WHAT IS THIS? · Sun dogs or mock suns
CLIMATE Carbon dioxide
is a greenhouse gas because
it retains heat within our
atmosphere. When sunlight
hits the Earth, our world emits
thermal energy back into
space in the form of infrared
electromagnetic radiation
with a lower frequency than
the incoming light. Green-
house gases absorb a major
part of the radiation energy in
these lower frequencies, and
the thermal energy is thereby
sent back to Earth. Normally,
there is an equilibrium
between the incoming heat
radiation and the amount
that is emitted again, but as
greenhouse gases absorb
more energy, temperatures
rise. Some greenhouse gases,
such as methane, are even
better at absorbing radiation
energy in the infrared
spectrum than is carbon
dioxide. See also p29.CO 2 IS NOT THE WORST
GREENHOUSE GAS
CO 2 = 1 GWP (Global
Warming Potential)
Methane = 86 GWP
Laughing gas = 268 GWP
Carbon tetrafluoride =
4950 GWPCO 2 makes global temperatures
rise because the gas absorbs
heat which would otherwise
be released back into space.Why does CO 2 heat the Earth?
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OCK3
If the crystals lie more
horizontally, the larger
hexagonal plate-like ice
crystals will refract light on this
plane. If the Sun is on the same
horizontal plane as the viewer,
as at sunset, the result can be
two very bright spots (‘sun dogs’),
one on each side of the Sun.2
If the ice crystals are
haphazardly orientated,
all you will see is a bright
circle around the Sun – a halo.
The most common halo has
a diameter of 22 degrees.1
‘Sun dogs’ occur when
sunlight passes through
thin clouds of hexagonal
ice crystals deep inside Earth's
atmosphere. The crystals work as
prisms that refract the light.Bright dots flanking
the Sun are known
as ‘sun dogs’ or ‘mock
suns’. The phenomenon
is due to light being
refracted in ice crystals.Sun dog Sun dog20 | SCIENCE ILLUSTRATED
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