Volcano Q&As

CAMS provides data for monitoring and tracking the effects of SO₂ relating to atmospheric composition and air quality. SO₂ emissions are not only a local problem as they are transported from one location to another by wind patterns in the atmosphere.

CAMS combines satellite and non-satellite observations with a numerical weather prediction model and air quality models to provide daily forecasts of the composition of the air worldwide. This combination of millions of daily observations and the predictive power of computer models is the real strength of CAMS.

The data that CAMS provides on the atmospheric impacts of SO₂ from volcanic eruptions, can help governments, decision-makers, and citizens alike to understand the effects of the emissions on air quality and the environment. This dedicated Q&As page is dedicated to provide information to help CAMS users interpret the data and its limits. The Copernicus Atmosphere Monitoring Service, implemented by the European Centre for Medium-Range Weather Forecasts on behalf of the European Commission with funding from the EU, provides free-to-access and regularly updated data on atmospheric conditions to a variety of stakeholders including the scientific community, policymakers, public organisations, private sectors and services, and individual citizens.

Following the eruption of the Cumbre Vieja volcano on the Spanish island of La Palma in the Canary Islands in September 2021, the Copernicus Atmosphere Monitoring Service (CAMS) has monitored the output of the resulting sulphur dioxide (SO2). CAMS has also monitored the outgassing of preceding volcano eruptions including Mt. Etna in Italy, Mt.  La Souffriere in St. Vincent Island and Mt. Nyiragongo in the Kongo. The following Q&As are designed to clarify what SO2 and its by-products are, how CAMS monitors SO2 from volcanic eruptions, and the impact it has on the atmosphere. The Q&As are created in a way as to provide explanations in the form of multiple angles to frequently asked questions in order to give a rounded understanding and perspective of the topics.

What is SO₂ and is it harmful to human health?

Sulphur dioxide (SO₂) is a colourless, reactive gas with a strong odour which is released into the atmosphere during the natural occurrence of volcanic eruptions. Sulphur dioxide in the air can come from many other activities including coal burning, oil at power plants and from copper or nickel smelting. High concentrations of SO₂ can have adverse effects on human health. It can aggravate asthma and other lung conditions and can also contribute to cardiovascular illnesses.

What information does CAMS provide on volcanic eruptions?

The main CAMS products related to volcanic eruptions are analyses and 5-day forecasts of total column SO₂, and 3-D concentrations of SO₂, initialized from satellite observations. By modelling the chemistry of the atmosphere, CAMS can also provide information on the conversion of SO from the gas phase into sulphate aerosol (see: What is sulphate aerosol and how does CAMS monitor it in the atmosphere?). For active, but non-erupting, volcanoes CAMS also provides an inventory of outgassing emissions from a number of active volcanoes around the world, based on measurements made in situ at the volcano crater. It is to be noted that CAMS monitors the outgassing from volcanoes and not the volcanic ash itself.

What is sulphate aerosol and how does CAMS monitor it in the atmosphere?

Sulphate aerosol results from the chemical conversion of SO₂ and is modelled in the CAMS system. In the CAMS models sulphate aerosol contributes to calculation of fine and coarse particulate matter (PM2.5 and PM10) and so CAMS can monitor potential air quality impacts. CAMS is able to monitor the impact of volcanic eruptions on the composition of the atmosphere as sulphur dioxide and other pollutants are transported away from the volcano.

It is important to note that CAMS forecasts show gaseous SO₂ in the atmosphere, but do not provide information on volcanic ash, which is monitored by the Volcanic Ash Advisory Centres (VAACs). 

How does CAMS monitor SO₂ from volcanic eruptions?

While CAMS does not monitor volcanic eruptions themselves, it is able to monitor and provide information on the atmosphere in terms of the SO₂ loading. This relies on near-real-time satellite observations of total column SO₂ detected locally to an erupting volcano. CAMS combine the satellite SO₂ observations with its global forecast system to initialize 5-day forecasts of global atmospheric composition and air quality.

How do CAMS data compare with independent measurements?

CAMS forecasts are routinely evaluated through comparisons against independent measurements which are not used in the CAMS system, such as ground-based remote sensing measurements of aerosol optical thickness from NASA’s Aerosol Robotic Network (Aeronet) and air quality measurement networks for SO₂ concentrations. For many volcanic eruptions the impact on the atmosphere is well above the surface and CAMS depends on evaluation against aerosol optical thickness. In the case of the eruption of Cumbre Vieja, Aeronet observations across Europe and as far away as the Caribbean, in September and October 2021 largely corresponded with observed enhancements in aerosol optical thickness as the volcanic plume was transported over each site.

For how long does CAMS monitor emissions from volcanoes and other natural phenonmena?

For as long as a volcano continues to be active, and SO₂ observations are available, CAMS is able to monitor the plumes and potential impacts on air quality for any regions affected.

How can CAMS predict the atmospheric impact of natural phenomena like the evolution of a volcanic SO₂ plume?

CAMS combines satellite data with a numerical model of meteorology which includes the chemistry of the atmosphere to initialize forecasts which help to predict how natural phenomena such as volcano eruptions affect the atmosphere. The evolution of an SO₂ plume and its possible implications, such as reduction of air quality, is tracked and measured through these methods as accurately as possible. By using data from satellite observations and combining it with its models, CAMS can assess many aspects of global air quality, including the impact of all natural phenomena, not only volcanic eruptions, but also wildfires and desert dust.

