Performance Benchmark E.12.A.1
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Students know the Sun is the major source of Earth’s energy, and provides the energy driving Earth’s weather and climate. E/S

More than 99% of the Earth’s energy comes from the Sun. This energy is transferred to Earth mostly through visible light. The Earth also sends energy back into outer space, mostly as infrared radiation. On average, this transfer of this incoming and outgoing energy is nearly equal. Scientist therefore state that the Earth is in radiative equilibrium with the Sun.

Of the Sun’s incoming energy, about 30% is reflected back to space. Another 19% of the incoming solar energy is absorbed by the Earth’s atmosphere and clouds. The remaining 51% is absorbed by the Earth’s surface. Most of the energy that reaches the Earth’s surface is in the form of visible light.

Figure 1: The global energy balance between the Earth’s surface and atmosphere (from http://rst.gsfc.nasa.gov/Sect14/Sect14_1a.html)

To maintain equilibrium, the Earth returns the energy it receives from the Sun back to space as infrared light. However, only 6% of the energy goes directly from the Earth’s surface to space. About 15% of the Earth’s surface energy is absorbed by water vapor, carbon dioxide and other gases in the atmosphere. This is called the greenhouse effect and is a common condition on planets with relatively thick atmospheres.

To learn more about the greenhouse effect go to http://epa.gov/globalwarming/kids/greenhouse.html

The remainder of Earth’s surface energy is transferred to the atmosphere in a more complex exchange involving sensible and latent heat.

Sensible heat is the energy associated with the temperature of a body. A warm surface will be at a higher temperature. Sensible heat flows from the surface to the atmosphere via convection (air circulations) or conduction (molecular motion).

Latent heat is the energy associated with phase changes. In the atmosphere, water vapor condenses forming clouds and precipitation. This releases latent heat to the atmosphere. Latent heat also flows from the atmosphere to the surface during evaporation. Evaporation cools the atmosphere.

To learn more about sensible and latent heat flux go to http://www.physicalgeography.net/fundamentals/7j.html

So, infrared radiative transfer combined with flux of sensible and latent heat provides the energy to the atmosphere. This energy, which ultimately originated from the Sun, drives all of Earth’s weather and climate.

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Performance Benchmark E.12.A.1

Students know the Sun is the major source of Earth’s energy, and provides the energy driving Earth’s weather and climate. E/S

Common misconceptions associated with this benchmark:

1. Students incorrectly think the Moon is the primary source of energy for weather and climate processes.

Tide effects from the Moon have virtually no effect on the atmosphere. Although sea and lake tides are often reported with the weather forecast, there is no appreciable relationship between weather, climate, and tides.

Ocean currents near the shore can affect how high or low tides can rise at a shoreline. The rising and falling of tides can cause flood and ebb currents, which may have result in substantial movement of water in and out of bays and harbors. But, tides do not have an effect on major ocean currents that strongly influence Earth’s global climate.

A detailed discussion of misconceptions associated with tides is found at http://www.lhup.edu/~DSIMANEK/scenario/tides.htm

2. Students incorrectly believe that the Earth’s internal energy is the primary source of energy for weather and climate processes.

While Earth’s internal energy is considerable, it is accounts for less than 1% of the Earth’s energy budget (energy from the Sun accounts for more than 99%).

To learn more about the Earth’s total energy budget, see http://www.tulane.edu/~sanelson/geol204/struct&materials.htm

The Earth’s internal energy comes from two sources. The first is the warming caused by the formation of the planet. Scientific evidence indicates Earth and the other planets were formed by accretion (collisions and sticking) of planetesimals. The kinetic energy of these impacts raised the planet’s temperature as it formed, so much so, that early Earth consisted of melted rock and metal. Since that time, Earth has been slowly cooling as this primordial internal energy is radiated back to space. The second source of internal energy is from decay of radioactive elements present in Earth materials. For example, the decay of Uranium-238 in the Earth’s crust, mantle, and core release energy that ultimately warms surrounding material.

A more detailed discussion of radioactive decay and its effect on Earth’s total energy is found at http://dev.nsta.org/ssc/moreinfo.asp?id=966

The Earth’s internal energy drives plate tectonics, which can results in amazing effects such as tearing apart continents and creating new mountain ranges. But plate tectonics work slowly (i.e., on a geologic time scale), with average movement of only a few centimeters per year. Energy from the Sun drives drastic changes to Earth’s atmosphere—called weather—causing the precipitation and wind that erodes these mountain ranges. Additionally, the atmosphere retains enough of the Sun’s energy to raise the Earth’s surface temperature by more than 30 degrees Celsius (60 degrees Fahrenheit). This is called the greenhouse effect and is a common occurrence on planet’s with relatively thick atmospheres.

More about the greenhouse effect can be found at http://www.epa.gov/climatechange/kids/greenhouse.html

3. Students confuse the properties of force and energy.

In Star Wars Episode IV, Obi Wan Kenobi tells Luke Skywalker that “The Force is an energy field created by all living things.” This statement typifies confusion about the terms energy and force. An appreciable part of this confusion resides in misconceptions about the relationship between force and motion. Many students incorrectly believe that a moving object must have an “impetus” force causing it to stay in motion. Students incorrectly believe that this impetus force is applied to an object by a collision with another object (i.e., hitting a baseball with a bat) and that this “impetus force” then resides within the object even after it has lost contact with the original impactor, causing it to continue moving until this impetus is somehow dissipated.

