1. Atmospheric and ocean composition, past and present
IV. Intersection: what we know, would like to know, will never know, and what can we contribute to the debate.
III. Atmospheric & Ocean Biogeochemistry: Second element of climate and environmental science
Atmospheric and ocean composition, past and present
Human impact, global change
II. Atmospheric & Ocean Physics: First element of climate and environmental science
Atmospheric structure (T, P in "4-D")
Winds, Weather, General Circulation, Climate
I. Physical Principles: The foundation & the tools
Newton's laws: forces, pressure, motion
Energy: Temperature, radiant energy
L-2
L-3

2. Road map to EPS 5 Lectures 3 and 4: Atmosphere Heat, Energy, Radiation
Black Bodies, Planck Function, Stefan Boltzmann Law
Effective T, greenhouse effect
Feedback!
Planets radiate on average at the Effective Temperature, to maintain energy balance with sun and space, Absorption of ir in the atmosphere traps energy, radiating back to the surface and causing it to warm up.
Teff = [Fs(1 - A)/(4σ)]¼
= K
Tg = [n + 1]1/4Teff.
Solid bodies emit thermal radiation at rates that depend on temperature. Hot bodies (sun) emit more radiation at shorter wavelengths than cold bodies (earth).
Emission rate=σT4
Start the oven demo

3. Atmospheric Radiation: The Earth receives energy from the sun (on average 344 W/m2) and emits the same amount to space
complicated, consider how this works out step by step: different process; solar flux/4 – look forward to that. Solar and longwave—look forward to that.

4. The energy balance of planet earth
The temperature of the earth’s surface has been remarkably constant over geologic time. Even the dramatic cooling during the ice age represented a change of only 3° C in the global average surface temperature, occurring over thousands of years. Seasonal changes in temperature, although large in a particular place, correspond to very tiny changes in global mean temperature.
How is this remarkably steady condition maintained?
To maintain the long-term stability of earth’s temperature, the planet must radiate to space a flux of energy sufficient to just balance the input from the sun, i.e. the earth is, to good approximation, in radiative energy balance.

5. 1.      Atoms form chemical bonds by rearranging electrons in the outer (valence) shell to localize the electrons between the nuclei.
2.      Light may be regarded as both a propagating electric field in the shape of a sine wave and as particles called photons. The relationship between the speed of light (c), its wavelength (λ), and its frequency (ν), is c = λν.
3. Every photon has a specific energy proportional to its frequency, or inversely proportional to its wavelength, E = hc/λ = hν.
Most atmospheric gases can neither emit nor absorb light at the long wavelengths (infrared) emitted by cold objects, such as the Earth. Those relatively rare atmospheric molecules that can absorb infrared radiation have asymmetric distribution of charge (e.g. a dipole, like the water molecule) that causes the molecules to experience a force due to the oscillating electric field of the light.
Matter can emit light only at wavelengths that it can absorb.
Matter emits radiation depending on its temperature. The total flux of radiation emitted is given by the Stefan-Boltzmann equation, Flux (W m-2) = σT4, where σ is the Stefan-Boltzmann constant, 5.67x10-8 W m-2 K-4. The flux as a function of wavelength is given by the Planck function, FLUX (λ) = [2π hc2 / λ5 ]/[exp( hc/(λ kT) ) – 1 ], (W m-2 m-1).

6. A brief introduction to light and matter

7. Protons, neutrons, electrons, and electrostatic forces.
Lecture 15 Science A-30
Protons, neutrons, electrons, and electrostatic forces.
Atoms are the fundamental chemical building blocks of matter, the smallest unit that retains chemical identity. An atom is made up of protons (positive charge), neutrons (zero charge), and electrons (negative charge). The protons and neutrons are packed together in the nucleus and the electrons forming a cloud of negative charge around the nucleus.
The size of an atom (diameter of the electron cloud) is ~10-10 m, but the nucleus is smaller by factor The atomic unit of length is the Ångström, 1 Å ≡ m, named to honor Anders Ångström ( ), Swedish physicist who improved the precision in measuring the wavelength of spectral lines.
Electrostatic forces are responsible for holding atoms together or forcing them apart. When electric charges, q1 and q2 are distance r apart, the electrostatic force between them is F = q1q2/r2, and the energy of interaction is E = q1q2/r (the energy it takes to bring them to distance r from infinity). If the charges are of like sign (both + or both -), the force is repulsive, the energy is positive, and the charges will tend to fly apart. Charges with opposite signs are attracted and the electrostatic force pulls the charges together. q is the charge, it comes in multiples of the electron charge.

