Download Lab - El Camino College

Lab 12A-1
Name:
Section:
Due Date:
Climate Change Lab
Before Coming to Lab: Read Chapter 16 (pages 491-525) in Thurman & Trujillo, 11th ed.
The purpose of this lab is for you to familiarize
yourself with climate change issues. You will begin
by examining how the greenhouse effect works, how
humans have affected the Earth’s atmosphere, and
recent temperature data. Then, you will examine
paleoclimate data from ice cores and consider its
implications for the present global warming trend.
Finally, you will consider how global warming will
affect the oceans and humans.
Names of Group Members:
1.
2.
3.
Lab 12A-2
Stamps
Activity #1: Carbon Dioxide
in the Atmosphere
Write your name in this box.
Each square meter of the Earth’s receives about 240 Joules of heat from the Sun each second.
The amount of heat received from the Sun is roughly the same as the amount of heat that is
emitted (“sent away”) by the Earth out into space. Otherwise, the Earth would just get hotter and
hotter and hotter over time. (If you receive heat, but do no lose heat, you get hotter.)
The amount of heat emitted by a “black body” is given by the graph below. It is based on
experiments done in laboratories: heat up an object, measure its temperature, and measure how
much heat it gives off. (It will serve as an approximation for the how much heat the Earth
emits.)
le s
Jo u
infr
are
24 0
le
o ule s
v is ib
24 0 J
d
The Earth must send away
as much heat as it receives,
or it will get warmer or colder.
Sun
1. Based on the amount of heat that the Earth is emitting,
what should the average temperature of the Earth be?
__________________
Based on your own experience, does this result seem right to you?
Is this the average temperature of the Earth?
__________________
As you can see, this estimate appears to be wrong. We must have missed something and that
something is, of course, the greenhouse effect. Most of the heat emitted by the Earth cannot pass
directly through the atmosphere into space owing to greenhouse gases like carbon dioxide in the
atmosphere that absorb infrared light, “trapping” its heat.
2. Why is the atmosphere’s “greenhouse effect” actually a good thing?
(Hint: Think about what the Earth would be like if there were no “greenhouse effect.”)
3. What is the primary way in which humans increase the amount of carbon dioxide
in the atmosphere? (Hint: What happens inside cars, power plants, etc?)
Lab 12A-3
Examine the chart below.
4. Prior to the 1800s (the industrial revolution), was the carbon dioxide
concentration in the atmosphere going up, going down, or fairly steady? _____________
Over the last century, has the carbon dioxide concentration in the
atmosphere been going up, going down, or remained fairly steady?
5. Estimate the percentage increase in the amount of carbon dioxide
in the atmosphere owing to human activities (i.e., since 1700).
(Show your work. Be clear. Circle your answer.)
_____________
Suppose that you
invested $100 and
later your investment
was worth $110.
What is the
percentage increase
in your investment?
In fact, the amount of
carbon dioxide in the
atmosphere is a lot
less than the amount
of carbon dioxide that
has been released into
the atmosphere owing
to the burning of fossil
fuels by humans. A
significant amount,
about 1/3 to 1/2, has
been absorbed by the
ocean.
We have no direct measurements of carbon dioxide in the atmosphere prior to the 1950s.
However, when snow piles up at the Poles, it traps small amounts of air between the flakes, and
these bubbles of air remain after the snow is compacted into ice. Scientists drill down into the ice
sheets at the Poles and extract ice “cores” (like sediment cores). By counting down through the
layers of ice (and other methods) and measuring the carbon dioxide in the air bubbles, scientists
can estimate how much carbon dioxide was present in the atmosphere prior to the 1950s.
6. How can we test whether the carbon dioxide in the air bubbles of ice really does
represent the carbon dioxide in the atmosphere at the time when the ice froze?
Describe what you would do to test this idea using a device that could measure carbon
dioxide in samples of air and ice.
Hint: Examine the figure above.
What do the circles mean?
What does the line mean?
Now compare them…
Lab 12A-4
Activity #2: Local and Global Changes in Temperature
Examine the graph below showing the average temperature each year at the Civic Center in
downtown Los Angeles.
