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Water vapor Nitrous oxide Aerosols

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Structure of the AtmosphereThermosphereMesosphereOzone MaximumStratosphereTroposphereTemperature

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Слайд 1Water vapor Nitrous oxide Aerosols

Water vapor Nitrous oxide Aerosols

Слайд 2Structure of the Atmosphere
Thermosphere
Mesosphere
Ozone Maximum
Stratosphere
Troposphere
Temperature

Structure of the AtmosphereThermosphereMesosphereOzone MaximumStratosphereTroposphereTemperature

Слайд 3Electromagnetic Spectrum
incoming
outgoing

Electromagnetic Spectrumincomingoutgoing

Слайд 41. Shorter, high
Energy wavelengths
Hit the earths
Surface

2. Incoming energy
Is

converted to heat

1. Shorter, highEnergy wavelengths Hit the earthsSurface2. Incoming energy Is converted to heat

Слайд 53. Longer, infrared
Wavelengths hit
Greenhouse gas
Molecules in the
atmosphere
4. Greenhouse gas
Molecules in

the
Atmosphere emit
Infrared radiation
Back towards earth

3. Longer, infraredWavelengths hitGreenhouse gasMolecules in theatmosphere4. Greenhouse gasMolecules in theAtmosphere emitInfrared radiationBack towards earth

Слайд 678% nitrogen

20.6% oxygen

< 1% argon

0.4% water vapor

0.036% carbon dioxide

traces

gases:
Ne, He, Kr, H, O3
Methane, Nitrous Oxide

78% nitrogen20.6% oxygen< 1% argon0.4% water vapor0.036% carbon dioxide traces gases:Ne, He, Kr, H, O3 Methane, Nitrous

Слайд 7Absorption Spectra of Atmospheric Gases
Anthes, p. 55
CH4
CO2
N2O
H2O
O2 & O3


atmosphere
WAVELENGTH (micrometers)
Infrared
Visible
UV

Absorption Spectra of Atmospheric GasesAnthes, p. 55 CH4CO2N2OH2OO2 & O3 atmosphereWAVELENGTH (micrometers)InfraredVisibleUV

Слайд 8Greenhouse gases absorb infrared radiation and prevent it from escaping

to space.

Carbon dioxide, methane, and nitrous oxide are very good

at capturing energy at wavelengths that other compounds miss




Greenhouse gases absorb infrared radiation and prevent it from escaping to space.Carbon dioxide, methane, and nitrous oxide

Слайд 9Climate Change - Greenhouse Gases
To be an effective greenhouse gas,

a molecule must:
- absorb light in the infrared region (must

have dipole moment for vibration mode)
- 3 modes of vibration for CO2 shown

O=C=O

O=C=O

O=C=O

Symmetric vibration not allowed

Climate Change  - Greenhouse GasesTo be an effective greenhouse gas, a molecule must:	- absorb light in

Слайд 10Earth’s Atmospheric Gases
Non- Greenhouse
Gases
99%
Greenhouse
Gases 1%

Earth’s Atmospheric GasesNon- GreenhouseGases99%GreenhouseGases 1%

Слайд 11Greenhouse Gases
Carbon Dioxide

Water

Methane

Nitrous Oxide

Greenhouse GasesCarbon DioxideWaterMethaneNitrous Oxide

Слайд 12 Greenhouse Gases
Molecules must absorb light in the right regions
-

roughly 7 to 25 μm region
- however, in some regions

(5 to 7 and 13 to 17 μm), essential no light from surface makes it to space due to current gases present
- for this reason, CO2 is less effective as a greenhouse gas (at least for additional CO2)
Greenhouse GasesMolecules must absorb light in the right regions	- roughly 7 to 25 μm region	- however,

Слайд 13 - Greenhouse Gases
Molecules absorbing light in the “IR window”

regions are more effective
Additional CO2 is not as effective as

additional N2O (absorbs at 7.5 to 9 μm) on a forcing per ppm basis

From Girard (old text)

- Greenhouse GasesMolecules absorbing light in the “IR window” regions are more effectiveAdditional CO2 is not

Слайд 14Selected Greenhouse Gases
Carbon Dioxide (CO2)
Source: Fossil fuel burning, deforestation


