SACE Stage 2 Earth and Environmental Science · Topic 4: Climate change

Climate evidence.

How do we know Earth’s climate is changing, why it is changing, and what comes next? This lesson is a circuit of eight learning stations. Each one looks at a different kind of evidence: measurements made today, records kept in ice, sea-floor mud, trees and coral, the records people have kept, the human causes, where carbon is stored, what policies can do, the effects on Earth’s spheres, and the models that look ahead.

CoolerWarmer than the 1951–1980 average

Global temperature each year from 1880 to 2025, one stripe a year, compared with the 1951–1980 average: blue years were cooler than that average and red years warmer. Data: NASA GISS Surface Temperature Analysis, version 4 (GISTEMP Team, 2026).

How learning stations work

1 · Rotate

Your teacher gives your group a station to start at. Spend about 12 minutes there, then move on to the next one in the circuit. After station 8 comes station 1.

2 · Record

Each station starts with what to do and ends with a check and a short checklist. Note your evidence on the record sheet, one box for each station, with numbers and where they come from.

3 · Bring it together

When all eight are done, screen 10 links the evidence into one explanation, and screen 11 has eight questions. Working alone? Do the stations in any order: the map shows which you have finished.

The stations

What we are learning

The evidence that Earth’s climate is changing, from today’s measurements back through human records to the geological record; how human activities are changing the greenhouse gases in the air; how carbon is stored and what policies can do; how climate change affects the Earth system; and how models use past climate to predict the future.

I can

1explain how carbon dioxide and temperature are monitored today, and what the measurements show.
2explain how proxies such as ice cores and foraminifera record past climates.
3use historical and prehistorical records to show that climate change has affected regions differently.
4explain the enhanced greenhouse effect, and describe the human activities that add greenhouse gases.
5explain how carbon is stored in Earth’s systems over time-scales from years to millions of years.
6compare how local, national and global policies can affect the levels of greenhouse gases.
7discuss the effects of climate change on Earth’s spheres, and how the spheres affect each other.
8explain how general circulation models are built, tested and used to predict future climate.

SACE Stage 2 Earth and Environmental Science, Topic 4: Climate change. This lesson covers the topic’s last four Science Understanding statements: anthropogenic activities, the effects of climate change on the Earth system, the evidence from records and proxies, and climate models. The natural drivers of climate are in the Climate drivers lesson.

My notebook

What would convince you that Earth’s climate is changing now? List the evidence you would look for. You will come back to this list on screen 10.

Earth’s climate changed many times before there were people. What do you think could be different about the change happening now?

Printable activity

Station record sheet

Three pages, with a box for each station to note the evidence, its numbers and where they come from, and a final question that brings the stations together. Print one per student, or one per group.

Record sheet (PDF) Editable (Word)

1Station 1

Measuring today.

How are carbon dioxide and temperature measured, and what do the measurements show?

The amount of carbon dioxide in the air and the temperature of the planet are measured every day, by instruments on mountains and coasts, on ships, buoys and floats in the ocean, and on satellites. This station looks at how the measurements are made and what the records show.

At this station · about 12 minutes

Read how carbon dioxide and temperature are measured.
Explore the carbon dioxide chart, then switch it to the last three years.
Compare the global and Australian temperature records.
Answer the two checks, and fill in box 1 on your record sheet.

Where the measurements come from

Mauna Loa, Hawaiʻi

The longest record

Charles David Keeling of the Scripps Institution of Oceanography began measuring carbon dioxide on Mauna Loa in March 1958, the start of the longest record of carbon dioxide measured directly in the air. The observatory, now run by NOAA, is 3,397 m up the side of the volcano, above the more polluted lower air and surrounded by bare lava. Since 2019 the carbon dioxide has been measured by cavity ring-down spectroscopy, and only the hours with clean background air go into the averages. When Mauna Loa erupted in November 2022, the measurements moved to the Maunakea Observatories, about 34 km away, until July 2023.

NOAA Global Monitoring Laboratory; Scripps (UC San Diego)

Kennaook / Cape Grim, Tasmania

Southern Ocean air

The Bureau of Meteorology runs this station near the north-west tip of Tasmania, with CSIRO, and it has measured greenhouse gases since April 1976. Westerly to south-westerly winds bring air that has crossed thousands of kilometres of the Southern Ocean: baseline air, representing the well-mixed atmosphere of the Southern Hemisphere. It measures more than 80 gases, including CFCs, and has kept an archive of air samples since 1978. In December 2025 its carbon dioxide was 423.4 ppm, up from 398.8 ppm ten years earlier.

Bureau of Meteorology; CSIRO

From space

Satellites

NASA’s Orbiting Carbon Observatory-2 (OCO-2), launched in July 2014, measures sunlight reflected off Earth’s surface. Carbon dioxide and oxygen each absorb particular wavelengths, so the strength of those bands gives the carbon dioxide in the column of air below. Japan’s GOSAT, launched in January 2009, measures carbon dioxide and methane over almost the whole Earth every three days.

NASA; JAXA

On land

Weather stations

The Bureau’s ACORN-SAT record uses 112 weather stations across Australia, back to 1910. Most stations have moved or had their equipment upgraded at some point, so the record is adjusted to remove those effects, a process called homogenisation, and years can be compared fairly. NASA’s global record uses more than 25,000 weather stations.

Bureau of Meteorology; NASA

In the ocean

Ships, buoys and floats

Global temperature records add sea surface temperatures from ships and buoys (NASA) and from profiling floats (NOAA). Close to 4,000 Argo floats drift through the oceans, sinking to about 2,000 m and rising every 10 days, measuring temperature and salinity on the way up. Australia manages about 7.5% of them, through IMOS and CSIRO.

NASA; NOAA; Argo; IMOS; CSIRO

North Pacific and Tasmania

Ocean pH

Since October 1988 the Hawaii Ocean Time-series has sampled Station ALOHA, in the North Pacific near Hawaiʻi, almost every month. Over nearly 20 years of measurements, surface pH fell by about 0.0019 a year, the rate expected from the ocean taking up carbon dioxide from the air. Off Tasmania’s east coast, a mooring at Maria Island has measured carbon dioxide in the surface water since April 2011.

Dore and others (2009); IMOS

The Keeling Curve

Data

Show the yearly averages as a table

Monthly means from NOAA’s Global Monitoring Laboratory (Dr Xin Lan) and the Scripps Institution of Oceanography (Dr Ralph Keeling). The last year of data is preliminary. NOAA gives 426.07 ppm for September 2026 and 432.3 ppm for May 2026, the peak of the year.

Up and down every year. In the Northern Hemisphere, plants take in carbon dioxide as they grow in spring and summer. Over autumn and winter, microbes break down fallen leaves and other dead plant material and give carbon dioxide back to the air. At Mauna Loa the highest monthly value each year usually comes in May (NOAA), and the swing is biggest in the far north, where plant growth changes most between summer and winter (Scripps).

Always higher. Underneath the yearly swing, the level keeps climbing, and faster than before. In the 1960s it rose by about 0.8 ppm a year; from 2015 to 2024 it rose by about 2.6 ppm a year (NOAA). The average at Mauna Loa was 424.61 ppm in 2024 (NOAA). Averaged over the world’s monitoring network, carbon dioxide reached 426.8 ppm in 2025, 53% above its level before 1750 (WMO).

Temperature: the world and Australia

Data

Show the numbers as a table

Each line is a yearly average compared with an average for a set of base years, called an anomaly. The two records use different base years, so read each against its own zero line. World: NASA GISS Surface Temperature Analysis, version 4 (GISTEMP Team, 2026). Australia: Bureau of Meteorology, ACORN-SAT version 2.7.

What the records show. NASA found 2024 the warmest year in its record, 1.28 °C above the 1951–1980 average; 2025 was 1.19 °C above, effectively tied with 2023. Measured against 1850–1900, the base the IPCC and the World Meteorological Organization use, 2024 was about 1.55 °C warmer and 2025 about 1.43 °C, and the eleven years from 2015 to 2025 were the eleven warmest on record (WMO). In 2025 the heat stored in the top 2,000 m of the ocean reached its highest level since records began in 1960 (WMO).

Australia. Australia’s climate warmed by 1.59 ± 0.23 °C between 1910 and 2025, with most of the warming since 1950 (Bureau of Meteorology). 2019 is still the warmest year on record; 2025 was the fourth warmest. In 2019 there were 40 days with extremely high national average temperatures, about three times more than in any year before 2000 (State of the Climate 2024).

At Mauna Loa, carbon dioxide falls from about May to September every year, then rises again. Why?

