Carbon Fluxes and the Small One-Way Addition

Lab Brief #8

🎯 Your mission

Understand the idea. Then look for it everywhere.

⚡ The twist

The slowest changes are the biggest ones.

What you'll learn

The fast carbon cycle moves roughly 200 gigatonnes of carbon a year between air, oceans and living things, and for thousands of years those flows nearly cancelled. Human emissions add about 10 gigatonnes a year — small against the gross flows, which is why the change is easy to dismiss — but they run one way only, so they accumulate. Roughly half is absorbed by ocean and land sinks and the rest stays airborne, which is exactly why atmospheric concentration climbs even though most of what we emit is taken up.

Key words

carbon flux
The amount of carbon moving between two reservoirs in a given time, measured in gigatonnes per year.
carbon sink
A reservoir such as the ocean or a growing forest that absorbs more carbon than it releases.

Make a hypothesis first

Predict: which will erode faster?

Say your guess out loud — then find out if you were right.

Step 1 of 4 · Read

Think about what you just learned: say what "carbon flux" and "carbon sink" mean in your own words before you start.

Step 2 of 4 · Do

Draw the fast carbon cycle as a flow diagram with arrow widths proportional to each annual flux, then add the 10 Gt human arrow at the same scale. Calculate what percentage of the gross flows it represents and explain why such a small share still raises concentration.

Step 3 of 4 · Observe

Record what actually happened, including anything that did not match what you expected.

Step 4 of 4 · Record

Write a conclusion that answers the question this lesson opened with, and state your uncertainty.

Question 1 of 3

Human emissions are small next to natural carbon flows but still matter because they:

How sure are you?😐 maybe

Question 2 of 3

Roughly what share of human carbon emissions is absorbed by land and ocean sinks?

How sure are you?😐 maybe

Question 3 of 3

A carbon sink is a reservoir that:

How sure are you?😐 maybe

Mind = blown

🪨 Every grain of sand on every beach used to be a mountain.

Nice work!

You got 0 of 3 right.

All lessons

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✨ More to explore

🌍 Where you see this in real life: This is shaping the ground you walk on, slowly, every single day.

🏆 Stretch challenge (try it this week): Find a rock outside and try to guess how old it is.

👨‍👩‍👧 For the dinner table: “What's the slowest change you can think of?”

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