Anthropogenic increase: 30%
Average atmospheric residence time: 200 years
Methane (CH4)
Source:

Rice cultivation, cattle & sheep ranching, decay from landfills, mining
Anthropogenic increase: 145%
Average atmospheric residence time: 7-10 years
Nitrous oxide (N2O)
Source: Industry and agriculture (fertilizers)
Anthropogenic increase: 15%
Average atmospheric residence time: 140-190 years
Selected Greenhouse GasesCarbon Dioxide (CO2) Source: Fossil fuel burning, deforestation Anthropogenic increase: 30%Average atmospheric residence time: 200

Слайд 15Greenhouse Effect & Global Warming
The “greenhouse effect” & global warming

are not the same thing.
Global warming refers to a

rise in the temperature of the surface of the earth

An increase in the concentration of greenhouse gases leads to an increase in the the magnitude of the greenhouse effect. (Called enhanced greenhouse effect)
This results in global warming
Greenhouse Effect & Global WarmingThe “greenhouse effect” & global warming are not the same thing. Global warming

Слайд 16Global Energy Redistribution

Global Energy Redistribution

Слайд 17Radiation is not evenly distributed over the
Surface of the earth.

The northern latitudes have an energy deficit and the low

latitude/ equator has an excess. But the low latitudes don’t indefinitely get hotter and the northern latitudes don’t get colder.

Why?

The atmosphere and ocean transfer energy from low
latitudes to high

Radiation is not evenly distributed over theSurface of the earth. The northern latitudes have an energy deficit

Слайд 18The climate engine II
Since earth does rotate, air packets do

not follow longitude lines (Coriolis effect)
Speed of rotation highest at

equator
Winds travelling polewards get a bigger and bigger westerly speed (jet streams)
Air becomes unstable
Waves develop in the westerly flow (low pressure systems over Northern Europe)
Mixes warm tropical air with cold polar air
Net transport of heat polewards
The climate engine IISince earth does rotate, air packets do not follow longitude lines (Coriolis effect)Speed of

Слайд 19Atmospheric Pressure Decreases With Height Most of the energy is captured

close to the surface That energy drives climate and weather
50 percent

of mass of the atmosphere is within 6 km of the surface
Atmospheric Pressure Decreases With Height  Most of the energy is captured close to the surface

Слайд 20Cloud effects
Low clouds over ocean
more clouds reflect heat (cooling)
fewer clouds

trap heat (warming)
High clouds
more clouds trap heat (warming)

high: 5-14 km;

low < 2km

Cloud effectsLow clouds over oceanmore clouds reflect heat (cooling)fewer clouds trap heat (warming)High cloudsmore clouds trap heat

Слайд 21Fig. 19-10, p. 513

Fig. 19-10, p. 513

Слайд 22 - Greenhouse Gases
H2O as a greenhouse gas
- the molecule

responsible for the most greenhouse effect heating
- the third most

prevalent molecule in the atmosphere (on average, but composition is variable)
- direct anthropogenic sources are insignificant (at least outside of deserts and the stratosphere)
- also responsible for cooling through increasing albedo (in clouds) so normally kept separate from other greenhouse gases
- water vapor is important indirectly as planet heating increases water vapor (this is covered under feedbacks)
- Greenhouse GasesH2O as a greenhouse gas	- the molecule responsible for the most greenhouse effect heating	-

Слайд 23The sun plays a key role in the earth’s temperature
Researchers

think that atmospheric warming is not due to an increase

in energy output from the sun
Since 1975
Troposphere has warmed
Stratosphere has cooled

Warmer temperatures create more clouds
Thick, low altitude cumulus clouds – decrease surface temperature
Thin, cirrus clouds at high altitudes – increase surface temperature

The sun plays a key role in the earth’s temperatureResearchers think that atmospheric warming is not due

Слайд 24Water vapor is one of the most important elements of

the climate system. A greenhouse gas, like carbon dioxide, it

represents around 80 percent of total greenhouse gas mass in the atmosphere and 90 percent of greenhouse gas volume.
Water vapor and clouds account for 66 to 85 percent of the greenhouse effect, compared to a range of 9 to 26 percent for CO2. So why all the attention on carbon dioxide and its ilk? Is water vapor the real culprit causing global warming?
The answer is that water vapor is indeed responsible for a major portion of Earth’s warming over the past century and for projected future warming. However, water vapor is not the cause of this warming. This is a critical, if subtle, distinction between the role of greenhouse gases as either forcings or feedbacks. In this case, anthropogenic emissions of CO2, methane, and other gases are warming the Earth. This rising average temperature increases evaporation rates and atmospheric water vapor concentrations. Those, in turn, result in additional warming.
Water vapor is one of the most important elements of the climate system. A greenhouse gas, like

Слайд 25Nitrogen (N) is an essential component of DNA, RNA, and

proteins, the building blocks of life.