8. apparatus for determining the charge on an electron E + - +
"electroscope"
apparatus for determining the charge on an electron E
torque on the dipole (molecule)
"click here" =>> web -
electric field
F = q1q2 / r2

9. Electrostatic forces hold the atoms in a molecule together (or can push them apart…).
without bonding, we would expect atoms to repel each other. Draw distributions around atoms. Explain bonding orbitals and delocalization.
Density of electron charge (net negative charge, shown in red and green) relative to the positions of the nuclei and inner-shell electrons (net positive charge, dark blue) in the molecule Si3. The maxima of electron density between the nuclei provide clouds of negative charge that attract the positively-charge nuclei and hold the molecule together. (Figure by Dr. Masao Arai, National Institute for Research in Inorganic Materials, Japan.)

10. Molecules that have opposite electric charges at either end (“dipole moment”) can absorb or emit electromagnetic radiation (light) in ways that affect the heat balance of the earth. The major molecules of air (O2, N2) do not have dipole moments, and they cannot emit or absorb light in this way.
To understand why dipole moments are important in absorption and emission of light, we need to study the properties of light.
The O atom in water partially pulls the electrons away from the H atoms, giving its side of the molecule a small negative charge (-2δ) and the H side a small positive charge (+δ on each H-atom).
Light and radiant heat (infrared radiation) propagate through space as waves, called electromagnetic waves because there are an electric field and a magnetic field associated with each wave (the magnetic field is not important for our purposes).

11. If we could take a snapshot of a light wave as it traveled for 1 s, it would be 3×108 m long, and would look like the sine wave shown in the figure. The distance between two successive crests on the wave is called the wavelength (denoted λ). The frequency (denoted ν) is the number of wave cycles (wavelengths) that pass a reference point per unit time, and since our snapshot shows exactly the number of peaks that passed in one second, ν is also the number of peaks in the picture, i.e. ν =c/λ. Alternatively, 1/ν is the time it takes the wave to travel one wavelength at speed c λ ν = c
Discuss this in detail, drawing on the board. Note that we are speaking of visible, infrared, x-ray, etc.

12. Electromagnetic radiation, although wave-like in nature, is composed of packets of energy called photons. Thus light is both a wave and a particle. For a given electromagnetic wave of wavelength λ the energy associated with each photon is given by
E = hc/λ = hν
where h is Planck's constant (h=6.626x10-34 J sec). This was one of Planck's great discoveries; it implies that photons with shorter wavelengths are more energetic than photons with longer wavelengths and light comes in defined packets with a particular amount of energy in each one (given by hν).
Light and matter in fact are always dual waves and particles.
Discuss the photoelectric effect –packets. Dual nature of light, electrons, etc—wave and particle.

13. Photoelectric effect
Observation: when certain metals are exposed to light, and electric current can be made to flow in a circuit. Only wavelengths shorter than a threshold make this happen. The energy in each electron is proportional to 1/λ, and the number of electrons depends on the intensity of the light. This is how a solar cell works…

14. Photovoltaic cell layout

15. λmax = b/T (Wien's displacement law: peak of Planck function)
Matter emits radiation if its temperature is above 0 K (absolute zero). An object that absorbs radiation at all wavelengths incident on it necessarily emits radiation at all wavelengths. This ideal material is called a black body; solid objects, such as the the earth, or liquid water, behave almost as black bodies. Planck showed that the intensity of light that is emitted from a black body as a function of wavelength (λ) or frequency (ν), is given by the following function (now called the Planck function):
[2π hc2 / λ5 ]
FLUX (λ) =
[exp( hc/(λ kT) ) – 1 ],
(units: Watts m-2 m-1; 1 W ≡ 1 J s-1) is the amount of energy in light with λ between λ and λ+Δλ passing through surface with area 1 m2 each second.
Planck’s Law indicates that the temperature of an object determines the intensity of radiation emitted by the object at any wavelength, provided that the object can absorb radiation at that wavelength.
λmax = b/T (Wien's displacement law: peak of Planck function)
<= Planck function
Planck’s Law is a consequence of the fact that matter and radiation must come into equilibrium if they are enclosed under steady conditions long enough. Discuss the Black Body experiment (cavity) and what was observed, viz total energy output, relationship of the "spectrum" (define this) vs T.