Why measure carbon dioxide at places like Mauna Loa and Cape Grim, rather than in a city?

My notebook

Use the chart. About how much did carbon dioxide at Mauna Loa rise from 1960 to 2025? About how big is one year’s swing? Compare the two numbers.

Give two pieces of evidence from this station that Earth is warming now. Include the numbers and where they come from.

2Station 2

Reading proxies.

How do ice, sea-floor shells, trees and corals record climates from before there were thermometers?

Global thermometer records go back to 1850 or 1880, depending on the dataset, and Australia’s national record to 1910. For older climates, scientists use proxies, which NOAA describes as “preserved physical characteristics of the environment that can stand in for direct measurements”. Ice sheets, sea-floor mud, trees, corals and caves all keep records like this.

At this station · about 12 minutes

Explore 800,000 years of carbon dioxide and temperature from Antarctic ice.
Step through how oxygen isotopes in shells record ice ages, then read the LR04 record.
Sort the proxies by what they record.
Answer the check, and fill in box 2 on your record sheet.

800,000 years in Antarctic ice

Data

Show the numbers as a table

Carbon dioxide: Bereiter and others (2015), a composite of Antarctic ice cores (Law Dome for the last 2,000 years, then Dome C, WAIS, Siple Dome, TALDICE, EDML, Dome C, Vostok and Dome C again). Temperature: Jouzel and others (2007), EPICA Dome C, as the difference from the average of the last 1,000 years. Both from NOAA’s National Centers for Environmental Information. Ages are counted back from 1950. The 2025 point is the global average measured in the air (WMO).

How ice keeps a record. As snow is buried and squeezed into ice, the air between the flakes is trapped in bubbles, which “act as time-capsules of the atmosphere” (Australian Antarctic Division). The ice itself keeps a second record: the mix of heavy and light isotopes of hydrogen and oxygen in it depends mostly on the temperature when the snow fell. Near the top of an ice core, yearly layers can be counted. Deeper down, the flowing ice stretches and thins them, so ages come from models of how the ice flows, checked against markers such as big volcanic eruptions (Australian Antarctic Division).

What the cores show. EPICA Dome C, drilled on the Antarctic plateau, reaches back 800,000 years (British Antarctic Survey). Carbon dioxide was low in the cold glacial times and high in the warm ones. In this record it never went above about 300 ppm before industry. At Law Dome, near Australia’s Casey station, snow piles up so fast that the ice keeps recent centuries in fine detail. Ice cores drilled there by CSIRO and the Australian Antarctic Division show carbon dioxide between 275 and 284 ppm before the industrial period, with the lowest values from 1550 to 1800, probably because the climate was colder (Etheridge and others, 1996).

Going further back. Sometime between 1.2 million and 900,000 years ago, the glacial cycles slowed from about every 41,000 years to about every 100,000 years (CNR), and older ice is being drilled to find out why (Australian Antarctic Division). In January 2025 the European Beyond EPICA team reached bedrock 2,800 m down at Little Dome C, and early analyses suggest the ice is at least 1.2 million years old (CNR). Australia’s Million Year Ice Core project began drilling at Dome C North in January 2025 and expects to reach its oldest ice around 2028–29.

Foraminifera. Forams are single-celled organisms, most with shells of calcium carbonate. Some float in the open ocean; others, the benthic forams, live on the sea floor (Burke Museum). Their shells pile up in sea-floor mud, layer on layer, so a sediment core holds a stack of shells in time order. Three things about the shells record climate: their oxygen isotopes; their magnesium/calcium ratio, which rises by about 9% for each 1 °C of warming (Anand and others, 2003) and, used with the oxygen isotopes, lets researchers separate temperature from ice volume (Elderfield and Ganssen, 2000); and which species are present, because some live in warm water and others in cold (Australian Museum).

5.3 million years in deep-sea shells

Data

Show the numbers as a table

The LR04 stack is “an average of 57 globally distributed benthic d18O records”, which measure global ice volume and deep-ocean temperature (Lisiecki, LR04 website). The scale runs downwards: higher values, lower on the chart, mean more ice on land and colder deep water.

What does each proxy record?

0 of 9 sorted

Proxies at a glance
Proxy	Where it is kept	What it records	How far back	Australian example
Ice cores	Ice sheets and glaciers	The air (bubbles), temperature (isotopes), dust and volcanic eruptions	800,000 years (EPICA Dome C); at least 1.2 million (Beyond EPICA, early analyses)	Law Dome: carbon dioxide over the last 1,000 years
Foraminifera	Sea-floor mud	Deep-ocean temperature and ice volume (isotopes), sea temperature (Mg/Ca, species)	5.3 million years (LR04); forams are common fossils for 540 million years	A sea-floor core off South Australia: sea temperatures from its foram species
Tree rings	Long-lived trees	Growing conditions each year: temperature and rainfall	Centuries to thousands of years	Huon pine, Mount Read: warm-season temperatures back to 1600 BC
Corals	Reefs	Sea temperature, salinity and river floods, season by season	The life of the coral, often several centuries	Great Barrier Reef cores back to the early 1600s
Pollen	Lake and swamp mud	The plants growing nearby, and so the climate	Two glacial cycles in north-east Australia	Lynch’s Crater, north Queensland
Speleothems	Caves	Wet and dry times (growth), oxygen isotopes	350,000 years in southern Australia	Naracoorte Caves, South Australia
Fossil leaves	Sedimentary rock	Temperature (leaf shape), carbon dioxide (stomata)	Millions of years	Cenozoic fossil floras (the last 66 million years)

Sources: Australian Antarctic Division; British Antarctic Survey; CNR; Lisiecki and Raymo (2005); University of California Museum of Paleontology; Australian Ocean Data Network; NOAA; Cook and others (2000); AIMS; Kershaw (1986); Turney and others (2001); Weij and others (2024); Greenwood and others (2004); Royer (2001).

Benthic forams from 20,000 years ago have more oxygen-18 in their shells than forams living today. What does this tell you?

My notebook

Use the ice-core chart. What was the lowest carbon dioxide level, and when? What was it in the last warm period, about 125,000 years ago? How does 2025 compare?

Choose two proxies. For each, say what it records, how far back it reaches, and one limitation.

3Station 3

Human records.

What do people’s records add, and did every region change in the same way?

Long before weather stations, people wrote down frosts, harvests and the weather at sea, painted the animals around them, and passed on knowledge of the land and the coast. These records are patchy and local, but they help test what the proxies say, and together with the proxies they show that the warm and cold periods of the last 2,000 years did not happen everywhere at the same time.

At this station · about 12 minutes

Read the six records: three historical and three prehistorical.
Look at when different regions had their coldest century.
Sort the records by type.
Answer the check, and fill in box 3 on your record sheet.

Historical records: written down

London, 1608 to 1814

Frost fairs on the Thames

From the early 1600s to the early 1800s the Thames froze over 24 times, and Londoners held frost fairs on the ice; the last was in early 1814. Winters were harsher in this Little Ice Age, but the river also froze because the 19 narrow arches of the old London Bridge could be blocked by ice. After a wider bridge opened in 1831 and the banks were built up, the river ran too deep and fast to freeze over. So the frost fairs are not a pure temperature record.

London Museum; Royal Museums Greenwich

Burgundy, France, 1354 to 2018

Grape harvests

The town of Beaune has a nearly unbroken record of the date its grapes were picked, from 1354 to 2018. From 1354 to 1987 the harvest began, on average, from 28 September. From 1988 to 2018 it began 13 days earlier. Hot, dry years that were rare in the past “have become the norm since the transition to rapid warming in 1988”.

Labbé and others (2019)

Sydney Cove, 1788 to 1791

A colonial weather journal

William Dawes kept daily weather observations at Sydney Cove from 1788 to 1791. Researchers have used them, with a temperature record kept on board HMS Sirius, to reconstruct Sydney’s climate for those years; the readings appear comparable with modern ones from Observatory Hill, though some biases are likely linked to where the thermometer was placed. The Bureau of Meteorology now holds 39 early sources like this, gathered by the SEARCH project.

Gergis and others (2009); Bureau of Meteorology

Prehistorical records: from before writing

The Sahara, Algeria

Rock art of a green Sahara

Between about 14,800 and 5,500 years ago the Sahara “was nearly completely vegetated and supported numerous perennial lakes” (deMenocal and others, 2000). At Tassili n’Ajjer, more than 15,000 drawings and engravings record the climatic changes and animal migrations, including water-dependent animals such as the hippopotamus (UNESCO).

deMenocal and others (2000); UNESCO

Kakadu, Northern Territory

Rock art and rising seas

Kakadu’s rock art and archaeological sites preserve a record of how people responded to major environmental change, including rising sea levels (Parks Australia). As the sea rose after the last ice age, Kakadu became mostly a saltwater ecosystem, and later its floodplains turned to fresh water again (CSIRO). Most of the X-ray paintings at Ubirr, of fish, waterfowl and other animals, are from what Parks Australia calls the freshwater period, within the last 1,500 years.

