Four interconnected dimensions of the climate crisis — global temperature, atmospheric carbon, human heat exposure, and economic damage — each explored independently across the 21st century. Drag any timeline or use the master control to animate all dimensions in synchrony.
Data: NASA GISTEMP · NOAA GML · IPCC AR6 · Lancet Countdown | H Heuristics © 2025
The master timeline synchronizes all four dimensions below. Each dimension also has its own independent control.
Four dimensions, one interconnected crisis
For every tonne of CO₂ emitted, the planet traps additional heat. Since 1880, global mean temperature has risen ~1.3°C. The rate of warming since 1970 is unprecedented in at least 2,000 years. The last time CO₂ exceeded 400 ppm (the Pliocene, ~3 million years ago), sea levels were 15–25 metres higher.
Wet-bulb temperature (TW) combines heat and humidity. At TW ≥ 35°C, even a healthy person resting in shade with water will suffer heat stroke within hours. This threshold has already been breached in parts of South Asia, the Persian Gulf, and Mexico — decades earlier than models projected.
The divergence between SSP2-4.5 and SSP5-8.5 after 2050 is stark. Under the moderate scenario, emissions peak mid-century and warming limits to ~2.7°C. Under continued fossil dependence, warming reaches ~4.4°C. Every fraction of a degree means hundreds of millions fewer people facing lethal heat.
The technologies exist: rapid clean energy deployment, urban cooling, early warning systems, heat-resistant crops, adaptation finance. The challenge is diffusion — how fast proven solutions reach the populations that need them most. This is the central research question of H Heuristics.
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