Understanding Climate Change DQC’s
What knowledge does a student, or citizen, need in order to understand a scientific document about
climate change, such as the reports published by the Intergovernmental Panel on Climate Change? In
addition to understanding the scientific method, students must decipher the complex chemical,
biological and physical processes involved in the accumulation of atmospheric greenhouse gases and the
ability of those gases to absorb infrared radiation reflected from the Earth’s surface back towards the
atmosphere. At the heart of understanding this complexity is tracing matter, particularly carbon, and
tracing energy associated with carbon containing molecules. Biofuels and Keeling Curve are two
parallel Diagnostic Question Clusters (DQC’s) that are intended to diagnose problems in student
reasoning about the processes involved in global climate change. Following an initial multiple process
question, students are asked about individual processes contributing to the multiple process question.
The names of individual questions categorized by process are shown in the table below.
Processes
Biofuels
Keeling Curve
Multiple Process
BIOFUEL (1)
KLGSEASON (1)
BIOFUEL (2)
Photosynthesis
CARBRESB (3b),
AMAZON (7)
SOILCARB (3)
Transformation – Plant to Soil
CARBATM (4)
FALEAVEA (5a)
SOILCARB (3)
FALEAVEA (4a)
Respiration – Decomposition
FALEAVEA (5a),
FALEAVEB (5a)
FALEAVEA (4a),
FALEAVEB (4b)
Combustion
BIOCOMBUST (5)
QANGASCO (5)
Atmosphere – Greenhouse effect
GLOBWAMC (2)
Carbon Residency Time
CARBRESA (3a)
Biofuel Production
BIOFUEL2 (4)
General Instructions for Coding DQC Responses
Responses to DQC questions can be grouped into three general categories; Informal, Mixed or
Scientific. These three categories encompass a wide range of reasoning abilities, but all three categories
are common among college students. The table below describes the general types of responses that
would be associated with each level of reasoning. In addition, the levels of reasoning are assigned a
numerical value for coding purposes. Codes 2-4 are used for responses that attempt to answer the
question, while codes 1a-1e are reserved for missing responses or those that provide no information
about student reasoning. Mixed reasoning presents itself in several different ways, thus level 3 answers
are divided up into subcategories to reflect different types of responses.
Code
4
3
2
1a
1b
1c
1d
1e
Level
Scale
Successful use of
other scales to
explain macroscopic
phenomena
Processes described
in terms appropriate
for that scale
Partially successful
attempts to connect
scales, but with some
inappropriate use of
macroscopic ideas at
other scales
Matter
Reactants and products described
as chemical substances
Accounts of processes describe
Principled
transformation of reactants into
reasoning
products in ways that conserve
atoms at the atomic-molecular
scale and mass at larger scales.
Less than completely successful
attempts to conserve matter.
Reactants and products described
as material kinds, but atoms not
Mixed
traced through chemical processes
reasoning
and matter-energy
transformations may be used as a
“fudge factor.)
No attempt to make
Material inputs or needs and
connections across
products or results are mentioned,
scales for questions
but not in ways that clearly
posed at
distinguish matter, energy, and
macroscopic scale
conditions.
Informal
Inappropriate use of
No indication that the student is
reasoning
macroscopic scale
reasoning about transformation of
ideas at other scales
matter: no account of how
material inputs are transformed
into results.
Missing data (e.g. responses or codes lost after exam was taken and coded)
Student did not reach question
Student skipped question
I don’t know or equivalent
Nonsense answer that is not responsive to question
Energy
Forms of energy are clearly
identified and distinguished
from forms of matter.
Energy transformation
described in ways consistent
with energy conservation.
Energy is recognized as a
distinct entity, but sometimes
in ways that do not clearly
distinguish energy from matter
(e.g., glucose, ATP) and/or
conditions (e.g., temperature).
Accounts fail to conserve
energy.
“Energy” used in an informal
sense as something that makes
events happen.
No clear distinction between
energy sources and other
needs or inputs.
These general ideas for coding above are applied to each individual question below to provide specific
details for how to code each question. Still, you will find that the specific coding rubric for each
question does not list every possible answer that you might see. In these cases, refer back to the general
rubric above, and try to be as objective as possible. You will undoubtedly find responses that don’t quite
fit a specific category, but seem to be in between. For these scenarios, we suggest that you assign a 2.5
or 3.5 code to the student.
Biofuels Diagnostic Question Cluster
Diagnostic Guide
Please answer the questions below as carefully and completely as you can.