16. Planck Function (W m-2 / cm-1) Planck Function (W m-2 / cm-1)
wavelength (μm)
wavelength (μm)
The Planck function for several temperatures is plotted versus wavelength λ (upper scale, 1 μm = 10-6 m) or wave number (≡ 1/λ = ν/c; wave numbers are proportional to photon energy, like ν, but in units more convenient than frequency).
Planck Function (W m-2 / cm-1)
Planck Function (W m-2 / cm-1)
Do the OVEN DEMO here, put them in:
Take two objects of different materials (e.g. a brick and a steel ball) that look different in reflected light, and placed them in an oven that can reach about 900 C (1200 Kelvin). At this temperature they emit light at a high rate at wavelengths that we can see visually.
then discuss these curves.
Then do the lantern slide demo. Note absolute scales, etc. RELATE THIS TO THE OVEN DEMO. Then take the stuff out of the oven.
wavenumber (cm-1)
wavenumber (cm-1)
Planetary Radiation
Solar Radiation

17. The Planck function gives the energy flux from an object divided up according to wavelength (or frequency), for a given temperature. Long before Planck, however, scientists had determined by direct experiment that the total energy flux from an object, at all wavelengths, depended only on temperature, and they derived an empirical equation called the Stefan-Boltzmann law to describe this relationship:
TOTAL ENERGY FLUX = σ T4 .
Here the total energy flux (units: W m-2) is shown to vary as the 4th power of the absolute temperature, T (K), with a constant of proportionality σ = 5.67 × 10-8 W m-2 K-4, the Stefan-Boltzmann constant. The Stefan-Boltzmann law was obtained in the 19th century by observing the rate at which real objects lost energy via radiation, with many decades passing before Planck showed that it could be derived from his radiation law.
relate to the DEMOS!

18. [exp( hc/(λ kT) ) – 1 ], FLUX (λ) =
Summary of Introduction to light and matter EPS-5
Molecules are made up of nuclei (positively charged) and electrons (negatively charged). The electrons have much lower mass than the nuclei and therefore move faster than the nuclei.
Electromagnetic radiation is composed of oscillating electric and magnetic fields that propagate through space at the speed of light c = 3 x 108 m/s.
Molecules interact with electromagnetic radiation if they have a dipole moment (separation of electrical charge, permanent or transient). The oscillating electric field exerts a torque on the molecule if the frequency matches a frequency for oscillation of the molecular dipole.
The speed of light c, frequency ν, and wavelength λ are related: c=λν.
A black body emits light according to Planck’s Law,
[2π hc2 / λ5 ]
FLUX (λ) =
[exp( hc/(λ kT) ) – 1 ],
and the total energy emitted (m-2 s-1) = σ T4. 

19. Electromagnetic spectrum: Atmospheric Radiation
106
© Yochanan Kushnir, personal communication via Annenberg. Not radioactivity. Note logarithmic X axis. Note scale factor.
Discuss the photoelectric effect –packets. Dual nature of light, electrons, etc—wave and particle.
Demos: Lantern slide projector. Steel ball in oven.

20. project the spectrum on this slide

21. visible "color temperature"
Wien….return to slide 6; (note lambda here…; sun is actually 106 x earth flux at the peak)
solar and planetary spectra; DISJOINT – phenomena such as clouds, aerosol particles, gases, changes in the earth's surface AFFECT THEM DIFFERENTLY !
"color temperature"

22. Lantern slide projector demo:
The oven demonstration:
We took two objects of different materials (e.g. a brick and a steel ball) that look different in reflected light, and placed them in an oven that can reach about 900 C (1200 Kelvin). At this temperature they emit light at a high rate at wavelengths that we can see visually.
Even though they looked different in reflected visible light, both objects look the same as they glow under these conditions. In fact it will often be difficult to see them at all inside the oven, which is also glowing. This experiment illustrates that ordinary solid objects emit and absorb radiation more or less like "black" bodies, which is the same as saying that their emission spectra follow Planck's equation.
Lantern slide projector demo:
Put a strong prism in front of a lantern slide projector to disperse the light, and varied the temperature of the lamp by changing the applied voltage (for example, using a variable transformer). The rapid disappearance of the blue light will be apparent as the temperature is lowered (and vice versa), as will changes in the total amount of light coming from the projector. This experiment visualizes Planck’s function directly and illustrates the phenomena that Planck sought to explain. The changes in emission rate at various wavelengths relate directly to our understanding of sunlight and of heat radiation from the earth.

