Science 7–10 · Years 9–10

The global carbon budget: where each year's emissions go

Science understanding: Earth and space sciences (ACARA Year 9 carbon cycle and Year 10 climate; NSW Stage 5 focus areas Environmental sustainability and Data science 2)

Calculation and dataLow risk

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The idea

Each year's carbon from fossil fuels and land clearing is shared between the atmosphere, the ocean and land plants, so the rise in atmospheric carbon dioxide equals emissions minus what the sinks take up.

What you need

the Global Carbon Budget 2024 figures for 2023 (Friedlingstein et al. 2025, open access): fossil 10.1, land-use change 1.0, ocean sink 2.9 and land sink 2.3 GtC per year; 419.31 ppm in 2023; 278.3 ppm in 1750; 1 ppm = 2.124 GtC
the Kennaook / Cape Grim monthly carbon dioxide file (CSIRO and Bureau of Meteorology) for the check against observation
graph paper or a spreadsheet, and a calculator

How to do it

Draw four boxes (fossil carbon, atmosphere, ocean, land) and arrows for the 2023 flows with widths to scale.
Compute the atmospheric growth as 10.1 + 1.0 - 2.9 - 2.3 GtC per year and convert it to ppm with 1 ppm = 2.124 GtC.
Compute the airborne fraction (growth divided by total emissions) and the ocean's share of emissions.
Compare the growth with the rise in the Cape Grim annual means from 2023 to 2024 and from 2024 to 2025.
Run the model with emissions held at 11.1 GtC per year for 10 years, then with emissions set to zero for 10 years, and record the carbon dioxide each time.
Evaluate the model's key assumption, that the sinks grow in proportion to the carbon dioxide above the 1750 level, and say how a warming ocean would change the result.

What you should see

Atmospheric growth = 5.9 GtC per year = 2.78 ppm per year (the Global Carbon Budget reports 2.79 plus or minus 0.1 ppm per year); airborne fraction 0.53; the ocean takes 26 percent of emissions. Cape Grim's annual means rose from 416.37 ppm (2023) to 420.01 ppm (2024), 3.64 ppm, then to 422.88 ppm (2025), 2.87 ppm: real years vary around the budget figure. In the model, holding emissions at 11.1 GtC per year takes carbon dioxide from 419.31 ppm to 444.8 ppm after 10 years (and toward 579 ppm eventually); setting emissions to zero lowers it to 396.8 ppm after 10 years, falling at first by 2.45 ppm per year. The learner knows the model is set up correctly when the 2023 inputs return 2.78 ppm per year.

What changes

This activity lists no variables to change, measure and keep the same.

Common misconceptions

Each of these ideas is wrong, and the activity is a chance to test it.

All the carbon dioxide emitted stays in the air; about half of each year's emissions is taken up by the ocean and land.
If emissions stopped, carbon dioxide would drop straight back to its 1750 level; the sinks draw it down only slowly.
A lower growth rate means carbon dioxide is falling; it is still rising, only more slowly.

Safety card

Low riskLearners carry it out

Hazards

No hazard is listed.

Controls

No control is listed.

Note

Screen-based model with no practical hazard; follow the school's guidelines for device use.

Curriculum references

The NSW syllabus outcomes and Australian Curriculum v9 codes this activity supports. They are references, not a verified or complete curriculum alignment.

Science 7-10 Syllabus (2023), NSW Education Standards Authority (implemented from 2026; codes read at curriculum.nsw.edu.au on 22 and 23 September 2026)SC5-ENV-01 SC5-DA2-01 SC5-WS-05 SC5-WS-06 SC5-WS-07
Australian Curriculum v9AC9S9U03AC9S10U04AC9S9I04AC9S9I05

Sources

The pages the author read to write this activity.

All Concept Studio activities