Lecture 15 Lecture 15 Global WarmingGlobal Warming

HRhHRh

View of the home planet, taken in 1972

by the Apollo crew, showing a fully sunlit hemisphere of the Earth

AtmosphereAtmosphere

Thin layer of gases that protects us from harmful UV radiation, solar x-Thin layer of gases that protects us from harmful UV radiation, solar x-rays and cosmic rays from spacerays and cosmic rays from space

Moderates temperatureModerates temperature Major component of hydrologic cycleMajor component of hydrologic cycle Great resource for all living thingsGreat resource for all living things Source of carbon dioxide for photosynthesisSource of carbon dioxide for photosynthesis Source of oxygen for respirationSource of oxygen for respiration Provides nitrogen for N-fixing bacteria and ammonia-manufacturing Provides nitrogen for N-fixing bacteria and ammonia-manufacturing

plants to produce chemically-bound N, essential component of all life plants to produce chemically-bound N, essential component of all life moleculesmolecules

Atmospheric layersAtmospheric layers

The atmosphere consists of several layers and transitional zones of The atmosphere consists of several layers and transitional zones of contrasting temperature due to differential absorption of solar energy, contrasting temperature due to differential absorption of solar energy, each of which has distinct propertieseach of which has distinct properties

Atmospheric layersAtmospheric layers TroposphereTroposphere StratosphereStratosphere MesosphereMesosphere ThermosphereThermosphere ExosphereExosphere

TroposphereTroposphere

It extends up to It extends up to 17 km at the equator17 km at the equator and about and about 9 km at the Earth’s 9 km at the Earth’s pole, varies with latitude and seasonspole, varies with latitude and seasons

Contains Contains roughly 80% of the roughly 80% of the massmass of the atmosphere of the atmosphere Temperature ranges from Temperature ranges from 15 15 00C to –60 C to –60 00CC TemperatureTemperature decreases with altitudedecreases with altitude at the rate of at the rate of 6.5 6.5 00C/kmC/km This promotes vertical mixingThis promotes vertical mixing At the top At the top tropopausetropopause, a transitional layer exists which acts as a , a transitional layer exists which acts as a

protective barrier reducing loss of water to the stratosphereprotective barrier reducing loss of water to the stratosphere

Atmospheric LayersAtmospheric Layers

StratosphereStratosphere Extends to an elevation of 51 Extends to an elevation of 51

kmkm Temperature Temperature increasesincreases with with

altitude from altitude from –60 –60 00C to 0 C to 0 00CC due to due to absorption of UV absorption of UV radiation by ozoneradiation by ozone

AboutAbout 90% 90% of the of the atmosphere’s ozone content is atmosphere’s ozone content is in this layerin this layer

The stratopause, which is the The stratopause, which is the boundary between the boundary between the stratosphere and mesosphere, stratosphere and mesosphere, typically is at 50 to 55 kmtypically is at 50 to 55 km

Mesosphere Mesosphere Extends Extends from the stratopause from the stratopause

at about 50 km to 80–85 kmat about 50 km to 80–85 km Temperature Temperature decreases decreases

steadily in the mesosphere (-steadily in the mesosphere (-85 85 00C) to the lowest in the C) to the lowest in the atmosphere—as low as atmosphere—as low as –100 –100 00CC in the in the mesopause the mesopause the coldest place on Earthcoldest place on Earth

Atmospheric LayersAtmospheric Layers

Thermosphere Thermosphere varies with solar varies with solar activity and ranges from about activity and ranges from about 350–800 km350–800 km

Temperature can rise to 1,500 °C, Temperature can rise to 1,500 °C, though the gas molecules are so though the gas molecules are so far apart that temperaturefar apart that temperature in the in the usual sense is not well definedusual sense is not well defined

Temperature inversion is a result Temperature inversion is a result of the extremely low density of of the extremely low density of moleculesmolecules

An individual molecule (of oxygen, An individual molecule (of oxygen, for example) travels an average of for example) travels an average of 1 kilometer between collisions 1 kilometer between collisions with other moleculeswith other molecules

International Space Station orbits International Space Station orbits in this layer, between 320 and 380 in this layer, between 320 and 380 kmkm

