SOAR: The Science behind
Solar Radiation, Greenhouse
Gases, and Greenhouse Effect
Suresh Dhaniyala, Mechanical and Aeronautical Engineering
Clarkson University, Potsdam, NY
315 268 6574; sdhaniya@clarkson.edu
Outline

Agenda



Introduction
Electromagnetic (EM) spectrum
Blackbody radiation


Greenhouse gases (GHGs)



EM emission spectrum of Sun, Earth lightbulb etc.
Absorption of EM radiation
GHG concentration and temperature
All applets will be accessed from:


Google “Clarkson K-12” (http://www.clarkson.edu/highschool/k12/)
Click on



Climate change education
Project-based climate modules
Greenhouse effect
Current state of the climate

Current state of the climate (NOAA)

http://www.climate.gov/#climateWatch
How globally-averaged temperatures have
changed over the past decade
Change in atmospheric CO2
concentrations over the past 50 years
Climate change



Documented increase in globally-averaged temperatures
over the past 40 year or so
Temperature increase has corresponded to increase in
CO2 concentrations
Questions:



Why is the temperature rising?
What is the connection with CO2 concentrations?
Need to understand:



Greenhouse effect
Greenhouse gases
Solar radiation and Terrestrial radiation
Electromagnetic radiation

How do cell phones communicate with towers?

Radiofrequency waves
Radiofrequency waves
In the spectrum of Electromagnetic waves
Source: Planet Adirondack, The Wild Center;
Electromagnetic (EM) radiation


Examples of other kinds of EM radiation?
Used for cooking in your kitchen


Microwaves
Night-time imaging

Infrared

Light, x-rays, gamma rays

What’s common?

They are all part of the Electromagnetic Spectrum.
Credit: NASA/JPL-Caltech/R. Hurt (SSC)
Electromagnetic radiation

EM radiation - background



http://imagine.gsfc.nasa.gov/docs/science/k
now_l1/emspectrum.html
EM radiation – applets

Under “Resources” - Click on
“Electromagnetic Spectrum Applet”

(http://lectureonline.cl.msu.edu/~mmp/a
pplist/Spectrum/s.htm)
Investigate:

What wavelengths correspond to:


Visible light
Heat radiation
Solar and Terrestrial radiation


All bodies emit electromagnetic radiation
Most of the energy is emitted in one form of Electromagnetic
(EM) radiation


The nature of emission depends on the body temperature.


e.g., light, IR, etc
Hotter bodies emit shorter wavelengths.
Applet – Click on “Blackbody radiation applet”

Investigate: What are the peak wavelengths of EM radiation
corresponding to:



Sun (~ 10,000 F)
Earth (~ 70 F)
Incandescent light bulb
Applet Source: PhET, University of Colorado. http://phet.colorado.edu/en/simulation/blackbody-spectrum
Note: Flash required to run this program (http://get.adobe.com/flashplayer/ )
Emission profiles
Sun
(5777K)
Earth
(300K)
Earth’s Energy Balance
Solar radiation
Terrestrial radiation
Source: http://earthobservatory.nasa.gov/Features/EnergyBalance/
Greenhouse effect

Energy radiated from Earth is trapped, but energy from Sun
is allowed through



Helps keep Earth’s temperature warm enough for humans to
survive
Applet
 Click on “Greenhouse effect simulation”
 In the applet, click on “Glass layers” tab
Investigate:
 What is Earth’s temperature in the absence of any “glass
layer”
 How does the temperature change as you add “glass
layers”
Applet Source: PhET, University of Colorado. http://phet.colorado.edu/en/simulation/greenhouse
Note: Need Java to run this program
Greenhouse gases

Certain gases in the atmosphere can act as “glass layers”
and absorb the out-going long-wave radiation


Applet



These gases are referred to as greenhouse gases (GHGs)
Click on “Greenhouse effect simulation”
In the applet, click on “Photon Absorption” tab
Investigate:

Which gases are greenhouse gases?
Applet Source: PhET, University of Colorado. http://phet.colorado.edu/en/simulation/greenhouse
Note: Need Java to run this program
Greenhouse Gases and Earth’s Temperature

The concentration of greenhouse gases in the atmosphere
determines Earth’s temperature

Applet
 Click on “Greenhouse effect simulation”
 In the applet, click on “Greenhouse effect” tab

Investigate:
 What is Earth’s temperature with no greenhouse gases?
 What is Earth’s temperature considering the greenhouse
gases during:
 Ice-age, pre-industrial
era (1750) and today?
Applet Source: PhET, University of Colorado. http://phet.colorado.edu/en/simulation/greenhouse
Note: Need Java to run this program
Radiation spectra
Source: Wikipedia
Future trends


The future emissions of greenhouse gases depends on
our lifestyle and societal developments
We can imagine scenarios and model (i.e., calculate) what
the future climate might look like



IPCC models different “scenarios”.
All models suggest much warmer climates
Upcoming SOAR Classes:



Susan Powers – “Sources of Greenhouse Gases and Your Own
Carbon Footprint. (3/25; CAMP 163)
Jon Rosales – “On the Front Lines.” (4/01; CAMP 175)
Stephen Bird – “Integrating Science into the Policy
Process.” (4/08; CAMP 175)
Applets


All Applets can be accessed from
http://www.clarkson.edu/highschool/k12/
Other References:




IPCC report, 2007
Hardy J.T., Climate change: Causes, Effects, and Solutions, Wiley
Publications, 2006
www.earthobservatory.nasa.gov
NOAA : www.climate.gov