HS-ESS3-6NGSS*ScienceEarth and Space ScienceGrades 9-12
HS-ESS3-6: Using Model Results to Show How Human Activity Changes Earth Systems
In plain English: HS-ESS3-6 is the NGSS high school performance expectation that asks students to use a computational representation to illustrate how the atmosphere, hydrosphere, cryosphere, geosphere and biosphere are connected and how human activity is changing those connections. Students interpret published model results such as carbon budgets and ocean pH projections. It is usually taught in Earth and Space Science.
Use a computational representation to illustrate the relationships among Earth systems and how those relationships are being modified due to human activity.
Clarification Statement: Examples of Earth systems to be considered are the hydrosphere, atmosphere, cryosphere, geosphere, and/or biosphere. An example of the far-reaching impacts from a human activity is how an increase in atmospheric carbon dioxide results in an increase in photosynthetic biomass on land and an increase in ocean acidification, with resulting impacts on sea organism health and marine populations.
Assessment Boundary: Assessment does not include running computational representations but is limited to using the published results of scientific computational models.
Next Generation Science Standards · Disciplinary Core Idea: Earth and Human Activity · Official standard
Students use computational representations, a carbon box model with numbers on every flux and the published-style output of climate and ocean models, to show how Earth systems are linked and how human activity is changing the links. They balance a carbon budget to find how fast atmospheric CO2 rises, convert between gigatonnes of carbon and parts per million, read model projections of ocean pH and shell-building conditions, and trace chains of effects from one system to the next.
The NGSS Clarification Statement says: "Examples of Earth systems to be considered are the hydrosphere, atmosphere, cryosphere, geosphere, and/or biosphere. An example of the far-reaching impacts from a human activity is how an increase in atmospheric carbon dioxide results in an increase in photosynthetic biomass on land and an increase in ocean acidification, with resulting impacts on sea organism health and marine populations." The Assessment Boundary says: "Assessment does not include running computational representations but is limited to using the published results of scientific computational models." So students never write or run model code on this page: every activity, homework problem and quiz item gives them model results to use. All model results are invented for teaching, with values rounded to sizes similar to published carbon budgets and ocean projections. Students do the practice of using computational representations: they calculate with model outputs, build box-and-arrow diagrams from them and explain the relationships the numbers show.
Learning Objectives
By the end of this lesson, students will be able to:
Use a carbon box model to compute the net change in the atmosphere from the fluxes among the atmosphere, ocean, land biosphere and fossil fuels
Convert between gigatonnes of carbon and parts per million of atmospheric CO2, using 1 ppm = 2.12 GtC
Use published model results to trace how added CO2 increases land photosynthesis and lowers ocean pH, with effects on sea organisms and marine populations
Identify relationships among the hydrosphere, atmosphere, cryosphere, geosphere and biosphere, including feedbacks, from model outputs
Explain how a specific human activity (burning fossil fuels, clearing land) changes a flux or a relationship in the model
Prior Knowledge Required
Students should already be comfortable with:
Modeling the cycling of matter among living and nonliving parts of an ecosystem MS-LS2-3
How human population and consumption affect Earth systems MS-ESS3-4
Percent change, and pH as a base-10 scale on which a drop of 1 means ten times as much acidity
Photosynthesis takes in CO2 and respiration releases it
Write "burning a tank of gasoline" in the center of the board and five labels around it: atmosphere, hydrosphere, cryosphere, geosphere, biosphere.
Warm-Up Prompt
"The carbon in gasoline came out of the geosphere. Draw arrows to show where it can go after it leaves the tailpipe, and one thing it could change in each system it reaches. Which of your arrows could you put a number on?"
Collect a few diagrams. Point out that the arrows are relationships, and that putting a size on each arrow turns the drawing into a computational representation that can be used to calculate. That is what the lesson builds.
Direct Instruction15-20 minutes
Computational representations of Earth systems. A box model shows reservoirs (boxes) and fluxes (arrows) with their sizes. If more flows into a box than out, the box grows: the change equals inflows minus outflows. Scientific models, from simple box models to global climate and ocean models, compute these flows over time, and their published results let us see how systems are connected. For carbon, 1 ppm of CO2 in the atmosphere is 2.12 GtC (gigatonnes of carbon). For the ocean, pH is a base-10 scale: a drop of 0.1 means about 26% more hydrogen ions (100.1 ≈ 1.26). Use Diagram 1 with the first example and Diagram 2 with the third.
