The Causes of these Changes in Climate

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The Causes of these Changes in Climate page 20
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1. Natural fluctuations
We know that CO2 does naturally vary ? a lot
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2. Anthropogenic cause (man-made)
Most of the observed changes have happened in the
past 250 years.
So what happened about 250 years ago?
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As long as we needed only a small source of power,
water, wind or horses were enough
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To operate a large mill or factory, you need the
power of steam.
And you make steam by boiling water
We used to burn wood,
but burning wood is not very efficient
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We switched from burning a small amount of wood.
To burning a large amount of coal.
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To power the factories and the mills of the
Industrial Revolution
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but now oil and natural gas are also big
initially coal was main energy source and remains
a big source
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So is the burning of fossil fuels (coal oil)
causing changes in global climate?
If so, how?
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This is a natural process in which atmospheric
gases trap radiated heat
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The Greenhouse Effect
Remember, without this Earth would have Moon-like
temperatures
So whats the problem?
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If one blanket keeps you warm at night, what
would be the effect of two blankets?
Youd be too warm!
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What gas is the main contributor to the
Greenhouse Effect?
CO2 ? the most famous greenhouse gas?
No!
CH4 (methane) ? another gas in the news a lot?
No!
N2O (nitrous oxide) ? a gas in the news a bit?
No!
No!
Some mysterious little known new gas?
Water vapor accounts for about 95 of Greenhouse
Effect
So if it is a natural phenomena, mostly caused by
water vapour, whats the big deal?
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Human activity is increasing the amount of the
other greenhouse gases in the atmosphere
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1. Deforestation
means less photosynthesis to soak up CO2.
as the forests are burned N2O is released
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2. Burning of fossil fuels
releases CO2 and N2O
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However neither releases a lot of CH4 (methane)
So where does the CH4 come from?
3. Methane from cows
Ruminants such as cows and sheep breakdown
cellulose
with the help of bacteria in their rumen
this produces waste methane
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But are there really more cows in North America
than we used to have in our buffalo herds?
used to be 60 million buffalo
now about 120 million cows
so has methane production only gone up by 2X?
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No, methane production is way up!
Why?
Buffalo eat grass at a slow and steady rate and
grow slowly.
Cows eat grain, silage and hay at high rates to
grow fast.
So one cow actually makes 2x or 3x as much
methane as one buffalo.
And remember, there are 2X more cows.
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4. Other chemicals
a. fluorocarbons
No longer used in aerosol cans where CO2 has
replaced them
Now used mostly as coolants in air conditioners
And as cleaners of circuit boards for computers
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b. sulphur hexfluoride SF6
production of magnesium and magnesium alloys
the cleaning of aluminum
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What human activities actually are causing the
most problems?
Rank these sources of Greenhouse Gases (in pencil)
a. transportation fuels
b. waste disposal/processing
c. power stations
d. industrial processes
e. residential/commercial use
f. agricultural
g. obtaining/processing fossil fuel
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Now lets get the actual values.
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Not all greenhouse gases are equal
GWP is global warming potential per molecule
a big GWP is bad!
carbon dioxide CO2 ? 1 GWP
methane CH4 ? 24 GWP
nitrous oxide N2O ? 300 GWP
fluorocarbons XFC ? 2000 GWP
sulphur hexafluoride SF6 ? 24000 GWP
Water (H2O) ? 0.28 GWP
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So if CO2 has such a low GWP why are we so
worried about that one gas?
Even though CO2 has a low GWP it is still the
major greenhouse gas after water vapour
http//www.geocraft.com/WVFossils/greenhouse_data.
html
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The other gases (including the greenhouse
gases) make up the 1.
Carbon dioxide accounts for 0.035 of the 1.
The percentage of carbon dioxide (and others) are
increasing.
The percentage of oxygen would decrease.
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What are the effects of all these excess
Greenhouse Gases?
What can we do about it all?
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