The Atmosphere - global warming L2

2006 自然科学の英語 -ENS-L2

The Atmosphere - global warming L2

English in Natural Science自然科学の英語



Vertical structure • Density decreases with altitude

– gravitational force• Layers of different

composition– Homosphere (90 km)– Heterosphere

Mesosphere

Stratosphere

Troposphere

90 km

48 km

12 km

Heterosphere

Homosphere Ozone layer

Mass

< 1%

14%

85%


Ozone layer• Filter (15-40 km) against UV solar radiation

90% ozone [O3] 2-8 ppm• Destruction by CFC: CFCl3 + hv CFCl3 + Cl O3 + Cl O2 + ClO Effects

1. Increased UV radiation DNA damage

(mutations, cancer) 2. Less absorption

of radiation Air cooling


• Current composition – N2 (78.08%)– O2 (20.95%)– Ar (0.93%)– CO2 (0.035%)– Other (0.005%)

• Ne, He, CH4, Kr, NO2-, H, Xe, O3

• Temperature decreases with altitude– average 1 oC for 100 m surface ~15 oC 1,500 m water condensates– Clouds form between 1500-3000 m

N278%

O221%

otherCO2Ar1%Troposphere


Evolution of atmosphere

95% N2

3.5% CO2

<1% O2

78% N2

21% O2

<1% CO2


Atmosphere is dynamic• Solar powered• Convection

– Hot air UP– Cold air DOWN

• Circulation routes– west east– tropics poles

• Jet streams• Effects:

– Mixing of gasses– Temperature buffer


Coriolis effect• Rotation of the Earth

– Air moves inward in circles cyclons

– Inertial circlesC

Centrifugal force

Tropical cyclon台風 typhoonhurricane


Hydrological cycleEnergy SunWater on Earth• Oceans (97%)

– Salty water• Atmosphere

– Evaporation (H2O vapour)– Condensation (cloud)– Precipitation (rain)

• Land– Snow icecaps water– Runoff rivers

• Dissolves materials• Erosion of land

– Evapotranspiration (plants)

Evapotranspiration


The Blue Planet


Hydrosphere - water distribution

Location Volume (km3) Percentage

Oceans 1,322,000,000 97.2

Icecaps + glaciers 29,200,000 2.15

Water on land 8,630,000 0.635

World total 1,360,000,000 100.0

Ground water 8,400,000 0.62Freshwater lakes 125,000 0.009Saline lakes/seas 104,000 0.008

Soil moisture 67,000 0.005Atmosphere 13,000 0.001

Rivers 1,250 0.0001


Interaction atmosphere - hydrosphere• Solar radiation

– Water evaporation (oceans) condensation (clouds)

– Hot air UP and cold air DOWN• Earth’s rotation

– Air + clouds move in inertial circles (cyclons)• Earth’s topography (e.g. mountains)

– Distort movement of cyclons– Cause precipitation (rain)– Region different weather pattern

CLIMATE


Climate patternsKoeppen System

1st level: latitude zone• Tropical• Subtropical• Temperate• Polar• Mountain/highland

2nd level: precipitation• Regular throughout year• Dry winter• Dry summer

3rd level: temperature• Hot• Mild• Cool• Cold


• Af: Tropical Rainforest• Aw: Tropical Wet & Dry (Savanna)• BSh: Tropical Steppe• BWh: Tropical Desert• BSk & BWk: Midlatitude Steppe &

Desert

• Cs: Mediterranean (dry summer subtropical)• Cfa: Humid Subtropical• CFb: Marine West Coast• Df & Dw: Humid Continental & Subarctic• ET: Tundra• Highland


Climate change: Causes• Weather changes - short term cycles

– Sun spots fluctuations (11 yr period)– Sea-temperature currents (El Niño oscillations)

• Climate changes - long-term oscillations– Solar radiation (insolation)

• Precession of equinoxes (23,000 yr period)• Tilt (1o) of Earth’s rotational axis (41,000 yr period)• Eccentricity cycle (100,000 and 400,000 yr period) Milankovitch cycles