What is the estimated amount of total SO₂ emitted by volcanoes in 2021 (starting the beginning of October?) 

CAMS is unable to provide a number for the total mass emitted from volcanoes on a monthly or yearly basis. This is because CAMS does not specifically monitor volcanic eruptions themselves, but their impact on the composition of the atmosphere as sulphur dioxide and other pollutants are transported away, sometimes for thousands of miles. Therefore, it does not have data on the specific emissions. However, CAMS does provide estimated emissions of outgassing volcanoes around the world based on measurements. For volcanic eruptions, CAMS SO₂ forecast information is initialised from satellite observations of total column SO₂.

If SO₂ plumes from the La Palma eruption can reach as far as the Caribbean, what are the expected levels of pollution and the effect on air quality?

The CAMS forecasts of total column SO₂ showed the plume from Cumbre Vieja reaching over 5,000 kilometres across the Atlantic, as far as the Caribbean based on the initial plume height assumed to be approximately 5 km. However, this does not necessarily mean that the SO₂ reaches the surface and therefore affect air quality. However, in late October when the volcano continued to be active, other plumes of high total column SO₂ coincided with reports of reduced air quality in the Caribbean, particularly in Puerto Rico, where visibility was reported to be down to five miles or less. This was more in relation to a mixture of sulphate aerosol (which is formed chemically from the SO₂ in the plume) and desert dust from the Sahara. The chemical conversion of SO₂ into sulphate aerosol is included in the CAMS model and CAMS analyses of aerosol optical depth for the period (see: How does CAMS measure SO₂ from volcano eruptions?) revealed long-range transport of these tiny particles in the atmosphere.

What is the effect of SO₂ emitted by volcanoes on climate change?

Plumes from active volcanoes which are monitored by CAMS can form sulphate aerosol in the atmosphere from SO₂. Large amounts of SO₂ may have a cooling effect on the atmosphere as it converts to sulphuric acid aerosols that block incoming solar radiation. This can lead to a temporary, local reduction in atmospheric temperatures. However, as a plume stays mostly in the troposphere, any impacts on atmospheric radiation is localised and usually won’t have a significant impact on the climate. When volcanic eruptions are powerful enough to inject SO₂ directly into the stratosphere, the resulting stratospheric sulphate aerosol can have an impact on the ozone layer over the poles, potentially resulting in higher levels of ozone depletion during the spring.

What are the pollutants of most concern for air quality?

Any SO₂ that reaches the surface will most likely be at very low levels. Sulphate aerosol can also be formed chemically in the plume and this can contribute to increased levels of fine particulate matter (e.g. PM2.5), leading to a reduction in air quality. When the air mass also includes some levels of dust from deserts, this can also have an impact on air quality in a particular region.

How can CAMS support predictions regarding possible health implications caused by SO₂ plumes of volcanoes?

CAMS scientists use a combination of satellite data and meteorological models which enables them to predict the height, probable route and development of the SO₂ plume caused by volcanic eruptions, allowing predictions on the implications for different realms, such as human health and impact on the environment. 

What is the impact of volcanic plumes on the weather and air quality at the surface, both for people close to the volcano as well as people in areas the pollutants are transported to?

The Copernicus programme and specifically CAMS does not provide any information about weather related issues, as its focus is on monitoring the Earth’s long-term climate and atmosphere rather than day-to-day weather events. In terms of air quality, CAMS monitors transport of the resulting SO₂ plumes and their effect. (See: How does CAMS measure SO₂ from volcano eruptions). The CAMS system includes interactions between the amount of aerosol in the atmosphere and the model meteorology, and in principle can be used to estimate the impact on surface temperature, for example, of atmospheric pollution events such as volcanic eruptions. 

Copernicus is the European Union’s flagship Earth Observation Programme which operates through six thematic services: Atmosphere, Marine, Land, Climate Change, Security and Emergency. It delivers freely accessible operational data and services providing users with reliable and up-to-date information related to our planet and its environment. The Programme is coordinated and managed by the European Commission and implemented in partnership with the Member States, the European Space Agency (ESA), the European Organisation for the Exploitation of Meteorological Satellites (EUMETSAT), the European Centre for Medium-Range Weather Forecasts (ECMWF), EU Agencies and Mercator Océan, amongst others.

ECMWF operates two services from the EU’s Copernicus Earth Observation Programme: the Copernicus Climate Change Service (C3S) and the Copernicus Atmosphere Monitoring Service (CAMS). They also contribute to the Copernicus Emergency Management Service (CEMS). The European Centre for Medium-Range Weather Forecasts (ECMWF) is an independent intergovernmental organisation supported by 34 states. It is both a research institute and a 24/7 operational service, producing and disseminating numerical weather predictions to its Member States. This data is fully available to the national meteorological services in the Member States. The supercomputer facility (and associated data archive) at ECMWF is one of the largest of its type in Europe and Member States can use 25% of its capacity for their own purposes.

The Copernicus Climate Change Service website can be found at https://climate.copernicus.eu/

The Copernicus Atmosphere Monitoring Service website can be found at http://atmosphere.copernicus.eu/

More information on Copernicus: www.copernicus.eu

The ECMWF website can be found at https://www.ecmwf.int/

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