All organisms require nitrogen

to live and grow.

The majority (78%) of the Earth’s atmosphere is N2.

Nitrogen

Nitrogen (N) is an essential component of DNA, RNA, and proteins, the building blocks of life. All

Слайд 26Nitrogen’s triple bond
Although the majority of the air we breathe

is N2, most of the nitrogen in the atmosphere is

unavailable for use by organisms.
This is because the strong triple bond between the N atoms in N2 molecules makes it relatively inert (like a noble gas).
Nitrogen’s triple bondAlthough the majority of the air we breathe is N2, most of the nitrogen in

Слайд 29Forms of Nitrogen
Urea  CO(NH2)2
Ammonia  NH3 (gaseous)
Ammonium  NH4
Nitrate

 NO3
Nitrite  NO2
Atmospheric Dinitrogen N2
Organic N

Forms of NitrogenUrea  CO(NH2)2Ammonia  NH3 (gaseous)Ammonium  NH4Nitrate  NO3Nitrite  NO2Atmospheric Dinitrogen N2Organic N

Слайд 30How can we use N2?
In order for plants and animals

to be able to use nitrogen, N2 gas must first

be converted to more a chemically available form such as ammonium (NH4+) or nitrate (NO3-).

WE CAN’T!

But BACTERIA & … can…

How can we use N2?In order for plants and animals to be able to use nitrogen, N2

Слайд 31Nitrogen Fixation (N2 --> NH3 or NH4+)

ENVIRONMENTAL
High-energy natural events

which break the bond N2
Examples: lightning forest fires hot lava flows

Nitrogen Fixation (N2 --> NH3 or NH4+)ENVIRONMENTAL  High-energy natural events which break the bond N2

Слайд 32Nitrogen Fixation
R-NH2
NH4
NO2
NO3
NO2
NO
N2O
N2

Nitrogen FixationR-NH2NH4NO2NO3NO2NON2ON2

Слайд 33Nitrogen Fixation N2 --> NH3 or NH4+
How?
HUMAN IMPACT
Burning fossil

fuels,
using synthetic nitrogen fertilizers,
and cultivation of legumes
all

fix nitrogen.
Nitrogen Fixation N2 --> NH3 or NH4+How? HUMAN IMPACT Burning fossil fuels, using synthetic nitrogen fertilizers, and

Слайд 34Ammonification or Mineralization
R-NH2
NH4
NO2
NO3
NO2
NO
N2O
N2

Ammonification or MineralizationR-NH2NH4NO2NO3NO2NON2ON2

Слайд 35Nitrogen Mineralization also called Ammonification Organic N --> NH4+

Decay of dead things,

manure, etc.
Done by decomposers (bacteria, fungi, etc.)
During this

process, a significant amount of the nitrogen contained within the dead organism is converted to ammonium (NH4+).
Nitrogen Mineralization also called Ammonification Organic N --> NH4+Decay of dead things, manure, etc.  Done by

Слайд 36Nitrification
R-NH2
NH4
NO2
NO3
NO2
NO
N2O
N2

NitrificationR-NH2NH4NO2NO3NO2NON2ON2

Слайд 37Nitrification NH3 or NH4+ --> NO2- --> NO3-
(Nitrifying) Bacteria

add oxygen to nitrogen in two steps:
STEP 1: Bacteria take

in NH3 or NH4+ & make NO2- = nitrite

Step 2: Bacteria take in NO2- & make NO3- = nitrate

Nitrification  NH3 or NH4+ --> NO2- --> NO3- (Nitrifying) Bacteria add oxygen to nitrogen in two

Слайд 38Denitrification
R-NH2
NH4
NO2
NO3
NO2
NO
N2O
N2

DenitrificationR-NH2NH4NO2NO3NO2NON2ON2

Слайд 39Denitrification NO3- --> N2
(Denitrifying) Bacteria do it.
Denitrification removes nitrogen from ecosystems,

and converts it back to atmospheric N2.

