ATMOSPHERE AND CLIMATE CHANGE CHAPTER 13 1
ATMOSPHERE AND CLIMATE CHANGE
CHAPTER 131
SECTION 1: CLIMATE AND CLIMATE CHANGE
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WEATHER AND CLIMATEWeather – the state of the atmosphere in one area at one time.
• What is the weather today here?• What is the weather in Anchorage, Alaska?
Climate - the long term prevailing weather at a
particular place
• What is the climate for here?
• What is the climate for Anchorage, Alaska?
Two places can have the same weather on the same day
• But they can have VERY different climates• Weather: Seattle and Phoenix might both have rain today• Climate : Seattle is wet and cool, Phoenix is dry and hot
**It depends on their proximity top the equator. 3
WHAT DETERMINES CLIMATEClimate is determined by:
• Atmospheric Circulation
Patterns• Oceanic Circulation Patterns• Local geography• Solar activity• Volcanic Activity
Which is most important?• Latitude
(How far above/below you are from the equator)
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LATITUDE
Latitude is the distance north or south of the equator. Measured in degrees.
• Equator is 0 degrees, the poles are 90 degrees
• Low Latitudes – get the strongest, most concentrated sunlight.
• Night and Day are 12 hours, all year round
• High temps all year round
• High Latitudes – sunlight is spread over a greater area, weaker, less energy
• Daylight hours vary• At the poles the sun sets
for only a few hours during the summer
• Dark almost all day during winter
• Average annual temperatures lower than at equator. 5
ATMOSPHERIC CIRCULATIONThree basic rules:
1. Cold air sinks – but pressure
is stronger at lower levels so cold air
gets compressed and thus warms.
2. Warm Air Rises – lower
pressure lets it expand and it cools
down
3. Warm Air holds more water vapor
than cold air – so as it rises the water vapor
cools and condenses
How do we get wind?
1. Sun heats the earth surface.
2. Hot Air Rises
3.Cold Air replaces it………wind! 6
•Earth gets heated differently
• More heat at equator, more air rising
• Rising air cools making lots of clouds! And rain!.(think where are our jungles?)
• Cool air can’t sink back down because of continuous rising hot air
• Has to spread north and south until it eventually cools enough that it begins to sink…and warm
• Dry warm air sinks at 30 North and 30 South
• What do we find at 30 North and South around the globe?
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•Prevailing winds – winds that blow predominantly in one direction most of the year.
• From what direction does our prevailing wind come from?
(They are deflected to the right in the Northern Hemisphere)•Trade Winds – the prevailing winds between 30° and equator.
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OCEAN CIRCULATION PATTERNS•Water holds a lot of heat
(think how much heat it
takes to boil water!)
• Ocean currents are caused by
winds and the movement of the earth
•The ocean currents move heat
around the globe.
• In the summer where would you rather swim?
Off California coast in LA or off the South Carolina coast• Colder water flows south from Alaska, warm water flows
north from the Caribbean
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EL NINO VS LA NINA
•Some ocean currents change the way they flow:
• El Nino- • Pacific Ocean water near
Americas warms – leads to
increased clouds and rainfall
in SW US
• La Nina • Opposite of El Nino, cooler
waters in Pacific near Americas,
droughts in the SW US
• Pacific Decadal Oscillation• Similar to El Nino but the
switching occurs every
20 – 30 years
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TOPOGRAPHY•Topography is a broad term used to describe the detailed study of the earth's surface.
•Where is Mt Kilimanjaro? (Tanzania)
• It has snow all year
round!• That’s due to its height
(colder as you go up in
atmosphere!)
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•Rain Shadow• Dry area on the
eastern sideof
mountains
SUN’S IMPACT•Solar Cycle – 11 year cycle of the sun.
• At the maximum – the sun emits UV radiation
• This can warm the lower atmosphere and Earth.
• On earth the Northern Lights can be seen as far south as Mexico on occasion.
• Increased radiation from the sun can cause warming of the atmosphere
Seasons – Why do we have them?