Exosphere Exosphere is the outermost is the outermost layer beyond the atmospherelayer beyond the atmosphere

extendsextends to approximately to approximately 1000 1000 kmkm

Composed of hydrogen, helium Composed of hydrogen, helium and some heavier molecules and some heavier molecules such as nitrogen, oxygen and such as nitrogen, oxygen and carbon dioxidecarbon dioxide

Atoms and molecules are so far Atoms and molecules are so far apart that they can travel apart that they can travel hundreds of kilometers without hundreds of kilometers without colliding with one anothercolliding with one another

Continues to thin until it Continues to thin until it converges with interplanetary converges with interplanetary spacespace

COMPOSITIONCOMPOSITION

COCO220.030.03%%

NN22 78%78%

ArAr 1%1%

OO22 21%21%

HH22OO 0.1%0.1%

CompositionNitrogen, oxygen, and argon comprise 99.9% by volumeCarbon dioxide, methane, nitrogen oxides, sulfur dioxide, ozone, CFCs, although minor in abundance are of particular importance to the chemistry of atmosphereChemical composition of lower atmosphere is relatively homogenous except in areas close to the Earth’s surface that are affected by air pollution

Global Air Circulation PatternGlobal Air Circulation Pattern On a global scale atmospheric On a global scale atmospheric

circulation results primarily from the circulation results primarily from the Earth’s rotationEarth’s rotation and the and the differential differential heating of Earth’s surfaceheating of Earth’s surface and and atmosphereatmosphere

The global circulation of the The global circulation of the atmosphere transfers warm air from atmosphere transfers warm air from low latitudes towards high latitudes, low latitudes towards high latitudes, and cold air from high latitudes and cold air from high latitudes towards low latitudes towards low latitudes

This exchange keeps low latitude This exchange keeps low latitude regions from continually heating up regions from continually heating up and high latitudes from continual and high latitudes from continual cooling.cooling.

The air and wind circulation patterns The air and wind circulation patterns shift massive amounts of energy over shift massive amounts of energy over long distances on Earth.long distances on Earth.

If it weren’t for this effect, the If it weren’t for this effect, the equatorial regions would be equatorial regions would be unbearably hot, and the regions closer unbearably hot, and the regions closer to the poles intolerably cold.to the poles intolerably cold.

Different Climatic ZonesDifferent Climatic Zones

ClimateClimate is commonly defined as the average weather condition over a long is commonly defined as the average weather condition over a long period (standard averaging period is 30 years )period (standard averaging period is 30 years )

WeatherWeather describes maximum and minimum temperature, wind speed and describes maximum and minimum temperature, wind speed and direction, precipitation patterns, cloud type and amount, and solar radiationdirection, precipitation patterns, cloud type and amount, and solar radiation

Two of the most important factors determining an area's climate are air Two of the most important factors determining an area's climate are air temperature and precipitationtemperature and precipitation

The world can be divided into The world can be divided into three major climatic zones three major climatic zones as we know: as we know: thethe tropicstropics which are warm; the which are warm; the cold polarcold polar regionsregions, and the , and the temperate zonestemperate zones which lie between themwhich lie between them

Six zonesSix zones: : Humid equatorial, Dry, Humid temperate, Humid cold, Cold Humid equatorial, Dry, Humid temperate, Humid cold, Cold polar, highland climatepolar, highland climate

But several other category are necessary including But several other category are necessary including Humid continental, Humid continental, Mediterranean, Monsoon, Desert, Tropical wet-dryMediterranean, Monsoon, Desert, Tropical wet-dry

Global WarmingGlobal Warming It is the natural or human induced It is the natural or human induced

increase in the average global increase in the average global temperaturetemperature of the atmosphere of the atmosphere near Earth’s surfacenear Earth’s surface

Actually global warming Actually global warming represents an represents an enhancement of enhancement of the greenhouse effectthe greenhouse effect

In fact, the natural greenhouse In fact, the natural greenhouse effect allows life to exist, but a effect allows life to exist, but a build-up in the gases that build-up in the gases that produce this warmth is produce this warmth is overheating our planet and overheating our planet and causing global warmingcausing global warming

Resulted in an increase in Resulted in an increase in extreme weather events, loss of extreme weather events, loss of polar ice and glaciers, rising sea polar ice and glaciers, rising sea level, and harm to wildlifelevel, and harm to wildlife