1. Explain why the use of biofuels instead of fossil fuels is a proposed strategy to slow the rate of global
climate change. Use as much detail in your answer as you can.
Correct, Scientific Answer: Biofuels are made from plants that were recently grown. Both biofuels and fossil fuels are
converted to carbon dioxide when combusted, but the carbon that is contained in biofuels was recently converted to organic
carbon through photosynthesis, and would have been returned to the atmosphere via decomposition of the plant material
anyway. Thus, burning biofuels contributes no net increase in atmospheric carbon dioxide levels, which are the primary
cause of climate change. The carbon contained in fossil fuels has been located in solid and liquid form in the Earth for
millions of years, and would not be expected to be converted to carbon dioxide by natural processes. Therefore, burning
fossil fuels does result in a net increase in atmospheric carbon dioxide levels.
Processes = Photosynthesis, Respiration/Combustion, Principles = Matter, Scale, Scale = Ecosystem -> Atomic/Molecular
Purpose of Question: In order to explain why biofuels are considered to reduce the effects of climate change, students need
to understand that the carbon dioxide released during biofuel combustion was recently taken out of the atmosphere via
photosynthesis, whereas fossil fuels have been located in the ground for millions of years and would not be released to the
atmosphere without human intervention. Students A) think that biofuels result in less carbon dioxide emissions than fossil
fuels when burned, failing to trace carbon during combustion, B) say that biofuels don’t give off greenhouse gases at all,
(similar reasoning to A, but essentially seeing fossil fuels as unnatural and biofuels as “natural”), C) Fail to recognize the age
of organic carbon in biofuels and fossil fuels, D) confuse the greenhouse effect with ozone layer depletion.
Coding Rubric
Code
Example Student Responses
Description
4 - Scientific
Biofuels remove Co2 while growing along with
the CO2 they release when burning staying
mostly carbon neutral. Fossil fuels have no CO2
balance.
-Student explains that carbon dioxide released from
biofuels during combustion is part of a short term
carbon cycle (plants remove CO2 from atmosphere
while growing, and most of this carbon would be
oxidized by decomposers soon after plant death.
3 - Mixed
A)-Biofuels are more organic substances that
when combusted do not let off CO2 admissions.
A) Student references greenhouse gases, CO2 or other
specific matter containing compounds in relation to
the combustion of biofuels, but cites incorrect facts,
such as the idea that biofuels do not emit, or emit less
CO2 or greenhouse gases when burned.
A) They do not emit greenhouse gases like fossils
fuels. They will not create a heat trapping smog.
That doesn’t allow heat to escape.
2 - Informal
B) Biofuels are actually just as bad as fossil
fuels. Both emit carbon dioxide into the air.
Biofuels take up a lot of land and aren't very
efficient. Biofuels cause bacteria to grow in the
soil that puts more carbon dioxide into the air.
Biofuel is not alternative strategy to fossil fuels.
B) Students understand oxidation of biofuels releases
CO2, but they do not reference the fact that plants
remove CO2 from the atmosphere while growing.
-Fossil fuels burn up the ozone layer, increasing
climate change, biofuels are more environment
friendly option.
-Student does not reference specific matter containing
entities in relationship to the combustion of biofuels.
Often, students repeat common “environmental”
slogans they’ve heard, sometimes including the ozone
layer.
2. Scientists believe that the average temperature of the earth’s atmosphere has been increasing
during the past 100 years. What is the major cause of this?
A) More heat is released from vehicles and factories into the atmosphere.
B) More particulate pollution (smog) is in the atmosphere.
C) More carbon dioxide is in the atmosphere.
D) Deterioration of the ozone layer
E) None of these causes global warming.
Processes = Greenhouse Effect, Principles = Tracing Matter and Energy, Scale = Ecosystem
Purpose of Question: Students must understand the process by which climate change is occurring, as
biofuel combustion results in carbon dioxide released to the atmosphere, which traps heat near the
Earth’s surface. Many students attribute climate change to the depletion of the ozone layer. All
responses are chosen by students at varying frequencies.
Coding Rubric
Code
Example Student Responses
Description
4 - Scientific
C
Student chooses C
3 - Mixed
A, B, D
Student chooses A, B or D
2 - Informal
E
Student chooses E
3a. On average, how long do you think a molecule of carbon dioxide remains in the atmosphere after
being released by a human being?
Anywhere between 2 and 20 years would be considered appropriate answers. Five – ten years is
considered to be the average residence time for CO2 in the atmosphere.
