Climate and Ecosystems

Chapter 11

• We’ve talked about Global Climate Change (sometimes called Global Warming).

• What is climate?

• What effects can a changing climate have on living organisms?

• Suppose your region has an especially hot summer, followed by a very cold winter that includes a snowstorm. Does this support, disprove, or have little to do with Global Climate Change?

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Climate• Climate is not the same thing as

weather!

• Climate consists of the prevailing weather patterns in a region over longs periods of time.

• Climate is caused by many factors, including location on the globe, nearness to an ocean, wind direction, geography.

True or False: Summer is warmer than winter because the earth is closer to the sun in the

summer.

1 2

62%

38%1. True2. False

True or false: When it is winter in the northern hemisphere, it is summer in the southern

hemisphere.

1 2

31%

69%

1. True2. False

Think about this…• If it were true that seasons were

caused by the earth being closer to or further away from the sun…

• …how would it be possible that the southern hemisphere is experiencing summer while the northern hemisphere is experiencing winter?

• Remember, we are 93 million miles from the sun. Small changes in distance aren’t going to have a big effect.

90° N

90° S

NorthPole

SouthPole

0°

0°

23.5°tilt

equator

June 21st :northern summersolstice; southernwinter solstice

December 21st :northern wintersolstice; southernsummer solstice

23.5°tilt

Summer in theNorthernHemisphere

Summer in theSouthernHemisphere

The sun drives climate as well as the seasons.

• Average temperature at any part of the globe is affected not by how close we are to the sun (a common misconception) but by the angle of incidence of the sun’s rays.

Less direct rays = less solar energy =

cooler region

More direct rays = more solar energy =

warmer region

• Global air circulation influences local climates.

• Rising air cools and drops moisture.

• Descending air tends to be dry.

cool, moistair rises(rain/snow)

warm, dryair falls

PolarEasterlies

hot,moistair rises(rain)

warm, dryair falls

cool, moistair rises(rain/snow)

polar cap90 S

60 S

30 S

30 N

90 Npolar cap

cold, dryair falls

60 N

0

Westerlies

S.E.Tradewinds

N.E.Tradewinds

rainforest

desert

rotation

Westerlies

PolarEasterlies

desert

rainforest

cold, dryair falls

• According to this diagram, where on the planet should we find:

• Deserts?

• Tropical rain forests?

• Permanent snowfields?

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A. Cool, moist, rising air

B. Warm, dry,

falling air

C. Warm, moist, rising

air

• Ocean current also affects climate.

• Water tends to absorb and retain heat, and lose it slowly.

• Ocean water near the equator tends to be warm, so currents from the equator are warm.

• Water near the poles is much cooler.

• The Gulf Stream carries warm water from the equator northward, warming the coast of Europe.

• There is evidence that the Greenland ice is melting, due to Global Climate Change, and pouring cold water into the North Atlantic. If enough cold water is dumped into the Atlantic, it could divert the Gulf Stream.

If the Greenland ice melts and disrupts the Gulf Stream, what will happen to the climate of

Northern Europe?

1 2 3

84%

2%

14%

1. It will get much colder.2. It will get much

warmer.3. There will be very little

change.

• Observe this diagram of the Jet Stream, prevailing winds across the North American Continent.

• Remembering that oceans tend to absorb more heat than land, and that currents and wind pattern affect climate, explain the pattern of climate across North America as shown by the map of USDA planting zones in the next slide.

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Climate Fluctuations

• Some natural processes can cause local climate to fluctuate from year to year.

• One example: El Niño/ La Niña weather cycles along the American Pacific coasts.

More info at: http://www.sbg.ac.at/ipk/avstudio/pierofun/atmo/elnino.htm

In an El Niño cycle, prevailing Trade Winds weaken. Warm water spreads back across

the Pacific, disrupting upwellings along the

South American coast.

As a result of El Niño, what happens to the fishing industry off of the coast of Peru?

1 2 3

22%

14%

63%

1. Warmer water increases the nutrients and the number of fish.

2. Loss of cold upwellings decreases nutrients and the number of fish.

3. There is no change to the fishing industry; this is just part of the weather cycle.

Local Climate

• Localized climate zones can be caused by:

• Proximity to oceans or large lakes.

• Position of mountain ranges.

• Wind direction.

Oregon Coast Peruvian Coast

Oregon is on the west side of the North American continent. Peru is on the west side

of the South American continent. Why do these two areas look so different?

moist climate

dry climate inrain shadow

Water is carriedfrom ocean byprevailing winds.

Water is releasedas air rises andcools.

Dry air sinks,warms andabsorbs waterfrom the land.

The rain shadow effect can cause moist conditions on one side of a mountain range and dryer conditions on the opposite side of

the mountains.

On the Peruvian coast, prevailing winds blow from the mountains toward the ocean. What

effect might that have on climate on the coast of Peru?

Lake Effect

Lakes, too, can influence local climate if they are large enough.

alti

tud

e

low

high

latitude

equator(0°)

poles(90°)

deciduousforest

tundra

rock, snow, ice

coniferousforest

tropicalforest

Altitude and latitude also interact to create local climates that support different types of

communities.

• Observe the map of Oregon on the next slide. Use what you have learned to explain the average rainfall in the different areas of the state indicated on the map.

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Coastal Mountains

Pacific Ocean

Cascade Mountains

Eastern Oregon:

6 – 8 inches

Willamette Valley:

25-30 inches

Oregon Coast:

70-100 inches

If the prevailing winds in Oregon blew from east to west, what would our coastline be like?

1 2 3

33% 33%33%1. Rainy, as it is

now.2. Dry, like Peru.3. A mixture of dry

and wet areas, depending on the local terrain.

• The prevailing winds blow from west to east on the North American continent. Why is the east coast of the U.S. NOT a dry desert like Peru?

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Recap

• Climate begins with the sun’s heat.

• Climate is influenced by ocean and atmospheric currents, which are driven by the sun’s heat.

• Geography influences local climate.

• Climate directly affects what organisms can live in an area.