7. Prior to 1920, was the average
temperature of Los Angeles going up,
going down, or remaining fairly steady?
_____________________________
After 1920, has the average
temperature of Los Angeles been
going up, going down, or
remaining fairly steady?
_____________________________
If the amount of carbon dioxide in the atmosphere has been going up significantly since the
industrial revolution, then you might expect that the temperature everywhere, including Los
Angeles, has been going up since that time as well (if carbon dioxide is really a significant
contributor to the greenhouse effect). Clearly, this is not what the Los Angeles temperature
record shows.
8. Does the one observation showing cooling in Los Angeles prove that global warming was
not happening prior to 1920? Explain your reasoning.
Hint: Suppose that you are a
scientist given the task of
determining whether or not
global warming is happening:
would you only measure the
temperature at one location?
9. The local climate of a region is certainly affected by the amount of carbon dioxide in the
atmosphere, but many other factors are also important: its latitude, whether it is close to
or far from the ocean, the presence of mountains, etc. Global warming can cause shifts in
other factors that also affect local climate.
Aside from making things warmer, how could global warming affect local climate?
Give at least 1 example of how global warming could cause a particular place to get
colder, wetter (more humid), or dryer (less humid). Be as specific as you can.
Lab 12A-5
Recent estimates of temperature are based on measurements from many places throughout the
world. Unfortunately, we don’t have accurate measurements from many places in the world
prior to the late 1800s. To determine the global temperature prior to this time, scientists have
used temperature “proxies” to “reconstruct” the global temperature. (A proxy is someone who
stands in for you to do something. For example, if someone takes your shift for you at work,
they are your “proxy.”) Scientists use many proxies to infer temperature: tree rings, the layers
and chemical composition of coral reefs, the chemical composition of fossils and ocean & lake
sediments, etc.
10. Prior to the 1900s, was the Earth’s average temperature
going up, going down, or fairly steady?
Over the last century, has the Earth’s average temperature been
going up, going down, or remained fairly steady?
__________________
__________________
11. In the graph above, the line shows the average temperature calculated using thermometer
measurements from around the world. The circles show temperatures estimated using
“proxies” (tree ring data, sea floor sediments, ice cores, coral reefs, etc.).
How well do the temperatures based on proxies reflect the measured temperatures after
1900 (the time period where line and circles overlap)? In other words, are they about the
same, and do they show approximately same upward trend?
Does your comparison suggest that we can trust the temperatures estimated using proxies,
or does it suggest that temperatures based on proxies are unreliable?
Lab 12A-6
Activity #3: Changes in the Earth’s Climate in the Past
Examine the graphs below showing the amount of carbon dioxide in the atmosphere and the
temperature in the past.
12. Label the Ice Ages and “Warm Periods” in the figures above.
Are we in an Ice Age or a “Warm Period” right now?
__________________
13. Describe the relationship – if any – between the amount of carbon dioxide in the
atmosphere and temperature.
Does your description support or undermine the idea
that carbon dioxide is related to temperature
by the greenhouse effect?
_______________________
Lab 12A-7
The figure below shows the same temperature and carbon dioxide information displayed on the
previous page but in a different format: a scatter plot. Each dot represents the global average
temperature for a specific carbon dioxide concentration. As you can see, temperature tends to
increase as carbon dioxide levels increase.
30.0
Temperature (degrees C)
25.0
20.0
15.0
10.0
5.0
0.0
150
200
250
300
350
400
Carbon Dioxide (ppm)
14. Amount of carbon dioxide currently in the atmosphere:
(Use the figures in activity #1.)
________________________
Place an arrow (↑) on the carbon dioxide axis (x-axis) of the figure above at this value,
and label the arrow “CO 2 now.”
15. Draw a line through the dots in the figure above representing the “trend” in the data.
(In other words, draw a straight line representing the approximate slope of the data.)
Label your line, “trend.”
16. Using the line, estimate the temperature at which the Earth’s climate
will stabilize (stop increasing) if the trend holds true at the current,
higher level of carbon dioxide (a big “if”):
________________
Place a dot in the figure at the temperature and carbon dioxide level.
