Download CH. 18 Climate and Climate Change I. Climate – long term “normal

CH. 18 Climate and Climate Change
I. Climate – long term “normal” weather for an area – ex) Pacific Northwest is wet most
of the year, not too hot, and not too cold
A. Causes of climate - temperature
1. Latitude – how far north or south of equator – measured as an angle
a. equator at 0o, poles 90o
b. farther away from equator, cooler temps
1) tropical zone – between 23.5o north or south of equator
a) never freezes
b) lots of rain forests
2) polar zone – 66.5o to 90o
3) temperate zone - 23.5o to 66.5o N and S of equator
a) warm summers and cold winters
2. altitude – higher alt. – cooler climate ex) snow covered mountains
3. large bodies of water
a. marine climate – close to oceans – not too hot, not too cold
b. continental climates – inland – hot summers and cold winters
4. ocean currents – warm currents make area warmer than should be for
latitude, cold currents colder climate
B. Causes of climate – precipitation
1. prevailing winds – normal wind direction
a. if come from over water, wetter climate
2. mountain ranges – cause air to lift or sink
a. windward – side of mountain that wind blows toward
1) causes air to rise, so wet
b. leeward – side of mountain away from wind
1) air sinks, so dry – causes many deserts – called rain
shadow
C. Microclimates – small area with different climate than the region due to
mountains, lakes, etc.
D. Seasons – caused by Earth’s tilted axis
1. axis tilts 23.5o toward north (diagram p 603)
2. summer, axis tilt causes sun’s rays to be more direct
a. noon sun higher in sky
b. longer days and shorter nights
3. winter, axis tilt causes sun’s rays to be less direct
a. noon sun lower in sky
b. shorter days, longer nights
II. Climate Regions – classified by temp. and moisture
A. Tropical Rainy Climates – low lands along equator
1. tropical rain forests – most different types of plants and animals
2. tropical savannas – have wet and dry seasons
a. grassland with scattered clumps of trees
B. Dry Climates
1. deserts – arid areas with under 10 in. precip. per year
a. may be cold
2. steppe – grassland or prairie – semiarid
a. 10 to 20 inches precip. per year
b. often in middle of contient
C. Temperate Marine Climate
1. temperate rain forest – 40o N or S of equator – our climate
2. Mediterranean – mild wet winters, long dry summers
a. Coastal California, Spain, etc.
b. chaparral – dense shrubs
c. temperate savanna
3. humid subtropical – near edge of tropics
a. hot wet summers, cooler drier winters
b. southeast US
D. Temperate Continental Climates
1. humid continental – most of northern US
a. warm moderately wet summers, cold a little drier in winter
2. Subarctic – Canada, Alaska, Russia
a. long cold winter, short warmish summer
b. Boreal Forest – small slow growing trees
E. Polar Climates – near North and South Poles
1. Ice cap – average temp. below freezing
2. tundra – short cool summer, long very cold winter, little precip.
a. permafrost – permanently frozen soil a couple of inches below
surface
1) water can’t drain, so lots of swampy areas – mosquitos
b. no trees
F. Alpine tundra – above tree line on mountains
III. Long-Term Changes in Climate – ice ages to tropical Earth
A. Studying climate change
1. fossils – a fossilized plant needed the same climate as the same type of
plant today
2. tree rings – thicker tree rings show good growing conditions that year
a. oldest living tree over 5,000 years old
3. pollen – finding pollen in sedimentary rock tells what plants lived there
B. Ice Ages – huge sheets of ice covered large areas of Earth
1. there were 4 ice ages of about 100,000 years each over the past 2
million years
C. natural causes of climate change
1. Earth’s position – hypothesis – Earth’s distance and axis tilt change
slightly over a 26,000 year cycle
2. Sun’s Energy – sun gives off different amount of energy from year to
year
3. Continental Drift – continents move over time
a. Antarctica was once over the equator
b. moving land will change ocean currents and wind patterns
IV. Global Changes in the Atmosphere
A. Global temperature change – world average temp is rising, though some areas
may get cooler
1. greenhouse gases – human burning of fossil fuels has increased the
amount of greenhouse gases in the atmosphere
a. holds in heat from sun
2. effects
a. increased drought – not enough rain for crops
1) more forest fires
b. more severe storms – thunderstorms and tornados
1) heavier rain – more flooding
2) larger hail
3) stronger wind
c. sea level rise – current estimates are lower than what we are
seeing
1) Island Countries in the Pacific have flooded and
population moved
2) many coastal cities expected to flood in next 200 years