Global Warming - Environmental Science - Lecture Slides, Slides of Environmental Science

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Global Warming

th 20

Century Climate Changes

• Global Warming– Average Global Temp. = 24 h, all seasons, all locations
  • Increased 0.

o^ C (1.

o^ F) from 1900—

• Not uniform: some places cooler (S. E. United States)• Largest increase is in the daily low temperature• Not a continuous change over time (largest change last 25 yr)
  • Other Global Weather Changes– Increased Average Precipitation (not uniform)– Shorter winters in N. Hemisphere (blooming/leaf loss)– Shrinking glaciers and polar ice caps– Dieing coral, rising sea level, more extreme weather

• Global Temperature Changes 1901--
• Global Precipitation Changes 1901--

Spectrum of Sunlight (dotted) and Earth’s Emitted light

The Greenhouse Effect

Greenhouse Gases (G.G.)

• Definition = atmospheric gas that efficiently absorbsIR light emitted by Earth– N

, O 2 2

, Ar = main atmospheric gases = not G. G.

• Water Vapor (H

O) is the most important G.G. 2

• Naturally present from evaporation• Concentration is variable depending on season, geography• Absorbs around 7

m and above 18

m

• Carbon Dioxide (CO

) next most important G.G. 2

• Most from natural sources: decay of plant matter• About one-third comes from man’s combustion of fossil fuels• Absorbs at 4

m and 15

m strongly

The IR absorption spectrum of CO

2

The atmospheric IR absorption spectrum

Carbon Dioxide Concentrations

• Analysis: how do we know what the CO

level is? 2

• now = clean air sample– past = bubbles trapped in glaciers• Results– Pre-Industrial Revolution (before 1750) = 280 ppm CO

2

• 2001: 371 ppm CO

2

• 1.6 ppm per year increase– Seasonal Concentrations• Low in summer as plants grow and use up CO

2

• High in winter as plants die and decay releasing CO

2

docsity.com

Anthropomorphic CO

Sources 2

• Fossil Fuel Combustion—major source– Coal, oil, natural gas, gasoline produce CO

when burned 2

• Propane: C

H 3 8

+ 5 O

----> 3 CO 2

+ 4 H 2

O 2

• Has slowed down recently due to collapse of SovietBlock economies• Quicklime Production—minor source (few %)– Used in cement production– CaCO

• Heat ----> CaO (quicklime) + CO 3

2

• Burning Vegetation: forests, farmland (25% of CO

) 2 docsity.com

World CO

Emissions from Fossil Fuel 1950-1999 2

Annual net movement of CO

in the Atmosphere 2

Methane and Global Warming

• Concentration doubled since 1750 (most since 1900)• CH

21 times worse than CO 4

for IR ----> Heat 2

– CO

concentration is 80 times that of CH 2

in air 4

– CH

not as important overall as CO 4

2

• Sink = oxidation to CO

2

– CH

+ 2 O 4

----> CO 2

+ 2 H 2

O 2

• Takes about 10 years for this to happen on average• Methane sources– Anaerobic Respiration: 2 CH

O ----> CH 2

+ CO 4

2

• Swamps, marshes (swamp gas, marsh gas)– Ruminant animal digestion (sheep, cows)– Landfill decomposition, pipelines, coal mines, oil wells