Global Warming

Earth's Energy Budget

Electromagnetic radiation

Majority of solar and earth radiation is within ultraviolet and infrared spectrum.

Earth receives shortwave radiation from the sun (above infrared), but emits infrared (longwave) radiation.

Energy Budget Equation

Earth's energy budget relies on 3 variables:

  • Insolation
  • Albedo
  • Emissivity

Albedo
Reflectivity of earth

Emissivity
How much energy earth can emit

Insolation
Shortwave incoming radiation

Io / 4 x (1 - a) = e x sigma x T^4

Greenhouse effect
Percent of outgoing longwave energy radiated back to earth
G = (1 - e)

Greenhouse Effect

Absorption Spectra
Greenhouse gases absorb a certain spectrum within earth's outgoing longwave radiation

Changes by latitude

  • Higher latitudes radiate back more heat than they absorb
  • Lower latitudes radiate back less heat than they absorb

Greenhouse gases
Water vapor (H2O)
Carbon Dioxide (CO2)
Methane (CH4)
Nitrous Oxide (N2O)
Ozone (O3)

Water Vapor
50% of greenhouse effect

Clouds
25% of earth's greenhouse effect

Carbon Dioxide
20% of earth's greenhouse effect
Despite being 0.04% of atmosphere by mass

Gases and Particles

Well-mixed GHGs

  • CO2

Short-lived GHGs

  • Ozone
  • Water

Aerosols

  • Black carbon
  • Sulfate Aerosols

CO2 increases
Concentrations of CO2 have been increasing since the start of the industrial revolution (around the 1750's)

Methane increases
Concentrations of methane have been increasing since the humans started emitting it

Nitrous Oxide Increases
Concentrations of NO2 have been increasing since the industrial revolution

Similar timing
All of the increases in these well-mixed GHGs began at the same time, indicating that humans are responsible

Feedback of CO2
Increasing CO2 warms the atmosphere, which allows it to hold more water vapor, which in turn warms the atmosphere even more

What determines if a gas is guilty?

  • Concentration
  • Lifetime
  • Radiative efficiency

Concentration

  • Water Vapor
  • CO2
  • Methane
  • N2O
  • O3
  • CFCs

Lifetime

  • CFCs (10,000s of years)
  • N2O (100)
  • CO2 (100)
  • Methane (12)
  • Ozone (hrs - days)

Radiative Efficiency

  • CFCs
  • N2O
  • Methane
  • CO2
  • Ozone

Ozone hole
TCFCs can destroy many molecules of ozone

Why the arctic/antarctic?
Ice molecules in the air free Cl from stabilizing compounds found in regular atmospheric conditions

Montreal Protocol
Succeeded in freezing production of ozone-depleting substances, worked to recreate much of the ozone hole

Ozone production
Ozone mostly produced in developed parts of the world

Sulfate Aerosols Production

  • Volcanic eruptions
  • Burning fossil fuels

Sulfate Aerosols Effect

  • Reflection of insolation (net cooling effect)
  • Creation of fog and clouds, due to charged status

Sulfur Aerosols Regulation

  • Decreasing with time, due to air pollutant status

Black Carbon Production

  • Natural biomass burning
  • Coal and diesel engines

Black Carbon Effect

  • Absorbs insolation (net warming effect)

Direct Aerosol Forcing

  • Net cooling effect across all, but some can be warming (like black carbon)

Aerosol Regulation

  • Helping to improve air quality, but may actually increase warming

Emissions to Concentrations

Carbon Dioxide

Methane

Nitrous Oxide

Carbon Reservoirs

Carbon Cycle

Carbon during the year