Transcript The Greenhouse

the
greenhouse
effect
Heat from the sun shines
onto the Earth.
It passes through a
blanket of gases in
our atmosphere.
Some of the heat
energy is reflected
back into space.
Some of the heat energy
is absorbed by the
blanket of gases.
The ‘greenhouse’ gases are
essential to life on Earth. Without
them heat energy would escape
back into space.
Earth would be a
very chilly place
with an average
temperature of
-18°C !
The greenhouse gases help to keep
the temperature of the earth in
balance. This process is called the
GREENHOUSE EFFECT.
The gases work a bit
like glass in a
greenhouse to trap in
warmth.
But the earth is
getting warmer and
warmer.
WHY?
Human activities are creating
more greenhouse gases
including carbon dioxide, CO2.
As we burn more
fossil fuels, for
example, the
blanket of
greenhouse gases
becomes thicker.
More greenhouse gases in the
atmosphere mean that more
heat energy is absorbed.
We call this increase
in the temperature
of the earth
‘global warming’.
R. A. Rohde (www.globalwarmingart.com/wiki/Carbon_Dioxide_Gallery)
What do you deduce from this graph?
“Human activities over the last 100 years, particularly
the burning of fossil fuels, have caused a rapid increase
in carbon dioxide and other greenhouse gases in the
atmosphere. Before the industrial age, these gases had
remained at near stable concentrations for thousands
of years.....
The rapid warming observed since the 1970s has
occurred in a period when the increase in greenhouse
gases has dominated over all other factors. ”
Intergovernmental Panel on Climate Change,
IPCC Fourth Assessment Report: Climate Change, 2007
“Models and observations show warming in the lower
part of the atmosphere (the troposphere) and cooling
higher up in the stratosphere....
If an increase in solar output had been responsible for
the recent climate warming, both the troposphere and
the stratosphere would have warmed...
Such considerations increase confidence that human
rather than natural factors were the dominant cause of
the global warming observed over the last 50 years.”
Intergovernmental Panel on Climate Change,
IPCC Fourth Assessment Report: Climate Change, 2007
Eleven
of theways
last twelve
years
have
been
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Credit
Adapted from a resource produced by CAFOD
Last updated Jan 2012