23. The IR camera demonstration:
We deployed an infrared camera that creates images using longwave infrared radiation. We observed how matter at different temperatures radiates longwave radiation, and we were able to create simple analogs of the "greenhouse effect" using materials like mylar, lexan, etc.

24. Albedo
The earth’s albedo (fraction of solar radiation *reflected* to space) was first measured by observing earthshine on the moon, reflected back to earth and visible just after the new moon. It is now measured from spacecraft. About 33% of the solar energy incident on the earth is reflected back to space, A=0.33.
Most of the reflection of solar radiation from earth is due to clouds, with help from sea ice and glacial ice in Antarctica and Greenland, plus snow and deserts (albedo 0.6—0.9).
The albedo of the earth’s surface is mostly much lower than 0.33, about .07 for land with vegetation, for the ocean.).
Thus the albedo, and the entire energy budget of earth, is sensitive to cloudiness and ice cover, factors that change on both weather and climate time scales (short and long times).
Albedo

25. Earth's albedo for March, 2005 (CERES satellite)
The earth’s albedo was first measured by observing earthshine on the moon, reflected back to earth and visible just after the new moon. It is now measured from spacecraft. About 33% of the solar energy incident on the earth is reflected back to space, A= The albedo of the earth’s surface is in general much lower than 0.33, about .07 for land with vegetation, for the ocean, with somewhat higher values for deserts (~0.2) and snow and ice (0.6 – 0.9). Most of the reflection of solar radiation from earth is due to clouds, with notable contributions from sea ice and glacial ice in Antarctica and Greenland. Thus the albedo, and the entire energy budget of the planet, is sensitive to cloudiness and ice cover, factors that change over both short time scales (weather) and long time scales (climate).
ALBEDO
The term has its origins from a Latin word albus, meaning “white”. It is quantified as the fraction of incident solar radiation of all wavelengths reflected by a body or surface. 

26. Diagram of the sun and earth, and an imaginary sphere with radius 1
Diagram of the sun and earth, and an imaginary sphere with radius 1.5x1011m with the sun at the center.
The surface area of this sphere is 4πr2.
r=1.5 x 1011 m O o
earth
sun
We can compute, using the Stefan-Boltzmann Law, the total amount of energy (L) radiated by the sun each second,
L = σTs4 ×4πRs2 = 3.9 x 1026 watts,
where 4πRs2 is the surface area of the sun (Rs=6.6 × 108m), σTs4 is the Stefan-Boltzmann law giving the energy flux per unit area, and Ts is the temperature of the sun’s surface, 5800 K.

27. Fs = L/(4πr2) = σTs4 ×(Rs2/r2) = 3.9x1026/( 4π(1.5x1011)2 ) =
The same total amount of energy L must also cross the sphere of radius r each second.
The solar flux (Watts m-2) at the earth, Fs, is defined as the energy crossing a square meter of the sphere at earth's orbit each second. It is given by
Fs = L/(4πr2) = σTs4 ×(Rs2/r2) = 3.9x1026/( 4π(1.5x1011)2 ) =
1379 W m-2
The solar flux Fs (also called the solar constant) is the radiant energy from the sun that falls per second a 1 m2 surface oriented perpendicular to the sun’s rays, at the top of the earth's atmosphere.
Note orbital variation with seasons; relationship to "solar flux"
1379 / 4  344

28. The amount of energy striking the earth is given by the
The total solar energy striking by the earth per second can be calculated by multiplying Fs by the shadow area (not the total surface area!) of the earth , i.e. the area of solar beam intersected the earth.
The amount of energy striking the earth is given by the
[shadow area (black circle) × the solar flux] =πRe2 Fs. (Re is the radius of the earth).
The total energy flux striking the surface of the earth is therefore Fs πRe2.
SUN
clicker question: give the energy balance of a planet that does not rotate, where the sunny side distributes energy evenly over 2*pi*R^2.

