Presentation on theme: "LESSON 4 Overview of Earth’s Heat- Trapping Gases."— Presentation transcript:
LESSON 4 Overview of Earth’s Heat- Trapping Gases
The Earth’s Atmosphere (60 miles thick)
The blue line indicates the approximate intensity of radiation that penetrates Earth's atmosphere at wavelengths from the ultraviolet (UV) through the visible to the infrared. Light at low UVC wavelengths is completely absorbed by the atmospheric ozone layer, so organisms on Earth have developed no tolerance to it. Sun’s Emission Spectrum able to penetrate Earth’s atmosphere
Being light, infrared travels through space at the speed of light. Matter is not space and the Earth’s atmosphere is obviously matter. Heat is a property of matter. The rate of transmission is slowed as this energy enters the atmosphere. Work is thereby done; so heat is created. Some atmospheric molecules are more sensitive to this energy than others based on their molecular shape and bonds. What does this penetrating energy do to Earth?
CONSTITUENTCHEMICAL SYMBOL MOLE %BONDING NitrogenN2N triple OxygenO2O double ArgonAr Carbon DioxideCO double NeonNe HeliumHe MethaneCH single KryptonKr HydrogenH2H single Nitrous OxideN2ON2O bonds (1 triple, 1 single) XenonXe OzoneO3O3 trace to single 99% 1% Earth’s Atmospheric Composition
Objects that absorb all radiation incident upon them are called "blackbody" absorbers. The earth is close to being a black body absorber. Gases, on the other hand, are selective in their absorption characteristics. While many gases do not absorb radiation at all some selectively absorb only at certain wavelengths of energy. Those gases that are "selective absorbers" of solar energy are the gases we know as “heat-trapping gases”. What is a “Heat-Trapping Gas”?
nm 3330 nm 5000 nm nm nm
Greenhouse gas ABSORBANCE (in white)
Effect of Heat-Trapping Gases l
CO2 levels (parts per million) over the past 10,000 years. Blue line from Taylor Dome ice cores (NOAA). Green line from Law Dome ice core (CDIAC). Red line from direct measurements at Mauna Loa, Hawaii (NOAA).NOAACDIACNOAA