the worksheet for the simulation will be in the student’s booklets

The worksheet for the simulation will be in the student’s booklets.

• Ask the candidates:– Try all of the controls to get a sense of what they do.– How does x affect y? (draw graph)

Simulation of “blackbody” is in Phet• Heineman has a greenhouse gas simSimulation of microwave oven is in Phet (has to do w why N2 and O2 do not act as greenhouse gases)

Simulation of greenhouse gases is in Heineman, and probably Phet too

Energy, Power, and Climate Change (8)

Mr. KlapholzShaker Heights

High School

http://www.google.com/imgres?imgurl=http://upload.wikimedia.org/wikipedia/commons/thumb/5/51/Mauna_Loa_Carbon_Dioxide-en.svg/800px-Mauna_Loa_Carbon_Dioxide-en.svg.png&imgrefurl=http://commons.wikimedia.org/wiki/File:Mauna_Loa_Carbon_Dioxide-en.svg&usg=__O_oYGV95EgWGRMOCpdngnXQ5gf4=&h=515&w=800&sz=80&hl=en&start=0&zoom=1&tbnid=x8dJZdK33FKBRM:&tbnh=113&tbnw=175&prev=/images%3Fq%3Datmospheric%2Bcarbon%2Bdioxide%2Bmeasured%2Bat%2Bmauna%2Bloa%2Bhawaii%26um%3D1%26hl%3Den%26sa%3DN%26biw%3D1280%26bih%3D645%26tbs%3Disch:1&um=1&itbs=1&iact=hc&vpx=286&vpy=185&dur=793&hovh=180&hovw=280&tx=99&ty=81&ei=90gqTaW_MoaKlwfElYXbCw&oei=90gqTaW_MoaKlwfElYXbCw&esq=1&page=1&ndsp=18&ved=1t:429,r:1,s:0

How does a greenhouse work?

http://blog.makezine.com/archive/2009/03/greenhouse_from_old_windows.html

Why do cars get so hot in the summertime?(And why doesn’t the color of the paint matter?)

Intro to the Greenhouse effect

“The ability of the atmosphere to capture and recycleenergy emitted by the Earth surface is the

defining characteristic of the greenhouse effect.”http://en.wikipedia.org/wiki/Greenhouse_effect

Greenhouse Effect in briefThe greenhouse effect is a process by which thermal radiation from a planetary surface is absorbed by atmospheric greenhouse gases, and is re-radiated in all directions. Since part of this re-radiation is back towards the surface, energy is transferred to the surface and the lower atmosphere. As a result, the temperature there is higher than it would be if direct heating by solar radiation were the only warming mechanism.

Details of the greenhouse effect

Understanding this effect gives us the opportunity to apply a lot of the physics that we have studied this year (and even a bit more).

Remember Electron Orbits

http://wisp.physics.wisc.edu/astro104/lecture6/lec6_print.html

These Electron Transitions Emit Light

http://www.files.chem.vt.edu/RVGS/ACT/notes/notes-electronic_structure.html

Atoms and Light

• Why do atoms only absorb photons of specific frequencies?

• Why do atoms emit the same frequencies that they absorb?

Ionization of Atoms

• What is an ion?• If a photon has enough energy, then it will

knock an electron off of an atom.• The energy (E = hf) does not need to be the

same as the transition between energy levels.

Molecules

http://www.erichufschmid.net/Global-warming/Global-warming.html

Molecules can do things that atoms can’t.

http://www.phy.davidson.edu/stuhome/derekk/resonance/pages/co2.htm

Molecules, Energy, and Light• Molecules can absorb light in the same way that

atoms can absorb light, and in a different way too.• Molecules can do things that atoms cannot do:

rotate (spin), vibrate (compress and extend), bend, …

• Molecules can absorb photons that have energies that resonate with all the things that they can do. These photons all are lower energy (frequency) than electron transitions. These photons are in the infrared (“heat”) part of the E-M spectrum.

Atoms, Molecules, Gases, Liquids, Solids

• As we consider systems with more particles, and as those particles get closer together, the systems are better at absorbing photons.

• When light hits the surface of the earth, it is usually absorbed.

Albedo

http://www.the-m-factory.com/portfolio/illustrated/illustrated_08.html

Albedo

• Albedo = reflected radiation / absorbed radiation• Snow Albedo = 90 %• Forest Albedo = 10 %• Average for Earth: 30 %

Blackbody Radiation• Everything glows to some

degree.• Solids emit a lot of

frequencies, but not all frequencies are equally intense.