Balancing the carbon box model
Invented, rounded yearly fluxes: burning fossil fuels moves 9.6 GtC from the geosphere to the atmosphere and land clearing adds 1.2 GtC. The ocean takes up 2.9 GtC and land plants and soils take up 3.1 GtC (Diagram 1).
Result: Atmosphere change = (9.6 + 1.2) - (2.9 + 3.1) = +4.8 GtC per year, which is 4.8 ÷ 2.12 ≈ 2.3 ppm per year. The fraction of the human emissions that stays in the air is 4.8 ÷ 10.8 ≈ 44%; the ocean and land take the rest.
Atmosphere to biosphere: more photosynthesis on land
An invented land-model result: global net primary productivity (the carbon plants fix each year after their own respiration) rises from 56 GtC per year in 1900, when CO2 was about 296 ppm, to 62 GtC per year in 2020, at 412 ppm.
Result: Productivity rose (62 - 56) ÷ 56 ≈ 10.7% while CO2 rose (412 - 296) ÷ 296 ≈ 39%. Extra CO2 increases photosynthetic biomass on land, which is part of why the land takes up 3.1 GtC a year, but the increase is far smaller than the emissions.
Atmosphere to hydrosphere: ocean acidification
An invented ocean-model result: surface ocean pH was 8.18 in 1850 and 8.06 in 2020, and reaches 7.75 by 2100 in a high emissions scenario (Diagram 2).
Result: From 1850 to 2020, hydrogen ions increased by a factor of 100.12 ≈ 1.32, or about 32%. From 2020 to 2100 in the high scenario, the factor is 100.31 ≈ 2.04: the ocean would be about twice as acidic as today.
Hydrosphere to biosphere: shell-building organisms
An invented model result for a polar surface sea: the aragonite saturation state, Ω, falls from 1.6 in 2000 to 1.2 in 2050 and 0.9 in 2100. When Ω is below 1, unprotected aragonite shells dissolve. Pteropods, small swimming snails with aragonite shells, are food for fish such as salmon.
Result: Between 2050 and 2100 Ω falls 0.3 ÷ 50 = 0.006 per year, so it drops below 1 after (1.2 - 1.0) ÷ 0.006 ≈ 33 years, around 2083. After that, the model predicts pteropod shells dissolving, with effects that pass up the food web to marine populations that eat them.
Cryosphere, hydrosphere and atmosphere: the ice-albedo feedback
In an invented Arctic model, sunlight delivers 200 W/m² in summer. Sea ice reflects 60% (albedo 0.60) and open ocean reflects 6% (albedo 0.06).
Result: Ice absorbs 200 × 0.40 = 80 W/m²; open water absorbs 200 × 0.94 = 188 W/m². Each square meter of ice that melts adds 108 W/m² of absorbed sunlight, which warms the water and melts more ice. Warming from human greenhouse gases started the melting, and this feedback amplifies it.
After each example, ask: "Which two systems does this result connect? Which way does the arrow point, and does it make the change larger or smaller? Which human activity changed it?"
Guided Practice15 minutes
Pairs use invented model output for one medium-high emissions path. They compute changes, then draw the chain of relationships it shows.
Guided practice data: model output for atmospheric CO2 and surface ocean pH (invented)
Year
CO2 (ppm)
Surface ocean pH
2000
370
8.10
2020
412
8.06
2040
470
8.02
2060
540
7.97
2080
640
7.92
Find the CO2 increase in each 20-year step (42, 58, 70 and 100 ppm). Is the rise steady or speeding up?
Find the pH change in each step (-0.04, -0.04, -0.05, -0.05). As CO2 rises, pH falls.
From 2000 to 2080, pH falls by 0.18, so hydrogen ions increase by a factor of 100.18 ≈ 1.51, about 51% more.
Draw the chain as boxes and arrows, starting from a human activity and passing through the atmosphere and the hydrosphere to living things in the ocean. Label each arrow with the model number from the table that supports it.
Independent Practice10-15 minutes
Each student modifies the carbon box model in Diagram 1 for a human decision. An invented land-use model finds that if tropical deforestation were cut sharply, the land-clearing flux would fall from 1.2 to 0.5 GtC per year; assume the other fluxes stay the same.