Label the dot “final global temperature.”
17. What is the “final global temperature” in degrees Fahrenheit?
(Use the formula: [Temp. in oF] = 1.8 × [ Temp. in oC ] + 32oF )
The current average global temperature is about 60oF. If your
estimate based on the past relationship between carbon dioxide
and temperature is correct, how much will the average global
temperature rise over the next few centuries?
__________________
__________________
Lab 12A-8
Examine the graphs below showing the Earth’s “most recent” warming and the warm period
before the last ice age.
18. Compare the current warm period with the last warm period (and the others in the
previous graphs). How are they different? What is unusual about the current warm
period?
Remains of fossil humans that are anatomically like us (i.e., homo sapiens) show that humans
have been on the Earth for at least a couple hundred thousand years. (My understanding is that
scientists have difficulty determining whether many 200,000 to 500,000-year-old fossils are from
homo erectus or homo sapiens: they are too similar.) However, human civilization (humans
farming and building cities in places like ancient Egypt, Mesopotamia (modern Iraq), China,
India, etc.) – is a very “recent” phenomena, say within the last 10,000 years.
19. A reasonable hypothesis is that civilization began about 10,000 years ago
because the world’s climate became much more stable about 10,000 years ago.
Why does civilization need a stable climate? In other words, what can hunter-gatherers
do that city dwellers and farmers cannot easily do if the climate changes?
Lab 12A-9
20. Estimate the rate (“how fast”) at which the world has gotten warmer over the last
century. (In other words, what is the slope of the recent part of the temperature curve?)
Answer in oC per year (oC /yr). (Use global temperature figure in activity #2.)
(Show your work. Be clear. Circle your answer.)
Recent
Global
Warming
Estimate the rate (“how fast”) at which the world becomes warmer at the end
of an ice age. (In other words, what is the slope of the temperature curve?)
Answer in oC per year (oC /yr). (Use the figure on the previous page.)
(Show your work. Be clear. Circle your answer.)
Natural
Global
Warming
(at the end of
the last ice age)
Divide your estimate of the “recent warming” by the “natural warming” at the end of the
last ice age. How many times faster is warming over the last century than the fast,
natural global warming at the end of an ice age?
(Show your work. Be clear. Circle your answer.)
Do your calculations support the idea that the recent warming
is just a “natural” climate fluctuation and not related to human activities?
Why or why not? (Select one answer from the list below.)
• The recent global warming is much faster than the fast, natural warming that occurs
at the end of an ice age, so the recent warming is unlike these previous natural
warmings. Therefore, these calculations suggest that natural causes may not be
sufficient to explain the recent warming and humans activities may be responsible.
• The recent global warming is occurring at about the same rate as the fast, natural
warming that occurs at the end of an ice age, so the recent warming is like these
previous natural warmings and therefore natural causes may be sufficient to explain
what is causing the recent warming.
• The recent global warming is much slower than the fast, natural warming that occurs
at the end of an ice age, so natural causes could explain and produce the recent
warming because we know that they produced much larger ones in the past.
Lab 12A-10
Activity #4: Global Warming and the Ocean
21. Why has the warming of the surface of the Earth
been small even though a lot more heat has been added
owing to trapping by greenhouse gases?
Hint:
Is the Earth mainly
covered by land or ocean?
How does it react
to being heated?
Consider your answer to the question above. If the temperature of the world only goes up
a little owing to the extra trapped heat, then the Earth will only radiate a little more heat away
as infrared “light.” In other words, more heat is still being trapped than sent away. Therefore,
the world will continue to get warmer and warmer. This means that the ocean is only slowing
down the warming; the Earth will eventually reach a much higher temperature at which it will
be hot enough to send away as much heat as it receives from both the Sun and the atmosphere.
22. Will global warming cause global sea level to rise or fall?
Why? (Give at least 2 reasons.)
________________________
(a)
(b)
23. Will global warming increase or decrease the
strength of hurricanes? In other words, will
there be stronger hurricanes or weaker hurricanes?
Why?
________________________
Lab 12A-11
24. How does the additional carbon dioxide
in the ocean affect ocean life? As part of your
answer, identify which organisms are affected
and explain how or why they are affected.