To learn more about the impetus misconception, go to http://modeling.asu.edu/R&E/forceConceptionTaxon92.doc

Before Galileo, the prevailing scientific thought upheld the belief of force impetus, where some incorrectly believed that this force depended on the speed and mass of the object. Note how closely the incorrect idea of force impetus relates to correct understandings about kinetic energy. Starting with Galileo and Newton, scientists now know that an object will remain in constant motion (either at rest or traveling in the same direction with the same speed) unless acted upon by a net force. Therefore, force is not required for motion, but only to change an object’s motion (direction and/or speed). Forces act upon objects, but are not an inherent quality within the object.

A detailed discussion of Newton’s First Law of Motion is found at http://www.physicsclassroom.com/Class/newtlaws/U2L1a.html

On the other hand, energy is an inherent quality of an object. If the object is moving, it has kinetic energy. Also, within the object there exists internal kinetic energy associated with molecular motions of the object’s material. The object would also have potential energy due to position within a gravitational, electrical, magnetic, and/or other type of force field.

An overview about the forms of energy can be read at http://www.eia.doe.gov/kids/energyfacts/science/formsofenergy.html

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Performance Benchmark E.12.A.1

Students know the Sun is the major source of Earth’s energy, and provides the energy driving Earth’s weather and climate. E/S

Sample Test Questions

1. Earth’s surface absorbs mainly which types of energy?
a. Ultraviolet light and x-rays
b. Infrared and visible light
c. Ultraviolet and infrared light
d. Visible and ultraviolet light

2. The energy source driving Earth’s weather comes from
a. the Earth’s core through heat conduction.
b. release of radiant heat energy through volcanic activity.
c. the Sun through visible light.
d. the Moon through tides.

3. The Earth’s surface mainly gives off (radiates) which form of energy?
a. Infrared light
b. Visible light
c. Ultraviolet light
d. The Earth’s surface does not give off energy

4. About 70% of the Sun’s energy directed toward Earth is absorbed by the Earth’s surface, clouds, and atmosphere. What happens to the rest of the energy?
a. The energy is lost as it overcomes the Sun’s gravity.
b. The energy is reflected by clouds, water, and land back into space.
c. The energy is diminished as it traveling through space.
d. The energy is reflected by the Moon back into space

5. Weather is caused by the Sun’s energy warming the Earth’s surface unevenly. Which of the following is NOT a contributing factor to this uneven warming?
a. Different surfaces warm at different rates.
b. Different surfaces retain energy differently.
c. The Sun is farther away during the winter.
d. The Sun’s rays strike the surface at different angles depending on latitude.

6. More of the Sun’s energy is received at the Earth’s tropical regions than in the arctic regions because the tropical regions
a. are covered by a greater area of land.
b. have more vegetation that absorbs the Sun’s energy.
c. have a thinner atmosphere than the polar regions.
d. receive sun rays closest to vertical.

7. The following figure shows the angle of the sun’s rays hitting two different locations on the Earth’s surface. Which of the statements about the figure is most correct?

a. Area A shows a location near the pole and Area B shows a location near the equator. Warming of the Earth is more with Area B than Area A because Sun’s energy is spread over a wider area.
b. Area A shows a location near the pole and Area B shows a location near the equator. Warming of the Earth is more with Area A than Area B because the atmosphere is thinner at the equator.
c. Area A shows a location near the equator and Area B shows a location near the pole. Warming of the Earth is more with Area A than Area B because the atmosphere is thinner at the equator.
d. Area A shows a location near the equator and Area B shows a location near the pole. Warming of the Earth is more with Area A than Area B because the Sun’s energy is spread concentrated within a smaller area.

Students know the Sun is the major source of Earth’s energy, and provides the energy driving Earth’s weather and climate. E/S

Answers to Sample Test Questions
1. (b)
2. (c)
3. (a)
4. (b)
5. (c)
6. (d)
7. (d)

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Performance Benchmark E.12.A.1

Students know the Sun is the major source of Earth’s energy, and provides the energy driving Earth’s weather and climate. E/S

Intervention Strategies and Resources

The following is a list of intervention strategies and resources that will facilitate student understanding of this benchmark.

1. Introduction to the Atmosphere
The National Center for Atmospheric Research has produced “An Introduction to the Atmosphere.” Content and lessons that relate the Sun’s energy to weather and climate are found at http://www.ucar.edu/learn/1_1_1.htm. Specifically, Activities 5, 6, and 7 are lessons that deal with the following atmospheric energy transfer processes: radiation, conduction, and convection. The direct links to these lessons are:
• Atmospheric Processes-Radiation (http://www.ucar.edu/learn/1_1_2_5t.htm)
• Atmospheric Processes-Conduction (http://www.ucar.edu/learn/1_1_2_6t.htm)
• Atmospheric Processes-Convection (http://www.ucar.edu/learn/1_1_2_7t.htm)

2. Sun’s Impact on the Earth’s Climate
For those that have access to an Internet lab, this series of lessons show the Sun’s effect on planetary temperatures and weather. These five lessons were developed by the Physics and Astronomy Education Research Group at Montana State University and are found at http://btc.montana.edu/CERES/html/Suns/suns1.html.

3. Sunspots and Climate
This lesson, found at http://eo.ucar.edu/educators/ClimateDiscovery/LIA_lesson7_9.28.05.pdf , was developed by the National Center for Atmospheric Research. In “Sunspots and Climate” students plot periods of high and low sunspot activity and correlate these to periods to temperature variation on Earth, which reinforces the Sun as the driver of Earth’s climate and weather.

4. Visualization of Seasonal Sunlight on Earth
Developed from Earth images captured by a geostationary satellite, a nice animation found at http://www.classzone.com/books/earth_science/terc/content/visualizations/es1704/
es1704page01.cfm?chapter_no=visualization shows how sunlight varies on the globe as the year progresses.

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