American Intercontinential University Meteorology Science Worksheet

Meteorologyearth science
Greenhouse Effect Simulations
You r N am e
What are greenhouse gases? How do greenhouse gases affect the flow of light and heat
energy through Earth’s atmosphere and affect Earth’s climate?
“Without the greenhouse effect, Earth would be a frozen planet.”
—NOAA Reports to the Nation, Our Changing Climate
The atmosphere is a mixture of gases, including natural and human-made trace
greenhouse gases such as carbon dioxide, methane, water vapor, nitrous oxide,
CFC’s, and HC’s. These gases interact with infrared heat energy trying to radiate
from Earth’s surface back into space, keeping the planet warmer than it would be
without these gases.
Simulation #1: Molecules and Light
1. Open the Molecules and Light simulation from PhET.
2. Working with your partner, explore all of the controls in the simulation for a few minutes. Click
on different things and figure out what each one does. What does the simulation do and
show?
3. Use the simulator to specifically examine how two different types of radiation interact with
different atmospheric gas molecules. In the data table below, record your observations for
each combination — draw a labeled sketch and add a few descriptive words.
Atmospheric Gas
Visible Radiation
(Light Energy)
Infrared Radiation
(Heat Energy)
Nitrogen (N2)
Oxygen (O2)
Carbon Dioxide (CO2)
Water Vapor (H2O)
Earth Science • Greenhouse Effect Simulations • 1
Meteorology
earth science
Greenhouse Effect Simulations
You r N am e
Reflection — based on your observations, answer the questions below.
•
Which atmospheric gas molecules were not affected by the visible or infrared radiation?
•
Which atmospheric gas molecules were affected by the visible or infrared radiation?
•
How were these atmospheric gas molecules affected by the radiation?
•
How was the radiation affected by these atmospheric gas molecules?
Put all the pieces together — connect what’s happening in this simulation to what’s happening in the
real world.
•
Based on the simulation, what makes a greenhouse gas a greenhouse gas?
•
How does energy flow in and out of Earth’s atmosphere, and how might this be related to
Earth’s climate?
•
What is one question that you are still wondering about?
Eldorado K-8 Science • Greenhouse Effect Simulations • 2
Meteorology
earth science
Greenhouse Effect Simulations
You r N am e
Simulation #2: The Greenhouse Effect
•
Use PhET’s Greenhouse Effect simulation to explore and explain the role of greenhouse gases
in Earth’s atmosphere and climate. Show what happens in each situation below.
Eldorado K-8 Science • Greenhouse Effect Simulations • 3
Meteorology
earth science
Greenhouse Effect Simulations
You r N am e
Fill in the data table below:
Atmospheric Gas:
What is the name of each gas?
Is it a
greenhouse gas?
Does it absorb
visible energy?
Does it absorb
infrared energy?
N2
O2
CO2
CH4
H2O
In the diagrams below, draw and explain how both the flow of visible (solar) and infrared (heat) energy
and the temperature of Earth’s atmosphere are affected by greenhouse gases.
Few greenhouse gases:
Many greenhouse gases:
Eldorado K-8 Science • Greenhouse Effect Simulations • 4
The Greenhouse Gases
“Without the greenhouse effect, Earth would be a frozen planet.”
—NOAA Reports to the Nation, Our Changing Climate
Carbon Dioxide, CO2
Methane, CH4
Water Vapor, H2O
Nitrous Oxide, N2O
Within Earth’s atmosphere, these naturally occurring greenhouse gases interact with heat energy trying to
radiate from the Earth back into space, slowing the process down. But what happens to the energy balance
when humans add even more of these (and other) gases to Earth’s atmosphere?
fr o
enhouse effect, Earth would be a
e
r
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e
t th
hou
t
i
W
z
la n
p
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e
et.
The Greenhouse Effect
Carbon dioxide gas constitutes a tiny fraction of
the atmosphere. Only about one air molecule in
three thousand is CO2. Yet despite their small
numbers, CO2 molecules can have a big effect on
the climate. To understand why they are so
important, we need to know about the greenhouse effect of the atmosphere. Earth’s atmosphere lets in rays of sunshine and they warm the
surface. The planet keeps cool by emitting heat
back into space in the form of infrared radiation—the same radiation that warms us when we
sit near a campfire or stove. But while the
atmosphere is fairly transparent to sunshine, it is
almost opaque to infrared radiation. Much like a
garden greenhouse, it traps the heat inside.