• Analyzing the light tells you the temperature of the body.

http://quantumfreak.com/introduction-to-blackbody-radiation/

Blackbody Radiation

• The greater the temperature, the more light is emitted.

• The greater the temperature, the higher the frequency of the most intense light.

• The greater T, the less l.

http://schools-wikipedia.org/wp/t/Thermodynamic_temperature.htm

Blackbody Radiation

http://www.ecse.rpi.edu/~schubert/Light-Emitting-Diodes-dot-org/chap18/F18-02%20Planck%20black%20body.jpg

Blackbody Radiation

• Notice where the red is. • At room temperature,

bodies emit mostly in the infrared.

• The sun is so hot that it emits in the visible range.

• Why do animals see so well in the range where the sun emits light?

http://www.egglescliffe.org.uk/physics/astronomy/blackbody/bbody.html

Wein’s displacement law

lmax = B / TB = 2.89 x 10-3 m K

Problem

Approximately what is the temperature of an object that radiates most of its energy as yellow light?

Solution

Yellow light has a wavelength of about 570 nm.570 nm = 570 x 10-9 m

lmax = B / Tlmax = 2.89 X 10-3 m K / TT = 2.89 X 10-3 m K / lmax

T = 2.89 X 10-3 m K / 570 x 10-9 m T ≈ 5000 K

( This is approximately the temperature of the surface of the sun. )

“Infrared” vs. “Heat”All objects radiate electromagnetic energy. When it’s in the visible range for humans, we call it

“light”, but it is light no matter what the frequency.

Objects at room temperature emit almost no light that we can see, but they do emit plenty of light in the ‘infrared’ region.

Since hotter objects emit more infrared light than cooler objects, we sometimes call infrared light “heat”, but it is not heat, it is just light that comes from hot objects.

Please see the next slide…

http://www.kollewin.com/blog/electromagnetic-spectrum/

\

Stefan-Boltzmann Law

• The hotter the object, the greater the intensity of radiation that is emitted:

• Power per unit area = s T4

• s = 5.67 x 10-8 W m-2 K-4

ProblemLight from the sun is most intense around the color blue. What temperature is the surface of the sun?

Solution

From , lmax = 2.89 x 10-3 m K / TT = 2.89 x 10-3 m K / lmax Blue light has a wavelength of about 420 nm.So T = 2.89 x 10-3 m K / (420 x 10-9 m) T = 6900 K

The earth absorbs the sun’s light…The earth is getting a lot of energy every second.

Why doesn’t the earth get hotter and hotter?Tell your buddy.

The earth radiates energy back into space…If the earth radiated less than it does, then the

earth would cool.If the earth radiated more than it does, then the

earth would warm.The earth radiates energy at the same rate that

the earth absorbs energy.

What if you put a very cold earth in our place?At first the earth would radiate very little energy. As the earth warmed up, the earth would radiate more and more.At equilibrium, the earth would radiate as much as it received.

Our first climate calculationIf the earth had no atmosphere, then the energy coming in from the sun would balance the energy it radiated out. What would be the average temperature of the earth? Givens:Solar constant: 1380 W m-2 Radius of earth = 6.4 x 106 m(Value to check at the end: Average temperature of the earth is 59˚F = 15˚C = 288 K)

Solution (1 of 5)• Since the temperature of the earth is steady, the

energy arriving equals the energy leaving.• The energy arriving is from the sun. • The energy leaving is by radiation.

Solution (2 of 5)• The energy arriving is from the sun. The product

of the solar constant and area gives the power (energy per second).Rate of energy arriving = {1380 W m-2}×{Area}

• Which area should we use? …

The area receiving the radiation is equivalent to a disc.

Solution (2 of 5)• The energy arriving is from the sun. The product

of the solar constant and area gives the power (energy per second).Rate of energy arriving = {1380 W m-2}×{Area}

• Which area should we use?• Area of a disc = pR2

Power arriving = {1380 W m-2}×{p(6.4 x 106 m)2}Power arriving = 1.75 x 1017 W

Solution (3 of 5)• Energy arrives from the sun at 1.75 x 1017 W. • But a portion of it goes right back out into space,

due to reflection. The reflected portion does not contribute to the energy balance on earth.

• The average albedo of the earth is 30 % = 0.30• So 70 % of the energy from the sun does enter

our energy balance.• 0.70 x 1.75 x 1017 W = 1.23 x 1017 W { }• This is the relevant value of solar energy that

arrives at earth.

