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Understanding the Greenhouse Effect:. Synposis : Students plot diurnal temperature observations to compare the relative magnitude of the greenhouse effect under clear and cloudy-sky conditions. Understanding the Greenhouse Effect:. Learning Objectives :

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Understanding the greenhouse effect
Understanding the Greenhouse Effect:

  • Synposis:Students plot diurnal temperature observations to compare the relative magnitude of the greenhouse effect under clear and cloudy-sky conditions


Understanding the greenhouse effect1
Understanding the Greenhouse Effect:

  • Learning Objectives:

  • 1) Relate strength of the greenhouse effect to common experience

  • 2) Apply physical principles to characterize response to increased greenhouse gases

  • 3) Critically evaluate human-caused vs solar-caused hypotheses for recent warming.


The greenhouse effect fundamental questions context
The Greenhouse Effect:Fundamental Questions & Context

  • What is the Greenhouse Effect?

  • How big is the effect?

  • Why are cloudy nights warmer than clear nights?


The greenhouse effect

The Greenhouse Effect


Background information
Background Information

  • Electromagnetic (EM) radiation

  • Solar and Terrestrial Emission

  • Radiation Processes and Interactions

  • Water Vapor is a Greenhouse Gas (selective absorpotion)


Understanding the greenhouse effect

Central Project Question

Knowing that water vapor is a potent greenhouse

gas, what do you expect is the short-term effect of

cloud cover on your local temperature?


The greenhouse effect1

The Greenhouse Effect


Understanding the greenhouse effect

Clear Sky Anticipation Questions

For a weather station located at Des Moines, Iowa ,

consider the following questions regarding the diurnal

cycle during both winter (January) and summer (July).

  • Why does temperature change through the day?

2) Assuming a cloudless day, plot your expectations

for the diurnal cycle of temperature using the blank

template figure.


Understanding the greenhouse effect

Hour of Day

Hour of Day


Understanding the greenhouse effect

Anticipation Questions (continued…)

Diurnal cycle during both winter (January) and summer

(July) at Des Moines Iowa.

3) Indicate the time of sunrise and sunset in your

figure.

4) What, specifically, causes temperature to increase

or decrease?

5) How do summer and winter differ? Why?


Understanding the greenhouse effect

Hour of Day

Hour of Day


Understanding the greenhouse effect

Anticipation Questions (summary)

  • Diurnal cycle during both winter (January) and summer

  • (July) at Des Moines Iowa.

  • Indicate the time of sunrise and sunset in your

    figure.

  • What, specifically, causes temperature to increase

    or decrease?

  • How do summer and winter differ? Why?


Understanding the greenhouse effect

Realization

Data Source:Airport at Des Moines, IA from 1945-2004 (NCDC Surface Airways)

Observation Variables:Temperature and cloud ceiling height (the height of the lowest cloud layer, if present)

  • Methodology:

  • Sort data and select only “clear sky” conditions

  • Compute the average diurnal cycle

  • Repeat for both January and July data


Understanding the greenhouse effect

Hour of Day

Hour of Day


Understanding the greenhouse effect

Clear Sky Contemplation

  • Why does temperature change through the day?

  • How does temperature decrease?

  • How do summer and winter differ?


The greenhouse effect2

The Greenhouse Effect


Radiation fundamental principles
Radiation: Fundamental Principles

  • All objects emit EM radiation; the wavelength and energy emitted depends on the object’s temperature

  • As Temperature increases,

  • total emission increases

  • As Temperature increases,

  • wavelength of peak emission decreases


Solar and terrestrial radiation
Solar and Terrestrial Radiation

UV | Visible | IR

NOTE:

Log

Scale!

Sun

Earth


Understanding the greenhouse effect

(No Atmosphere Case)

=

Earth,

Absorbed = Emitted


Understanding the greenhouse effect

Solar Radiation

Terrestrial Radiation

“Radiative Equilibrium”

Incoming = Outgoing

Stable Temperature


The greenhouse effect3

The Greenhouse Effect



Greenhouse gases are

  • …“transparent” for sunlight

  • …only partially transparent to

    Infrared Radiation (…from Earth’s Surface)

  • … “warmed” via radiation

    (However, sensible heat and convection also

    “warm” the atmosphere)

Greenhouse Gases are…


The greenhouse effect4

The Greenhouse Effect


Understanding the greenhouse effect

Cloudy Sky Anticipation Questions

Diurnal cycle during both winter (January) and summer

(July) at Des Moines Iowa.

1) How might temperature differ between clear and cloudy sky conditions?

2) Draw your expectations on the figure provided,

labeling the clear and cloudy sky lines.


Understanding the greenhouse effect

Hour of Day

Hour of Day


Understanding the greenhouse effect

Hour of Day

Hour of Day


Understanding the greenhouse effect

Cloudy Sky Contemplation

  • Why is the cloudy sky temperature relatively flat?

  • How does clear sky temperature get both hotterand

    colder than the cloudy sky temperature?


Greenhouse process

Incoming

Solar

Earth’s Surface Emits

Infrared Radiation

Greenhouse Process


Greenhouse process1
Greenhouse Process

  • Greenhouse Gases

  • Absorb IR


Greenhouse process2
Greenhouse Process

  • Greenhouse Gases

  • Absorb IR

  • Emit IR


Greenhouse process3
Greenhouse Process

NET EFFECT:

Earth’s surface

Warmed by

TWO

Heating sources


Greenhouse process4
Greenhouse Process

What if we add

more Greenhouse

Gases??

TWO

Heating sources


The greenhouse effect5

Summary

  • GHGs absorb IR emitted by Earth’s Surface

  • The gases also emit IR back to the surface,

    providing an additional heating source.

  • An example of this effect is the relative warmth of

    cloudy nights.

  • Additional GHGs will increase surface temperature

    in the same way as enhanced cloud cover.

The Greenhouse Effect