About half of the solar energy that reaches
Earth passes through the atmosphere and is
absorbed at the surface. In contrast, about 90%
of the infrared radiation emitted by the surface
is absorbed by the atmosphere before it can
escape to space. In addition, greenhouse gases
like CO2 as well as clouds can re-emit this radiation, sending it back toward the ground. The fact
is, Earth’s surface receives almost twice as much
Outgoing
longwave
radiation
235 W
Upward infrared
emission from
atmosphere
195 W
The Greenhouse Effect
The atmosphere allows solar radiation to enter the climate system relatively easily, but
absorbs the infrared radiation emitted by the Earth’s surface. Although about half of
the energy coming from the sun is absorbed at the surface of the Earth, almost twice
as much surface heating is provided by downward infrared emission from the
atmosphere as from sunshine. This “greenhouse effect” causes the
surface of Earth to be much warmer than it would be without the
atmosphere. The graphic on this page shows the flow of solar
(yellow) and infrared (red) radiative energy through the
climate system in watts per square meter of surface
area. On average, 168 watts of solar radiation
energy reach each square meter of the surface
area, but the heating of the surface from
the downward infrared radiation
emitted by the atmosphere is
almost twice that, 324 watts
per square meter.
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R e p o r t s t o t h e N a t i o n • Fall 1997
Infrared
transmitted
through
atmosphere
40 W
Back
radiation
Infrared
emission
from surface
350 W
Infrared
absorbed
by surface
324 W
energy from infrared radiation coming down
from the atmosphere as it receives from sunshine. If all greenhouse gases were removed
from the atmosphere, the average surface temperature of Earth would drop from its current
value of 59˚F (15˚C) to about 0˚F (-18˚C). Without the atmosphere’s greenhouse effect, Earth
would be a frozen and nearly lifeless planet.
Incoming
solar
radiation
342 W
Reflected solar radiation 107 W
E
S
U
O
H
N
E
GRE
GASES
Solar radiation
reflected by
clouds, aerosols
and atmosphere
77 W
Latent heat
of condensation
78 W
Solar
radiation
absorbed by
atmosphere
67 W
Thermals 24 W
Solar
radiation
reflected
by surface
30 W
Evaporation,
transpiration
78 W
Solar radiation
absorbed by surface
168 W
R e p o r t s t o t h e N a t i o n • Fall 1997
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R e p o r t s t o t h e N a t i o n • Fall 1997
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It is the distinctive molecular structures of the
greenhouse gases that make them strong absorbers and emitters of infrared radiation. About
99% of air molecules are nitrogen and oxygen,
which have a simple structure consisting of two
identical atoms. Because of this simple structure, they have a relatively minor effect on the
transmission of solar and infrared radiation
through the atmosphere. Molecules with three
or more atoms like water vapor, carbon dioxide, ozone, and a host of other trace gases can
efficiently absorb and emit infrared energy by
storing and releasing it in molecular vibration
and rotation. Though some of these gases
constitute only a tiny fraction of the atmosphere, they can nevertheless make significant
contributions to the greenhouse effect.
The molecule that makes the largest contribution is water vapor, which is a relatively
abundant greenhouse gas. An average water
molecule stays in the atmosphere only a few
days from the time it evaporates from the
surface to the time it falls out of the atmosphere
as precipitation, so the water vapor content
of the atmosphere adjusts quickly to changes in
surface temperature. Humanity can do little to
directly control the global amount of atmospheric water vapor. Because atmospheric water vapor tends to increase with increasing
temperature, however, it can amplify climate
changes produced by other means—a process
called water vapor feedback.
Denali National Park, Alaska.
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Reports to the Nation
• Fall 1997
Why Are Greenhouse
Gas Amounts Increasing?
Carbon dioxide has a much longer lifetime in the
atmosphere than water vapor. If CO2 is suddenly
added to the atmosphere, it takes 100 to 200 years
for the amount of atmospheric CO2 to establish a
new balance, compared to several weeks for
water vapor. That’s because the carbon in CO2 is
cycled between the atmosphere and the ocean or
land surface by slow chemical and biological
processes. Plants, for example, use CO2 to produce energy in a process known as photosynthesis. Through millions of years of Earth’s history,
trillions of tons of carbon were taken out of the
atmosphere by plants and buried in sediments
that eventually became coal, oil, or natural gas
deposits. In the last two centuries humans have
used these deposits at an increasing rate as an
economical energy source. In a similar way,
cement manufacture releases carbon atoms buried in carbonate rocks. Today humanity releases
about 5.5 billion tons of carbon to the atmosphere every year through fossil fuel burning and
cement manufacture. Approximately another 1.5
billion tons per year are released through land
use changes such as deforestation. These releases result in an increase of atmospheric CO2 of
about one-half percent per year.
