Met Office

Iceland volcano - May 2011

On 21 May, little over a year after the previous eruption, a second volcano in Iceland erupted.

Grímsvötn volcano
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As the Grímsvötn volcano in Iceland erupted, weather conditions meant that the volcanic ash plume started to head towards the UK. The Met Office had a key role in accurately predicting the spread of the ash and advising the relevant authorities.

In our role as a Volcanic Ash Advisory Centre (VAAC), we're responsible for monitoring and reporting the spread of volcanic ash over the UK, Iceland and the north-eastern part of the North Atlantic Ocean.

From 21 May onwards the Met Office London Volcanic Ash Advisory Centre (VAAC) continued to provide forecast guidance up to 24 hours ahead to support decision-making. This guidance was provided to the Civil Aviation Authority as the lead agency, NATS, airports and airline operators in order to support their decisions on whether aircraft can fly safely.

Volcanic ash can have a major impact on aircraft, potentially causing engines to fail. The International Civil Aviation Organisation (ICAO) along with the CAA and aircraft manufacturers set safety thresholds for flying planes through volcanic ash. Our forecasts of ash plume trajectories are based on these thresholds.

What we did

During the Eyjafjjallajökull the UK Civil Aviation Authority (CAA) working with aircraft engine manufacturers and European transport ministers defined volcanic ash concentration safety thresholds levels for European and North Atlantic airspace. These thresholds supplemented the global ICAO standard of 'avoid all ash'. Responding to this new requirement the Met Office NAME model was used to produce supplementary volcanic ash concentration charts depicting concentration contours of 200 and 2000, and then latterly 4000 micrograms per cubic metre.

  • Satellite imagery, scientific balloons and ground-based radar systems, including LIDAR, were also used to observe the ash cloud and verify our forecasts.
  • Met Office staff worked closely with the British Geological Survey (BGS) and Icelandic Met Office (IMO) who were monitoring the volcano activity.
  • Our guidance showed areas where ash concentrations were expected to be.
  • We regularly updated the public via Twitter and Facebook and our website.

The result

Our charts were largely used by respective European airspace authorities as the basis for informing their flight safety related decisions.

Timeline of the event

Volcano timeline
21 MayVolcano erupts. Ash reported to be ejected to a height of almost 20 km. Met Office VAAC forecasts start to be issued.
22 MayVolcano continues to erupt. Met Office VAAC forecasts go live on the public area of our website. Flights in parts of Europe start to be affected.
23 MayMet Office forecasts that ash is likely to reach parts of northern and western Scotland overnight and 24 May. The research ship Discovery entered an area of thick volcanic ash between Scotland and Iceland with ash being deposited onboard.
24 May
  • Satellite and Lidar observations confirmed the presence of ash over northern Britain in the previous 24 hours.
  • A plane flying from Aberdeen to the Shetlands encountered volcanic ash during the flight with ash being deposited on the aircraft.
  • Ash deposits were found on a plane that had be flying in the Orkney area on morning of 24 May.
  • A plane flying from Stansted to Belfast observed a layer of ash to the north /northwest of the flight path.
  • A plane flying at a height of 18,000 feet in the Manchester area around 2pm observed a layer of ash of approximately 1000-2000 feet thick.
  • Professional observers reported ash being deposited in northern Britain.
  • Ash was deposited on vehicles on Orkney.
  • Air quality sensors across Scotland indicated an increased amount of ash particles (PM10s) during the day.
25 MayInformation received from the Icelandic Meteorological Office (IMO) indicated the GrÍmsvötn volcano was no longer emitting ash, and only minor steam plumes from the crater up to around 300 metres
29 May IMO announces the volcano has 'paused'.

The future

The effect of volcanoes on our climate has led some to doubt the human impact on climate change. For example, it's been suggested that volcanoes put out more carbon dioxide (CO2) than human activity, but this is not the case.

In an average year, volcanoes put out an estimated 100-130 million tonnes of CO2 globally. Estimates suggest human activity puts out more than 200 times as much - about 26,000 million tonnes of CO2 per year, magnifying the greenhouse effect and causing our climate to change.

Last Updated: 19 December 2011

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