Summary of Tuesday September 20

Greenhouse Effect

• Cooling due to human released sulfates
• Major Feedback mechanisms
• Positive - Forcing function causes something which enhances the forcing function
• Glacial retreat reduces albedo
• Polar thawing releases methane
• Warm water evaporates more water vapor into the atmosphere so more greenhouse warming
• Negative - Forcing function causes something which deminishes the forcing function
• More water vapor in the atmosphere creates more clouds which reflect sunlight
• More carbon dioxide makes plants grow faster which absorbes more carbon dioxide
• Deforestation makes tropics more reflective
• Modeling Climate Change
  • Models are tested by comparing to past climate change
  • Models predict 3-8 degrees Celcius increase by end of century
• Possible effects of global warming
• storms and major snowmelt farther north (moisture moves north)
• less precipitation in US especially Midwest
• higher temperatures detrimental to cattle
• greater extinction of endangered species
• diseases may move north
• many more days over 90°F
• Sea level will rise
• slight rise could harm Bangladesh & Maldives
• most likely rise about 4-36 in by end of century
• possible collapse of west Antarctic ice sheet

Earth's heat balance (text Fig 2-20)

• most solar radiation absorbed in surface
• next most reflected back to space
• least amount absorbed in atmosphere
• most earth radiation returned to surface
• latent heat more significant than sensible
• overall balance so no long term heating or cooling of earth or atmosphere

Seasons

• more daylight hours in summer than winter
• more daylight hours as you go north in summer or south in winter
• solstice, equinox and months they occur
• sun rises N of E in summer, S of E inwinter
• sun closest to earth in January(Perihelion)
• sun farthest from earth in July (Aphelion)

Colder in winter due to:

• sunlight more spread out
• more atmospheric absorption & scattering of sunlight
• fewer daylight hours
• snow reflects sunlight away
• dry air decreases greenhouse effect

Energy balance by latitude (text Fig 2-21)

• excess near equator and deficit near poles
• energy in and out the same at 37 deg latitude
• need to transport energy from Eq to poles
• most transported by atmosphere
• rest transported by oceans