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Good morning.
Today's lecture is about the Greenhouse Effect.
The “greenhouse effect" often gets a bad rap
because of its association with global warming,
but the truth is we couldn't live without it.
First,
I'd like to ask you
what causes the greenhouse effect.
Life on earth depends on energy from the sun.
About 30% of the sunlight
that beams toward Earth
is deflected by the outer atmosphere
and scattered back into space.
The rest reaches the planet's surface
and is reflected upward again
as a type of slow-moving energy called infrared radiation.
As it rises,
infrared radiation is absorbed by greenhouse gases
such as water vapor,
carbon dioxide,
ozone and methane,
which slows its escape from the atmosphere.
Although greenhouse gases
make up only about 1% of the Earth's atmosphere,
they regulate our climate
by trapping heat
and holding it in a kind of warm air blanket that surrounds the planet.
This phenomenon
is what scientists call the “greenhouse effect."