Students redraw the box model with the new flux, compute the new atmospheric gain (4.1 GtC per year, about 1.9 ppm per year instead of 2.3) and write two sentences: one on how this human activity changes the relationship between the biosphere and the atmosphere, and one on a second system that would also be affected (for example, rainfall made by forests, or biodiversity).
Closure5 minutes
Exit ticket: "If fossil fuel emissions fell by 2.0 GtC per year and the ocean and land took up the same amounts as before, by how many ppm per year would the rise in atmospheric CO2 slow? Name one reason the real answer could be a little different." (About 0.94 ppm per year; the sinks would also change, for example the ocean takes up less when the air holds less extra CO2.)
Differentiation Strategies
For Struggling Students
Give the box model with every flux already labeled "in" or "out" for the atmosphere, and a two-line calculation frame: total in, total out
Provide a pH card that shows how to find 10 raised to the pH drop on a calculator, with the one case from Direct Instruction (a drop of 0.1 gives about 26% more hydrogen ions)
Use a relationship frame: "When ___ in the ___ increases, ___ in the ___ increases/decreases, because ___. The model shows ___."
For Advanced Students
Ask students to explain why the fraction of emissions that stays in the atmosphere has stayed near half even as emissions grew, using the ACT1 decade cards
Have students find how many years of the current atmospheric gain equal the carbon in all land vegetation (about 450 GtC)
Ask students to compare two model outputs that disagree and propose what observations would tell them which is closer to reality
Assessment Guidance
What to Look For
Check that students balance a box model as inflows minus outflows and keep the units (GtC per year or ppm per year). Look for relationship statements that name both systems, the direction of the effect and the model number that supports it. Listen for students who think the ocean or plants "cancel" emissions, or who treat pH as a linear scale. Check that students use model results as evidence and say what the model assumed, rather than treating a projection as a certainty.
02
Classroom Activities
3 Activities
1
Build the Carbon Budget Model from Published Results
20 minGroups of 3-4
Groups receive invented decade-average cards for two decades, sized like published carbon budgets. They build a box-and-arrow model for each decade on poster paper and use it to compute how the atmosphere changed.
Result Cards (invented, GtC per year)
1980s: fossil fuels 5.4, land clearing 1.3, ocean uptake 1.8, land uptake 1.5.
2000s: fossil fuels 7.8, land clearing 1.4, ocean uptake 2.2, land uptake 2.6.
Conversion card: 1 ppm of atmospheric CO2 = 2.12 GtC.
Tasks
Draw the four reservoirs (atmosphere, ocean, land plants and soils, fossil fuels) and label each arrow with its flux for each decade.
Compute the atmospheric gain (1980s: 3.4 GtC per year, about 1.6 ppm; 2000s: 4.4 GtC per year, about 2.1 ppm).
Compute the fraction of emissions that stayed in the air (about 51% and 48%).
Discussion Questions
Both the ocean uptake and the land uptake were larger in the 2000s than in the 1980s. What relationship between the atmosphere and the sinks does that suggest?
Which flux on your poster is controlled most directly by human decisions, and which are Earth-system responses?
Why can the ocean and land never take up all of the emissions in this model?
Modification for Distance Learning
Groups build the model in a shared slide with arrow shapes and post their calculations beside it.
2
Ocean Acidification in a Cup, Then the Model Results
25 minPairs
Pairs use a physical model to see CO2 lowering the pH of water and to see how dissolved bicarbonate slows the change, then use invented model results to connect ocean chemistry to shell-building organisms.
Procedure
Pour 100 mL of tap water into cup 1. Into cup 2, pour 100 mL of tap water with ½ teaspoon of baking soda and a pinch of salt stirred in (a buffered "model seawater"). Add 10 drops of bromothymol blue to each; both turn blue.
Through a clean straw, one student breathes out gently into cup 1 for 5 seconds at a time, counting the breaths until the water turns yellow. Repeat with cup 2 using a new straw, stopping at 25 breaths.
Record the number of breaths and the color after each set of five.
Safety
Wear goggles. Breathe out through the straw only, never suck in, and use your own straw once and throw it away.
