US)

Humid Tropical ClimatesHumid Tropical Climates

• Hot year round – near the equator…Hot year round – near the equator…ITCZITCZ

• Two sub climates…Tropical wet & Two sub climates…Tropical wet & Tropical wet and dry – wet summers, Tropical wet and dry – wet summers, dry winters.dry winters.

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

• Mild winter – There are 3 typesMild winter – There are 3 types– Humid subtropical – SE U.S. – Hot muggy Humid subtropical – SE U.S. – Hot muggy

summer, mild winterssummer, mild winters– Marine west coast – west coast of Canada Marine west coast – west coast of Canada

and NW U.S. – cool summers, mild wintersand NW U.S. – cool summers, mild winters– Mediterranean – west coast of SW U.S. & Mediterranean – west coast of SW U.S. &

the Mediterranean Sea – dry summers – the Mediterranean Sea – dry summers – wet winters with mild temperatureswet winters with mild temperatures

• Severe winters – snow often covers Severe winters – snow often covers ground in winter but summers are ground in winter but summers are warm – subclimates humid continental warm – subclimates humid continental and the subarcticand the subarctic– Humid continental – found in the interior Humid continental – found in the interior

of continents and on eastern coasts of continents and on eastern coasts including the N U.S. east of the great including the N U.S. east of the great plains – winters very cold and summers plains – winters very cold and summers very warmvery warm

– Subarctic – near poles – short summersSubarctic – near poles – short summers

• Highlands – mountainous regions in Highlands – mountainous regions in which multiple climates existwhich multiple climates exist

Chapter 21.3Chapter 21.3

Climate ChangeClimate Change

Cause of Climate ChangeCause of Climate Change

• Global mean temperature during the Global mean temperature during the last Ice Age was only 5°C cooler than last Ice Age was only 5°C cooler than today’s global mean temperaturetoday’s global mean temperature

• If an increase in cloud or ice cover If an increase in cloud or ice cover causes more sunlight to be reflected causes more sunlight to be reflected out to space, Earth may coolout to space, Earth may cool

There is thought to be 4 There is thought to be 4 basic causes for climate basic causes for climate changechange

– Earth’s Motion – shape of its orbit, tilt of Earth’s Motion – shape of its orbit, tilt of its axis varies between 22.1° to 24.5° in its axis varies between 22.1° to 24.5° in a 41,000 year perioda 41,000 year period• These changes affect sun intensity which may allow ice These changes affect sun intensity which may allow ice

to grow on surfaceto grow on surface

– Plate tectonics – moving of the Plate tectonics – moving of the continentscontinents• e.g. Greenland is thought to once have a warmer climate e.g. Greenland is thought to once have a warmer climate

(close to equator) because of tropic fossils found in (close to equator) because of tropic fossils found in GreenlandGreenland

– Sunspots – the more sunspots the more Sunspots – the more sunspots the more energy given off by the sunenergy given off by the sun

– Volcanoes – increase dust, clouds and Volcanoes – increase dust, clouds and COCO22 – may add to warming the – may add to warming the atmosphere like what happened during atmosphere like what happened during the cretaceous period.the cretaceous period.

Human Effects on ClimateHuman Effects on Climate

• Due to deforestation and fossil fuel Due to deforestation and fossil fuel burning COburning CO22 in the atmosphere has in the atmosphere has increased since the 1800’sincreased since the 1800’s– Computer models not accurate because Computer models not accurate because

of all the variablesof all the variables

Measuring Climate ChangeMeasuring Climate Change

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