– Carbon dioxide and methane in atmosphere• Biomass amount and distribution


Climate indicators

• 18O ice-sheet thickness sea level

• 13C biomass (productivity)• CO2 atmospheric temperature

carbonate deposition/dissolution• CH4 wetland expansion/reduction

monsoonal precipitation


Weather cycles

SouthernOscillation Index(El Niño)• cold dryness• warm rainfall

Humdbolt Current

Temperature cycles11 x 2 yr period


Orbit eccentricity

Axial tilt

Astronomic variations insolation

Precession

Polaris<-->Vega


Holocene (10,000 yr)• Insolation

– perihelion from July to January– 8% more insolation summer and less in winter NH

• Effects– Global ice-volume decreased (18O from 15,000 to

6,000 yr) – Sea-surface temperature up (8 oC Atlantic winter)– Sea level up (100 m)

• CO2 increased– 200 ppm (15,000 yr) 250 ppm (6,000 yr)



Pleistocene (175,000 yr)

• Insolation– superimposition 23, 41 and 100 year cycles

• Effects– Ice-sheet (18O)– Sea-level– CO2

– methane– Monsoon (SE Asia)



Quaternary (3 million yr)

• Directly related to insolation cycles• Patterns of variation

– Several ice-age periods– Cooling trend in last 700,000 yr – Changes in biomass (productivity)– Irreversible variations due to continental drift

• Mountain uplift regulate the magnitude of monsoonal oscillations

2006 自然科学の英語 -ENS-L2 (Webb and Bartlein, 1992)


Greenhouse gasses• Transparent to incoming solar radiation• Absorb outgoing infrared radiation ( > 0.78 m) emitted

by Earth (surface + atmosphere)

CFC

Radiative forcing W/m2 relativeCO2 1.56 1CH4 0.5 58NO2 0.1 206CFC 0.3 3970 5750

CO2

+36%

CH4

+150%

NO2

+20%


Carbon dioxide (CO2) and temperature

AntarcticaVostok lake (160,000 yr)

What causes CO2 cycles?

(Barnola et al., 1987)


Keeling curve

Current CO2 in atmosphere

• Atmospheric CO2

– Initially (3.5 bya) 100 x– Reduction…

• Biomass• Carbonate deposition

– Now 300 Gt (x109 tons)• Upward trend

• Sources– 98% natural

• Biological• Volcanic eruptions

– 2% human activities

Before 1800 190-290 ppm 1800 280 ppm 2004 380 ppm

Total increase +36%Current rate 1.8 ppm/yr


Human impact on the carbon cycle

Sources of CO2 6-8 Gt/year (1995)– Emissions (83%)

• Fossil fuels (CO2, CH4) 6.5 Gt• Fertilizers (NO2) 0.140 Gt

– Deforestation(17%) 0.4 m Km2/year 36,000 Km2 Amazon


Carbon balance44% 36% 20%


Effects: global warming

• Average air temperature increased

I) 0.7 oC in 30 yr ii) 2003 heat wave in Europe 94 mt harvest lost

(5% world grain)


Effects in theocean… …

start to be felt.

• Sea levels in Gulf of Mexico

• Wild weather– Katrina, Rita– Japan 2004

(11 typhoons)


Global climatic impact of CO2

• Global warming [CO2] UP Temperature UPTemperature– Air: more H2O vapour rainfall increase

pressure wild weather (typhoon)– Water: melting icecaps increase sea levels[CO2]– Air: photosynthesis UP more plant biomass

– Water:dissolved CO3-2 coral and marine plankton

• Ice-age [CO2] DOWN Temperature DOWN– Air: less H2O vapour rainfall decrease

dryness dust UP less radiation (cooling)– Water:icecaps increase decrease sea levels


Alternating warm/cold cycles

Warmperiods

[CO3Ca•Mg]

[CO2]

[CO3-2]

Ice

Temp

Vegetation

dissolve

[HCO3-]

Iceage

Vegetation

[CO3Ca•Mg]

[CO3-2]

Ice

[CO2]

Temp

precipitate

[HCO3-]


References

• Schneider, S. H. 1989. The greenhouse effect: Science and policy. Science 243: 771-81.

• Webb III, T. and Bartlein, P.J. 1992. Global changes during the last 3 million years: Climatic controls and biotic responses. Annu. Rev. Ecol. Syst. 23: 141-173

• Wuebbles, D.J. and Jain, A.K. 2001. Concerns about climate change and the role of fossil fuel use. Fuel Proces. Technol. 71: 99-119

• Feely R.A. et al.2004. Impact of anthropogenic CO2 on the CaCO3 system in the oceans. Science 305: 362-366

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The Atmosphere - global warming L2