Denitrification NO3- --> N2(Denitrifying) Bacteria do it.Denitrification removes nitrogen from ecosystems, and converts it back to atmospheric

Слайд 40Denitrification
Removes a limiting nutrient from the environment
4NO3- + C6H12O6 2N2

+ 6 H20
Inhibited by O2
Not inhibited by ammonia
Microbial reaction
Nitrate is

the terminal electron acceptor
DenitrificationRemoves a limiting nutrient from the environment4NO3- + C6H12O6 2N2 + 6 H20Inhibited by O2Not inhibited by

Слайд 42Nitrous oxide N2O
Nitrous oxide, commonly known as laughing gas, nitrous, nitro, or NOS is a chemical

compound with the formula N2O.
At room temperature, it is a colorless, odorless non-flammable gas,

with a slightly sweet taste.
It is used in surgeryand dentistry for its anaesthetic and analgesic effects.
It is known as "laughing gas" due to the euphoric effects of inhaling it, a property that has led to its recreational use as a dissociative anaesthetic.
It is also used as an oxidizer in rocket propellants, and in motor racing to increase the power output of engines.
At elevated temperatures, nitrous oxide is a powerful oxidizer similar to molecular oxygen.

Nitrous oxide gives rise to nitric oxide (NO) on reaction with oxygen atoms, and this NO in turn reacts with ozone.
As a result, it is the main naturally occurring regulator of stratospheric ozone.


Nitrous oxide N2ONitrous oxide, commonly known as laughing gas, nitrous, nitro, or NOS is a chemical compound with the formula N2O. At room temperature, it is

Слайд 43N2O/O2 sedation
It is necessary to use oxygen with nitrous oxide

so that the blood remains appropriately oxygenated.
A mixture of 20%

nitrous oxide and 80% oxygen has the same analgesic equipotence as 15 mg of morphine.
N2O/O2 sedationIt is necessary to use oxygen with nitrous oxide so that the blood remains appropriately oxygenated.A

Слайд 44Nitrous oxide can be used as an oxidizer in a rocket motor
In vehicle racing, nitrous

oxide (often referred to as just "nitrous") allows the engine

to burn more fuel by providing more oxygen than air alone, resulting in a more powerful combustion. The gas itself is not flammable at a low pressure/temperature, but it delivers more oxygen than atmospheric air by breaking down at elevated temperatures. Therefore, it is often mixed with another fuel that is easier to deflagrate. 
Nitrous oxide can be used as an oxidizer in a rocket motorIn vehicle racing, nitrous oxide (often referred to as just

Слайд 45The gas is approved for use as a food additive (also known

as E942), specifically as an aerosol spray propellant. Its most common

uses in this context are in aerosol whipped cream canisters, cooking sprays, and as an inert gas used to displace oxygen, to inhibit bacterial growth, when filling packages of potato chips and other similar snack foods.
The gas is approved for use as a food additive (also known as E942), specifically as an aerosol spray propellant.

Слайд 46Of the entire anthropogenic N2O emission (5.7 teragrams N2O-N per year),
agricultural soils provide

3.5 teragrams N2O–N per year.
 Nitrous oxide is produced naturally in the

soil during the microbial processes of nitrification, denitrification, nitrifier denitrification and others.

The production of adipic acid is the largest source to nitrous oxide. It specifically arises from the degradation of the nitrolic acid intermediate derived from nitration of cyclohexanone.

Of the entire anthropogenic N2O emission (5.7 teragrams N2O-N per year), agricultural soils provide 3.5 teragrams N2O–N per year. Nitrous oxide is produced

Слайд 47Cumulative effect
Recent experiments show that interaction between water vapor, N2O

and cosmic radiation increases cloud production.

Cumulative effectRecent experiments show that interaction between water vapor, N2O and cosmic radiation increases cloud production.