Other naturally occurring greenhouse gases
such as methane and nitrous oxide have also
been increasing, and entirely man-made greenhouse gases such as halocarbons have been
introduced into the atmosphere. Many of these
gases are increasing more rapidly than carbon
dioxide. The amount of methane, or natural
gas, in the atmosphere has doubled since the
Industrial Revolution. Although its sources are
many, the increase is believed to come mainly
from rice paddies, domestic animals, and leakage from coal, petroleum, and natural gas
mining. Halocarbons are a family of industrial
gases that are manufactured for use in refrigeration units, as cleaning solvents, and in the
production of insulating foams.
They were
first manufactured in the 1940s, and because
they do not readily react with other chemicals
Methane
0.47 W/m 2
Nitrous Oxide
0.14 W/m 2
Halocarbons
0.24 W/m 2
Carbon Dioxide
1.56 W/m 2
Climate Forcing by Greenhouse Gas Increases Since the Industrial Revolution.
Changes in the atmospheric concentration of CO2 , methane, nitrous oxide, and
halocarbons that have occurred since the Industrial Revolution have altered the energy
budget of Earth. The difference is about 2.4 watts per square meter, or roughly 1% of
the energy flow through the global climate system.
R e p o r t s t o t h e N a t i o n • Fall 1997
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Clouds r eflect sunlight, he
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Aerosols: Sunscreen for the Planet?
Although raising the levels of greenhouse gases
in the atmosphere is our most important direct
influence on the global climate, human actions
also contribute to the aerosol content of the
atmosphere. Aerosols are tiny particles of liquid
or solid matter that are suspended in air. They
are different from water cloud droplets or ice
particles in that they are present even in relatively dry air. Atmospheric aerosols have many
sources and are composed of many different
materials including sea salt, soil, smoke, and
sulfuric acid. Although aerosols have many
natural sources, it is estimated that aerosols
resulting from human activities are now almost
Reports to the Nation
• Fall 1997
rapping infrared radiation.
f a ce b y t
h.
they can have a lifetime in the atmosphere of
more than 100 years. Halocarbons are also
responsible for the Antarctic ozone hole and a
more general decline in global stratospheric
ozone, but this is a separate problem from the
greenhouse warming contributed by the halocarbons. Production of some of the halocarbons that are important greenhouse gases has
been regulated by international agreements to
preserve Earth’s protective ozone layer, so their
influence on climate should decline in the
future. Nearer to Earth’s surface, in the troposphere, ozone amounts have been increasing
because of human activities. Ozone at the
surface has harmful effects on the health of
plants, animals, and humans.
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w ar m
’s s u r
Earth
as important for climate as naturally produced
ones. Most of the human-induced aerosols
come from sulfur released in fossil fuel burning
and from burning vegetation to clear agricultural land. Human production of sulfur gases
accelerated rapidly in the 1950s.
It appears that the cooling effect of aerosols
has canceled out part of the warming that might
have been associated with recent greenhouse
gas increases. Aerosols can reflect solar radiation or absorb and emit infrared radiation, and
are often visible as haze or smog. By reflecting
sunlight, they cool the climate. The humaninduced increase in atmospheric aerosols since
preindustrial times is believed to have reduced
the energy absorbed by the planet by about half
a watt per square meter, enough to offset about
20% of the greenhouse gas warming effect.
The aerosols produced by humans could also
have a significant effect on the amount or
properties of clouds. Every cloud droplet or ice
particle has at its center an aerosol called a cloud
condensation nucleus, on which the water vapor collected to form the cloud droplet. Aerosols
that attract water, such as those composed of salt
or sulfuric acid, are particularly effective as
cloud condensation nuclei. The increased number of aerosols produced by humans could
cause the water in clouds to be distributed into
more, but smaller, cloud droplets. With their
water spread more diffusely, the clouds would
reflect more solar radiation. The existence of