Greenhouse GasesGreenhouse Gases

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Greenhouse GasesGreenhouse Gases

The principal greenhouse gases that trap The principal greenhouse gases that trap infrared radiation in the atmosphere are:infrared radiation in the atmosphere are:

• Water vapourWater vapour

• Carbon dioxideCarbon dioxide

• MethaneMethane

• Chlorofluorocarbons (CFCs)Chlorofluorocarbons (CFCs)

• OzoneOzone

• Nitrous oxideNitrous oxide

SourcesSources

These can be These can be produced by produced by natural processes natural processes (e.g. carbon (e.g. carbon dioxide is a dioxide is a product of product of respiration) but are respiration) but are increasingly increasingly produced by produced by human activities.human activities.

SourcesSources

For this reason we For this reason we differentiate the differentiate the natural natural greenhouse effect greenhouse effect from the from the anthropogenic anthropogenic greenhouse greenhouse effecteffect (the excess (the excess produced by produced by human activities).human activities).

Fossil FuelsFossil Fuels

The primary human activities that The primary human activities that produce greenhouse gases are fossil produce greenhouse gases are fossil fuel extraction and use.fuel extraction and use.

Trucks carrying oil-laden sand in Fort McMurray, Alberta

Fossil FuelsFossil Fuels

Fossil fuels (oil, coal, and natural gas) Fossil fuels (oil, coal, and natural gas) formed underground from the formed underground from the remains of once-living organisms.remains of once-living organisms.

Fossil FuelsFossil Fuels

As they are extracted from the ground, As they are extracted from the ground, they release methane and carbon they release methane and carbon dioxide, and as they are burned to dioxide, and as they are burned to produce energy, they release large produce energy, they release large amount of nitrous oxide and carbon amount of nitrous oxide and carbon dioxide.dioxide.

The Nanticoke coal-burning plant on Lake Erie.

Fossil FuelsFossil Fuels

A lot of fossil fuel use occurs where A lot of fossil fuel use occurs where you would not expect, such as you would not expect, such as farming; e.g. modern industrial farming; e.g. modern industrial farming uses fertilizer synthesized farming uses fertilizer synthesized from natural gas in a process that from natural gas in a process that itself consumes energy.itself consumes energy.

HistoryHistory

The discovery that these gases The discovery that these gases absorbed infrared radiation absorbed infrared radiation dates to 1861.dates to 1861.

Back in 1896, Nobel Prize winner Back in 1896, Nobel Prize winner Svante Arrhenius calculated Svante Arrhenius calculated that the world temperature that the world temperature would rise by 5-6would rise by 5-6ooC if carbon C if carbon dioxide levels were doubled.dioxide levels were doubled.

Rising ConcentrationsRising Concentrations

And carbon dioxide levels have been And carbon dioxide levels have been rising:rising:

This famous graph is known as the Keeling curve.

The Annual CycleThe Annual Cycle

Carbon dioxide levels decrease during the Carbon dioxide levels decrease during the spring and summer months because that spring and summer months because that is when the Northern Hemisphere (most of is when the Northern Hemisphere (most of the world’s landmass) is experiencing the world’s landmass) is experiencing growth in carbon-dioxide absorbing growth in carbon-dioxide absorbing vegetation.vegetation.

http://www.youtube.com/watch?v=l8tPKj20GFo

SinksSinksForests act as Forests act as carbon sinkscarbon sinks

(mechanisms that remove carbon dioxide from the air).

A significant fraction of the increase in carbon dioxide can be attributed to deforestation.

Looking Back Into the PastLooking Back Into the PastTo show that the increases in greenhouse To show that the increases in greenhouse

gases are unprecedented and significant, gases are unprecedented and significant, we can look back into the past by looking we can look back into the past by looking at layers of ice in Greenland and at layers of ice in Greenland and Antarctica.Antarctica.

Looking Back Into the PastLooking Back Into the Past

http://www.ted.com/talks/lee_hotz_inside_an_antarctic_time_machine.html

More PracticeMore Practice

Read pages 358-361Read pages 358-361

Answer questions on Answer questions on

p. 361 #1 – 7p. 361 #1 – 7