WMO says wildfire smoke and heat are undoing clean-air gains

The World Meteorological Organization warned on 7 September that smoke from larger wildfires and ozone built by heatwaves are offsetting the clean-air work done on cars and factories. Bulletin No. 6 was released for the International Day of Clean Air for blue skies. It reviews air and climate in 2025.

Lorenzo Labrador, a WMO scientific officer, put the point in one sentence. Air quality and climate cannot be treated as separate subjects. They are tied and have to be handled together.

Where the particles sat in 2025

Fine particles known as PM2.5 ran above long-term averages in northern Canada, parts of Russia and western-central Africa because of fire. Northwestern Spain was a late-summer hot spot after large burns. Europe and North America have cut industrial and traffic emissions with tighter rules. Fire smoke is filling part of that gap. The bulletin also flags ground-level ozone, which forms faster in still, hot, sunny air of the kind that sat over Spain, France and Greece this year.

A study cited in the report says extreme wildfire events have tripled since the 1990s and contributed to almost 100,000 deaths a year between 2010 and 2018. Smoke is linked in the reviews the WMO collected to more asthma attacks, more hospital admissions for chronic obstructive pulmonary disease, more use of respiratory drugs, and effects on mental health and birth outcomes. PM2.5 can reach the bloodstream. Ozone irritates airways and also damages crops.

What the agency wants measured

The bulletin asks for better observations of PM2.5, ground-level ozone, black carbon and microplastics. The last two, it says, are common in the air and still poorly tracked. Aerosols change how the atmosphere holds heat and how clouds form. Black carbon from fire is both a health particle and a climate forcer. Treating smoke as only a local air problem misses that second job.

The WMO has already said this year's El Nino may run beyond the modern chart into early 2027. Heat that lasts into a second summer raises the chance of another fire year and another ozone season. The bulletin is not a forecast of deaths. It is a statement that the old clean-air story, built on tailpipes and stacks, is now incomplete.

Countries that meet a WHO guideline in a quiet year can miss it in a fire year. That is the practical warning. Coordinated policy, in the agency's language, means fire management, heat plans and emission rules have to sit on the same desk. They do not, in most capitals. The 2025 maps in Bulletin No. 6 are the evidence the agency is using to say so.