Environmental and human health in a warming atmosphere

Environmental and human health in a warming atmosphereWarming trends are reshaping the composition and function of the airborne microbiome, with direct consequences for indoor air quality and human health. Yet systematic assessment at scale has been constrained by sparse sampling, inconsistent protocols, and the difficulty of attributing exposure and risk in complex built environments. We address this gap with a uniquely comprehensive resource of 10,000 shotgun metagenomes from air samples collected across global and local sites, both indoors and outdoors, spanning diverse climates, seasons, and land uses. Paired indoor–outdoor transects from offices, homes, transport hubs, schools, and hospitals enable unprecedented resolution of how atmospheric warming imprints on community dynamics across the building envelope.Using standardized sampling and genome-resolved metagenomics with AI-assisted annotation, we quantify how temperature, humidity, and heatwave intensity modulate taxonomic turnover, metabolic potential, and source–sink exchange between outdoor air and interiors. We reveal reproducible shifts toward thermotolerant and desiccation-resistant taxa, altered bacterial–fungal balance, and functional signatures consistent with heightened stress responses (e.g., osmoprotection, sporulation) under higher apparent temperatures. Coupled with meteorological data, our analyses show that HVAC regimes, occupancy patterns, moisture gradients, and ventilation effectiveness mediate these climate signals, amplifying microbial persistence within poorly managed buildings and dampening them in well-ventilated spaces.These findings link atmospheric warming to measurable restructuring of indoor microbiomes that is especially salient for “sick building” syndromes—conditions that remain difficult to diagnose because symptoms are nonspecific and microbial exposures are heterogeneous in space and time. By integrating climate covariates with building metadata, we partition the fraction of indoor risk attributable to outdoor warming versus remediable indoor factors, identifying actionable levers such as ventilation rates, filtration performance, humidity control, and source management. Our results suggest that while a warmer atmosphere increases the likelihood of stress-adapted, potentially pro-inflammatory or allergenic communities, building-level interventions can buffer these effects. This framework provides an evidence base for climate-resilient indoor air standards and targeted mitigation in high-risk settings, advancing the assessment of “sick buildings” from anecdotal reports toward quantitative, health-relevant prediction and prevention.