Climate · Heat

Heat, devices and regional exposure

The metrics that decide functional outcomes — not just headline temperature. Toggle between air, feels-like and work-safety (WBGT) heat; switch °C/°F; and compare how much of each region lives in unsafe conditions.

Heat explorer

3 views · °C / °F

Peak late-century urban temperature — weak path (~2090)

Bands span plausible peak across cities in each region.

Air = dry-bulb · Feels-like = heat index · WBGT = wet-bulb globe (work safety). Ranges across SSP scenarios; illustrative.

Three metrics, three questions

Air (dry-bulb) answers "how hot is the day." Feels-like (heat index) adds humidity for human discomfort. WBGT is the work-safety metric — above ~30.5°C in sun, sustained outdoor labor becomes unsafe. They are not interchangeable.

The mean-temperature niche

Cities crossing >29°C MAT

17cities

cross a >29°C mean annual temperature in 2011–2040

≈30M residents · Scientific Reports 2025

57cities

cross a >29°C mean annual temperature in 2041–2070

≈105M residents · Scientific Reports 2025

217cities

cross a >29°C mean annual temperature in 2071–2100

≈320M residents · Scientific Reports 2025

Mean annual temperature (MAT) is the chronic-niche metric: it measures the climate people live inside year-round, not the single hottest afternoon. Crossing ~29°C MAT pushes a city outside the historical human niche.

Regional exposure

Share in unsafe conditions

Population in “unsafe” conditions by region · ~2050 middle path

Share of regional population exposed to each layer (overlapping, not additive).

Illustrative synthesis. “Unsafe” per tier definitions in Methodology.

Latin America

~7–9% of 2100 population

Binding constraint

PM basins + drought-power + informality

Worst-exposed

N. Brazil, Caribbean, Central America

Buffer zone

Andes, Southern Cone

Verdict

Warming taxes development but does not foreclose it. Stratified region — buffered upland cities versus a lowland chronic-risk envelope. Elevation buys time on physiology, not on basin PM.

Heat & your devices

Heat is not only a human problem — it throttles the infrastructure of modern work. Lithium-ion charging slows or pauses, silicon down-clocks to protect itself, and sustained workloads fall below spec. Ambient temperature, not just the chip, sets the ceiling.

< 25°C

Normal charge speed, full boost clocks

28–32°C

Fans max; sustained workloads start throttling

32–35°C

Charging throttled or paused; sustained compute below spec

35–40°C

Heavy throttling; many phones stop fast charging

> 40°C

Protective shutdown risk; battery chemistry degrades

In cities where afternoon ambient sits at 38–45°C, phones and laptops operate in the throttle-or-pause band for hours daily — a quiet tax on productivity and learning.

The four unsafe tiers

"Unsafe" is layered. Most people already live in Tier A; the physiological tail (Tier D) is rare but absolute.

Tier	Definition	Today
A — Cognitive / pollution	Annual PM₂.₅ above WHO 5 µg/m³ + heat that degrades attention, memory, learning	~80–98% urban
B — Functional heat	WBGT > 30.5°C in sun — unsafe for sustained outdoor / informal labor	~70% of workers episodic
C — Infrastructural	Grid, transit, cooling chain and compute fail under peak demand	~10–20% urban, rising
D — Physiological	Noncompensable / wet-bulb ~35°C — body cannot thermoregulate unprotected	<1–2%, episodic