The Atmosphere

1
The Atmosphere Climate Change
2
Climate

• Climate - average weather conditions in an area
  over a long period of time.
• Determined by
• Latitude
• atmospheric circulation patterns
• oceanic circulation patterns
• local geography
• solar activity
• volcanic activity
• Most important latitude

3
Latitude

• Latitude - distance north or south from the
  equator
• The equator is located at 0 latitude.The most
  northerly latitude is the North Pole, at 90
  north, whereas the most southerly latitude is the
  South Pole, at 90 south.
• Latitude affects climate because the amount of
  solar energy an area receives depends on its
  latitude.

4
Low Latitudes

• More solar energy falls on areas near the equator
  than on areas closer to the poles.
• Incoming solar energy is concentrated on a small
  surface at the equator.
• Night and day are about 12 hours long throughout
  the year.

5
High Latitudes

• In the northern and southern latitudes, sunlight
  hits the Earth at an angle and spreads over a
  larger surface area.

6
High Latitudes

• The hours of daylight also vary.
• At 45 north and south latitude, there is as much
  as 16 hours of daylight each day during the
  summer and as little as 8 hours of sunlight each
  day in the winter.
• Sun sets for only a few hours each day during the
  summer and rises for only a few hours each day
  during the winter near the poles.
• Yearly temperature range near the poles is large.

7
(No Transcript)
8
(No Transcript)
9
Atmospheric Circulation

• 3 important properties of air
• Cold air sinks because it is denser than warm
  air.
• As the air sinks, it compresses and warms.
• Warm air rises.
• It expands and cools as it rises.
• Warm air can hold more water vapor than cold air.
  
• When warm air cools, the water vapor it contains
  may condense into liquid water to form rain,
  snow, or fog.

10
Atmospheric Circulation

• Solar energy heats the ground, which warms the
  air above it.
• Warm air rises, cooler air moves in to replace it
  wind
• Because the Earth rotates, and because different
  latitudes receive different amounts of solar
  energy, a pattern of air circulation results.
• This circulation determines Earths precipitation
  patterns.

11
(No Transcript)
12
Atmospheric Circulation

• Warm air can hold large amounts of water vapor.
  As warm air rises and cools, its ability to hold
  water is reduced.
• Low latitudes receive large amounts of rain.

13
Global Circulation Patterns

• Cool air over the equator cannot descend because
  hot air is rising up below it.
• Air is forced to about 30º N and 30º S.
• Some air sinks and becomes warmer as it descends.
  
• Warm, dry air causes water to evaporate from the
  land below, creating dry conditions.

14
Prevailing Winds

• Winds that blow mostly in one direction are
  called prevailing winds.
• Winds are deflected to the right in the Northern
  Hemisphere and to the left in the Southern
  Hemisphere.

15
Prevailing Winds

• Belts of winds are called trade winds.

16
(No Transcript)
17
Prevailing Winds

• Westerlies are produced between 30º and 60º N and
  S.
• Northern Hemisphere southwest winds
• Southern Hemisphere northwest winds
• The polar easterlies blow from the poles to 60º
  north and south latitude.

18
Oceanic Circulation

• Water holds large amounts of heat.
• Surface ocean current movement is caused mostly
  by winds and the rotation of the Earth.
• Surface currents redistribute warm and cool
  masses of water around the world
• Affects climate

19
(No Transcript)
20
(No Transcript)
21

• Deep Ocean Currents
• Not driven by wind
• Driven by thermohaline circulation (density)

22
Global Warming?...

• Many scientists fear that global warming could
  affect the global conveyor belt. If global
  warming leads to increased rain, as some believe
  it might, the added fresh water could decrease
  the salinity levels at the poles. Melting ice,
  another possibility of global warming, would also
  decrease salinity levels. Regardless of the
  means, the end scenario is the same Warmer, less
  dense water won't be dense enough to sink, and
  the global conveyor belt could stop -- having
  far-reaching and devastating consequences
• NOAA "Currents"

23
Oceanic Circulation

• Warm water nutrient poor, little biodiversity
• Cool water nutrient rich, much biodiversity

24
Ocean Circulation

• El Niño - occurrence in the eastern Pacific Ocean
  in which the surface-water temperature becomes
  unusually warm.
• Winds in the western Pacific Ocean, strengthen
  and push warm water eastward.
• Rainfall follows warm water eastward
• Produces increased rainfall in the southern half
  of the U.S. and drought in Australia.

25
(No Transcript)
26
Ocean Circulation

• La Niña - occurrence in the eastern Pacific Ocean
  in which the surface water temperature becomes
  unusually cool.
• El Niño (warm) and La Niña (cool) are opposites

27
(No Transcript)
28
(No Transcript)
29
(No Transcript)
30
(No Transcript)
31
Topography

• Elevation effects climate.
• Temperatures fall by about 6C (about 11F) for
  every 1,000 m increase in elevation.
• Mountain ranges effect the distribution of
  precipitation rain shadow

32
(No Transcript)
33
Other influences on climate

• The sun and volcanic eruptions influence Earths
  climate.
• Increased solar radiation can also warm the lower
  atmosphere and surface of the Earth a little.

