OBSERVER: Air Quality Challenges in 2025: Europe’s Summer of Smoke, Dust and Ozone
OBSERVER: Air Quality Challenges in 2025: Europe’s Summer of Smoke, Dust and Ozone
sonia
Wed, 15/10/2025 – 17:05
The summer of 2025 significantly affected Europe’s atmosphere. From record-breaking wildfires in southern and western Europe, to intense Saharan dust intrusions and repeated peaks in surface ozone during prolonged heatwaves, air quality was negatively impacted by multiple events. Data from the Copernicus Atmosphere Monitoring Service (CAMS) show how these overlapping events combined to create serious risks for human health and the environment across the continent. In this Observer, we take a closer look at what the data show.
Record emissions and widespread smoke
The European summer of 2025 was marked by intense and widespread wildfire activity, especially in southeast and southwest Europe, with significant impacts on air quality. Wildfire smoke is a mixture of air pollutants, such as nitrogen oxides, and particulate matter, with PM2.5 (particulate matter of 2.5 microns or less in diameter) being of particular concern because of its potential impacts on human health. While the season began with relatively low emissions overall, conditions quickly escalated, culminating in record-breaking fire events in parts of the continent.
Greece, Turkey, and Cyprus experienced large wildfires during late June and early July, with total estimated fire emissions in June at their highest level since 2007 for Greece, and the highest in the 23 years of the CAMS Global Fire Assimilation System (GFAS) dataset for Turkey. CAMS global forecasts of PM2.5 surface concentrations showed a clear signal of the fire emissions throughout the first week of July.
In early August, wildfire activity in Europe predominantly affected southwestern Europe. This region had already experienced some significant events in July, when large wildfires broke out in southern France, Catalonia, and Portugal early in the month, and in Spain and Portugal from 27 July onwards. Fires in Portugal’s Vila Real district in early August were reflected in a clear increase in ground-level PM2.5 concentrations in the CAMS global and regional forecasts.
The scale of the wildfires in Portugal and northwestern parts of Spain increased rapidly through mid-August, with Spain seeing its highest annual total fire emissions in the 23 years of the GFAS dataset by 17 August. The increased smoke emissions contributed to significant PM2.5 concentrations at the surface, which exceeded the Air Quality Guidelines set by the World Health Organization (WHO) of 15 μg/m3 for a 24-h average across a large region of the Iberian Peninsula in the CAMS global and regional forecasts.
The smoke and air quality impacts from the wildfires around southern Europe coincided with the long-range transport of smoke plumes across the North Atlantic from the ongoing wildfires in central Canada. Large smoke plumes originating from Canada were a common feature of the North Atlantic and European atmosphere throughout much of the summer, from late-May into early-August.
Dust crossing continents
CAMS also tracked several episodes of long-range transport of mineral dust originating from the Sahara over Europe in the first months of 2025, and these continued into June during which dust intrusions, both across the Mediterranean to southern Europe and across the Atlantic towards the Americas, were unusually frequent and intense.
Dust transport episodes are the result of Saharan dust storms, when powerful winds lift vast amounts of sand into the air. Depending on weather patterns and atmospheric circulation, these particles can travel thousands of kilometres before eventually settling. CAMS uses a number of parameters to track atmospheric dust transport, including aerosol optical depth (AOD), which measures the amount of light that is blocked by aerosols like dust, smoke, and pollution in a vertical column of the atmosphere, and PM10 concentrations at ground level (PM10 refers to airborne particles with a diameter of 10 micrometres or less).
Throughout June, several Saharan dust episodes crossed the Mediterranean to southern Europe, with increased surface concentrations of PM10 monitored in the Iberian Peninsula, Italy, and southeastern Europe. These dust intrusions continued throughout the summer, and CAMS reported a Saharan dust intrusion crossing southeastern Spain and the western Mediterranean in late August.
Beyond their visibility in the sky, Saharan dust intrusions have wide-ranging consequences. They are well known for worsening air quality and aggravating respiratory and cardiovascular problems, but their influence extends further. Dust deposits can alter ocean biogeochemistry by delivering nutrients such as iron, which in turn affect marine ecosystems. Ongoing research continues to explore how dust interacts with atmospheric chemistry, influencing cloud formation and even rainfall patterns.
Heatwaves and ozone: A hazardous summer mix
The summer of 2025 was characterised by a series of heatwaves, as reported by the Copernicus Climate Change Service (C3S). Combined with the strong seasonal solar radiation, these conditions are often linked to elevated surface ozone levels. The first high ozone concentrations were observed in early June, when CAMS reported maximum daily 8-hour average ozone concentrations of between 120-140 μg/m3 covering much of the Mediterranean region. High surface ozone concentrations continued across large parts of Europe, with peaks during the major heatwaves of mid-June, early July, and early August. During the first days of August, surface ozone levels rose sharply across much of Europe, with northern Portugal experiencing particularly high concentrations alongside severe heatwave conditions.
Ozone at ground-level is not emitted directly and is generated by complex photochemical reactions involving nitrogen oxides (NOx) and volatile organic compounds (VOCs) and triggered by sunlight. During heatwaves, strong solar radiation and higher temperatures accelerate these reactions and trap pollutants near the ground. This creates ideal conditions for ozone build-up, often leading to concentrations well above air quality guidelines. Moreover, because of its long lifetime in the atmosphere, ozone can travel very long distances, meaning that ambient concentrations are also influenced by the hemispheric transport of ozone produced outside Europe.
The European Union’s Ambient Air Quality Directive (EU/2024/2881) sets a limit for the maximum daily eight-hour average of 120 µg/m³, which may not be exceeded more than 18 times per year in order to protect human health. It also establishes an information threshold of 180 µg/m³ for the hourly mean, the level at which authorities must inform the public because ozone concentrations may pose risks, particularly for vulnerable groups. According to CAMS data, the 120 µg/m³ limit was exceeded on several occasions in many regions.
Where to explore the data
CAMS provides open and free-to-use datasets on the Atmosphere Data Store (ADS). The service regularly updates information on wildfire location, intensity, and estimated emissions worldwide, and tracks smoke transport and composition (see the CAMS Global fire monitoring page). CAMS forecasts surface ozone and its precursor pollutants concentrations thanks to its modelling systems fed by satellite and in situ observations to assess levels and their impacts on air quality and climate. Ozone forecast maps can be accessed here.
For Saharan dust and other aerosols, the free CAMS Aerosol Alerts app can be configured to monitor and generate alerts for aerosol concentrations in major European cities up to three days ahead. CAMS has also developed a number of other tools allowing anyone to access the data via intuitive charts and the recently released Methane Hotspot Explorer, in addition to its tools for policymakers, especially adapted for air quality and emissions reporting.
Thu, 16/10/2025 – 12:00