Do not drink the solutions. Bromothymol blue from a school supplier is dilute and low hazard, but it stains: wipe spills at once and wash hands at the end. Pour the solutions down the sink with plenty of water.
Students with asthma or who feel dizzy should not blow into the straw. Instead, they add plain seltzer water to the cups with a dropper, counting drops instead of breaths.
Sample Data and Model Results (invented)
Cup 1 turned yellow after 4 breaths. Cup 2 was still blue-green after 25 breaths. Model result card: in lab studies summarized by an invented model, pteropod shell growth is 100% at Ω = 1.6, 75% at Ω = 1.2 and 40% at Ω = 0.9, with visible dissolution below Ω = 1.
Discussion Questions
Which cup is more like the real ocean, and what did the baking soda do? Does buffering stop the pH from falling, or slow it?
Your breath holds far more CO2 than air does. How does that limit what the cup model can tell you about the real ocean?
Using the model result card, by what percent does shell growth fall between Ω = 1.6 and Ω = 0.9? Which marine populations could be affected, and how?
Modification for Distance Learning
The teacher records the two cups side by side. Students count breaths from the video and complete the model-result questions at home.
3
Earth System Connections: Model-Result Stations
25 minGroups of 3-4
Four stations each show one invented model result. Groups rotate every 5 minutes, add each result to a class relationship map with a labeled arrow (+ for "increases", - for "decreases") and name the human activity that is changing the relationship.
Stations (invented model results)
Station 1, water vapor: for each 1 °C of warming, the model atmosphere holds about 7% more water vapor, and water vapor is a greenhouse gas. For 1.1 °C of warming, that is about 7.7% more.
Station 2, permafrost: in a high emissions scenario, thawing frozen soils in the Arctic release 60 GtC as CO2 and methane by 2100, about 7% of the carbon now in the atmosphere (870 GtC).
Station 3, rainforest and rain: clearing 40% of a tropical forest reduces the rainfall the region makes for itself by 12%, because fewer trees move water from the soil to the air.
Station 4, ocean oxygen: warmer surface water holds less dissolved oxygen and mixes less with deeper water; in a high emissions scenario, the ocean's oxygen falls by about 3% by 2100 and low-oxygen zones, where many fish cannot live, grow larger.
Tasks
For each station, name the two or three Earth systems the result connects and draw the arrows with signs.
Mark any loop where a change feeds back to increase itself.
For each station, write the human activity that is modifying the relationship.
Discussion Questions
Trace the loops at Stations 1 and 2 around the map. Does each loop add to the warming or reduce it?
At Station 4, which human activity links the atmosphere to fish living below the surface, and through which systems does the effect pass?
Which station links the biosphere to the hydrosphere most directly?
Challenge Variation
Groups choose one station and find the published model study it resembles, then compare the real result with the invented card and report the difference.
03
Diagrams & Visual Aids
2 diagrams
Diagram 1: A Carbon Box Model of Four Earth Systems
A computational representation used in the first worked example. Boxes are reservoirs and arrows are yearly net fluxes (invented, rounded values similar in size to published carbon budgets). Two arrows come from human activity: burning fossil fuels moves carbon from the geosphere, and land clearing moves it from the biosphere. The atmosphere gains the difference between what flows in and what the ocean and land take up.
Diagram 2: Model Output for Surface Ocean pH Under Two Emissions Paths
Invented model output drawn to scale. Both paths start at pH 8.06 in 2020. On the high emissions path, pH falls to 7.75 by 2100; on the low emissions path, pH levels off near 8.04 and then rises slightly as atmospheric CO2 declines. The difference between the lines is the effect of a human choice on the link between the atmosphere and the ocean.
04
Homework Assignment
~30 min
HS-ESS3-6 Homework: Earth System Relationships from Model Results
Directions: All model results are invented for practice, with realistic sizes. You do not need to run any model: use the results given. Use 1 ppm of CO2 = 2.12 GtC. Show each calculation with units, and end each problem with a sentence that names the Earth systems involved and the human activity that changes the relationship.
Part 1: Reading a Carbon Box Model (Problems 1-2)
Decade-average model results for the 1960s are: fossil fuels 3.1 GtC per year, land clearing 1.5, ocean uptake 1.1 and land uptake 1.7. (a) Draw the box model. (b) Find the atmospheric gain in GtC per year and in ppm per year. (c) What fraction of emissions stayed in the air? (d) By what factor are the emissions in Diagram 1 larger than in the 1960s?
