The Causes of these Changes in Climate page 20

1. Natural fluctuations We know that CO 2 does naturally vary  a lot

2. Anthropogenic cause (man-made) Most of the observed changes have happened in the past 250 years. So what happened about 250 years ago?

watermill windmill As long as we needed only a small source of power, water, wind or horses were enough

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

We switched from burning a small amount of wood. To burning a large amount of coal.

To power the factories and the mills of the Industrial Revolution

initially coal was main energy source and remains a big source but now oil and natural gas are also big

So is the burning of fossil fuels (coal & oil) causing changes in global climate? If so, how?

This is a natural process in which atmospheric gases trap radiated heat

Remember, without this Earth would have Moon-like temperatures So what’s the problem? The Greenhouse Effect

If one blanket keeps you warm at night, what would be the effect of two blankets? You’d be too warm!

What gas is the main contributor to the Greenhouse Effect? CO 2  the most famous greenhouse gas?No! CH 4 (methane)  another gas in the news a lot?No! N 2 O (nitrous oxide)  a gas in the news a bit?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, what’s the big deal?

Human activity is increasing the amount of the other greenhouse gases in the atmosphere

1. Deforestation means less photosynthesis to soak up CO 2. as the forests are burned N 2 O is released

releases CO 2 and N 2 O 2. Burning of fossil fuels

However neither releases a lot of CH 4 (methane) So where does the CH 4 come from? Ruminants such as cows and sheep breakdown cellulose this produces waste methane 3. Methane from cows with the help of bacteria in their rumen

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?

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.

4. Other chemicals a. fluorocarbons No longer used in aerosol cans where CO 2 has replaced them Now used mostly as coolants in air conditioners And as cleaners of circuit boards for computers

b. sulphur hexfluoride [SF 6 ] production of magnesium and magnesium alloys the cleaning of aluminum

a. transportation fuels b. waste disposal/processing c. power stations d. industrial processes e. residential/commercial use f. agricultural g. obtaining/processing fossil fuel What human activities actually are causing the most problems? Rank these sources of Greenhouse Gases (in pencil)

Now let’s get the actual values.

Not all greenhouse gases are equal: carbon dioxide CO 2  1 GWP methane CH 4  24 GWP nitrous oxide N 2 O  300 GWP fluorocarbons XFC  2000 GWP sulphur hexafluoride SF 6  GWP GWP is global warming potential per molecule a big GWP is bad! Water (H 2 O)  0.28 GWP

So if CO 2 has such a low GWP why are we so worried about that one gas? Even though CO 2 has a low GWP it is still the major greenhouse gas after water vapour

Carbon dioxide accounts for 0.035% of the 1%. The “other gases” (including the greenhouse gases) make up the 1%. The percentage of carbon dioxide (and others) are increasing. The percentage of oxygen would decrease.

What are the effects of all these excess Greenhouse Gases? What can we do about it all?