Greenhouse EffectGreenhouse Effect

Greenhouse gases trap some Greenhouse gases trap some of the heat energy radiating of the heat energy radiating from earth’s atmospheric from earth’s atmospheric system system

Trapping of Sun’s radiation by Trapping of Sun’s radiation by greenhouse gases is somewhat greenhouse gases is somewhat like glass does in a like glass does in a greenhouse, thus the process greenhouse, thus the process has been called has been called greenhouse greenhouse effecteffect

Without its current greenhouse Without its current greenhouse gases the Earth would be a gases the Earth would be a cold (cold (33 33 00C lower than the C lower than the present average temperature of present average temperature of ± 15 ± 15 00CC) and mostly lifeless ) and mostly lifeless planetplanet

Greenhouse effect Anthropogenic Greenhouse Effect

Major greenhouse gasesMajor greenhouse gases A A greenhouse gasgreenhouse gas is a gas in an atmosphere that absorbs and is a gas in an atmosphere that absorbs and

emits radiation emits radiation This process is the fundamental cause of the greenhouseThis process is the fundamental cause of the greenhouse effecteffect In order, the most abundant primary greenhouse gasesIn order, the most abundant primary greenhouse gases are: are: waterwater vaporvapor,,

carboncarbon dioxidedioxide,, methane methane,, nitrous nitrous oxide, and ozoneoxide, and ozone Other GHGs include sulfurOther GHGs include sulfur hexafluoridehexafluoride,, hydrofluorocarbons and hydrofluorocarbons and

perfluorocarbons, (fluorinated gases)perfluorocarbons, (fluorinated gases) Water vaporWater vapor can also be considered a greenhouse gas since it too can also be considered a greenhouse gas since it too

absorbs and releases radiationabsorbs and releases radiation Its concentration is controlled by the climate itself, water vapor acts as a Its concentration is controlled by the climate itself, water vapor acts as a

fast feedback, reacting to, and amplifying the warming provided by the fast feedback, reacting to, and amplifying the warming provided by the forcing greenhouse gasesforcing greenhouse gases

The first fourThe first four are naturally occurringare naturally occurring although humans have had a although humans have had a profound impact on their concentrations in the atmosphereprofound impact on their concentrations in the atmosphere

Although CFCs are greenhouse gases, their contribution is to ozoneAlthough CFCs are greenhouse gases, their contribution is to ozone depletion rather than to global warmingdepletion rather than to global warming

Ozone depletion has only a minor role in greenhouse warming though the Ozone depletion has only a minor role in greenhouse warming though the two processes often are confused in the mediatwo processes often are confused in the media

GHGs Concentration change1800-2010

Natural sources Anthropogenic 100 yr GWP*

Proportion of total effect apart from water vapor (approx)

CO2 280 - 390 ppm

Emission: 207 Pg; removal 204

Pg; net gain 3Pg, i.e 3 b tons;

One million kg CO2 is released

to air every second

decomposition,

ocean release

{43%},

respiration and

volcanoes

fossil fuel

burning

deforestation

1 60

CH4 0.75 - 1.75 ppm

Annual: about 525 Tg

wetlands,

termites and the

oceans

agriculture, fuel

leakage 23 20

CFCs 0 - 0.7 ppb Refrigerants 1800-

12,000

14

N2O

275 - 310 ppb

soils under

natural

vegetation and

the oceans

agriculture,

combustion 296 6

O3 15? - 20-30 ppb urban pollution

Table: Characteristics of the primary greenhouse gases (Q)

Top-10 annual energy-related CO2 emitters for the year 2009

Country % of global totalannual emissions

Tonnes of GHGper capita

People's Rep. of China 23.6 5.13

United States 17.9 16.9

India 5.5 1.37

Russian Federation 5.3 10.8

Japan 3.8 8.6

Germany 2.6 9.2

Islamic Rep. of Iran 1.8 7.3

Canada 1.8 15.4

Korea 1.8 10.6

United Kingdom 1.6 7.5

In 2009, the annual top ten emitting countries accounted for about two-thirds of the world's annual energy-related CO2 emissions.

In May 1913, the daily mean con of CO2 in the atm of Mauna Loa, Hawaii, surpassed 400 ppm for the first time since measurements began in 1958, It has increased by one third in the last 200 yrs, and half of that in the last 30 years.

End of SlidesEnd of SlidesThank YouThank You