Solution (4 of 5)• The energy leaving is by radiation. • Use the Stefan-Boltzmann law:

Rate of energy leaving per area= s T4 Rate of energy leaving = Area×s×T4

• Which area should we use?• Over what area does the earth radiate?• Area of a sphere = 4pR2

Rate of energy leaving = (4pR2)×s×T4 Power leaving =4p(6.4x106m)2(5.67x10-8Wm-2K-4)×T4

Solution (5 of 5)Power arriving = Power leaving

1.23x1017W = 4p(6.4x106m)2(5.67x10-8Wm-2K-4)×T4 Solve for TemperatureT = 255 K = -18˚C = 1˚F

This is colder than the average temperature of the earth (288 K), but we left out the earth’s atmosphere. We left out the (natural) greenhouse effect.

Emissivity (1 of 4) A big help in getting the energy equation to work out better comes from realizing that the earth does not act like a perfect “blackbody”. Real objects do not act like perfect black bodies; real objects emit less energy than a perfect black body would at the same temperature.Because the atmosphere acts like a blanket, the earth radiates energy at a rate less than sT4.

Emissivity (2 of 4) Emissivity is a unitless number that describes how it resembles a perfect black body.Emissivity is calculated by dividing the real output of the object by the perfect blackbody output.A dull, black lump of rock has an emissivity of about 0.9 A mirror has an emissivity of about 0.1

Emissivity (3 of 4) If the earth did radiate like a perfect blackbody, then it would radiate at this rate:

Power Leaving = (Area of sphere)×sT4 Power Leaving = [4p(6.4x106)2]×(5.67x10-8)×(288)4

Power Leaving = 2.0 x 1017 WThe real power leaving the earth is the same as the real power arriving at the earth:

1.23 x 1017 W { }How would you calculate the emissivity of the earth?

Emissivity (4 of 4) The emissivity of the earth is:

e = { 1.23 x 1017 W } ÷ { 2.0 x 1017 W } e = 0.6

The role of the atmosphere in climate• Every molecule can absorb radiation, and when it

does, it often emits that same frequency, but in a random direction.

• Our atmosphere has an upper layer with ozone (O3) and a lower layer with water vapor and carbon dioxide (CO2)

Ozone (O3) is one of the forms of oxygen.

https://www.windows2universe.org/physical_science/chemistry/oxygen_ozone.html&edu=elem

Recall what is meant by an “absorption spectrum”

Recall what is meant by an “absorption spectrum”

http://www.cbu.edu/~jvarrian/252/emspex.html

Why are only specific colors emitted / absorbed by hydrogen?

How do the emitted colors relate to the absorbed colors?

Hydrogen

Hydrogen

Hydrogen

Hydrogen

Absorption Spectra(for the moment, just read everything on the graph).

http://chriscolose.wordpress.com/2008/03/09/physics-of-the-greenhouse-effect-pt-1/

Absorption Spectra.


Notice that the atmosphere does not absorb visible

light!

Absorption Spectra.


Ozone absorbsUV light,

making lifepossible on earth!

Greenhouse gases are transparent to incoming solar radiation…

Greenhouse gases are transparent to incoming solar radiation, but absorb the earth’s radiation.

Conceptual QuestionsImagine light that hits the ground and is reflected right back.a)What is the most likely color of the earth in that region?b)What is the most likely thing for that light to do when it hits the atmosphere?

Conceptual AnswersImagine light that hits the ground and is reflected right back.a)What is the most likely color of the earth in that region?

The earth there is likely white, due to snow or ice.b)What is the most likely thing for that light to do when it hits the atmosphere?Since the light just made it through the atmosphere, it is visible light, and it will go back through it again.

More Conceptual QuestionsImagine light that hits the ground and is absorbed, and as a result, a moment later the earth re-radiates. What is the most likely thing for that light to do when it hits the atmosphere?

More Conceptual AnswersImagine light that hits the ground and is absorbed, and as a result, a moment later the earth re-radiates. What is the most likely thing for that light to do when it hits the atmosphere?The earth is not terribly hot, so when it radiates, it sends out infrared radiation. Atmospheric CO2 and

H2O will likely absorb that light.

Another look at the Greenhouse effect

http://connect.in.com/greenhouse-effect-definition/images-detailed-greenhouse-effect--1-327176358885.html

Surface Heat Capacity• Surface heat capacity is the amount of energy

required to raise the temperature of a unit area of ground by 1 K.

• For the earth this is 4 x 108 J km-2.

The Greenhouse Effect by Hamper and OrdThe infrared radiation from the ground travels

upwards through the atmosphere and as it does it is absorbed by CO2 and H2O.

