2. The Greenhouse Effect
 Earth's atmosphere does the same thing as the
greenhouse. Gases in the atmosphere such as
carbon dioxide do what the roof of a greenhouse
does.
 During the day, the Sun shines through the
atmosphere. Earth's surface warms up in the
sunlight.
 At night, Earth's surface cools, releasing the
heat back into the air. But some of the heat is
trapped by the greenhouse gases in the
atmosphere. That's what keeps our Earth a warm
and cosy 59 degrees Fahrenheit, on average.

3. Greenhouse Effect

4. Carbon Dioxide
 Plants take in CO2. They keep the carbon and give
away the oxygen. Animals breathe in the oxygen
and breathe out carbon dioxide.
 Plants and animals depend on each other. It works
out well. For hundreds of millions of years, plants
and animals have lived and died. Their remains
have gotten buried deep beneath Earth's surface.
 So what happens to all this dead plant and animal
stuff? It turns into what we call fossil fuels: oil,
coal, and natural gas. This is the stuff we now use
to energize our world. We burn these carbon-rich
materials in cars, trucks, planes, trains, power
plants, heaters, speed boats, barbecues etc.

5.  Here's the big, important thing about CO2:
It's a greenhouse gas. That means CO2 in the
atmosphere works to trap heat close to
Earth. It helps Earth to hold on to some of
the energy it gets from the Sun so the
energy doesn't all leak back out into space.
 If it weren't for this greenhouse effect,
Earth's oceans would be frozen solid. Earth
would not be the beautiful blue and green
planet of life that it is.

6. Burning Fossil Fuels
 Over the last century the burning of fossil
fuels like coal and oil has increased the
concentration of atmospheric carbon dioxide
(CO2).
 This happens because the coal or oil burning
process combines carbon with oxygen in the air
to make CO2. To a lesser extent, the clearing
of land for agriculture, industry, and other
human activities have increased concentrations
of greenhouse gases.

7. Human Activities
 The industrial activities that our modern
civilization depends upon have raised
atmospheric carbon dioxide levels. Human-
produced greenhouse gases such as carbon
dioxide, methane and nitrous oxide have caused
much of the observed increase in Earth's
temperatures over the past 50 years.
 It is said the rate of increase in global
warming due to these gases is very likely to be
unprecedented within the past 10,000 years or
more.