Parks Australia; CSIRO

Around Australia’s coast

Stories of the sea coming in

Stories belonging to Aboriginal groups at 21 places around the coast tell of a time when the coastline was flooded by the rising sea. Nunn and Reid worked out how deep the water must have been for each story’s details to be true, compared this with the sea-level record, and calculated that the stories have endured for between 7,250 and 13,070 years. The stories belong to their peoples; the ages are the researchers’ calculations.

Nunn and Reid (2016)

When was it coldest?

Reconstruction

Coldest century of the last 1,000 years
Warmest period of the last 2,000 years

From the PAGES 2k reconstruction of global temperatures for the past 2,000 years (Neukom and others, 2019). “Mid-1800s” is drawn as 1830 to 1870.

Warm and cold periods. Two periods come up often: the Medieval Climate Anomaly, from about 950 to 1250, also called the Medieval Warm Period, and the Little Ice Age, from about 1450 to 1850 (IPCC, 2013). In some regions the medieval warm decades were as warm as the mid-20th century, and in others as warm as the late 20th century, but they were “not as synchronous across regions as the warming” that has come since the mid-20th century (IPCC, 2013). The IPCC’s 2021 report seldom uses either name, “because the timing of these episodes is not well defined and varies regionally”.

Neukom and others (2019) used reconstructions of the past 2,000 years for the whole globe and found “no evidence for preindustrial globally coherent cold and warm epochs”. By contrast, the warmest period of the past two millennia came in the twentieth century “for more than 98 per cent of the globe”.

Different places, different changes

Riversleigh, Queensland

Fossil mammals from 10 to 30 million years ago show habitats changing from humid lowland rainforest to dry eucalypt forests and woodlands, and that most mammal groups living in arid Australia today have rainforest origins.

UNESCO

Great Barrier Reef

Over the past 30,000 years the reef moved seaward as the sea fell and landward as it rose again. It died back five times, when it was left high and dry or when the sea rose faster than it could grow.

Webster and others (2018)

Naracoorte, South Australia

More stalagmites and other cave formations were growing during glacial periods, so southern Australia was wetter in the cold times, not drier, as glacial times have often been portrayed. The warm interglacials were consistently dry.

Weij and others (2024)

Southern Greenland

Norse farmers settled here from the 10th to the 15th century. Lake mud next to a Norse farm shows no big change in temperature while they were there, but a long drying trend, which the researchers think mattered more.

UNESCO; Zhao and others (2022)

Today

The Arctic has warmed nearly four times faster than the globe since 1979, and land has warmed faster than the ocean: 1.59 °C against 0.88 °C between 1850–1900 and 2011–2020.

Rantanen and others (2022); IPCC (2021)

Which kind of record?

0 of 9 sorted

Some people say the Medieval Warm Period shows that today’s warming is natural. What do the PAGES 2k reconstructions show?

My notebook

Choose one historical and one prehistorical record. What does each tell us about past climate, and what is its main limitation?

Use two examples from this station to explain how climate change has affected different regions or species differently.

4Station 4

The human fingerprint.

What is the enhanced greenhouse effect, which human activities add the gases, and how do we know the extra gases come from people?

The natural greenhouse effect keeps Earth habitable: without greenhouse gases, Earth’s average climate would be about 33 °C cooler (CSIRO and Bureau of Meteorology). Human activities are adding greenhouse gases to the air, and these “enhance the natural greenhouse effect and further warm the surface” (Australian Academy of Science).

At this station · about 12 minutes

Step through the model of the enhanced greenhouse effect.
Match each activity to the gas it adds, and read where the emissions come from.
Read the four fingerprints of human carbon dioxide.
Answer the check, and fill in box 4 on your record sheet.

Out of balance. Earth’s energy imbalance, the extra energy coming in compared with going out, grew from 0.50 W/m² over 1971–2006 to 0.79 W/m² over 2006–2018 (IPCC, 2021), and to about 1.12 W/m² over 2013–2025 (Forster and others, writing in Carbon Brief, 2026). How much of the warming is human-caused? The IPCC’s best estimate of the warming caused by people from 1850–1900 to 2010–2019 is 1.07 °C (IPCC, 2021). A 2026 update estimates that human-induced warming reached 1.37 °C in 2025 (Forster and others, 2026), close to the 1.43 °C observed that year (WMO).

Which gas does each activity add?

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Carbon dioxide. Fossil fuels were projected to give off 38.1 billion tonnes of carbon dioxide in 2025, a record, and land-use change such as clearing forests another 4.1 billion tonnes (Global Carbon Budget). Clearing land removes plants “that would otherwise take carbon out of the atmosphere as they grow”, and exposed soil “vents carbon from decayed plant matter into the atmosphere” (NASA Earth Observatory).

Methane, nitrous oxide and HFCs. In 2010–2019, about 65% of methane emissions came directly from human activities: mostly agriculture and waste, then fossil fuels (Saunois and others, 2025). Agriculture produced 74% of human nitrous oxide emissions in the 2010s, mainly from fertilisers and animal waste on crops (Tian and others, 2024). HFCs are synthetic greenhouse gases, mostly used in refrigeration and air conditioning (Australian Government).

In Australia. Australia’s emissions in the year to March 2026 were 25% below 2005, after falling 1.6% over the year (Department of Climate Change, Energy, the Environment and Water, reported by RenewEconomy). South Australia emitted 21.5 million tonnes in 2023–24, and its net emissions were 40% lower than in 2004–05 (SA Department for Environment and Water). After the progress in decarbonising its electricity, transport and agriculture are now its biggest sources (SA EPA, 2023).

Emissions since 1900

Data

Show the numbers as a table

Global Carbon Budget 2025, via Our World in Data. The Budget’s headline totals, such as 38.1 billion tonnes in 2025, take away the carbon dioxide that cement takes back up over time, so they are a little lower than the values here. Land-use change is estimated by models and varies a lot from year to year, and the Budget’s figures for one country are not the same as that country’s own inventory.

Four fingerprints

Carbon isotopes

Less carbon-13

Plants take up carbon-12 in preference to carbon-13, so they have less carbon-13 than the air, and so do fossil fuels, which are ancient plant and animal material. The air’s δ13C, a measure of its share of carbon-13, was about −6.5‰ before the industrial revolution and is now about −8‰. On its own this could come from plants or from fossil fuels, but with carbon-14 measurements and fuel records NOAA concludes that “this decrease is from fossil fuel emissions”, an example of the Suess effect.

NOAA Global Monitoring Laboratory

Oxygen

Less oxygen

Burning uses up oxygen. “Oxygen levels are decreasing globally due to fossil-fuel burning”, by about 19 molecules in every million oxygen molecules each year. The changes are too small to affect human health.

Scripps O2 Program

The budget

Half stays in the air

From 2015 to 2024, the rise in the air’s carbon dioxide was 50% of all human emissions. The ocean took up 29% and the land 21%. The ocean and land are taking carbon dioxide in, not giving it off, so they cannot be the source of the rise.

Global Carbon Budget 2025

Volcanoes

Not volcanoes

Volcanoes on land and under the sea “release less than a percent of the carbon dioxide released currently by human activities”. In 1980, Mount St Helens gave off about as much carbon dioxide in 9 hours as people now release in 2.5 hours.

USGS

The IPCC (2021) puts it this way: “It is unequivocal that the increases in atmospheric carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) since the pre-industrial period are caused by human activities.”

Which observation shows that the extra carbon dioxide comes mainly from burning fossil fuels, rather than from volcanoes or the ocean?

My notebook

Explain the enhanced greenhouse effect in two or three sentences, using the words infrared, absorb and balance.

Which fingerprint do you find most convincing, and why?

5Station 5

Carbon stores.

Where is Earth’s carbon stored, how long does it stay there, and can we put some back underground?

Carbon moves between the air, living things, soil, the ocean and rocks. In the fast carbon cycle it moves through living things, and the time it takes “is measured in a lifespan”. In the slow carbon cycle, “carbon takes between 100-200 million years to move between rocks, soil, ocean, and atmosphere” (NASA Earth Observatory).

At this station · about 12 minutes

Compare how much carbon each store holds.
Sort ten ways carbon moves into the fast cycle and the slow cycle.
Read how carbon dioxide can be stored deep underground, and weigh up the benefits and risks.
Answer the check, and fill in box 5 on your record sheet.