29. Eemit = 4πRe2 σT4 . OUTPUT Energy INPUT to the earth from the sun
Not all solar radiation intercepted by the earth is absorbed. The fraction of incident solar radiation reflected is defined as the albedo, A, and the fraction absorbed is therefore (1-A).
The total energy input to earth (Joules per second) is thus
Eabs = FsπRe2(1 - A). INPUT
Energy OUTPUT from earth by thermal radiation
The total energy emitted per unit area is given by σT4, and the emitting area is the surface area of the earth, 4πRe2.
The total energy emitted by the planet per second is therefore
Eemit = 4πRe2 σT OUTPUT
The earth’s albedo was first measured by observing earthshine on the moon, reflected back to earth and visible just after the new moon. It is now measured from spacecraft. About 33% of the solar energy incident on the earth is reflected back to space, A= The albedo of the earth’s surface is in general much lower than 0.33, about .07 for land with vegetation, for the ocean, with somewhat higher values for deserts (~0.2) and snow and ice (0.6 – 0.9). Most of the reflection of solar radiation from earth is due to clouds, with notable contributions from sea ice and glacial ice in Antarctica and Greenland. Thus the albedo, and the entire energy budget of the planet, is sensitive to cloudiness and ice cover, factors that change over both short time scales (weather) and long time scales (climate).

30. Teff = [Fs(1 - A)/(4σ)]¼ = 252.6 K.
Energy balance requires that input=output, when averaged over a long-enough period of time, i.e. on average Eemit = Eabs. Thus
4πRe2σT4 = FsπRe2(1 - A) . 
(This is the Energy Balance Equation). This equation can be solved for the average temperature at which the earth must emit radiation to bring the energy budget into balance, called the effective temperature Teff of the planet:
Teff = [Fs(1 - A)/(4σ)]¼ = K.  
energy output of the earth. Consider an idealized planet at earth's orbit, with the same albedo, but with no atmosphere. We will take into account the effect of the atmosphere shortly. The planet rotates quickly and is an efficient conductor of heat, so the input is absorbed on all sides and the whole planet reaches a single temperature. Let us further assume that this idealized planet is neither heating up nor cooling off, so the amount that it radiates to space each second equals the amount absorbed (input). What temperature will this body have?
The effective temperature of the earth is a basic quantity determined by the balance between solar radiation absorbed and terrestrial radiation (the heat emitted by earth to space, with much longer wavelengths than solar light). It is the temperature of the earth that you would infer by looking from space and measuring the total heat output.
The peak of the blackbody curve for terrestrial radiation is about 15 μm, with most energy emitted between 10 and 30 μm, wavelengths not visible to the eye.
Note that Teff is much colder than the surface temperature of the earth. Thus if there were no atmosphere the earth would be too cold for liquid water to exist and there would be no life on the planet. We will now discuss how absorption and re-emission of terrestrial radiation by molecules in the atmosphere raises the surface temperature, the so-called greenhouse effect.
NOTE what each factor here means (class): 4 ; sigma ; A ; solar flux ; ¼ PHYSICAL INTERPRETATION

31. Which of the following statements concerning the figure below are true?
A) The peak of the solar radiative flux is within the visible range of the electromagnetic spectrum
B) The radiative flux at the surface of the Sun is greater than the radiative flux at the surface of the Earth at all wavelengths
C) The total energy flux from the Earth is much less than the total energy flux from the Sun
D) A and C only
E) All of the above

32. Effective Temperatures of the Planets
planet solar flux orbit radius albedo Te Tg Ground pressure
(W m-2) (1011 m) (K) (K) (bar)
Mercury ~0
Venus
Earth
Mars
Jupiter (no surface) (no surface)
Note the anomaly at Venus; range for life to exist probably or so; only one planet cuts it!
Issues: albedo , thickness of the atmosphere
After Goody and Walker, "Atmospheres"

33. Effects of vegetation, sea ice…visible from space, changes on annual and longer time scales  climate forcing !
2001

34. Earth's Albedo can change with time, affecting the energy budget and temperature of the planet.
Top of Atmosphere Flux Anomaly W m-2

