FACTS ABOUT CLIMATE CHANGE
1. What is climate change?
Climate change is a long-term shift in
the climate of a s
pecific location, region or planet.
The shift is measured by changes in features
associated with average weather, such as
temperature, wind patterns and pr
ecipitation. What most peo
ple don’t know is that a
change in the variability
of climate is also considered
climate change, even if average
weather conditions remain the same.
Climate change occurs when the climate of a s
pecific area or planet is altered between
two different periods of time. This usually
occurs when something changes the total
amount of the sun's energy absorbed by the
earth's atmosphere and
surface. It also
happens when something changes the amount of
heat energy from the earth's surface
and atmosphere that escapes to space
over an extended period of time.
Such changes can involve both changes in
average weather conditions and changes in
how much the weather varies
around these averages. T
he changes can be caused by
natural processes like volcanic eruptions, variati
ons in the sun's intensity, or very slow
changes in ocean circulation or land surfaces
which occur on time scales of decades,
centuries or longer.
But... humans also cause climates to
change by releasing greenhouse gases and
aerosols into the atmosphere, by changi
ng land surfaces, and by depleting the
stratospheric ozone layer. Both natural
and human factors that can cause climate
change are called ‘climate forcings', since they
push, or ‘force' the climate to shift to new
2. Why “global warmi
ng” is the wrong term
Climate change refers to general shifts in clim
ate, including temperat
winds, and other factors. Global wa
rming (as well as global cooli
ng) refers specifically to
any change in the global average surface
temperature. Global warming is often
misunderstood to imply that the
world will warm uniformly. In fact, an increase in average
global temperature will also cause the circulat
ion of the atmosphere to change, resulting
in some areas of the world warming more
, others less. Some areas can even cool.
Unfortunately, although it significantly mi
srepresents what really happens, the term
‘global warming' is still often used by
media and others to describe climate change.
Climate Change Fact Sheet – page 2
3. What is the Greenhouse Effect?
A natural system known as the "greenhouse effe
ct" regulates temperature on Earth.
Just as glass in a greenhouse keeps heat in, our atmosphere traps the sun’s heat near earth’s surface, primarily through heat-trapping
properties of certain “greenhouse gases”.
Earth is heated by sunlight. Most of the s
un's energy passes through the atmosphere, to
warm the earth's surface, oceans and atmos
phere. However, in order to keep the
atmosphere's energy budget in balance, the wa
rmed earth also emits heat energy back
to space as infrared radiation.
As this energy radiates upward, most
is absorbed by clouds and molecules of
greenhouse gases in the lower atmosphere. Thes
e re-radiate the energy in all directions,
some back towards the surface and some upw
ard, where other mole
cules higher up can
absorb the energy again. This process of
absorption and re-emission is repeated until,
finally, the energy does escape from
the atmosphere to space.
However, because much of the energy has been recycled downward, surface temperatures become much warmer then if
the greenhouse gases were absent from the
atmosphere. This natural process is known as the greenhouse effect. Without greenhouse gases, Earth's average te
mperature would be
-19°C instead of
or 33°C colder
Over the past 10,000 years,
the amount of greenhouse gases
in our atmosphere has
been relatively stable. Then a few centuries
ago, their concentrations began to increase
due to the increasing...
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