The atmosphere holds about 875 GtC as CO2. (a) What CO2 level in ppm is that? (b) At a gain of 4.8 GtC per year, by what percent does the atmospheric reservoir grow each year? (c) At 2.3 ppm per year, how many years does it take to add 50 ppm?
Part 2: Ocean and Biosphere Connections (Problems 3-4)
An invented ocean model projects that surface pH near a coral reef falls from 8.05 to 7.85 by 2080 in one scenario. (a) By what factor does the hydrogen ion concentration increase? (b) Express it as a percent increase. (c) Use the relationship chain atmosphere → hydrosphere → biosphere to explain one likely effect on the reef and on the fish populations that depend on it.
An invented land model shows global net primary productivity rising from 58 to 63 GtC per year as atmospheric CO2 rises from 340 to 410 ppm. (a) Find the percent increase in productivity and in CO2. (b) Suppose the land uptake in Diagram 1 (3.1 GtC per year) grew by the same percent as productivity in (a). How much extra carbon would land take up each year, what would the atmospheric gain become, and what percent of the 10.8 GtC per year of human emissions would the extra uptake cancel? Use your numbers to explain why more photosynthesis does not cancel human emissions.
Part 3: Human Modifications and Feedbacks (Problems 5-6)
Two invented emissions paths start at 425 ppm in 2025. On path A, the atmosphere gains 5.0 GtC every year until 2050. On path B, the yearly gain falls steadily from 5.0 to 1.0 GtC, an average of 3.0 GtC per year. (a) Find the total carbon added from 2025 to 2050 on each path. (b) Find the CO2 level in 2050 on each path. (c) Which flux in the box model must change to move from path A to path B, and what human activity controls it?
In an invented Arctic model, sunlight delivers 180 W/m² in summer. Melting sea ice has an albedo of 0.50 and open ocean 0.07. (a) Find the sunlight absorbed per square meter by ice and by open ocean. (b) Find the difference. (c) Draw the feedback loop among the cryosphere, hydrosphere and atmosphere with + or - on each arrow, and say how human activity started it.
Rubric
Criterion
Full Credit (2 pts)
Partial Credit (1 pt)
Using Model Results
Box-model balances, conversions and percent changes are correct with units
Correct method with one calculation or unit error
Relationships Among Systems
Names the systems, the direction of each effect and the model number that shows it
Names the systems but not the direction or the evidence
Human Modification
Identifies the specific human activity and the flux or relationship it changes
Mentions human activity in general terms
Diagrams
Box models and loops are complete, labeled and consistent with the calculations
Diagram is present but missing labels or signs
05
Quiz: 20 Questions
Interactive, with answers
Instructions
All model results are invented for practice. You never need to run a model: every question gives you the results to use. Use 1 ppm of CO2 = 2.12 GtC. Your score updates as you answer, and Reset quiz clears everything so you or your students can try again.
Multiple choice: pick an option to check it. Short answer: write your answer, then reveal the model answer.
0 of 20 answered · 0 correct
Question 1 of 20 · Multiple Choice
Which of these is a computational representation of the relationships among Earth systems?
Answer: A
A box model with numbers on its fluxes can be used to calculate how the reservoirs change, which is what makes it computational. Choice B is an observation, choice C is a physical sample, and choice D names the systems without showing any relationship.
Question 2 of 20 · Multiple Choice
In a model year, human emissions are 10.0 GtC, the ocean takes up 2.8 GtC and land takes up 3.2 GtC. How much carbon does the atmosphere gain?
Answer: C
Gain = inflow - outflows = 10.0 - (2.8 + 3.2) = 4.0 GtC. Choice A adds the sinks to the emissions. Choice B subtracts only the ocean uptake, and choice D subtracts only the land uptake.
Question 3 of 20 · Multiple Choice
A model shows the atmosphere gaining 6.36 GtC of carbon in a year. How large is the rise in atmospheric CO2?
Answer: B
6.36 ÷ 2.12 = 3.0 ppm. Choice A multiplies by 2.12 instead of dividing. Choice C skips the conversion. Choice D divides 2.12 by 6.36, the wrong way round.
