# Data Story — Heatline: Global Temperature Rise & Cascading Effects

## Story brief
A scrollytelling data story tracing the arc of global temperature rise from 1880 to present day, through six narrative chapters. Each chapter introduces one dimension of how a warming planet reshapes physical systems, biological rhythms, and economic structures. The writing grounds each section in a single question that the accompanying chart answers, so the reader moves from evidence to understanding without feeling lectured.

## Section outline

| # | Chapter | Question the chart answers | Chart type |
|---|---|---|---|
| 1 | The Fever Chart | How fast has the planet warmed since 1880? | Annotated line chart (annual anomaly + smoothed trend) |
| 2 | Oceans on the Boil | Where is the excess heat actually going? | Stacked area chart (ocean heat content by layer depth) |
| 3 | The Great Migration | How far are marine species moving to stay in their thermal envelope? | Connected scatter / shift map (latitudinal displacement by decade) |
| 4 | Coasts Under Pressure | How much sea-level rise is already locked in for different regions? | Grouped bar chart (regional SLR projections, low/high scenarios) |
| 5 | The Economic Cascade | Which sectors and regions bear the largest GDP drag? | Horizontal lollipop chart (GDP impact by sector, regional split) |
| 6 | Crossroads | What do the mitigation pathways actually look like relative to current trajectory? | Range chart / pathway fan (emissions scenarios vs. observed) |

## Visual direction
- **Theme**: Dark oceanic palette — deep navy background (#0a1628), thermal oranges and corals for emphasis, muted teals for balance.
- **Typography**: System font stack prioritising readability. Section headers large and anchored to left rail. Body text restrained in measure (max 65ch).
- **Charts**: SVG-based, built inline in JavaScript. Each chart renders when its section comes into view via Intersection Observer. Annotations use callout lines and background-highlighted data points.
- **Navigation**: Fixed right-side chapter dots that fill as the user scrolls. Click to jump. Mobile collapses to a thin progress bar at the top.
- **Transitions**: Sections fade and slide up on entry. Charts animate their data lines on reveal. No parallax gimmicks — the reporting stays front and centre.
- **Mobile**: Single-column. Charts rescale to viewport width. Annotations move below rather than beside. Navigation bar slides to top.

## Quality targets
- Five chart types across six sections (line, area, connected scatter, bar, lollipop, range fan).
- Every chart answers the section's core question.
- Scroll reveals are subtle — opacity and gentle translateY, not theatrical.
- Annotations are anchored to specific data points with dotted connectors.
- All data is plausible, constructed from real trendlines (anomaly series from NASA GISTEMP, OHC from NOAA, SLR from IPCC AR6, economic impact from NGFS/IAM literature).