Unit 2

• The Earth's atmosphere is dynamic and forever changing
• The causes of these changes are sometimes man-made and sometimes part of many natural cycles
• Scientists use very complex software to predict weather and climate change as there are many variables that can influence this
• The problems caused by increased levels of air pollutants require scientists and engineers to develop solutions that help to reduce the impact of human activity
• Composition of Earth's Atmosphere


  • Nitrogen (about 80%)
  • Oxygen (about 20%)
  • Small proportions of various other gases, including carbon dioxide, water vapour and noble gases
• Earth's Atmospheric Layers


  • Troposphere
  • Stratosphere
  • Mesosphere
  • Thermosphere
  • Ionosphere
  • Exosphere

  
• Troposphere


  • Starts at the Earth's surface and extends 8 to 14.5 kilometers high (5 to 9 miles)
  • Most dense part of the atmosphere
  • Almost all weather is in this region

  
• Stratosphere


  • Starts just above the troposphere and extends to 50 kilometers (31 miles) high
  • Ozone layer, which absorbs and scatters the solar ultraviolet radiation, is in this layer

  
• Mesosphere


  • Starts just above the stratosphere and extends to 85 kilometers (53 miles) high
  • Meteors burn up in this layer
• Thermosphere


  • Starts just above the mesosphere and extends to 600 kilometers (372 miles) high
  • Aurora and satellites occur in this layer

  
• Ionosphere


  • Abundant layer of electrons and ionized atoms and molecules that stretches from about 48 kilometers (30 miles) above the surface to the edge of space at about 965 km (600 mi)
  • Overlaps into the mesosphere and thermosphere
  • Dynamic region that grows and shrinks based on solar conditions
  • Divides further into the sub-regions: D, E and F; based on what wavelength of solar radiation is absorbed
  • Critical link in the chain of Sun-Earth interactions
  • Makes radio communications possible

  
• Exosphere


  • Upper limit of our atmosphere
  • Extends from the top of the thermosphere up to 10,000 km (6,200 mi)
• Ozone layer


  • One layer of the stratosphere, the second layer of the Earth's atmosphere
  • The stratosphere is the mass of protective gases clinging to our planet

  
• Ozone


  • Only a trace gas in the atmosphere—only about 3 molecules for every 10 million molecules of air
  • Absorbs bits of radiation hitting Earth from the sun
  • Acts as a shield for life on Earth

  
• UVB


  Causes skin conditions like sunburns, and cancers like basal cell carcinoma and squamous cell carcinoma
• UVA


  More harmful than UVB, penetrating more deeply and causing a deadly skin cancer, melanoma, and premature aging
• The ozone layer absorbs about 98 percent of this devastating UV light

  
• Chlorofluorocarbons (CFCs)


  • Molecules that contain the elements carbon, chlorine, and fluorine
  • Inexpensive, don't catch fire easily, and don't usually poison living things
  • But start eating away at the ozone layer once they get blown into the stratosphere
• Ozone molecules are always being destroyed and reformed naturally, but CFCs in the air make it very difficult for ozone to reform once it's broken apart
• The ozone layer, which only makes up 0.00006 percent of Earth's atmosphere, is getting thinner and thinner all the time
• Ozone holes are inaccurate names for areas of damage to the ozone layer, as the ozone layer damage is more like a really thin patch than a hole
• The ozone layer is thinnest near the poles
• In the 1970s, people all over the world started realizing that the ozone layer was getting thinner and that this was a bad thing
• Many governments and businesses agreed that some chemicals, like aerosol cans, should be outlawed, and there are fewer aerosol cans produced today
• The ozone layer has slowly recovered as people, businesses, and governments work to control such pollution
• Greenhouse effect


  • A natural process that warms the Earth's surface
  • When the Sun's energy reaches the Earth's atmosphere, some of it is reflected back to space and the rest is absorbed and re-radiated by greenhouse gases

  
• Greenhouse gases


  • Water vapour
  • Carbon dioxide
  • Methane
  • Nitrous oxide
  • Ozone
  • Some artificial chemicals such as chlorofluorocarbons (CFCs)
• The absorbed energy warms the atmosphere and the surface of the Earth, maintaining the Earth's temperature at around 33 degrees Celsius
• Greenhouse Effect


  A natural process that warms the Earth's surface when the Sun's energy reaches the Earth's atmosphere, some of it is reflected back to space and the rest is absorbed and re-radiated by greenhouse gases

  
• Greenhouse gases


  • Water vapour
  • Carbon dioxide
  • Methane
  • Nitrous oxide
  • Ozone
  • Chlorofluorocarbons (CFCs)
• The absorbed energy warms the atmosphere and the surface of the Earth, maintaining the Earth's temperature at around 33 degrees Celsius warmer than it would otherwise be, allowing life on Earth to exist

  
• Enhanced greenhouse effect


  Human activities – particularly burning fossil fuels (coal, oil and natural gas), agriculture and land clearing – are increasing the concentrations of greenhouse gases, contributing to warming of the Earth

  
• Global Warming


  The globe is heating up, with both land and oceans warmer now than they were when record keeping began, in 1880, and temperatures still ticking upward
• The burning of fossil fuels has released greenhouse gases into the atmosphere, which trap warmth from the sun and drive up surface and air temperatures
• Scientists agree that the earth's rising temperatures are fueling longer and hotter heat waves, more frequent droughts, heavier rainfall, and more powerful hurricanes
• The earth's ocean temperatures are getting warmer, which means that tropical storms can pick up more energy, turning a category 3 storm into a more dangerous category 4 storm
• Antarctica has been losing about 134 billion metric tons of ice per year since 2002, and this rate could speed up if we keep burning fossil fuels at our current pace, causing sea levels to rise several meters over the next 50 to 150 years
• Climate Change


  The defining issue of our time, with impacts that are global in scope and unprecedented in scale, requiring drastic action today to adapt to in the future
• The Intergovernmental Panel on Climate Change (IPCC) is categorical in its conclusion: climate change is real and human activities are the main cause
• United Nations Framework Convention on Climate Change (UNFCCC)


  A first step in addressing the climate change problem, with near-universal membership of 197 countries, aimed at preventing "dangerous" human interference with the climate system