Слайд 48 - Other Effects on Climate
Tropospheric Ozone
Anthropogenic emissions have lead

to increase
Increases are heterogeneous, plus hard to determine pre-industrial concentrations
Stratospheric

Ozone
Loss in Stratosphere leads to cooling (more loss of energy out to space)
However, loss of stratospheric ozone also leads to greater UV absorption (and heating) in troposphere
As ozone loss is reversed, some heating may occur


- Other Effects on ClimateTropospheric OzoneAnthropogenic emissions have lead to increaseIncreases are heterogeneous, plus hard to

Слайд 49 - Other Effects on Climate
Aerosol Effects – Light Scattering

Aerosol
As was discussed previously in visibility, aerosol particles of diameter

0.2 to 1 mm is very efficient in scattering light
A significant fraction is scattered in the backwards direction, so this effectively increases planetary albedo
Increase in albedo leads to cooling

Notice how smoke from Star fire is whiter vs. forest background

- Other Effects on ClimateAerosol Effects – Light Scattering AerosolAs was discussed previously in visibility, aerosol

Слайд 50 - Other Effects on Climate
Aerosol Effects – Light Absorption
Most

aerosol constituents do not absorb significantly in the visible region

(where light is most prevalent)
A big exception is soot (elemental carbon emitted in inefficient combustion)
Soot clouds lead to atmospheric warming (even if cooling the surface over short-term)

Notice how smoke from Kuwait oil fires is black vs. desert background

http://www.lpi.usra.edu/publications/slidesets/humanimprints/slide_16.html

- Other Effects on ClimateAerosol Effects – Light AbsorptionMost aerosol constituents do not absorb significantly in

Слайд 51 - Other Effects on Climate
Indirect Effect of Aerosols
One type

is through modification of cloud reflectivity
Clean Case:
fewer but larger droplets
Polluted

Case:
more but smaller droplets
- Other Effects on ClimateIndirect Effect of AerosolsOne type is through modification of cloud reflectivityClean Case:fewer

Слайд 52Climate Change - Other Effects on Climate
Indirect Effect of Aerosols
Larger

droplets reflect light more poorly per g of cloud water
Polluted

clouds look whiter from space

Source: http//www-das.uwyo.edu/~geerts/cwx/notes/chap08/contrail.html

Ship tracks are indicative of localized pollution

Most apparent where: clouds are normally clean and with thin clouds (thick clouds have high albedos regardless)

Climate Change  - Other Effects on ClimateIndirect Effect of AerosolsLarger droplets reflect light more poorly per

Слайд 53Aerosol and soot pollutants
Can enhance or counteract projected global warming
Sulfate

particles reflect sunlight
Soot particles absorb sunlight


Outdoor Air Pollution Can Temporarily

Slow Atmospheric Warming
Aerosol and soot pollutantsCan enhance or counteract projected global warmingSulfate particles reflect sunlightSoot particles absorb sunlightOutdoor Air

Слайд 55Feedback Effect
The climate system is very complicated. A change in

one component of the system may cause changes in other

components. Sometimes the changes in other components enhance the initial change, then we say that these changes have positive feedback to the system. If the changes result in the reduction of the original change, then they have negative feedback.

Both positive and negative feedback processes may exist in the climate system. In studying the global climatic change, we cannot make conclusions based on intuition, but have to take all such possible complicated effects into account. A good climate model would have treated all of them realistically.
Feedback EffectThe climate system is very complicated. A change in one component of the system may cause

Слайд 56An example of positive feedback
When the climate becomes warmer (either

due to the increase of CO2 in the atmosphere or

other unknown mechanisms), the ocean may also become warmer. A warmer ocean has lower solubility of CO2 and hence will release more CO2 into the atmosphere. This may cause the climate to become even warmer than before. Thus the dependence of solubility of CO2 on temperature has a positive feedback on the climate system.
An example of positive feedbackWhen the climate becomes warmer (either due to the increase of CO2 in

Слайд 57An example of negative feedback
Consider a clear region over the

ocean. Since there is no cloud, the sun shines on

the ocean surface, causing it to warm up. This makes this part of the ocean warmer than other parts and the air over it tends to rise (causing convection). Rising air expands and cools, causing clouds to form. The formation of clouds will block out the sun and the solar heating of the ocean surface will cease. The surface will start to cool down. Thus the cloud formation due to surface heating and convection is a negative feedback to the climate system.
An example of negative feedbackConsider a clear region over the ocean. Since there is no cloud, the

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