Transcript Greenhouse Gases

Greenhouse Gases
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Greenhouse Gases
The principal greenhouse gases that trap infrared
radiation in the atmosphere are:
• Water vapour
• Carbon dioxide
• Methane
• Chlorofluorocarbons (CFCs)
• Ozone
• Nitrous oxide
Sources
These can be produced
by natural processes
(e.g. carbon dioxide
is a product of
respiration) but are
increasingly
produced by human
activities.
Sources
For this reason we
differentiate the
natural greenhouse
effect from the
anthropogenic
greenhouse effect
(the excess produced
by human activities).
Fossil Fuels
The primary human activities that produce
greenhouse gases are fossil fuel extraction
and use.
Trucks carrying oil-laden
sand in Fort McMurray,
Alberta
Fossil Fuels
Fossil fuels (oil, coal, and natural gas)
formed underground from the remains of
once-living organisms.
Fossil Fuels
As they are extracted from the ground, they
release methane and carbon dioxide, and
as they are burned to produce energy,
they release large amount of nitrous oxide
and carbon dioxide.
The Nanticoke coalburning plant on
Lake Erie.
Fossil Fuels
A lot of fossil fuel use occurs where you
would not expect, such as farming; e.g.
modern industrial farming uses fertilizer
synthesized from natural gas in a process
that itself consumes energy.
History
The discovery that these gases
absorbed infrared radiation dates
to 1861.
Back in 1896, Nobel Prize winner
Svante Arrhenius calculated that
the world temperature would rise
by 5-6oC if carbon dioxide levels
were doubled.
Rising Concentrations
And carbon dioxide levels have been rising:
This famous graph
is known as the
Keeling curve.
The Annual Cycle
Carbon dioxide levels decrease during the spring
and summer months because that is when the
Northern Hemisphere (most of the world’s
landmass) is experiencing growth in carbondioxide absorbing vegetation.
http://www.youtube.com/watch?v=l8tPKj20GFo
Sinks
Forests act as carbon 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 Past
To show that the increases in greenhouse gases
are unprecedented and significant, we can look
back into the past by looking at layers of ice in
Greenland and Antarctica.
Looking Back Into the Past
http://www.ted.com/talks/lee_hotz_inside_an_ant
arctic_time_machine.html
More Practice
Read pages 358-361
Answer questions on
p. 361 #1 – 7