LESSON 4

Overview of Earth’s Heat-Trapping Gases

http://9-4fordham.wikispaces.com/Electro+Magnetic+Spectrum+and+light

Electromagnetic Spectrum

Earth’s Magnetosphere

http://www.grc.nasa.gov/WWW/k-12/airplane/atmosphere.html

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.

http://www.nature.com/nature/journal/v441/n7091/fig_tab/441299a_F1.html

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?

http://www.windows2universe.org/physical_science/chemistry/molecules_vibrate.html

http://www.agci.org/classroom/atmosphere/index.php

Earth’s atmosphere

http://www.globalchange.umich.edu/globalchange1/current/lectures/Perry_Samson_lectures/evolution_atm/index.html

CONSTITUENT

CHEMICAL

SYMBOL

MOLE % BONDING

Nitrogen N2 78.084 1 tripleOxygen O2   20.947 1 double

Argon Ar   0.934 -Carbon Dioxide CO2   0.035 2 double

Neon Ne   0.00182 -Helium He   0.00052 -

Methane CH4   0.00017 4 singleKrypton Kr   0.00011 -

Hydrogen H2   0.00005 1 singleNitrous Oxide N2O   0.00003 2 bonds (1

triple, 1 single)

Xenon Xe   0.00001 -Ozone O3   trace to

0.000802 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”.

http://www.globalchange.umich.edu/globalchange1/current/lectures/Perry_Samson_lectures/evolution_atm/index.html

What is a “Heat-Trapping Gas”?

http://www.elmhurst.edu/~chm/vchembook/images/irgreengas.JPEG

2500 nm 3330 nm 5000 nm 10000 nm 1000000 nm

http://www.elmhurst.edu/~chm/vchembook/images/irwater.JPEG

http://www.elmhurst.edu/~chm/vchembook/images/irmethane.JPEG

http://www.elmhurst.edu/~chm/vchembook/images/irN2O.JPEG

http://en.wikipedia.org/wiki/File:Atmospheric.transmittance.IR.jpg

Greenhouse gas ABSORBANCE (in white)

Effect of Heat-Trapping Gases

http://mrsdlovesscience.com/greenhouse/greenhouse.html

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).

This Is What Worries Many Scientists

0

http://www.realclimate.org/index.php/archives/2004/12/temperaturevariations-in-past-centuries-and-the-so-called-hockey-stick/

Simplified Example of a Combustion Reaction