(a) potential benefits:
Note: Discuss the effect of the
carbon dioxide in the ocean water,
not the additional carbon dioxide
in the atmosphere or the warming
of the ocean water.
(b) negative effects:
25. (a) Will global warming increase or decrease the number
of phytoplankton in the oceans? In other words, will
there be more or fewer phytoplankton in the oceans?
Explain your reasoning.
Note: Discuss the effect of
warmer water at the surface
of the ocean, not the
additional carbon dioxide
in the atmosphere and ocean.
(b) Will global warming increase or decrease the number of animals in the ocean?
Explain your reasoning.
Lab 12A-12
Humans have dumped more and more carbon dioxide into the atmosphere by burning fossils fuels
like oil and natural gas, raising atmospheric levels by over 33% (a third), and as a result, more and
more carbon dioxide has leaked into the ocean from the atmosphere. In fact, scientists estimate
that the ocean absorbs somewhere between 33% and 50% of our carbon dioxide pollution.
26. Phytoplankton absorb carbon dioxide from ocean water, allowing the ocean to absorb more
carbon dioxide from the atmosphere – but only if the carbon is not released back into the
water (only if it is “permanently” removed from the ocean water).
(a) Why does most of the carbon in phytoplankton bodies end up back in the ocean water?
What happens to them as they sink toward the bottom (on their own or in fecal pellets)?
(i) __________________________________________________________________
(ii) __________________________________________________________________
(b) The carbon in one body part is less likely to go back into ocean water.
Which body part? What happens to the carbon in the body part? (In other words,
if the carbon does not go back into the water, where does the carbon go?)
(c) Suppose that there will be fewer phytoplankton in the ocean owing to global warming.
Will the absence of phytoplankton help the world become even warmer,
or help cool down the world? Explain your reasoning.
Lab 12A-13
Activity #5: Thermohaline Circulation
In the global thermohaline circulation, ocean water moves in giant loops called convection cells
owing to changes in its temperature and salinity: “thermo” refers to temperature and “haline”
refers to salinity. In this activity, we will begin to study the thermohaline circulation by
examining how water’s temperature determines whether it floats or sinks.
Begin the experiment by doing the following:
• Fill the plastic bag with 3 ice cubes,
and then add enough water to the bag to just barely cover the ice cubes.
• Put the bag at one edge of the tank of water. Make it float as close as the surface as you
can, and wrap the top of the bag over the edge of the tank so that it does not float away.
• Let the tank rest for a minute or more so that the thermohaline circulation can establish
itself. Then, add a drop of blue dye (next to the bag).
Plastic Bag
27. Sketch the behavior
of the dye into the
figure on the right.
Color the blue water
into the picture, and
draw blue arrows to
show the motion of
the water about a
minute into the
experiment.
Add blue dye here
Ice
Cube
28. Describe the motion of the cold (blue) water in the tank in words.
Add red dye here
Lab 12A-14
The thermohaline circulation starts in certain special places near the Poles where water becomes
dense enough to sink deep beneath the surface. As a result, warmer water flows towards the
Poles at the surface to replace the water which sank. Once the water has sunk, the water slowly
changes as the water mixes with neighboring water or via other processes (for example, oxygen
is used up as animals breathe it in or bacteria use it to decompose sinking organic matter). As
deep water warms owing to contact with the water above, it rises slowly over a broad area. (It
gets lifted above colder water that sank more recently). The small amount which sinks quickly is
exactly balanced by a large amount rising very slowly.
Examine the side-view (cross-section) shown below. Ships traveled from India at the north end
of the Indian Ocean all the way down to Antarctica and stopped occasionally to measure the
temperature and other water properties deep beneath them.
29. Highlight the 2oC
contour line (isotherm)
in blue.
Indian Ocean Temperature (degrees Celsius)
Then, color all
the water with a
temperature less
than 2oC in blue.
30. Add a a blue arrow
to show the motion
of the deeper water,
and a red arrow to
show the motion of
the water near the
surface of the ocean.
31. Where does the water sink, near Antarctica or India?
Why does the water sink at this location?