Question 4 of 20 · Multiple Choice
In a different model year, human emissions are 9.0 GtC and the atmosphere gains 3.6 GtC. What fraction of the emissions stays in the atmosphere?
Answer: D
3.6 ÷ 9.0 = 0.40, so 40% stays in the air. Choice A is the share taken up by the ocean and land. Choice B confuses 3.6 GtC with 3.6%. Choice C divides the emissions by the gain, the wrong way round.
Question 5 of 20 · Multiple Choice
An ocean model projects that surface pH in one region falls from 8.1 to 7.7. How does the hydrogen ion concentration change?
Answer: A
pH is a base-10 scale, so a drop of 0.4 multiplies the hydrogen ion concentration by 100.4 ≈ 2.5. Choice B uses the drop of 0.4 itself as the multiplier, and in the wrong direction, since lower pH means more hydrogen ions. Choice C turns the drop of 0.4 pH units into a 40% increase, as if pH were a linear percent scale. Choice D confuses a drop of 0.4 with a factor of 4.
Question 6 of 20 · Multiple Choice
An invented ocean model gives the carbonate ion concentration in surface seawater as 250 µmol/kg in 1850, 215 µmol/kg in 2020 and 150 µmol/kg in 2100 on a high emissions path. By what percent does it fall from 2020 to 2100?
Answer: C
The drop is 215 - 150 = 65 µmol/kg, and 65 ÷ 215 ≈ 0.30, about 30%. Choice A reports the drop in µmol/kg as a percent. Choice B divides by the 2100 value instead of the 2020 value. Choice D divides by the 1850 value. Corals and shellfish build shells from carbonate ions, so this change in the hydrosphere reaches the biosphere.
Question 7 of 20 · Multiple Choice
A model shows that warmer summer air over Greenland melts more of the surface of its ice sheet each year. Which two Earth systems does this result connect first?
Answer: B
Warm air is part of the atmosphere and the ice sheet is part of the cryosphere, so the result first links those two. The meltwater then reaches the ocean (hydrosphere), but that is the next link in the chain. The other pairs leave out the air, the ice or both.
Question 8 of 20 · Multiple Choice
An ocean model gives an aragonite saturation state of Ω = 1.5 in 2020, falling by 0.012 per year. In about what year does Ω fall to 1, below which unprotected shells dissolve?
Answer: D
Ω must fall 1.5 - 1.0 = 0.5, which takes 0.5 ÷ 0.012 ≈ 42 years, so about 2062. Choice A divides 1.5 by 0.012, as if Ω had to reach 0. Choice B divides by 0.12 instead of 0.012 (0.5 ÷ 0.12 ≈ 4 years), a place-value slip. Choice C assumes shells are already dissolving at Ω = 1.5.
Question 9 of 20 · Multiple Choice
In an Arctic model, sunlight delivers 150 W/m². Sea ice reflects 60% and open ocean reflects 10%. How much more sunlight does a square meter of open ocean absorb than a square meter of ice?
Answer: A
Ice absorbs 150 × 0.40 = 60 W/m² and open ocean absorbs 150 × 0.90 = 135 W/m², so the difference is 75 W/m². Choice B is the difference in albedo, not in energy. Choices C and D are the two absorbed amounts, not their difference.
Question 10 of 20 · Multiple Choice
Climate models show the atmosphere holding about 7% more water vapor for each 1 °C of warming. About how much more water vapor would 2 °C of warming bring?
Answer: C
Two degrees at about 7% per degree gives about 14% (compounding gives 14.5%). Choice B ignores the second degree. Choice A confuses the temperature change with the percent. Choice D squares 7 instead of doubling it. Because water vapor is a greenhouse gas, this relationship between the hydrosphere and the atmosphere amplifies warming.
Question 11 of 20 · Multiple Choice
A permafrost model projects that thawing Arctic soils release 40 GtC to the atmosphere by 2100. How much would that add to atmospheric CO2 if all of it stayed in the air as CO2?
Answer: B
40 ÷ 2.12 ≈ 18.9 ppm. Choice A multiplies by 2.12. Choice C skips the conversion. Choice D is 40 as a percent of the 870 GtC in the atmosphere (4.6%), labeled as ppm. In reality the ocean and land would take up part of it, so the rise would be smaller.
