"The high emissions caused by these fires have the potential to affect not only Spanish cities, but also the rest of Western Europe and the entire continent," said the chief scientist of the World Meteorological Organization (WMO).

At a press conference, Lorenzo Labrador emphasized that the impact of emissions caused by the fires—which affected up to 1% of the Iberian Peninsula—often crosses borders.

The expert recalled the wildfires that affected Canada last year, whose effects on air quality were also felt in Europe, crossing the North Atlantic.

Labrador also noted that wildfires are a permanent source of the most polluting and harmful particles in the atmosphere, those with a diameter of less than 2.5 microns (known as PM 2.5).

The expert made these comments while presenting the annual edition of the WMO air quality bulletin, which compiles data for 2024.

The report highlights an increase in PM 2.5 particle pollution, mainly in South America due to forest fires that hit regions like the Amazon, and also in Canada, Siberia, and Central Africa, under similar circumstances.

Conversely, this type of pollution has declined again in eastern China, where cities like Beijing were once among the most polluted in the world, but where systematic mitigation measures have yielded positive results.

The report also analyses variations in the presence of aerosols (small suspended particles), with some types contributing to global warming, while others produce cooling.

For example, aerosols produced by sulfuric emissions have decreased over the years thanks to measures taken to reduce their presence in fuels, which has improved air quality and reduced premature deaths and childhood asthma. However, this reduction also contributed to a 0.04 degree Celsius increase in global temperatures by 2025, Labrador indicated, as these aerosols reflect some of the sun's radiation.

The UN agency also highlights the increase in winter smog in many regions of the world, including the overpopulated north of India, and warns that it is "not a mere seasonal meteorological phenomenon," but a symptom of increased pollutant emissions due to human activity.

This forecast comes a day after the release of a study concluding that climate change caused by human activity has increased the risk of heat waves like the one that fuelled wildfires in Portugal and Spain in August by 40 times.