3b. Where could the carbon atom go next after it is in the atmosphere?
Carbon in the atmosphere is in the form of carbon dioxide. It leaves the atmosphere when a plant
utilizes the molecule of carbon dioxide in photosynthesis. During this process, carbon dioxide is
combined with water to form glucose, an organic carbon molecule. The carbon could also dissolve into
a body of water and be incorporated into carbonate molecules.
Processes = Photosynthesis, Principles = Tracing Matter, Scale = Atomic-Molecular, Ecosystem
Purpose of Question: Part A: The major reason for asking this question is to lead into question 3b.
However, students don’t tend to recognize how long a molecule of carbon dioxide remains in the
atmosphere before being transformed to organic carbon through photosynthesis or dissolving into a
water body. In multiple choice format, students tend to choose either a 5 year, 50 year, or 350 million
year residence time. Students providing very long time frames don’t appear to understand the path that
carbon takes between the biosphere and atmosphere.
Part B specifically asks students to recognize the process of photosynthesis without being explicitly
asked about photosynthesis. Students may respond with answers that say carbon escapes the atmosphere,
which incorrectly conserves matter. They may also say it is incorporated into animals during breathing,
or dissolved into the Earth. They may also respond with an alternative correct answer that carbon
dioxide dissolves into water bodies, and is converted to carbonate molecules, but this is unlikely unless
they have learned this process. Codes for this question are generated based on part B of the question..
Coding Rubric
Code
Example Student Responses
Description
4 - Scientific
Into a plant for photosynthesis, sugar to feed
plant.
Student describes carbon leaving the atmosphere to
plants via photosynthesis, with correct details about
the process
3 - Mixed
A) Absorbed by plants.
A) Student describes carbon leaving the atmosphere to
plants,
B) It will be used by a plant to make oxygen.
C) Into any living organism.
B) Student describes carbon leaving the atmosphere to
plants via photosynthesis, but includes incorrect
details about the process (e.g. carbon converted to
oxygen)
C) Student describes carbon leaving the atmosphere
and going into other living organisms
2 - Informal
A) It is reused and cycles back into the world.
B) Into outer space.
A) Student states that the carbon is recycled back into
the earth, world,, etc..
B) Student states that the carbon remains in the
atmosphere forever or goes into outer space
4. Carbon exists in the atmosphere, where could it have come from? Circle all correct answers.
A) Photosynthesis by plants
B) Diffusion from the ocean
C) Cellular respiration by plants
D) Cellular respiration by animals
E) Cellular respiration by bacteria
F) Photosynthesis by fungi
G) Burning of biofuels
H) Burning of fossil fuels
I) Depletion of the ozone layer
Processes = Photosynthesis, Respiration, Principles = Tracing Matter, Scale = Ecosystem
Purpose of Question: This question assesses whether students understand that carbon enters the
atmosphere from a variety of sources and processes. It also assesses whether students have specific
omissions/misconceptions about gasses entering and exiting the atmosphere.
A) Student who do not know the correct reactants and products of photosynthesis may think that plants
release CO2 into the atmosphere via photosynthesis.
B) Many students do not recognize that there is gas exchange between the oceans and the atmosphere.
This is a topic rarely addressed in introductory texts.
C/D) Students who fail to continue to trace carbon after it enters the plant may think that plants and/or
animals don’t respire.
E) Students think bacteria don’t eat or respire. Students commonly do not recognize that the same
process that occurs in animals and plants could also occur in single-celled organisms.
F) Students who chose this answer may think that fungi are autotrophs AND that carbon dioxide is a
product of photosynthesis.
G/H) The majority of students recognize that burning of fossil fuels releases carbon to the atmosphere,
but do not see that biofuels are also a source of carbon in the atmosphere.
I) Some students think that the depletion of the ozone layer is related to the carbon cycle in a direct way.
They are not accounting for the specific atoms in ozone. They may not know what ozone is made of or
they may think that oxygen can become carbon.
Coding Rubric
Code
4 - Scientific
3 - Mixed
Example Student Responses
C, D, E, G, H
Student circles C, D, E, G, and H (May or may not
circle B)
A, C, D, E, F
Student chooses A, F or I
C, D, E, H
Student fails does not choose at least one of the
correct responses (C, D, E, G, H)
B, C, D, E, G, H
B, C, D
2 - Informal
Description
NA
5. One liquid biofuel often used as a transportation fuel is ethanol (C2H5OH). Decide whether each of
the following statements is true (T) or false (F) about what happens to the atoms in a molecule of
ethanol when it burns.
