Emergency medical services as sentinel infrastructure for climate-health surveillance

Emergency medical services (EMS) operate at the front line of climate-health impacts, yet how weather changes demand and response capacity is unclear. We analyzed 16.5 million EMS incidents in New York City (2012–2023) across 19 endpoints and 6 response-time components, identifying three dimensions of weather-associated stress: demand surges, operational degradation, and information degradation. Heat increased call volume by 10% and cumulative response time by 65 seconds (+21 per call); dispatch time showed the largest increase (+42.6%). Cold reduced demand and response time, though cardiac arrest increased at winter extremes. Precipitation reduced volume but increased respiratory and obstetric emergencies, with travel-dominated delays. Heat increased non-specific classifications and severity under-triage for symptom-overlapping conditions but not cardiac arrest, consistent with information constraints at the caller–dispatcher interface. Heat-related delays were 2.4× larger in low- versus high-income neighborhoods. These results position EMS as sentinel infrastructure and identify dispatch protocols and travel infrastructure as adaptation targets.