Earth’s carbon stores

Data

Show the numbers as a table

Sizes in billions of tonnes of carbon, mostly from the IPCC (2013), Figure 6.1 and Section 6.1. The air’s carbon is for 2011; before industry it held about 589 billion tonnes. Permafrost: IPCC (2019). Methane hydrates: Ruppel and Kessler (2017), not counting Antarctica. Rocks: NASA Earth Observatory. Estimates for rocks differ a great deal between sources, so no number is drawn.

How long carbon dioxide stays in the air. The ocean and plants take up about half of what people release each year (station 4), and the rest stays in the air, some of it for a very long time. The IPCC (2013) estimates that “about 15 to 40% of emitted CO2 will remain in the atmosphere longer than 1,000 years”, and that removing it all by natural processes “will take a few hundred thousand years”.

The ocean. The ocean holds about 38,000 billion tonnes of carbon dissolved in its water (IPCC, 2013), more than 40 times as much as the air. Before industry, it gave off carbon dioxide “in balance with the carbon the ocean received during rock weathering” (NASA Earth Observatory). Now it takes up carbon dioxide: 29% of human emissions from 2015 to 2024 (Global Carbon Budget).

Frozen ground and frozen gas. Arctic and boreal permafrost holds 1,460 to 1,600 billion tonnes of organic carbon, “almost twice the carbon in the atmosphere” (IPCC, 2019). Methane hydrates are stable only “within a narrow range of pressure and temperature conditions”: mostly in sea-floor sediments under more than about 300 to 500 m of water, and in and beneath permafrost (USGS). About 99% of them are in marine sediments (Ruppel and Kessler, 2017). Warming water is probably breaking some down, but “there is no conclusive proof that hydrate-derived methane is reaching the atmosphere now” (Ruppel and Kessler, 2017), and the IPCC (2021) finds it “very unlikely” that clathrates in permafrost will make a detectable difference to emissions this century.

Blue carbon. Mangroves, seagrasses and tidal marshes “lock up carbon at faster rates than most land ecosystems” (CSIRO). Australia has the largest area of these blue carbon ecosystems in the world, 11 to 15 million hectares, holding 5 to 11% of the carbon they store worldwide (Serrano and others, 2019).

Fast cycle or slow cycle?

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Does the carbon move through living things, within a lifespan, or through rocks, over millions of years? Some activities take carbon out of the slow cycle and put it into the fast one.

Storing carbon dioxide underground

Geosequestration, or carbon capture and storage, pumps carbon dioxide “deep underground, more than a kilometre down, into porous rock formations called reservoirs” (Geological Survey of Western Australia). The carbon dioxide is stored “in the tiny pore spaces present between the grains” of rocks such as sandstone, held in by “overlying impermeable rocks that act like seals”. Over time it dissolves into the water in the rock and reacts to form new minerals (Geoscience Australia).

How the carbon dioxide is held

Diagram

Slide sideways to see the whole picture.

Not to scale sideways. Depths follow the Geological Survey of Western Australia (reservoirs more than a kilometre down; carbon dioxide supercritical below about 800 m) and the Gorgon project, about 2,000 m beneath Barrow Island (Geoscience Australia).

Cooper Basin, South Australia

Moomba

Santos’ Moomba project captures carbon dioxide at the Moomba Gas Plant and stores it in depleted gas reservoirs in the Cooper Basin. It started in September 2024, is designed to store up to 1.7 million tonnes a year, and had stored more than 2 million tonnes by 30 April 2026. Its monitoring plan is regulated by the South Australian Government.

Santos (the operator)

Barrow Island, Western Australia

Gorgon

Since August 2019, Chevron has injected carbon dioxide into sandstone more than 2 km beneath Barrow Island: more than 11 million tonnes by May 2025. The carbon dioxide occurs naturally in the gas fields and is removed from the gas. The plan was to inject 3.3 to 4 million tonnes a year (WA Government), but in 2024–25 it stored only about a third of its target (IEEFA).

WA Government; Chevron; IEEFA

Otway, Victoria

A research site

The CO2CRC Otway site has injected carbon dioxide since 18 March 2008, first into a depleted gas field and later into a saline aquifer 1.5 km down: 100,000 tonnes by December 2024. Fibre-optic sensors detected the carbon dioxide within two days, with less than 300 tonnes injected, and yearly surveys have found “no measurable adverse impacts on soils, groundwater or the atmosphere”.

CO2CRC; Shashkin and others (2022)

Benefits

If the site is chosen and managed well, “the CO2 can be permanently isolated from the atmosphere” (IPCC, 2022). For such sites, the IPCC’s 2005 report judged that the share kept underground is likely to exceed 99% over 1,000 years.
The world’s geological storage capacity, about 1,000 billion tonnes of carbon dioxide, is more than is needed to 2100 to hold warming to 1.5 °C (IPCC, 2022).
For cement and chemicals production, the IPCC (2022) calls it “a critical mitigation option”, though it is less developed there than in the oil and gas industry.

Risks and limits

It depends on the cap rock holding; reservoirs need a seal “to prevent CO2 from escaping to the surface” (Geological Survey of Western Australia), so sites must be monitored.
A power station with capture needs roughly 10 to 40% more energy to make the same electricity (IPCC, 2005).
About 50 million tonnes a year is captured worldwide (Geoscience Australia), compared with the 38.1 billion tonnes of carbon dioxide from fossil fuels projected for 2025 (Global Carbon Budget).
About 65% of capture capacity is at natural gas processing plants (IEA), and the IPCC (2022) notes that “CCS can allow fossil fuels to be used longer”.

Burning coal, oil and gas moves carbon from the slow cycle into the fast cycle. Why does this matter for the climate?

My notebook

Choose three carbon stores. For each, say how much carbon it holds and whether carbon stays there for years, thousands of years or millions of years.

A company plans to store carbon dioxide under South Australia. Give one benefit and one risk, with evidence, and say what you would want to know before deciding.

6Station 6

Policies.

How can local, national and global policies change the levels of greenhouse gases in the air?

Policies are decisions by councils, state and national governments, and groups of countries. They can limit how much of a gas is made or released, or change how energy is produced and used. One global policy has a clear result in the air itself: the treaty that controls CFCs.

At this station · about 12 minutes

Compare CFCs and carbon dioxide in the air since 1979.
Read the policies at each level, from the world to your council.
Sort ten policies by level.
Answer the check, and fill in box 6 on your record sheet.

CFCs and carbon dioxide since 1979

Data

Show the numbers as a table

CFCs: global yearly means from NOAA’s Global Monitoring Laboratory, in parts per trillion (ppt), a million times smaller than ppm. Carbon dioxide: yearly means at Mauna Loa (NOAA and Scripps); the last year is preliminary. Each gas has its own panel and scale.

The Montreal Protocol. Adopted on 16 September 1987, it “regulates the production and consumption of nearly 100 man-made chemicals” that deplete the ozone layer, including CFCs, and it is “one of the rare treaties to achieve universal ratification” (UNEP). NOAA says the falls in CFCs in the air “reflect large declines in emissions in response to global controls on production and trade of these gases”. CFCs also trap heat, and NOAA counts them in its greenhouse gas index. Cutting the emissions of ozone-depleting substances such as CFCs is estimated to avoid about 0.5 to 1 °C of warming by the middle of this century (WMO, 2022). Over Antarctica, the ozone layer is expected to return to its 1980 levels around 2066 (WMO, 2022).

Carbon dioxide is different. Carbon dioxide comes from burning fossil fuels for energy, and from clearing land, all over the world. Fossil fuel emissions were projected to reach a record in 2025 (Global Carbon Budget), and about half of each year’s emissions stays in the air (station 4), so the level keeps rising.

Policies at four levels

Global

Treaties between countries

Montreal Protocol (1987) and its Kigali Amendment (2016), which added a phase-down of HFCs. HFCs do not deplete the ozone layer but are powerful greenhouse gases (UNEP), and the phase-down is expected to avoid 0.3 to 0.5 °C of warming by 2100 (WMO, 2022).

Kyoto Protocol (adopted 1997, in force 2005): binding targets for 37 industrialised countries and economies in transition, on average 5% below 1990 levels over 2008–2012 (UNFCCC). Australia’s target was 8% above 1990.

Paris Agreement (2015): to keep warming “well below 2°C” and pursue efforts to limit it to 1.5 °C. Each country sets its own targets, on “a five-year cycle of increasingly ambitious climate action” (UNFCCC).