___________________
Lab 12A-15
Scientists are interested in the thermohaline circulation for a variety of reasons. For example, the
slowly rising water brings the deep, nutrient-rich water closer to surface, where wave orbitals can
reach down and bring nutrients up to phytoplankton who live at the surface. In this lab, though,
we will consider how the thermohaline circulation affects climate and life in the deep ocean.
Antarctica
32. Sketch the currents of the thermohaline circulation
into the side-view picture on the right, and label the
surface currents as “warm” or “cool.”
33. Does the thermohaline circulation warm
or cool the higher latitudes (“the Poles”)?
_____________
How? Why? Explain.
Examine the figure on the right.
North
Pole
Equator CO2
lots of
CO2
34. (a) How does the thermohaline circulation help
the ocean absorb more carbon dioxide?
little
CO2
lots of
CO2
Land
(b) Does the thermohaline circulation
make the world warmer or cooler overall?
Why? How?
___________________________
Lab 12A-16
Activity #6: Winners and Losers from Global Warming
35. Is global warming a good thing or a bad thing?
Your answer to this question probably depends on upon who you are.
Are you a “winner” or a “loser”?
In other words, will you benefit from global warming, or will it harm you?
Consider whether global warming is a good or bad for the following people and
organisms. Explain your reasoning.
Actor
Air Conditioner
Manufacturer
Ski Resort
Employee
Farmer
in Canada
Farmer
in Mexico
Dockworker on
the Northern Coast
of Russia
Owners of
Beachfront Property
Diatom
(a silica-shelled
phytoplankton)
Copepods
(crustacean
zooplankton)
Good or Bad?
Reasoning
Lab 12A-17
Climate Change Lab (12A) Review: Hints & Advice
Activity #1
To use the graph to estimate the temperature of the Earth, first determine how much heat the
Earth is sending back into space as infrared light. Find this number on the y-axis, then go across
the graph and place a dot on the curve at this value. Next, find the value on the x-axis that is
below the dot. This is the temperature of the Earth – more precisely, this is the temperature that
the Earth should have IF there were no greenhouse gases trapping the heat escaping from the
Earth as infrared light.
Do not forget to include the UNITS after every numerical answer.
To calculate a percentage increase, divide the increase in the amount by the original amount.
percentage increase = ( increase or “gain” ) / original amount
For example, if you invested $100 and later it was worth $110, then your original investment
of $100 has increased by $10, so the percentage increase is $10 / $100 = 0.10 = 10%.
In question 6, the hypothesis is:
“The proportion of carbon dioxide in air bubbles in ice is the same as
the proportion of carbon dioxide in the atmosphere when the ice formed.”
You need to propose an experiment that would test this hypothesis. You have equipment that
measures carbon dioxide in the atmosphere and in bubbles in ice. All you need to do is to
describe how you will use the equipment: When will you take samples from the air? From what
layers of the ice will you take samples? When? Are any of the old observations of carbon
dioxide in the atmosphere (the circles in the graph) useful to you?
Activity #3
30.0
25.0
Temperature (degrees C)
The “trend line” represents the slope of the data.
The graph on the right shows several possible
trend lines. Draw your trend line so that it goes
through the data points “best” according to your
own judgment. Your trend line does NOT need
to go through “0.0” on the y-axis.
20.0
15.0
10.0
5.0
The temperature where the trend line meets the
current level of carbon dioxide in the atmosphere
is the (estimated) temperate that the Earth will
eventually reach.
0.0
150
200
Do not forget to include the UNITS after every numerical answer.
(Continued on the Next Page)
250
300
350
Carbon Dioxide (ppm)
CO2 now (?)
400
Lab 12A-18
Civilization requires “cities” which require agriculture (farming) to support them,
since (most) people are no longer hunters and gatherers roaming around looking for food.
To calculate the speed at which the world
is warming, you need to calculate the
slope of the warming trends. Draw a line
through the warming trend that represents
the slope of the data “best” according to
your judgment. Measure the “rise” and
the “run:” the sides of the triangle of your
trend line. The slope is the rise divided
by the run:
slope = ( rise ) / ( run )
rise
run