35. Atmospheric absorption of infrared radiation
The most abundant gases in the atmosphere, N2, O2, and Ar, neither absorb nor emit terrestrial radiation. (They also neither absorb nor emit most wavelengths of solar radiation, except for ultraviolet light).
The relatively rare molecules that can absorb long-wave (terrestrial) infrared radiation are called greenhouse gases. They can trap infrared radiation emitted by the Earth much as the glass in a greenhouse traps heat.
The most important greenhouse gases in the atmosphere are H2O and CO2, and gases such as methane (CH4) and chlorofluorocarbons are also significant.
do not have dipole moments, they cannot be bent. Therefore they cannot interact with infrared radiation and
[review how a dipole interacts with electromagnetic radiation]—show IPCC bar chart

36. Greenhouse gases: Water, CO2, CH4
O = C = O -δ -δ
O O = = C
+2δ
CO2 with electromagnetic waves with only dynamic ("transition") dipole moment due to the changes in the +δ and –δ as the molecule vibrates (bending or "asymmetric stretch").
The dipole moment—puzzle for CO2==it's symmetric (mirror image, how can it have a dipole moment?)
Explain "transient".
Water interacts with electromagnetic waves with both a permanent dipole moment (left) and dynamic ("transition") dipole moment due to the changes in the +δ and –δ as the molecule vibrates.
molecules radiate frequencies they can absorb: Kirchhoff's Law

37. The atmosphere is warmed by the absorbed terrestrial radiation.
Due to the presence of gases that can absorb infrared radiation, the atmosphere acts as a blanket, allowing solar energy to reach the surface but preventing the heat from escaping directly back to space.
The atmosphere is warmed by the absorbed terrestrial radiation.
Molecules that can absorb radiation of a particular wavelength can also emit that radiation according to Kirchhoff's radiation law. The Greenhouse gases in the atmosphere will therefore radiate, both to space and back towards the earth's surface. This back- radiation warms the earth's surface.
demo heat shield; relate to SLIDE 3.

38. The Greenhouse Effect: influence of atmospheric absorption and emission of planetary (infrared) radiation
reflected
solar
(A)
incoming solar radiation (Fs)
(visible, near infrared) σ Tg 4
terrestrial (far infrared)
radiation from the surface T e
far infrared radiation
from the atmosphere
z=H
IN = σTg 4; out = 2 σT1 4; Tg= (2)1/4 T1 and T1 = Te

39. σTg4 = 2σT14 . { T1 =>> Teff}
The atmosphere and the ground radiate energy according to the Stefan-Boltzmann law. Examine the energy balance of the layer at H (intended to be a scale height, or ~ 7km, on earth) in this hypothetical planet. The total amount of energy radiated per square meter per second is 2σT14, (OUT) because the layer radiates equally both up and down. But the amount received by the layer is σTg4, (IN) (heated only from below!). If the layer has a balanced energy budget, these two fluxes must be equal (IN = OUT),
σTg4 = 2σT { T1 =>> Teff}
Thus the ground is warmer than the atmosphere by Tg = 21/4Teff. This happens because the atmosphere is warmed only by absorbing radiation from the earth's surface, i.e. from one side (below), but it radiates both up and down.
The atmosphere must have a lower temperature than the ground in order to satisfy its energy balance. This result for 1 layer in the atmosphere can be generalized to any number (n) of layers,
σTg4 = [n + 1] σT14
Tg = [n + 1]1/4Teff .
The atmosphere therefore gets colder as we go up due to the effects of absorption and emission of radiation (terrestrial infrared radiation).
solve for the T of each layer: show that it gets colder.

40. SOLAR RADIATION SPECTRUM: blackbody at 5800 K
move to later – after absorption return to slide 3

41. TERRESTRIAL RADIATION SPECTRUM FROM SPACE: composite of blackbody radiation spectra for different T
Scene over
Niger valley,
N Africa
WINDOWS !! Not a grey atmosphere; different efficiency for GHGs. Water, Water, everywhere
cf. clouds, aerosols

42. Climate forcing due to human—caused changes in concentrations of greenhouse gases, atmospheric aerosols, and clouds, since 1850
(Hansen, 2001).