T
T
T
T
T
T
F
F
F
F
F
F
Some of the atoms in the ethanol are incorporated into carbon dioxide in the air.
Some of the atoms in the ethanol are incorporated into air pollutants such as ozone or nitric oxide.
Some of the atoms in the ethanol are converted into energy that moves the car.
Some of the atoms in the ethanol are burned up and disappear.
Some of the atoms in the ethanol are converted into heat.
Some of the atoms in the ethanol are incorporated into water vapor in the atmosphere.
Processes = Combustion, Principles = Tracing Matter and Energy, Scale = Atomic-Molecular
Purpose of Question: Biofuels are combusted to release heat energy which is converted to mechanical
energy. However, many students believe that biofuel combustion results in fewer emissions than fossil
fuel combustion, or zero emissions. Therefore, they don’t trace matter effectively, often because they
convert matter to energy. Incorrect student responses are found for all six true/false questions. Most
commonly, students incorrectly convert matter to energy. Students who choose true for “Air Pollutants”
are not entirely incorrect, but indicates slight problems with reasoning.
Coding Rubric
Code
4 - Scientific
Example Student Responses
A) T, F, F, F, F, T
B) T, T, F, F, F, T
Description
A) Student chooses true for Carbon Dioxide and
Water
B) Student chooses true for Carbon Dioxide, Water
and “Air Pollutants)
3 - Mixed
A) T, T, F, T, F, T
B) T, F,F, T, F, F
A) Student answers true for the correct responses
(Carbon Dioxide and Water), but also chooses true for
at least one of the distracters (Energy, Used Up, Heat.)
B) Student answers true for one of the correct
responses and at least one distracter
2 - Informal
A) F, T, T, F, F, F
B) T, T, T, T, T, T
A) Student chooses False for Carbon Dioxide and
Water
B) Student chooses True for all responses
6. On March 10, 2004, National Public Radio reported that “forests in a remote part of the Amazon
are suddenly growing like teenagers in a growth spurt.” Though, the radio report added, “This
shouldn't be happening in old, mature forests.” Scientists have speculated that our actions may
have caused this phenomenon. What do you think could be the scientific basis behind such a
speculation?
Processes = Photosynthesis, Combustion, Principles = Tracing Matter, Scale = Ecosystem
Purpose of Question: Many students can recite and/or write the chemical equation for photosynthesis,
but do not properly apply it to questions about mass gain in plants. Most often, students think that mass
is gained by absorbing materials through their roots – including carbon based substances. In addition,
students must account for increasing carbon dioxide levels in the atmosphere due to human activities,
potentially resulting in increased photosynthesis.
Coding Rubric
Code
Example Student Responses
Description
4 - Scientific
There is more carbon dioxide present, we know
that plants use carbon dioxide to grow.
Student response makes a connection between rising
CO2 levels and increased plant growth due to higher
photosynthetic rates. Student may or may not mention
rising temperatures due to climate change.
3 - Mixed
A) The constant and rapid usage of heat by us
humans could be the result. Heat energy can
cause growth amongst plants.
A) Student response attributes forest growth to rising
temperatures
B) We have added something to the atmosphere
that wasn't there before, that helps the plants
grow.
C) There is an increased amount of sunlight and
heat incubating the trees.
D) Trees taking in something at a faster rate than
they usually do. Carbon dioxide? Nitrogen?
Radioactivity (Godzilla style)?
2 - Informal
A) Maybe that is happening because the ozone
layer is thinner and carbon atoms are leaving
faster and causing a faster growth in trees. I
don't know.
B) This didn't happen back when humans didn't
have as big of an impact.
C) The forest may be affected by less pollutants.
Better air and water quality - less invasive people
or cars. Plants need water and air to grow - but
too much of the wrong chemicals can prevent
growth.
D) The adaptation of trees has forced them to
grow to live.
B) Student attributes plant growth to changes in the
atmosphere without specifically mentioning CO2
C) Student attributes plant growth to changes in
sunlight levels
D) Student cites changes in a mixture of specific
human activities that could result in tree growth, but
not sure
A) Student attributes increased plant growth to
changes in the ozone layer
B) Student restates question
C) Student blames a host of human pollutants without
identifying a specific mechanism
D) Student states that the forest adapts to the new
conditions, which is why it is growing faster