As a result, these molecules become excited, raising the temperature of the atmosphere.

The molecules radiate IR radiation in all directions, some of which goes back to the earth.

The temperature of the earth is determined by the point at which the radiation leaving the earth is equal to that arriving.

By reducing the amount leaving, the temperature at which this balance will be achieved will be higher.

Greenhouse Gases• Water (H2O) – Oceans– Lakes

• Carbon Dioxide (CO2)– Fires– Cars– Power plants

• Methane (CH4)– Farm animals– Fossil fuels

• Nitrous Oxide (N2O)– Many sources

Ice Cores

http://earthobservatory.nasa.gov/Features/Paleoclimatology_IceCores/

Ice Cores

http://blogs.sun.com/factotum/entry/messaging_server_no_core_dumps

http://en.wikipedia.org/wiki/File:GISP2D1837_crop.jpg`

Data from Ice Cores

• The number of different types of data that have been collected from ice cores is staggering.

• The most famous result is the correlation between temperature and CO2 level.

• Historically, the greater the CO2 level, the greater the temperature.

• There is a difference between correlation and causation.

http://www.google.com/imgres?imgurl=http://upload.wikimedia.org/wikipedia/commons/thumb/5/51/Mauna_Loa_Carbon_Dioxide-en.svg/800px-Mauna_Loa_Carbon_Dioxide-en.svg.png&imgrefurl=http://commons.wikimedia.org/wiki/File:Mauna_Loa_Carbon_Dioxide-en.svg&usg=__O_oYGV95EgWGRMOCpdngnXQ5gf4=&h=515&w=800&sz=80&hl=en&start=0&zoom=1&tbnid=x8dJZdK33FKBRM:&tbnh=113&tbnw=175&prev=/images%3Fq%3Datmospheric%2Bcarbon%2Bdioxide%2Bmeasured%2Bat%2Bmauna%2Bloa%2Bhawaii%26um%3D1%26hl%3Den%26sa%3DN%26biw%3D1280%26bih%3D645%26tbs%3Disch:1&um=1&itbs=1&iact=hc&vpx=286&vpy=185&dur=793&hovh=180&hovw=280&tx=99&ty=81&ei=90gqTaW_MoaKlwfElYXbCw&oei=90gqTaW_MoaKlwfElYXbCw&esq=1&page=1&ndsp=18&ved=1t:429,r:1,s:0

CO2 levels have been rising

Why is rising CO2 a concern?If CO2 level causes temperature, then increasing CO2 would cause an increase in temperature.

Temperatures are going up.

http://en.wikipedia.org/wiki/Global_warming

Glaciers are getting smaller(The photos are 33 years apart)

http://en.wikipedia.org/wiki/Retreat_of_glaciers_since_1850

Rise in Sea Level• As the temperature of a liquid increases, it

usually gets larger: DV = bV0DT.• We do observe an increase in sea level.• The rise could be due to warming oceans or

melting icecaps.

Global Warming• “Global Warming” refers to any long-term

increase in the temperature of the earth.• For example, if the sun got hotter, it would cause

global warming.• If global warming is observed, it could be due to a

dozens of different causes.

Computers and Global Warming• The calculations involved in global warming are

famous for being complicated, and for being important.

• In order to make responsible predictions for the long-term future of the earth, scientists have been pressing hard to accurately describe how climates work.

The forecast…• Weather is not Climate.• Day-to-day weather, and even data over just a

few years, are not the concerns of climatologists.• Most models forecast more rain in the North and

more heat around the equator.

How is global warming different from the greenhouse effect?

What is the cause and what is the effect?

IPCC• The United Nations and the World Meteorological

Organization established the Intergovernmental Panel on Climate Change.

• The IPCC reviewed the data and wrote:THE EXPERTS CONCLUDED THAT THEY ARE CERTAIN THAT EMISSIONS FROM HUMAN

ACTIVITIES ARE SUBSTANTIALLYINCREASING THE ATMOSPHERIC

CONCENTRATIONS OF GREENHOUSE GASES AND THAT THIS WILL ENHANCE THE GREENHOUSE EFFECT AND RESULT IN AN ADDITIONAL WARMING OF THE EARTH’S SURFACE.

Global Warming is an international problem.

SolutionsAll of the solutions deal with minimizing the emission of CO2.

• Cleaner cars.• Power plants that do not use coal, or at least that

do not emit so much CO2.

• Capture the CO2 and store it.

the worksheet for the simulation will be in the student’s booklets

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