National

Australian Government

Climate Change Act 2022: net emissions 43% below 2005 levels by 2030 and zero by 2050. In September 2025 the government set a 2035 target of 62 to 70% below 2005.

Safeguard Mechanism: each facility emitting more than 100,000 tonnes of carbon dioxide equivalent a year has a limit, its baseline, which falls by 4.9% a year to 2030 (Clean Energy Regulator).

Renewable Energy Target: an extra 33,000 GWh of renewable electricity every year from 2020 to 2030, met in January 2021. HFC import quotas from 2018, falling to 15% of the starting level by 2036.

Carbon price, 2012 to 2014: starting at $23 a tonne of carbon dioxide equivalent, repealed from 1 July 2014.

State

South Australia

The state’s climate change Act, amended in March 2025, sets three targets: net emissions at least 60% below 2005 levels by 2030, net zero by 2050, and 100% net renewable electricity by the end of 2027.

South Australia’s last coal-fired power station, the Northern Power Station at Port Augusta, closed on 9 May 2016 (AER). In 2023–24, 69.7% of the state’s electricity was renewable on a net basis (SA Government).

Local

Councils

The City of Adelaide buys 100% renewable electricity for its operations and has 1.1 MW of solar panels. By 2023–24 it had cut its operations’ emissions by 54% from 2019–20, and its goal is 75% by 2029–30. It stopped buying offsets in 2024–25.

Councils also build to cut emissions: the City of Charles Sturt has built an all-electric community centre and library with a 50 kW solar system (SA Department for Environment and Water case study, supplied by the council).

What has changed. Australia’s emissions in the year to March 2026 were 25% below 2005 levels, and electricity emissions fell 3.7% in that year as renewable generation grew (Department of Climate Change, Energy, the Environment and Water, reported by RenewEconomy). Working out how much one policy did is harder. For the carbon price, a working paper from the Australian National University estimated it cut electricity emissions by 11 to 17 million tonnes over its two years, but warned of “fundamental difficulties in attributing observed changes in demand and supply to specific causes” (O’Gorman and Jotzo, 2014).

Comparing the levels. When you compare policies, ask three questions. How much of the world’s emissions does it cover? Can it be enforced, or does it rely on each country, state or council choosing to act? Can its effect on the gases be measured?

Which level is it?

0 of 10 sorted

CFCs in the air began to fall after the Montreal Protocol, but carbon dioxide has kept rising. Which explanation fits the evidence?

My notebook

Compare one global policy and one national or state policy: which gas each targets, how much of the emissions it covers, and the evidence of its effect.

Suggest one thing your school or council could do. Which greenhouse gas would it change, and how would you measure the effect?

7Station 7

Effects on the spheres.

What is climate change doing to the atmosphere, hydrosphere, biosphere and geosphere, and how does a change in one sphere affect the others?

The Earth system has four interacting spheres: the geosphere, atmosphere, hydrosphere and biosphere. The SACE subject outline puts it this way: “A change in any one ‘sphere’ can affect others on a range of temporal and spatial scales.” Water in all its forms, including ice, belongs to the hydrosphere.

At this station · about 12 minutes

Read the effects on each sphere, then sort eight of them.
Melt the ice in the two tanks, and read the sea-ice records.
Put the permafrost chain in order.
Answer the check, and fill in box 7 on your record sheet.

Effects on each sphere

Atmosphere

Heat, rain and fire weather

Hot extremes, including heatwaves, have become more frequent and more intense across most land regions since the 1950s (IPCC, 2021). In Australia, very high monthly maximum temperatures that occurred under 2% of the time in 1960–1989 occurred 11% of the time in 2009–2023. Cool-season rainfall in the south-west has fallen by around 16% since 1970, wet-season rainfall in the north has risen by around 20% since 1994, and dangerous fire weather days have become more frequent across most regions.

IPCC (2021); State of the Climate 2024

Hydrosphere

Sea level, acidity and ice

Global mean sea level rose 0.20 m between 1901 and 2018, and the rate reached 3.7 mm a year in 2006–2018. From 1971 to 2018, 50% of the rise came from thermal expansion, 22% from glaciers, 20% from ice sheets and 8% from water stored on land. Marine heatwaves have about doubled in frequency since the 1980s. The surface waters around Australia are about 30% more acidic than in the 1880s, and between 2002 and 2025 Greenland lost about 264 billion tonnes of ice a year and Antarctica about 135 billion.

IPCC (2021); State of the Climate 2024; NASA

Biosphere

Reefs, kelp, fish and farms

The Great Barrier Reef has had mass coral bleaching in 1998, 2002, 2016, 2017, 2020, 2022, 2024 and 2025 (AIMS). Off Tasmania, at least 95% of the dense giant kelp forests have been lost as the warmer East Australian Current reached further south (IMAS), and 45 species of Tasmanian fish have shifted their ranges in ways thought to be climate related (Last and others, 2011). The Bramble Cay melomys, a rodent, is listed as extinct; its extinction “has been linked to human-induced climate change leading to the inundation of its coral cay habitat” (Australian Government). Changes in seasonal conditions from 2001 to 2020 cut average farm profits by 23% (ABARES).

AIMS; IMAS; Last and others (2011); Australian Government; ABARES

Geosphere

Frozen ground, coasts and soil

Permafrost warmed by 0.29 °C worldwide between 2007 and 2016 (IPCC, 2021). When the ice in it melts, “the ground can collapse”, damaging roads, pipelines and buildings, and triggering landslides (NSIDC). On the coast, Victoria’s Commissioner for Environmental Sustainability says: “Sea-level rise is one of the biggest threats associated with climate change to coastal areas.” Where ice-age ice sheets once pressed the land down, the land is still “rebounding from the heavy weight of those long-vanished glaciers” (NASA).

IPCC (2021); NSIDC; CES Victoria; NASA

Which sphere?

0 of 8 sorted

Sea ice at its smallest

Data

Show the numbers as a table

Monthly average extent, in millions of square kilometres: September in the Arctic and February around Antarctica, the months when each is smallest. NSIDC Sea Ice Index, version 4, via Our World in Data; 1979 is not in this copy.

Two poles, two stories. Arctic sea ice in September has shrunk by 11.6% per decade since 1979 (NSIDC), and in 2011–2020 the late-summer Arctic sea ice area was smaller than at any time in at least the past 1,000 years (IPCC, 2021). Antarctic sea ice showed no significant trend from 1979 to 2020 (IPCC, 2021), but it has mostly been low since 2016, and February 2023 was the lowest February on record (NSIDC data). NSIDC says the low extent since 2016 “is now thought to be linked to warming in the uppermost ocean layer”.

Fire joins the spheres. In the 2019–20 Black Summer, more than 24 million hectares burnt and nearly three billion animals were killed or displaced (Royal Commission, 2020). From November 2019 to January 2020 the fires released about 715 million tonnes of carbon dioxide (van der Velde and others, 2021). In an extreme fire year such as the Black Summer, fires in Australia can release as much carbon dioxide as all of the country’s fossil fuel use, or more, though regrowth over the following years to decades takes back a large part (State of the Climate 2024). After the fires, soil erosion and runoff into waterways increased (Parliamentary Library). Climate models show that human-caused climate change made fire weather as extreme as in 2019–20 at least 30% more likely than in 1900 (van Oldenborgh and others, 2021).

Weaker carbon sinks. The ocean and land take up about half of the carbon dioxide people release (station 4), but climate change is making them less effective. Averaged over 2015–2024, the land sink was 25% and the ocean sink 7% smaller than they would have been without climate change and climate variability (Global Carbon Budget). The IPCC (2021) projects that under scenarios with increasing emissions, “the ocean and land carbon sinks are projected to be less effective at slowing the accumulation of CO2 in the atmosphere”.

When permafrost thaws

Chain

Tap the steps in order, starting with the air. Each step happens in one or more of the spheres.

Past warm climates as analogues

A climate analogue is a time in the past whose climate resembles a possible future one. Its rocks, fossils and ice show what happened to the spheres when Earth was warmer. The IPCC finds that projections of sea level over thousands of years “are consistent with reconstructed levels during past warm climate periods”.

Two warm periods compared with today
Period	When	Carbon dioxide	Global temperature, compared with 1850–1900	Sea level
Last Interglacial	129,000 to 116,000 years ago	266 to 282 ppm	0.5 to 1.5 °C warmer, about 125,000 years ago	Likely 5 to 10 m higher than today
Mid-Pliocene Warm Period	3.3 to 3.0 million years ago	360 to 420 ppm, for a sustained period	2.5 to 4 °C warmer	Very likely 5 to 25 m higher than today
Today	2025	426.8 ppm (WMO)	About 1.4 °C warmer (WMO)	0.20 m higher in 2018 than in 1901

Source: IPCC (2021), Working Group I, Summary for Policymakers (A.2.2, B.5.4), Chapter 2 and Table 2.1. The mid-Pliocene’s temperature range is similar to the range projected under the intermediate scenario for the end of the 23rd century, 2.3 to 4.6 °C (IPCC, 2021).

Why does melting land ice raise sea level, while melting sea ice barely does?

My notebook

Choose two spheres. Give one effect of climate change on each, with a number and where it comes from.

Use the Black Summer fires or thawing permafrost to explain how a change in one sphere affects the others.

8Station 8

Climate models.

How do general circulation models work, how are they tested on past climates, and what do they predict?

NOAA describes a global climate model, or GCM, as “a complex mathematical representation of the major climate system components (atmosphere, land surface, ocean, and sea ice), and their interactions”. The SACE outline calls them general circulation models. They are built from the laws of physics, tested against past climates, and improved as computers become more powerful and the evidence grows.

At this station · about 12 minutes

Look at Australia on six model grids, from 1990 to today.
Read how a model runs and how models are tested.
Compare the warming projected under five scenarios.
Answer the two checks, and fill in box 8 on your record sheet.

How a model runs

Divide the world into boxes. “Climate models divide the globe into a three-dimensional grid of cells representing specific geographic locations and elevations” (NOAA GFDL).
Use the laws of physics. In each cell, equations based on the conservation of energy, mass and momentum work out how fast the temperature, wind, moisture and other quantities are changing.
Step forward in time. The model assumes each rate of change holds for a short time, updates every cell, and then “calculations start over again for the next time interval” (NOAA GFDL).
Simplify what is too small to see. Processes smaller than a cell, “such as the transformation of cloud moisture into rain”, are “treated in a simplified way” (IPCC, 2021). This is called parameterisation, and it is guided by physics and observations.
Couple the parts. The atmosphere, land, ocean and sea ice “exchange fluxes of heat, water, and momentum” and “interact with one another as a coupled system” (NOAA GFDL). Earth system models add the carbon cycle: CSIRO’s ACCESS-ESM1.5 “simulates the carbon cycle alongside climate”.

Australia’s model. ACCESS, the Australian Community Climate and Earth System Simulator, was developed by CSIRO with the Bureau of Meteorology, Australian universities and international collaborators. ACCESS-CM2’s atmosphere grid is 1.875° by 1.25°, with 85 levels, coupled to an ocean model at 1° (CSIRO). Global models’ cells are about 200 km across, so for regional detail their results are downscaled (Climate Change in Australia): NARCliM2.0 runs regional models at 20 km for Australasia and at 4 km for south-east Australia (Di Virgilio and others, 2025).

Testing models on the past

The last 170 years

Hindcasts

Models are run from 1850 and compared with what was observed. CMIP6 models reproduce the observed global temperature trend and its variability closely enough to detect the human-caused warming. Runs with only natural drivers, the Sun and volcanoes, do not warm like the real world: “The observed rate can only be reproduced when human influence is added to the simulations.”

IPCC (2021), Chapter 3 and FAQ 3.1

Past climates

Ice ages and warm times

Proxies like those at station 2 give the temperatures of past cold and warm climates. The average of many models “captures the proxy-reconstructed global-mean surface air temperature (GSAT) change during past high- and low-CO2 climates”, though models often underestimate large differences from the present day.

IPCC (2021), Chapter 3

Old predictions

Did they come true?

Hausfather and others (2020) compared 17 projections of global temperature, made between 1970 and 2007, with the warming observed up to 2017. Ten closely matched. After allowing for differences between the carbon dioxide and other drivers each model assumed and what really happened, 14 did.

NASA; Hausfather and others (2020)

Models keep changing. The models in the IPCC’s first report, in 1990, typically had ten atmospheric layers over a single-layer “slab” ocean; by 2007 they had about thirty levels in both atmosphere and ocean (IPCC, 2007). Modelling groups keep adding processes, such as “land and ocean carbon cycles, interactions between cloud droplets and aerosols, and ice sheets” (NOAA GFDL). More than 50 modelling centres took part in the sixth phase of the Coupled Model Intercomparison Project, CMIP6 (WCRP), and for most large-scale indicators its models simulate recent climate better than the previous generation (IPCC, 2021).

What the models project

Projections

Show the numbers as a table

Change in global surface temperature from 1850–1900, in °C: the best estimate (the line) and the very likely range (the bar). IPCC (2021), Working Group I, Summary for Policymakers, Table SPM.1, assessed from models and other lines of evidence.

Why a range? Each scenario is a possible path of emissions, from very low (SSP1-1.9) and low (SSP1-2.6) through intermediate (SSP2-4.5) to high (SSP3-7.0) and very high (SSP5-8.5); which path the world follows depends on people. “Global surface temperature will continue to increase until at least mid-century under all emissions scenarios considered”, and “Global warming of 1.5°C and 2°C will be exceeded during the 21st century unless deep reductions in CO2 and other greenhouse gas emissions occur in the coming decades” (IPCC, 2021). Within each scenario, the bar shows the uncertainty in how strongly the climate responds. The IPCC’s best estimate of the long-term warming from doubling carbon dioxide is 3 °C, very likely between 2 °C and 5 °C.

Predicting El Niño. The Bureau of Meteorology’s ACCESS-S “brings together atmosphere, ocean, land and ice models”, and the Bureau uses it to forecast the El Niño–Southern Oscillation and the Indian Ocean Dipole. Each long-range forecast is based on 99 runs started from different initial conditions, which is why “most of our long-range forecast information is provided as probabilities”. Near Australia its grid boxes are about 60 km square for the atmosphere and land, and about 25 km for the ocean. Forecasts made in autumn for winter and spring are less certain, because of “the autumn predictability barrier” (Bureau of Meteorology).

Climate models reproduce the warming since 1850 only when human influences are included. What does this test show?

For 2081–2100, the best estimates range from 1.4 °C under SSP1-1.9 to 4.4 °C under SSP5-8.5. What mostly causes this spread?

My notebook

Explain how a general circulation model works in three or four steps, and give one of its limitations.

How useful are climate models for predicting future climate? Use the tests on the past in your answer.

10All the stations

Putting it together.

How do we know Earth’s climate is changing, why it is changing, and what comes next?

Each station gave one kind of evidence. Together they make one argument. Build it step by step, then sort ten pieces of evidence by the claim each one supports.

Build the argument

Chain

Tap the steps in order. Each one rests on evidence from the stations shown in brackets.

Which claim does it support?

0 of 10 sorted

Key idea

Measurements, proxies and people’s records show that Earth’s climate is changing, and changing almost everywhere at once. Isotopes, oxygen and the carbon budget show that the extra carbon dioxide comes from fossil fuels and land clearing. The warming is changing every sphere, and models tested on the past show that how much more comes depends on how much greenhouse gas people release.

My notebook

Look back at the evidence you listed on screen 1. Which pieces did you find at the stations, and what would you add now?

How do we know Earth’s climate is changing, and that human activities are the main cause? Use evidence from at least three stations, with numbers and where they come from.

11Show what you know

Show what you know.

Eight questions, one for each of the I can statements on screen 1. You get one try at each, so think before you tap.

Which single measurement best shows that Earth as a whole is gaining heat?

One layer of an Antarctic ice core holds air with 280 ppm of carbon dioxide; another holds 190 ppm. What does the 190 ppm layer most likely record?

Which finding shows that past climate change affected different regions differently?

What makes the enhanced greenhouse effect “enhanced”?

Which store holds most of Earth’s carbon, and changes most slowly?

Why is a global agreement needed to change the level of carbon dioxide in the air?

Which is an example of a feedback between two spheres?

Clouds are far smaller than a model’s grid cells. How do climate models include them?

Printable activity

Station record sheet

Three pages, with a box for each station to note the evidence, its numbers and where they come from, and a final question that brings the stations together. Print one per student, or one per group.

Record sheet (PDF) Editable (Word)

For teachers

Curriculum

SACE Board of South Australia, Stage 2 Earth and Environmental Science Subject Outline (accredited for teaching at Stage 2 from 2018, reissued for 2025), Topic 4: Climate change. NT students take the subject as part of the NTCET. The topic outline says:

In this topic, students explore how climate variables have changed over geological time, due to natural processes occurring in the Earth’s atmosphere, outside the atmosphere, and within the Earth. They recognise why significant variation in the Earth’s climate has the potential to produce a major effect on the Earth’s systems and on life on this planet.

This lesson covers the topic’s last four Science Understanding statements. The first five, the natural drivers of climate, are in the Climate drivers lesson.

Anthropogenic activities affect climate conditions.
Explain the enhanced greenhouse effect.
Describe anthropogenic activities that are changing the levels of greenhouse gases.
Compare how local, national, and global policies can affect the levels of these gases.
Explain how carbon is stored in Earth’s systems over a variety of time-scales.

Climate change affects the Earth system.
Discuss the effects of climate change on the Earth’s spheres.

Geological, prehistorical, historical, and contemporary records provide evidence that climate change has affected different regions and species differently over time.
Investigate how contemporary levels of CO2 and temperature are monitored, and provide evidence of contemporary climate change.
Explore how climate proxies are used to provide evidence of climate change.

Models for predicting climate change are based on past climate data and are continually changing.
Explain how general circulation models can be used to predict future climate change.

Where the lesson covers them:

Anthropogenic activities: the enhanced greenhouse effect and the activities that add the gases, station 4 (a four-step model, a sort of activities and gases, emissions since 1900 and four fingerprints of human carbon dioxide); local, national and global policies, station 6 (CFCs and carbon dioxide since 1979, policies at four levels and a sort); carbon stored over a variety of time-scales, station 5 (the sizes of Earth’s carbon stores, the fast and slow carbon cycles, permafrost, methane hydrates and blue carbon). The outline’s contexts on land clearing and fossil fuels (station 4), the carbonate–silicate cycle (station 5; screen 6 of Climate drivers goes further), state and national policies and global policy on CFCs (station 6) are covered.
Climate change affects the Earth system: station 7 (effects on each sphere, sea ice and land ice in a two-tank model, sea-ice records since 1980, fire, weakening carbon sinks, the permafrost chain, and past warm climates as analogues). Clathrates and the risks and benefits of geosequestration, two more of the outline’s contexts, are at station 5.
Records: how carbon dioxide and temperature are monitored, and the evidence of contemporary change, station 1; proxies, station 2 (800,000 years of ice cores, oxygen isotopes in forams and the LR04 stack, and seven proxies with Australian examples); historical and prehistorical records, and different regions and species, station 3 (frost fairs, grape harvests, a colonial weather journal, rock art, Aboriginal stories of the rising sea, when each region was coldest, and examples from Riversleigh to Greenland). The Medieval Warm Period and the Little Ice Age, from the outline’s contexts, are at station 3.
Models: station 8 (Australia on six model grids, how a model runs, hindcasts, past climates and past projections, how models have changed, the IPCC’s scenarios, and El Niño forecasts with ACCESS-S).

Science as a human endeavour runs through the lesson. Its key concepts in the outline include these, used at the stations shown:

Development of complex scientific models and/or theories often requires a wide range of evidence from many sources and across disciplines.

The stations behind screen 10 draw on chemistry (isotopes and oxygen), physics (the energy balance), geology (ice, sea-floor shells and caves), biology (reefs, kelp and fish), and history and archaeology (harvests, journals and rock art). Station 8 tests models against past climates reconstructed from proxies.

New technologies improve the efficiency of scientific procedures and data collection and analysis. This can reveal new evidence that may modify or replace models, theories, and processes.

Station 1: cavity ring-down spectroscopy at Mauna Loa, satellites and Argo floats; station 2: drilling ice older than a million years; station 3: the PAGES 2k reconstructions, which found no evidence for globally coherent warm or cold epochs in the 2,000 years before industry; station 8: model grids shrinking from about 500 km to 20 km.

Collaboration between scientists, governments, and other agencies is often required in scientific research and enterprise.

Station 1: Kennaook / Cape Grim (Bureau of Meteorology and CSIRO) and Argo (IMOS and CSIRO); station 2: EPICA, Beyond EPICA and the Million Year Ice Core project; station 8: ACCESS (CSIRO, the Bureau and universities), CMIP6 (more than 50 modelling centres) and the IPCC.

Science informs public debate and is in turn influenced by public debate; at times, there may be complex, unanticipated variables or insufficient data that may limit possible conclusions.

Station 6: how much the carbon price cut emissions, and how to compare policies; station 5: Gorgon’s results against its plan; station 3: the frost fairs as a temperature record, and the Medieval Warm Period.

The acceptance and use of scientific knowledge can be influenced by social, economic, cultural, and ethical considerations.

Station 6: policies at four levels; station 3: Aboriginal stories of the rising sea, which belong to their peoples.

The use of scientific knowledge may have beneficial or unexpected consequences; this requires monitoring, assessment, and evaluation of risk, and provides opportunities for innovation.

Station 5: monitoring the carbon dioxide stored at Moomba and Otway; station 6: HFCs, which do not deplete the ozone layer but are powerful greenhouse gases (UNEP), added to the Montreal Protocol by the Kigali Amendment.

Assessment design criteria the tasks give practice for: KA1 and KA2 (the checks, sorts and record sheet), KA3 (comparing policies at station 6, weighing geosequestration at station 5, and people’s records at station 3), KA4 (the record sheet and the explanation on screen 10), IAE3 (reading the data at stations 1, 2, 4, 6, 7 and 8) and IAE4 (the limits of records and models: adjusting temperature records at station 1, the frost fairs at station 3, and testing models at station 8).

How the lesson is taught

The lesson is a circuit of learning stations. Small groups move through a set of stations, each with its own task, so the class works on different parts of the topic at the same time and comes together at the end. Bulunuz and Jarrett (2010) ran six hands-on learning stations on earth science concepts with 29 practising teachers in a graduate program, and found that “participation in hands-on stations on these science concepts changed teachers’ understandings of these topics”. Here each station opens with a question and a short task list, gives evidence to read and something to do with it, and ends with a check and a box on the record sheet.

Setting up. The stations are screens, not places, so each group keeps its own device and its own saved progress. Make eight groups of three or four, or four groups that each do two neighbouring stations per rotation. Give each group a different starting station. The strip at the top of each station and the map on screen 1 show which stations are done. If you use fixed station devices instead, clear saved answers between classes (below), and use the record sheets as the record of each group’s work.
Timing. About 12 minutes a station, plus a minute to move, so the eight rotations take about 105 minutes. With 60-minute lessons, allow three. Lesson 1: screen 1 together (the stripes, the notebook questions and how the stations work), then three rotations. Lesson 2: four more rotations. Lesson 3: the last rotation, screen 10 in pairs, a class discussion in which each group reports the evidence from one station, then screen 11 alone. With 50-minute lessons, allow four: screen 1 and two rotations, three rotations in each of the next two lessons, then screens 10 and 11.
Working alone. Students can do the stations in any order; the map on screen 1 shows which are done.
The record sheet has one box for each station and a final question that matches screen 10. Collect it as evidence of learning, or use the final question as KA4 practice.

Handle with care

Some students are anxious about climate change. Keep the focus on evidence and on what people can change: station 8 shows that how much more warming comes depends on emissions, and stations 4 and 6 show emissions already falling in Australia and South Australia. Avoid doom framing, and point students who are distressed to your school’s wellbeing staff.
The stories of the sea coming in, at station 3, belong to the Aboriginal groups whose stories they are. The lesson does not retell any story, and the ages are the researchers’ calculations (Nunn and Reid, 2016). If you discuss them, follow your school’s protocols and, where you can, the guidance of local Aboriginal communities. Treat the Kakadu rock art with the same care: it is part of the living culture of the park’s Aboriginal traditional owners.
Some students may have lived through the 2019–20 fires. Station 7 reports the fires’ effects on the spheres, not personal losses; students can choose permafrost instead of fire for the notebook question.
Station 6 describes what policies do and the evidence of their effects. Students may hold strong views about particular policies or parties; keep the discussion on the evidence, and on the three questions the station asks: how much of the emissions a policy covers, whether it can be enforced, and whether its effect can be measured.
Australia’s emissions figures change as the national inventory is revised. The Minister reported the year to June 2025 as 28.5% below 2005; the update for the year to March 2026 gave 25% below 2005 even though emissions fell 1.6% over that year (RenewEconomy), which suggests the whole series was revised. The lesson uses the March 2026 figure. Compare figures only within one edition, and check the Department’s latest quarterly update before quoting a number.

Misconceptions the stations target

Climate has always changed, so today’s change must be natural (stations 3, 4 and 8). Over the past 2,000 years, warm and cold periods came at different times in different regions; today’s warming is almost everywhere at once, the extra carbon is fossil carbon, and models reproduce the warming only with human influence.
Volcanoes give off more carbon dioxide than people (station 4). They give off less than 1% as much (USGS).
The yearly zigzag in the Keeling Curve comes from people burning more fuel in winter (station 1). It follows northern plants growing and decaying.
Melting sea ice is a main cause of sea level rise (station 7). Floating ice already displaces its own weight of water; the rise comes from warming water expanding and from ice on land.
Carbon dioxide will fall as soon as emissions start to fall (station 6). About half of each year’s emissions stays in the air, so the level keeps rising until emissions fall to what the ocean and land can take up.
The ozone hole causes global warming (station 6 and screen 11). They are different problems, linked because CFCs both destroy ozone and trap heat.
The Medieval Warm Period was warmer everywhere than today (station 3). Its warm decades came at different times in different regions.
Geosequestration takes carbon dioxide out of the air (station 5). Most capture is at gas plants and other large sources, before the carbon dioxide reaches the air; only capture from the air or from biomass removes it (IEA; IPCC, 2022).
Climate models are guesses that can be made to say anything (station 8). They are built from physics, tested against past climates and the observed warming, and most past projections matched what happened.

About the data and the pictures

Temperature (the stripes on screen 1 and the chart at station 1): NASA GISS Surface Temperature Analysis, version 4 (GISTEMP Team, 2026), global yearly means compared with 1951–1980. NASA’s data files refuse automated download, so the values come from the datasets/global-temp mirror on GitHub; 2024 (1.28 °C) and 2025 (1.19 °C) match NASA’s published figures, and the other years were not checked against NASA’s file. Australia: the Bureau of Meteorology’s ACORN-SAT yearly means compared with 1961–1990, read from the Bureau’s time-series file. That file gives 2025 as 1.25 °C; the Bureau’s Annual Climate Statement, issued before ACORN-SAT version 2.7, printed 1.23 °C.
The Keeling Curve: NOAA Global Monitoring Laboratory (Dr Xin Lan) and Scripps Institution of Oceanography (Dr Ralph Keeling), monthly and yearly means at Mauna Loa, from the datasets/co2-ppm mirror on GitHub because NOAA’s files refuse automated download. These match NOAA’s published figures: the yearly means for 2022 and 2023 (an older copy of NOAA’s file) and 2024 (NOAA Climate.gov), the monthly means for September 2025 and September 2026 (NOAA’s pages), and May 2026 (NOAA’s 432.3 ppm, as reported by UC San Diego). The 2025 yearly mean in the file, 427.35 ppm, is preliminary and was not confirmed from NOAA; the page quotes the WMO’s global figure for 2025, 426.8 ppm.
Ice cores and forams: Bereiter and others (2015), the Antarctic carbon dioxide composite; Jouzel and others (2007), the EPICA Dome C temperature estimate; Lisiecki and Raymo (2005), the LR04 stack. The files are NOAA NCEI’s, as packaged with the open-source Pyleoclim library, version 1.3.0. Spot checks against NCEI’s and Lisiecki’s originals matched (six carbon dioxide rows, including the lowest value, 173.7 ppm about 667,000 years ago; two temperature rows; the first LR04 row).
Emissions (station 4): Global Carbon Budget 2025, via Our World in Data (licence CC BY 4.0). The Budget’s headline totals, such as 38.1 billion tonnes of fossil carbon dioxide in 2025, include the carbon dioxide that cement takes back up, so they are a little lower than the values in the data file.
CFCs (station 6): NOAA Global Monitoring Laboratory, global yearly means used for the Annual Greenhouse Gas Index, read twice and compared value by value. Sea ice (station 7): NSIDC Sea Ice Index, version 4 (Fetterer and others, 2025), via Our World in Data, because NSIDC’s files refuse automated download; September 2026 matches NSIDC’s published 4.81 million km². Projections (station 8): IPCC (2021), Table SPM.1.
Carbon stores (station 5): IPCC (2013), Chapter 6, Section 6.1 and Figure 6.1; IPCC (2019) for permafrost; Ruppel and Kessler (2017) for methane hydrates. The fossil fuel reserves are the ranges printed in Figure 6.1. Rocks hold most of Earth’s carbon (NASA Earth Observatory gives 65,500 billion tonnes), but published estimates differ widely, so no number is drawn.
The models and diagrams say what they simplify. The greenhouse model shows the idea, not the real sizes of the energy flows. The isotope model draws far more heavy water than the real one molecule in about 500. The two tanks hold fresh water, so they leave out the small extra rise, about 2.6%, from fresh meltwater in salty sea. The geosequestration cross-section is to scale downwards but not sideways. The model grids were drawn by Ausgeology from the Natural Earth coastline: the four IPCC-era grids are regular grids of 5.625°, 2.8125°, 1.875° and 1.125°, close to the cell sizes the IPCC (2007, Figure 1.4) shows, as given by Windows to the Universe; ACCESS-CM2’s grid is CSIRO’s; the regional grid is 0.2°, about 20 km.
Station 3’s timeline of the coldest century is from Neukom and others (2019); their “mid-nineteenth century” is drawn as 1830 to 1870. The station 7 table of past warm climates is from IPCC (2021), Working Group I, Chapter 2 and Table 2.1.

Answers at a glance

Station checks: q-today1, plants growing and decaying; q-today2, well-mixed background air; q-proxy, more ice on land and colder deep water; q-records, different times in different regions, today almost everywhere at once; q-finger, less carbon-13 and less oxygen; q-carbon, carbon locked away for millions of years added faster than the slow cycle can take it back; q-policy, global controls cut CFC emissions while carbon dioxide emissions are at a record; q-spheres, sea ice already floats; q-models1, natural causes alone cannot explain the warming; q-models2, the different emissions paths.
Station 1 notebook: carbon dioxide rose from 316.9 ppm (1960) to 427.35 ppm (2025, preliminary), about 110 ppm; one year’s swing is about 6 ppm (May 2025, 430.5 ppm; September 2025, 424.4 ppm).
Station 2 notebook: lowest carbon dioxide 173.7 ppm, about 667,000 years ago; about 273 to 277 ppm from 125,000 to 128,000 years ago, and 286 ppm about 128,500 years ago; 426.8 ppm in 2025 (WMO).
Proxies: bubbles, the air; isotopes in the ice, temperature; oxygen isotopes in benthic forams, ice on land or temperature; magnesium and calcium, temperature; Huon pine, temperature; coral layers, temperature or wet or dry; stalagmites, wet or dry; pollen, wet or dry or temperature; stomata, the air.
Records: frost fairs, Beaune harvests and Dawes’s journal, historical; Sahara rock art, Aboriginal stories and the Ubirr X-ray paintings, prehistorical; Riversleigh fossils and reef cores, geological; Mauna Loa, contemporary.
Activities: coal power, forest clearing and petrol, carbon dioxide; cattle and sheep, methane or nitrous oxide; landfill, methane; mining coal and producing gas, methane or carbon dioxide; fertiliser, nitrous oxide; air conditioners and fridges, HFCs.
Fast or slow: gum tree, bacteria, phytoplankton and forest clearing, fast; rain weathering rock, limestone, volcanoes and coal forming, slow; coal power station and jet fuel, slow to fast.
Policies: Montreal Protocol, Kigali Amendment and Paris Agreement, global; Safeguard Mechanism, Renewable Energy Target and HFC quotas, national; 100% net renewable electricity and net zero in South Australia, state; City of Adelaide and the council library, local.
Spheres: fire weather, atmosphere; south-west rainfall, atmosphere or hydrosphere; sea level and acidity, hydrosphere; bleaching and kelp, biosphere; permafrost, geosphere or hydrosphere; soil erosion, geosphere. Tanks: the sea-ice tank does not change; the land-ice tank rises 1 cm. Permafrost chain: air warms; permafrost thaws; microbes break down plant remains; carbon dioxide and methane released; more warming.
Model grids: Tasmania has no cells at least half land on the 500 and 250 km grids, 2 on the 180 km grid, 7 on the 110 km grid, 3 on ACCESS-CM2’s, and 186 on the regional grid. Projections for 2081–2100: 1.4, 1.8, 2.7, 3.6 and 4.4 °C.
Screen 10: the argument runs carbon dioxide risen; fossil carbon; energy imbalance; warming; almost everywhere at once; every sphere changing; models; emissions and policies. Claims: 1.55 °C, it is changing; carbon-13, volcanoes, models and record emissions, people are the cause; Arctic sea ice, Beaune and bleaching, changing or the spheres; the projections and the mid-Pliocene, what comes next.
Exit check: x1 ocean heat; x2 a cold glacial period; x3 the coldest century at different times; x4 extra gases absorb more infrared; x5 rocks; x6 the gas mixes through the whole atmosphere; x7 melting Arctic sea ice; x8 parameterisation.

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