43. ATMOSPHERIC CO2 INCREASE OVER PAST 1000 YEARS

44. Atmospheric and ocean composition, past and present
IV. Intersection: what we know, would like to know, will never know, and what can we contribute to the debate.
III. Atmospheric & Ocean Biogeochemistry: Second element of climate and environmental science
Atmospheric and ocean composition, past and present
Human impact, global change
II. Atmospheric & Ocean Physics: First element of climate and environmental science
Atmospheric structure (T, P in "4-D")
Winds, Weather, General Circulation, Climate
I. Physical Principles: The foundation & the tools
Newton's laws: forces, pressure, motion
Energy: Temperature, radiant energy
aerosols
albedo
"Feedback"
L-2
L-3

45. FEEDBACKS + positive feedback + negative feedback
Consider how these factors may change, what may cause these changes, and how the various changes may interact with each other. This brings us to the concept of feedback:
property A increases →
property B changes →
causes property A to increase further
causes property A to decrease
Positive feedback makes the climate system more sensitive to a change in property A; negative feedback makes it less sensitive. The concept of feedback depends on a formulation of direct vs. secondary effects, based on separation in time or some other criterion.
+ positive feedback
(amplification)
+ negative feedback
(damping)
microphone feedback. proximate cause:
Ex. 1: a billiard set-up
Ex. 2: a fireplace set-up: burn one log ? but it takes 2…trapping; feedback by adding a 3rd log.

46. FEEDBACKS INVOLVING ALBEDO (continued)
ice-albedo feedback – solar radiation
Temperature increases → polar ice recedes → Albedo decreases
→ Temperature increases
This is a very strong feedback when there is a lot of polar ice, for example, at the height of the last ice age. It works both ways, helping the ice sheets to advance as the earth cooled, by amplifying the cooling, and accelerating the retreat of the ice sheets as the climate started to warm. There is rather little polar ice in glaciers today, so feedback on land ice is not likely to play a major role in climate change. But sea ice coverage is significant, and uptake of heat by the underlying ocean could have effects on both temperature and rainfall. Sea ice will be discussed in detail later. +
Feedbacks will be discussed in much greater detail in CO2 and related sections, later in the course.

47. FEEDBACKS INVOLVING ABSORPTION OF IR (HEAT)
Examine some of the most important feedbacks in the Earth’s atmosphere.
water vapor feedback.
Temperature increases → atmosphere H2O increases (Clapeyron equation)
→ atmospheric absorption increases (n) → Temperature increases
This is the strongest feedback mechanism in the atmosphere. It is also the best understood since it is based simply on the measured increase in water vapor pressure increase with temperature (Clapeyron equation).
cloud feedback – terrestrial radiation
→ cloudiness increases (n) → Temperature increases
This is a very strong feedback that is not well understood because it is hard to know whether or how much cloudiness would increase as temperature does—cloudiness depends on upward air motion more than on T or H2O directly. +
Work through this with the students, step by step.Talk thru the ice-albedo feedback first—not in the slides! (Add later) +

48. FEEDBACKS INVOLVING ALBEDO
cloud feedback – solar radiation
Temperature increases → atmosphere H2O increases (Clapeyron equation)
→ cloudiness increases (n) → Albedo increases
→ Temperature decreases
This is also very strong feedback that is not well understood because it is hard to know whether or how much cloudiness would increase as temperature does, and because of the trade-off (competition) between the effects of clouds on absorption of infrared radiation versus reflection of solar radiation. Low-altitude clouds affect albedo more than they affect ir radiation, and conversely for high clouds (discussed below).
vegetation feedback – solar radiation
Temperature increases → deserts expand → Albedo increases
This is a very complex feedback that will take a long time to be realized. Maybe deserts won't expand, or plants will be greener because there is more CO2 ? -
Discuss the concept of the runaway greenhouse effect (Venus) -- have the students work this through stepwise. Give them the endpoint, all Venus's water in the atmosphere. -

49. 3. Smoke from fires 4. Both 1 and 2 are correct.
Longwave radiation as viewed from the satellite sensor "ERBS" on NOAA-9, April, 1985
Low OLR in the tropics is due to: 1. Obscuring the surface by clouds; 2. Cold T at cloud tops
3. Smoke from fires 4. Both 1 and 2 are correct.
what are we seeing … greenhouse effect. IR camera demo (for 2nd lecture !). Clicker questions (can spend time on this:
Low OLR in the tropics is due to: 1. Obscuring the surface by clouds; 2. Cold temperatures at cloud tops 3. Smoke from fires 4. Both 1 and 2 are correct
No Data
Watts m-2

50. Climate forcing due to human—caused changes in concentrations of greenhouse gases, atmospheric aerosols, and clouds, since 1850
(Hansen, 2001).
Water vapor is not listed. Why not ?
Water vapor does not emit infrared radiation
It is assumed that humans have not changed concentrations of water vapor.
A mistake—it should be listed.
Effects of water vapor are already included in cloud effects.