34
Other influences on Climate

• In large volcanic eruptions, sulfur dioxide gas
  can reach the upper atmosphere.
• The sulfur dioxide (remains for up to 3 years)
  reacts with water vapor and dust to form a layer
  of haze that reflects sunlight global temp
  declines

35
Greenhouse Effect

• The Earths atmosphere acts like the glass in a
  greenhouse.
• As this heat radiates up from Earths surface,
  some of it escapes into space. The rest of the
  heat is absorbed by gases in the troposphere.

36
(No Transcript)
37
Greenhouse Gases

• A greenhouse gas is composed of molecules that
  absorb and radiate heat from the sun.
• The major greenhouse gases are
• water vapor
• carbon dioxide
• CFCs
• Methane
• nitrous oxide.
• Water vapor and carbon dioxide account for most
  of the absorption that occurs in the atmosphere.

38
Greenhouse Gases

• Ranking by contribution to greenhouse effect
• water vapor, 3672
• carbon dioxide, 926
• methane, 49
• Characteristics and abundance of the gas affect
  contribution.
• Example - methane is a much stronger greenhouse
  gas than carbon dioxide, but is present in
  smaller concentrations so that its total
  contribution is smaller.

39
Greenhouse Gases

• Carbon dioxide levels rise and fall with the
  daily rhythms of photosynthesis.
• Near cities, carbon dioxide from traffic and
  industrial pollution raises the concentration of
  the gas.

40
Greenhouse Gases

• Carbon dioxide levels drop in the summer due to
  more photosynthesis.
• In the winter, dying grasses and fallen leaves
  decay and release carbon that was stored in them,
  causing levels to rise.

41
Greenhouse Gases

• Many scientists think that because greenhouse
  gases trap heat near the Earths surface, more
  greenhouse gases in the atmosphere will result in
  an increase in global temperature.

42
(No Transcript)
43
Greenhouse Gases

• Today, we are releasing more carbon dioxide than
  any other greenhouse gas into the atmosphere.
• Carbon Dioxide gets into the atmosphere by
• Burning fossil fuels
• Burning forests
• Decaying organisms

44
(No Transcript)
45
Global Warming

• Global warming is a gradual increase in the
  average global temperature that is due to a
  higher concentration of greenhouse gases in the
  atmosphere.
• Earths average global temperature increased
  during the 20th century and many scientists
  predict that this warming trend will continue
  throughout the 21st century.

46
(No Transcript)
47
Global Warming

• However, not all scientists agree that the
  observed global warming is due to greenhouse
  gases.
• Some scientists believe that the warming is part
  of natural climatic variability.
• Widespread fluctuations in temperature have
  occurred throughout geological time.

48
Global Warming

• Harmful Effects of Global Warming
• Disruption of global weather patterns
• Deep ocean currents stop circulating
• More hurricanes
• Flooding and drought
• Rise in sea level
• Ice at the poles melts
• Increases the distance that storms can penetrate
  land
• Destroys agricultural land because of salts left
  behind by receding water
• Impact Human health
• Increased malaria, other water borne diseases

49
Global Warming

• Harmful Effects
• Impact agriculture
• Shift in growing zones
• Decreased crop yields
• Increased demand
• Change animal and plant populations
• Extinction
• Flooding
• wetlands/coastal areas will flood and wipe out
  real estate
• Worlds most productive rice growing areas would
  be destroyed
• Changing Salinity
• Marine fisheries go under
• Salt water enters drinking water aquifers

50
(No Transcript)
51
Global Warming

• Harmful Effects
• More heat related deaths
• Young and old at greatest risk
• Increased ground level ozone
• Increased respiratory problems
• Reduction of plankton and algae
• Reduces organisms higher in the food chain
• Reduces coral reefs that depend on algae
• Change in geographic range of animals
• Some birds will not fly as far south

52
Global Warming

• Beneficial Effects
• Lower heating costs in winter
• Reduces fossil fuel demand
• Northern land suitable for human settlement
• Tundra biomes may become nicer places to live
• Extended ranges of fish, birds, mammals
• Mockingbird, cardinal, opossum
• Increased rainfall/Longer growing seasons
• Increase in food production
• Could change the political/economic clout of
  nations
• Increase in photosynthesis
• Increase in crop yields

53
Global Warming

• The International Panel on Climate Change (IPCC)
  reported that the average global surface
  temperature increased by 0.6ºC during the 20th
  century, snow and ice cover has dropped, and the
  global sea level has risen.

54
Global Warming

• The IPCC reported that greenhouse gases have
  increased as a result of human activities.
• IPCC predicted that human influences will change
  the composition of the Earths atmosphere and
  warm the Earth throughout the 21st century.

55
World Response

• The Kyoto Protocol is an international treaty to
  reduce emissions of greenhouse gases that may
  contribute to global warming by the year 2012.
• United States did not ratify the Kyoto Protocol.
• Most other developed nations signed the treaty.

56
World Response

• Conflict has already arisen between developed and
  developing countries over future CO2 emissions.
• Developing countries are projected to make up
  half of all CO2 emissions by 2035.

57
(No Transcript)
58
Why would anyone think global warming is not true?
59
(No Transcript)
60

• Over 32,000 scientists have signed The Petition
  Project over 9,000 of them with PhDs proclaiming
  that man is not the chief cause of warming and
  that this warming will not be disastrous.

61
The Petition Project
Petitionproject.org
62
(No Transcript)
63
(No Transcript)
64
(No Transcript)
65
(No Transcript)
66
Why do people think that global warming is
happening?
67
(No Transcript)
68
(No Transcript)
69
(No Transcript)