Question 12 of 20 · Multiple Choice
In a carbon box model, the flux of carbon from the atmosphere into the ocean has grown over the past 60 years. Which human activity is the main reason?
Answer: D
The ocean takes up CO2 faster when the air holds more of it, and burning fossil fuels is what raised atmospheric CO2. So a human activity in the geosphere changes the atmosphere-ocean relationship. Choices A and B change rivers and rock but not this flux. Choice C collects data and changes nothing.
Question 13 of 20 · Multiple Choice
An invented coastal model shows that oyster larvae survival falls by 40% as the water becomes more acidic. Adult oysters filter the water, and oyster reefs shelter young fish and crabs. Which forecast do the model results support?
Answer: C
Fewer larvae surviving means fewer adults, which filter less water and build less reef, so the animals that depend on the reefs lose habitat. This is how a change in the hydrosphere reaches marine populations. Choice A has no support in the results. Choice B forgets that today's larvae are tomorrow's adults. Choice D claims a fast adaptation the model does not show.
Question 14 of 20 · Multiple Choice
Models show that warming thaws permafrost, the thawing releases CO2 and methane, and those gases cause more warming. What kind of relationship is this?
Answer: B
The change (warming) causes an effect (gas release) that increases the original change, so the loop is a positive, amplifying feedback. Choice A has the sign backwards. Choice C ignores that permafrost connects the cryosphere, geosphere, biosphere and atmosphere. Choice D misses the loop back to warming.
Question 15 of 20 · Short Answer
An invented land-use model finds that cutting deforestation lowers the land-clearing flux by 1.1 GtC per year, and regrowing forests add 0.3 GtC per year to land uptake. If the other fluxes do not change, by how much does the atmospheric gain fall, in GtC and in ppm per year?
The inflow to the atmosphere falls by 1.1 and the outflow rises by 0.3, so the gain falls by 1.4 GtC per year, which is 1.4 ÷ 2.12 ≈ 0.66 ppm per year. The human activity changes the relationship between the biosphere and the atmosphere in both directions.
Question 16 of 20 · Short Answer
Invented ocean-model results give surface pH 8.06 in 2020, and for 2100, 8.02 on a low emissions path and 7.92 on a medium path. (a) By what factor does the hydrogen ion concentration rise by 2100 on each path? (b) Explain what the difference shows about human activity.
(a) Low path: 100.04 ≈ 1.10 (about 10% more). Medium path: 100.14 ≈ 1.38 (about 38% more). (b) The atmosphere-ocean relationship is the same on both paths, but the amount of CO2 people add differs, so human emissions decide how far the ocean's chemistry changes.
Question 17 of 20 · Short Answer
An invented reef model finds that coral skeleton growth falls by about 15% for each 0.1 drop in pH. Write the chain of relationships from a human activity to the reef, and use the model result to estimate the growth change for a pH drop of 0.2.
Chain: burning fossil fuels (human activity) → more CO2 in the atmosphere → more CO2 dissolving in the ocean, lower pH and fewer carbonate ions (hydrosphere) → slower coral growth (biosphere). For a 0.2 drop, the model gives about 2 × 15% = 30% slower growth (or 1 - 0.85² ≈ 28% if the effect compounds). Slower reef growth also affects the fish and other animals that live on the reef.
Question 18 of 20 · Short Answer
An invented model of a glacier-fed river gives summer flow of 100% of the 2020 level in 2020, 120% in 2050 and 60% in 2100. Explain the relationships among the cryosphere, the hydrosphere and the biosphere that the results show, and how human activity is changing them.
Warming caused by human greenhouse gas emissions melts the glacier faster (cryosphere), so at first more meltwater reaches the river and summer flow rises to 120% (hydrosphere). As the glacier shrinks, there is less ice to melt, and flow falls to 60% by 2100. Fish that need cold summer water, and the farms and towns downstream, lose water in the dry season (biosphere and people).
Question 19 of 20 · Short Answer
A student says: "CO2 helps plants grow, so rising CO2 is good for Earth's systems." Use the kinds of model results in this lesson (land productivity and ocean pH) to evaluate the claim.
The claim is partly supported and incomplete. Land models do show more photosynthesis with more CO2, a real relationship between the atmosphere and the biosphere, but the increase is small compared with human emissions. The same added CO2lowers ocean pH, which ocean models link to weaker shell building and effects on marine populations, and it causes warming with its own impacts. A computational representation shows that one change reaches several systems, so a single benefit cannot be judged on its own.
