Properties of Greenhouse Gases
What is Temperature?
• Come up with a definition.
What is Temperature?
• Average Kinetic Energy of a Substance.
• Measurement of How Fast the molecules are moving.
• Rub your hands together.
• What do you notice?
• Getting Warm Yet?
• Ball Drop Example
Temperature Scales
•Fahrenheit – based on
body temp
•Celsius – based on
water
•Kelvin – measures
energy of a substance
Kelvin Temperature
K = C + 273
What happens at 0K?
Absolute Zero = Absolutely No Molecular
Motion
ALWAYS use Kelvin for Temp when measuring energy!
• Can you move at 0c or 0F?
• Zero C and F still have ENERGY.
• It does not work in math
• Kelvin is a true measure of the amount of ENERGY.
• 0K = 0 energy
Thermal Energy & Heat
•Heat is the movement of thermal energy.
•Thermal energy of matter changes as light
energy interacts with that matter.
•Light comes in many different wavelengths.
• Rope Example
Electromagnetic Wave (Light) Spectrum
Radiance
• ALL objects radiate energy unless their temperature is 0 K.
• The Sun radiates UV, Visible, and Infrared (IR) light.
• The Earth Reflects Visible light.
• The Earth radiates Infrared light.
• IR range = 0.7 to 1000 micrometers
Radiance
Sun &
Earth
Earth IR
radiation image
Molecules - Greenhouse Gases
• Carbon Dioxide (CO2)
• Methane (CH4)
• Chlorofluorocarbons (CFCs)
(example:
Trichlorofluoromethane)
• Ozone (O3)
• Nitrous Oxide (N2O)
14
Carbon Dioxide
• CO2 absorbs energy within the Earth’s natural IR radiance spectrum.
• CO2 has a warming potential that lasts 100 - 300 years (how long the extra
will last at current levels).
• Current level of CO2 in the atmosphere is 400 ppm (see trend).
• Video: A year in the life of the Earth’s CO2
• Sources of CO2 include:
• Volcanoes
• Respiration
• Burning plants and fossil fuels
• CO2 sinks include:
• Solubility in Ocean Water
• Photosynthesis
• Video: Upsetting the Natural Balance
Energy absorption cycle
1) Light photons at a specific
wavelength (energy) are absorbed
by the molecule.
2) The energy is turned into kinetic
energy (vibration).
3) The excess energy is re-emitted
from the molecule to the
atmosphere.
4) Some energy goes to space.
5) Some energy returns to Earth.
Atmospheric Carbon Dioxide (ppm)
Methane (CH4)
• Methane absorbs energy within the Earth’s natural IR radiance spectrum
(different wavelength than CO2).
• Methane stays in the atmosphere only about 12 years.
• Current level of CH4 in the atmosphere is 1820 ppb (see trend).
• Sources of Methane include:
• Decay of organic matter
• Landfills
• Cattle
• Methane sinks include:
• Reaction in atmosphere to create water and CO2
• Uptake by soil microorganisms
• Website: Greenhouse Gas Information
Major Greenhouse Gas
% of Greenhouse Effect
Water vapor
36% to 66%
Water vapor & Cloud droplets
66% to 85%
Carbon dioxide
9% to 26%
Methane
4% to 9%
Ozone
3% to 7%
Uncertainties
• Strength of energy from the Sun
• 0.5% change over 100 years
• Greenhouse gases since the industrial revolution has had
a 1% equivalent effect, so what part is from solar
energy?
Uncertainties
• Impact of Water Vapor
• The entire effect of the water cycle is very complicated
• cloud formation
• Snowfall
• precipitation patterns
• soil moisture
• vegetation response
• ocean circulation
Uncertainties
• Positive feedback effects
• A decrease of the ability of a warming ocean to take up
heat and carbon dioxide
• Methane addition from permafrost regions
• Disappearance of snow cover and sea ice (less light
reflection)