Block 4: Human Acceleration of Carbon + The Warming Signal
The Keeling curve rises every year, but it also wiggles down every northern summer.
Task: Why would atmospheric CO₂ drop a little every June to September? (Hint: think about what half the planet's land plants are doing.) One sentence.
Answer in your Field Notebook, dated.
I can describe the major anthropogenic carbon sources and rank them by scale, interpret the Keeling curve and 1850-present temperature record, and explain why attribution to greenhouse forcing rules out solar and volcanic explanations.
I can use a model to show how energy in vs. energy out sets Earth's climate.
"Use a model to describe how variations in the flow of energy into and out of Earth's systems result in changes in climate."
Where this runs:
- U4 B1: The Greenhouse Effect: How Earth Keeps Warm Enough
- U4 B2: Earth's Energy Balance: The Math
- U4 B4: Human Acceleration of Carbon + The Warming Signal ← you are here
- U4 B8: Tipping Points + Feedback Loops
Assessed:
Chennai Climate Brief: the science sections (K/U components)
On track looks like:
Your brief's physics section traces an energy flow, not just names 'greenhouse effect.'
I can follow carbon through Earth's four spheres, with numbers.
"Develop a quantitative model to describe the cycling of carbon among the hydrosphere, atmosphere, geosphere, and biosphere."
Where this runs:
- U4 B3: The Carbon Cycle: Fast + Slow
- U4 B4: Human Acceleration of Carbon + The Warming Signal ← you are here
Assessed:
Chennai Climate Brief science sections (K/U)
On track looks like:
You can say where the ~10 GtC/year of human carbon goes, and why the one-way flux matters.
I can estimate what my AI use costs in electricity and water, and decide when it's worth it.
In brief: "Understand how AI systems consume energy and natural resources (paraphrased)"
Where this runs:
- U0 B1: Welcome + How We Work
- U4 B4: Human Acceleration of Carbon + The Warming Signal ← you are here
Assessed:
U4: the Footprint Decision task
On track looks like:
You can put rough numbers on an AI choice and name one limitation of your own estimate.
What today is about
Add humans to Block 3's model. Then read the warming signal in the data.
Anthropogenic carbon fluxes are tiny compared to the natural carbon cycle's gross fluxes (~10 GtC/year human vs. ~120 GtC/year photosynthesis). But here's the catch: human emissions are one-way. They move carbon from the slow reservoir (fossil fuels: million-year storage) to the fast reservoir (atmosphere: decadal residence). The natural cycle's huge counterflows balance each other. The human contribution doesn't have a return path on our timescales.
The response is visible: the Keeling curve from 1958-present (annual CO₂ rise from ~315 ppm to ~420 ppm) plus the global temperature record from 1850-present (~1.2°C warming) plus IPCC AR6 attribution evidence ruling out solar variation and volcanic forcing as alternative explanations. By the exit ticket, you can defend the warming-signal claim against the most common alternative explanations.
This block also previews adaptation focus for the rest of the unit: "so what now?" enters the conversation. The Block 9 adaptation-vs-mitigation work depends on you having internalized today's "one-way flux" insight.
One accelerant is new enough that you evaluated it before you knew this vocabulary. In week one, you OPVL'd an AP article about AI data centers: 448 TWh of electricity in 2025, projected to more than double by 2030, with AI's share doubling inside it. Today that story gets its physics: electricity demand growth means more carbon moved the one-way direction, unless grids decarbonize faster than demand grows. And the UNU report adds a twist worth keeping: low-carbon electricity is not automatically low-water or low-land. The footprints don't all move together, which is why 'just switch to renewables' is the beginning of an answer, not the end of one.
Before you start the work
Start with the Interact: it extends the model you built in Block 3. The Watch is projected first, and the Reads are your references.
Today's work: choose one path
All four paths end with an extended carbon-cycle model + a 3-sentence attribution claim.
Open your Class Notebook and type today's entry header as Heading 2:
A: Jan 28 | U4 B4 | Human Acceleration of Carbon + The Warming SignalB: Jan 29 | U4 B4 | Human Acceleration of Carbon + The Warming Signal
What you're submitting today
A 3-sentence claim about attribution. Each sentence has to land.
Three sentences. Why can the post-1850 warming signal not be explained by natural forcing alone? Sentence one: name the observed pattern (e.g., warming + Arctic amplification + stratospheric cooling). Sentence two: name a specific natural-forcing alternative (solar / volcanic / orbital / internal variability) and the specific evidence ruling it out. Sentence three: cite the IPCC AR6 attribution finding's confidence level ("virtually certain" / "very likely").
Submit via Google Classroom (link posted in August)A one-page estimation task: three real scenarios (a poster, a research session, a showcase video), the UNU report's per-unit figures, your arithmetic, your own decision rule, and one specific Limitation of your estimate. Printed handout in class; also in Classroom. This one is collected and read closely.
Submit via Google Classroom (link posted in August)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.
The "I used to think" move surfaces shifts about scale.
Today's reflection is in Google Classroom, under Reflection Journal.
Link posted in AugustSign in with your school account. Your teacher can see what you write here.