Transcript 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
• 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.
• 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
• 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