Question 20 of 20 · Short Answer
Invented results for two emissions paths in 2050: path A has 560 ppm of CO2 and surface pH 7.96; path B has 450 ppm and pH 8.03. (a) How many GtC more carbon is in the atmosphere on path A? (b) By what factor is the hydrogen ion concentration higher on path A? (c) Which relationship does this comparison illustrate?
(a) 110 ppm × 2.12 ≈ 233 GtC more. (b) 100.07 ≈ 1.17, about 17% more hydrogen ions. (c) It shows how the amount of CO2 humans add to the atmosphere controls the acidity of the ocean, the atmosphere-hydrosphere relationship, with effects that then reach sea organisms.
0 of 20 answered · 0 correct
06
Frequently Asked Questions
10 Questions
What does HS-ESS3-6 mean?
HS-ESS3-6 asks students to use a computational representation, such as a box model with numbers or the output of a climate model, to show how Earth systems are connected and how human activity is changing those connections. The standard names the hydrosphere, atmosphere, cryosphere, geosphere and biosphere as the systems to consider. The code means High School, Earth and Space Science, core idea 3 (Earth and Human Activity), performance expectation 6.
Do students have to run computer models for HS-ESS3-6?
No. The Assessment Boundary says assessment does not include running computational representations and is limited to using the published results of scientific computational models. Students calculate with, graph and explain those results. A teacher may show a simple online model in class, but students are not tested on running one.
What is a computational representation in Earth science?
It is any representation that uses numbers and rules to calculate how a system changes, from a small spreadsheet to a global climate model. Scientists publish the results as tables, graphs and maps, which students can read, compute with and compare like data.
Is HS-ESS3-6 taught in Earth science or chemistry?
It is usually taught in Earth and Space Science, and it connects to Biology (the carbon cycle, food webs) and Chemistry (pH and ocean acidification). Integrated science courses often place it at the end of a climate unit.
What is the official HS-ESS3-6 example about carbon dioxide?
The Clarification Statement describes how an increase in atmospheric CO2 increases photosynthetic biomass on land and increases ocean acidification, with impacts on sea organism health and marine populations. This page works through both parts with model results: land productivity in one worked example, and ocean pH and shell-building conditions in two others.
Why does a small change in ocean pH matter?
Because pH is a base-10 scale, so a drop of 0.1 means about 26% more hydrogen ions. Lower pH also means fewer carbonate ions, which corals, shellfish and pteropods use to build shells and skeletons. Model results link these chemical changes to organism health and to the populations that feed on them.
Why doesn't extra plant growth cancel out CO2 emissions?
Because the extra carbon plants take up each year is much smaller than what people add. In the box model on this page, land takes up 3.1 GtC per year and the ocean 2.9, while human activity adds 10.8, so the atmosphere still gains about 4.8 GtC. Much of what plants fix also returns to the air through respiration and decay.
What mistakes do students make with HS-ESS3-6?
Frequent mistakes are subtracting only one sink when balancing a box model, forgetting to convert GtC to ppm, and treating pH as linear. Students also describe relationships in one direction only, missing feedback loops, or name "pollution" instead of the specific human activity that changes a flux.
How does HS-ESS3-6 connect to other NGSS standards?
It builds on HS-ESS2-6, where students develop a quantitative model of carbon cycling among the hydrosphere, atmosphere, geosphere and biosphere, and on HS-LS2-5, which models photosynthesis and respiration in the carbon cycle. HS-ESS3-5 uses model results to forecast climate change, and HS-ETS1-4 uses simulations to test solutions.
Is there a safe lab for HS-ESS3-6?
Yes. Breathing out through a straw into water with bromothymol blue shows CO2 lowering pH, and a second cup with baking soda shows buffering. Students wear goggles, breathe out only, use their own straw once, and never drink the solutions; students with asthma add plain seltzer water with a dropper instead. The lab is a physical model; the computational part uses model results.
07
Related Standards
6 standards
These standards connect to HS-ESS3-6: prerequisites to review first, parallel standards at the same level, and next steps that build on it.
Before this lesson
MS-LS2-3Prerequisite
Model the cycling of matter and flow of energy among parts of an ecosystem
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