All due to the tilt of the earth – 23.5° relative to the plane of its orbit. (Angle of the sun’s rays striking the Earth)
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http://www.nasa.gov/mov/143924main_AmazChangeSun_QT%20big%20progre.mov
THAT’S ALL FOR 13.1
Time for a reading quiz
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SECTION 2: THE OZONE SHIELD
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OZONE LAYER
•Ozone is the chemical compound O3
• Large concentration is found in the stratosphere
• Ozone Layer absorbs most UV radiation coming from the sun
• UV radiation can damage organisms cells
•Chemicals Can Destroy Ozone
• CFCs – chlorofluorocarbons• CFCs are non flammable, non poisonous,
and non reactive at the Earth’s surface• CFCs used as propellants in spray cans
and coolants in fridges/air conditioners• It takes 10 -20 years for CFCs to reach
the stratosphere from the Earth's surface
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•CFCs are broken apart in the stratosphere
• High energy of the UV radiation breaks it down
• The single chlorine from CFC can react with O3 and changes it, depleting the O3
• Scientists estimate that a single chlorine atom can break down 100,000 ozone molecules.
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OZONE HOLE• First noticed in 1970 from satellite
photos over the South Pole
• What Causes it?
• During the cold polar winters, dry stratospheric air over the pole is isolated.
• Air becomes so cold that it condenses and forms clouds
(Polar Stratospheric clouds: high-altitude clouds made of water and nitric acid at - 80° C)• Chlorine from CFCs builds up
on the surface of the clouds• When the pole begins to warm
the chlorine goes back to depleting ozone. 17
VIDEO ON OZONE DEPLETION
http://video.nationalgeographic.com/video/news/environment-news/antarctica-ozone-vin/
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WHY CARE ABOUT OZONE?• Ever have a bad sunburn?
• UV radiation can damage organisms DNA
• Can lead to skin and other cancers• Notable impact to amphibian eggs (death/mutations)
• Phytoplankton can be killed by UV
• Phytoplankton is the producer for most ocean food chains
• Phytoplankton loss would also effect atmospheric CO2 levels
• Montreal Protocol
• Many nations banned the use of CFCs in 1992 (US stopped production by 2000)
• CFCs still a problem….Why?
• CFCs molecules remain in the stratosphere for 60 – 120 years
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THAT’S ALL FOR 13.2
Time for a reading quiz
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SECTION 3: GLOBAL WARMING 21
GREENHOUSE EFFECT• The earth is like a greenhouse
• The atmosphere acts like the glass – which lets the sun’s rays pass through.
• The earth absorbs this as heat energy and keeps it in, only letting a little heat out
• The gases in the atmosphere absorb the radiation keeping it from escaping out to space
• This absorption of radiation by gases is called the greenhouse effect
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GREENHOUSE GASES• Water Vapor, CO2, CFCs, Methane and NOx all absorb radiation
• Water vapor and CO2 are the primary greenhouse gases
• Since 1958 (in Hawaii) CO2 levels have been measured – reflective of the entire earth (the gases have traveled across the entire Pacific Ocean)
• Levels are higher in the winter: fewer leaves on the trees (dying grasses and leaves release carbon)
• General increase because of burning fossil fuels(not just in winter)
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GLOBAL WARMING• Where does all the CO2 come from?
• Power plants and cars that burn fossil fuels and deforestation
• Why be concerned?
• CO2 is a greenhouse gas
• Scientists believe the increase will warm earth more than normal
• Direct correlation between CO2 levels and global warming
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WHAT HAPPENS IF THE EARTH WARMS?• Melting Ice and Rising Sea Levels
• Coastal areas flooded• Nearly 3 billion people live
within 100 km of a coast• Excess sea water can change
freshwater aquifers near coasts
• Changing Weather Patterns
• Warming the oceans could change
currents that influence weather today
• Human Health Problems
• Deaths due to heat waves• Longer growing seasons, more pollen, more asthma• Warmer weather allow mosquitoes and other disease carrying
organisms to live longer 25
• Agriculture
• Heat leads to droughts, severe impact to crops
• May change where plants and animals live
• Kyoto Protocol
• Nations met and laid out timelines for reducing CO2
emissions• Decrease emissions by 5%
from 1990 levels by 2012.
• Reducing CO2 is difficult for developing countries
• Need industry using cheap fossil fuel to improve economies
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THAT’S ALL FOR 13.3
Time for a reading quiz
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