1 Earth's Atmosphere • Today we will talk about the part of Earth that is most important to our survival - the atmosphere • Earth's atmosphere is unique in the Solar System and has changed greatly over time • Recent changes may be leading to global warming and an increased threat to life on Earth Atmospheric Layers • _ • As altitude increases, pressure decreases and the air becomes 'thinner' • Surprisingly, temperature does not constantly decrease, but fluctuates throughout the different layers Atmospheric Layers • The troposphere is the lowest layer, rising to ~12 km above the surface with decreasing temperature • Temperature increases through the stratosphere up to ~45 km above the surface (airplanes fly in the lower stratosphere) • _ • The last layer is the ionosphere, where sunlight breaks up molecules/atoms and increases the temperature slightly
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1
Earth's Atmosphere
• Today we will talk about the part of Earth that is most important to our survival - the atmosphere
• Earth's atmosphere is unique in the Solar System and has changed greatly over time
• Recent changes may be leading to global warming and an increased threat to life on Earth
Atmospheric Layers
• _
• As altitude increases, pressure decreases and the air becomes 'thinner'
• Surprisingly, temperature does not constantly decrease, but fluctuates throughout the different layers
Atmospheric Layers• The troposphere is the lowest
layer, rising to ~12 km above the surface with decreasing temperature
• Temperature increases through the stratosphere up to ~45 km above the surface (airplanes fly in the lower stratosphere)
• _
• The last layer is the ionosphere, where sunlight breaks up molecules/atoms and increases the temperature slightly
• In the late 80's and 90's, many nations agreed to begin phasing out CFC's from many of their products
• Progress has been made, but it will take decades to eliminate all CFC's from the atmosphere
• _
Why is the Sky Blue?• The sun emits all colors from red to
blue, so why does the sky appear blue?
• When sunlight hits our atmosphere, the gas and dust scatter some of the light
• _
• This means the bluer light gets spread over the entire sky, while the redder light comes directly from the Sun
• Note that when the Sun is low in the sky, the light is passing through much more atmosphere and even the red light becomes scattered
This type of scattering is known asRayleigh scattering.
Evolution of Our Atmosphere
• The primary (first) atmosphere of the Earth would have consisted mainly of the elements found in the solar nebula, like hydrogen and helium
• _
• The secondary atmosphere of the Earth was formed when volcanic activity released carbon dioxide, sulfur dioxide, and nitrogen compounds into the atmosphere
• There is no doubt that since the industrial revolution, there has been a major increase in the amount of carbon dioxide in the atmosphere
• There is also no doubt that increased amounts of CO2 in the atmosphere will produce an enhanced greenhouse effect and increase temperatures on the surface
• Put the two together ...
Will It Affect Us in Our Lifetimes?
• This is the most controversial question we have faced, as evidenced by the quiz
• Many would say small effects can be seen already
• But will major changes occur in our lives?– The answer shouldn't
matter ...
0
5
10
15
20
25
YES NO
YES NO
22 18
Affect climate/world in our lifetime?
Glacial Melting• Evidence for increased
temperatures are seen around the world with receding glaciers
• In the past 60 years (a lifetime) many glaciers have shrunken by miles in size
• Glacier National Park has gone from ~150 glaciers in 1850 to ~35 today– There will be none left by
change in the natural habitat range for many disease carrying insects (like mosquitoes)
• Increased medical costs and preparations strain nations already financially burdened
• Undeveloped countries have even less access to fresh, clean water
Changes in Government
• A decrease in the amount of fertile land will cause dramatic changes in global politics
• Some models show drought conditions will occur for the majority of the Midwest, while former tundra in Canada and Siberia will open up large tracts of farming land
• When the food supply of a nation like America is threatened, how far would we go?
Past the Point of No Return?
• There are many scientists who believe that conditions will worsen severely over the next 100 years whether action is taken or not
• The current political climate is not favorable for a worldwide commitment to curb global warming
• It will be our generation who shoulders the majority of the burden