Climate change
Climate change is a slow-burn global pressure axis: cumulative emissions push a warming index (°C) upward, which drags food, stability and GDP — hitting tropical and coastal nations hardest while cold states briefly benefit.
How it works
Warming starts at a baseline of 1.3°C (approx. warming vs. pre-industrial) and is clamped between 1.0°C and 5.0°C. Every quarter the index creeps up in proportion to the world's emission ratio — total emissions divided by the 2025 baseline — but the ratio is raised to the power 0.6 to cushion the emission surge that comes with GDP growth. A green world (ratio below 1) slows the climb; each country's emissions scale with GDP, industrial share, and how 'dirty' it is, which green transitions, science agendas and climate treaties reduce.
Only warming above the 1.3°C baseline causes damage. That excess is multiplied by each country's regional vulnerability: Africa is 1.5×, South/Western Asia 1.45×, Oceania 1.35×, Central/Caribbean/South America 1.3×, and Northern/Eastern Europe is relieved at 0.75×. Cold states (Russia, Canada, Kazakhstan, Mongolia, Finland, Sweden, Norway) get a further relief of warming×0.85, which can flip their net effect negative — early warming actually expands their arable land.
For countries taking a hit each quarter, food stock drains by effect×0.9, stability falls, GDP is multiplied down, and a climate-stress meter accumulates. Once stress climbs past 55 the population itself begins a small decline from famine and displacement. Cold-benefiting states instead gain food stock and shed climate stress. It's a background pressure that compounds over a full game — invisible early, decisive late.
Formulas
climate = clamp(climate + pow(emitRatio, 0.6) * 0.006, 1.0, 5.0)eff = warming*vuln − (isCold ? warming*0.85 : 0); where warming = climate − 1.3food −= eff*0.9; stability −= eff*0.28; gdp *= (1 − eff*0.004); stress += eff*0.55Key numbers
How to play
- ▸Invest in green transition, science agendas and climate treaties early — they lower your emissions and slow the global warming climb for everyone.
- ▸If you play a tropical, arid or low-lying nation (Africa, South Asia), budget for climate stress from the start; your vulnerability multiplier is brutal.
- ▸Cold northern states can ride early warming as a bonus — but don't get complacent, since the global clamp keeps rising toward 5.0°C.
- ▸Watch the climate-stress meter: crossing 55 starts shrinking your population, so ease the pressure before it compounds.