51. FUTURE TEMPERATURE PROJECTIONS FROM CLIMATE MODELS (IPCC, 2001)

52. Road map to EPS 5 Lectures 3 and 4: Atmosphere Heat, Energy, Radiation
Black Bodies, Planck Function, Stefan Boltzmann Law
Effective T, greenhouse effect
Feedback!
Planets radiate on average at the Effective Temperature, to maintain energy balance with sun and space, Absorption of ir in the atmosphere traps energy, radiating back to the surface and causing it to warm up.
Teff = [Fs(1 - A)/(4σ)]¼
= K
Tg = [n + 1]1/4Teff.
Solid bodies emit thermal radiation at rates that depend on temperature. Hot bodies (sun) emit more radiation at shorter wavelengths than cold bodies (earth).
Emission rate=σT4
Start the oven demo

53. Atmospheric aerosols: Global cooling?
Aerosols are suspended particles in the air which are small enough to resist gravitational sedimentation (i.e. they remain afloat despite the force of gravity acting on them). Aerosols can be solid, liquid, or a combination of both. They typically range in size from 0.1 to 1.0 micrometers. The main sources of aerosols are dust from the surface, sea spray (liquid droplets and solid sea-salt particles), volcanoes, forest fires, and anthropogenic combustion.
Direct effect: aerosols scatter sunlight, increasing albedo, cooling the atmosphere.
Black carbon effect: if aerosols have black carbon (soot…) inside, they can be heated by sunlight, warming the atmosphere.
Indirect effect: aerosols affect the formation of cloud droplets. Increased aerosols may lead to smaller droplets, more cloudiness, and higher albedo, cooling the earth by lowering Teff.
Cover : direct (albedo); new—black carbon; really difficult—effects on clouds; demo on scattering? Pinatubo picture? wrap up.

54. Aerosol Optical Depth after the eruption of Mt. Pinatubo
(SAGE-II Satellite data)

55. Temperature Change (oC) Global Temperature Climate Model
Mt. Pinatubo eruption
Temperature Change (oC)
Global Temperature
Climate Model
Introduce Mt. Pintubo; discuss the spread of the aerosols in the stratosphere, globally, and the sunsets etc. examine the response and compare to the recent global climate changes.
discuss what this tells us about climate sensitivity—and what it does not tell us (feedbacks ineffective; relationship to seasonal
Effect of a major volcanic eruption on climate ( after Hansen et al., 1993). Note: many feedbacks have not come into play.

56.
Volcanic eruptions can inject millions of tonnes of dust and gaseous sulfur dioxide into the stratosphere. The finer dust particles remain aloft for years and spread around the world while the sulphur dioxide evolves to an aerosol of sulfur acids that add to the particulates. The dust and aerosol produce vivid sunset and twilight effects like the intense yellow-red horizon and purple-pink glows of the photograph. The purple glow is probably a combination of red-orange light transmitted through the lower atmosphere and scattered blue light from still sunlit stratospheric dust.

57. AEROSOL OBSERVATIONS FROM SPACE
Biomass fire haze in central America (4/30/03)
                                                                                                                         
Fire locations
in red
Modis.gsfc.nasa.gov

58. BLACK CARBON EMISSIONS
DIESEL
DOMESTIC
COAL BURNING
BIOMASS
BURNING
“…Kyoto also failed to address two major pollutants that have an impact on warming:  black soot and tropospheric ozone.  Both are proven health hazards.  Reducing both would not only address climate change, but also dramatically improve people's health.” (George W. Bush, June Rose Garden speech)

59. moderately polluted day
EPA REGIONAL HAZE RULE: FEDERAL CLASS I AREAS TO RETURN TO “NATURAL” VISIBILITY LEVELS BY 2064
clean day
moderately polluted day
Acadia National Park

60. Photo: E. Kort
Latitude 80 N; Date: