The Carbon Cycle: Fast + Slow · Earth & Env Science

Home › Unit 4: Atmosphere & Climate › Block 3: The Carbon Cycle

Bell ringer: start here (while attendance happens)

Prior-knowledge probe · 5 min

From last block: Earth's energy balance sets the temperature. But what sets the CO₂?
Task: List every place you think carbon is stored on Earth: 60 seconds, go for count. Today we organize your list into a cycle.

Answer in your Field Notebook, dated.

Today we are learning

I can name the four major carbon reservoirs, distinguish fast (photosynthesis / respiration / ocean exchange) from slow (weathering / sedimentation / volcanism) pathways, and explain why timescale matters for climate adaptation reasoning.

I can: tick as you go (for you, not for marks)

I can name the four major carbon reservoirs.
I can sort the carbon pathways into fast and slow, and say what makes them different.
I can explain why carbon timescales matter for climate adaptation decisions.

full course map →

AI Partners available for today's work

The Climate Modeler

Remember: every AI use gets documented. → AI Documentation Template

Story

What today is about

Carbon doesn't sit still. It moves between reservoirs on wildly different timescales.

Atmosphere ↔ biosphere on seasonal scales (photosynthesis takes CO₂ out in summer; respiration puts it back in winter). Atmosphere ↔ ocean on decadal scales (the ocean absorbs ~25% of human CO₂ emissions, slowly). Atmosphere ↔ geosphere on million-year scales (rock weathering removes CO₂; volcanic outgassing puts it back). The Keeling curve's seasonal sawtooth pattern is the fast cycle in real time. The 100,000-year ice-age oscillations are partly the slow cycle.

Today you build the model. Next class (Block 4) you add humans to it and see what breaks. The distinction between "fast" reservoirs (responsive to human action on human timescales) and "slow" reservoirs (geologic-time only) is foundational to every adaptation-vs-mitigation argument the Climate Brief Recommendations section will make.

Concepts

Before you start the work

Start with the Interact: the day's anchor, solo or in pairs. The Watch is projected first, and the Read is your reference for the modelling.

Placeholder

Watch (~6 min)

TBD: fast vs. slow cycles animation. Atmosphere-biosphere seasonal pulse, ocean uptake, geological weathering + volcanism. Each pathway shown with its dominant timescale.

Whole-class, projected.

Placeholder

Read (~8 min)

TBD: reservoir-size + flux quantification handout. Numbers from IPCC AR6 + NASA Global Carbon Project. Sizes in gigatons of carbon (GtC); fluxes in GtC/year.

Reference for the modeling activity.

Live in class

Interact (~30 min)

Carbon-cycle flow-diagram modeling activity. Students build their own diagram: four boxes for the major reservoirs (atmosphere, ocean, biosphere, geosphere), arrows for the major fluxes, numbers from the Read handout.

Solo or pairs · the day's anchor activity.

Everyone does this

Vocabulary support

The U4 pre-teach: 15 terms with definitions and sentence stems. Several are in today's block.

Real link · Foundations · EAL

Today's work: choose one path

All four paths end with a carbon-cycle flow diagram + an exit ticket about storage timescales.

Learning Intention: I can name the four major carbon reservoirs, distinguish fast (photosynthesis / respiration / ocean exchange) from slow (weathering / sedimentation / volcanism) pathways, and explain why timescale matters for climate adaptation reasoning.

Standard 4-reservoir flow diagram (default)

Build the diagram. Four boxes (atmosphere, ocean, biosphere, geosphere). Arrows for the major fluxes between them. Number each flux. Distinguish fast pathways (one color) from slow pathways (another color).

Solo · Default

Diagram + timescale + human-leverage annotations (stretch)

Same as A, plus annotate each flux with its dominant timescale (years vs. decades vs. millennia vs. geologic). Then mark which fluxes humans can influence on a 30-year planning horizon; these are your adaptation/mitigation levers.

Solo · Stretch

Climate Modeler consultation (choice)

Open the Climate Modeler. Ask a specific reservoir question: "what happens to ocean carbon uptake if surface water warms 2°C?" or "how much carbon does Tamil Nadu agriculture cycle annually?" Document the exchange in your AI Doc.

Solo · Choice

Fast-vs-slow peer-help (practice)

If the fast/slow distinction is fuzzy, come to the peer-help table. Pair with a student who's solid. Use the Watch + Read materials. The point: by exit time, you can confidently put any pathway in the right bucket.

Pairs · Practice

Open your Class Notebook and type today's entry header as Heading 2:

A: Jan 25 | U4 B3 | The Carbon Cycle: Fast + SlowB: Jan 27 | U4 B3 | The Carbon Cycle: Fast + Slow

Show

What you're submitting today

Exit ticket: three reservoirs + three timescales. Specificity is the bar.

Carbon storage timescale exit ticket

Name three places carbon is stored on Earth and the timescale of release for each. Format: bullet list. Examples: "Atmosphere (gas, CO₂): seasonal to decadal." "Deep ocean: centennial to millennial." "Limestone (sedimentary rock): million-year." Carry this answer forward to Block 4 when we add humans to the picture.

Submit via Google Classroom (link posted in August)

Rubric link: Naming reservoirs + timescales accurately is K/U bedrock for the Chennai Climate Brief's Background section. Adaptation reasoning (T/T) depends on you knowing which carbon flows are addressable on a 30-year horizon and which aren't. See the rubric.

Reflect

One question before you leave

Three to five minutes. Your answer is saved to your reflection journal, where you can read back everything you have written this year.

Today's reflection is in Google Classroom, under Reflection Journal.

Link posted in August