Monitoring Ship Pollution from Space

 Monitoring Ship Pollution from Space

Ships emit significant amounts of air pollution, including sulphur dioxide (SO2), nitrogen oxides (NOx) and small particles (PM), causing serious damage to health and the environment. As a result of both EU and global regulations for ship pollution, sulphur emissions from ships are expected to gradually come down, but there is currently no regulation that will ensure any significant cuts in their NOx emissions.

Monitoring Shipping Lanes from Space

recent post on Twitter by Spanish Earth Observation visualisation specialist Iban Ameztoy showed the world again how NOx (Nitrogen Oxide) pollution is still a major issue. Even at the very low spatial resolution of this clip, the main source of this NOx pollution jumps out very clearly: Ship pollution.Animation of Sentinel-5P 5-day average NOx measurements from January to March 2022. Credit: Copernicus/Iban Ameztoy

Apart from a few inland sources, that point to industry and land transport, the NOx pollution clearly highlights the main shipping routes and port cities. In this example the narrow Straight of Gibraltar and the coastal routes towards northern Europe and across the Mediterranean are clearly visible, as well as the Spanish port cities of Barcelona, Valencia, Lisbon and Gijon, plus a few smaller ones.

Read more about Nitrogen Oxides or NOx ship pollution in a Marine Insight article here.

Nitrogen Oxide Pollution in the Windy App

This maritime-caused air pollution is also visible in the static maps that are available on (and the Windy mobile app). For example the NOx map of 18 March 2022 very clearly shows Europe’s main shipping lanes by the NOx levels in the lower atmosphere. The same routes around Spain are shown, but also the English Channel and the routes from western Europe to the Baltic Sea.

NOx levels over Europe on 18 March 2022 (source:

With more and more ships traveling each day to different parts of the world, the air pollution caused by them is on the rise and is one of the major global concerns. The two main pollutants from a ship’s emissions are Nitrogen Oxides (NOx) and Sulphur Oxides (SOx). These gases have adverse effects on the ozone layer in the troposphere area of the earth’s atmosphere which results in the green house effect and global warming.

Both NOx and SOx are combustion products that are emitted in to the environment in the form of smoke.

Regulating Maritime Emissions

The issue of controlling air pollution from ships – in particular, noxious gases from ships’ exhausts was discussed at the International Maritime Organisation (IMO) as early as the 1970s, but drew more attention in 1988, when the Marine Environment Protection Committee (MEPC) agreed to include the issue of air pollution in its work programme. In 1991, IMO adopted Assembly Resolution A.719(17) on Prevention of Air Pollution from Ships. The Resolution called on the MEPC to prepare a new draft Annex to the International Convention for the Prevention of Pollution from Ships (MARPOL) on the prevention of air pollution.

The regulations for the Prevention of Air Pollution from Ships (Annex VI) seek to minimise air emissions from ships (including SOx and NOx) and their contribution to local and global air pollution. Annex VI entered into force (as late as) in 2005 and a revised Annex VI with significantly tightened emissions limits was adopted in October 2008 which entered into force in 2010.

In 2016 IMO designated the North Sea and the Baltic Sea as NOx Emission Control Area (NECA), starting from January 1, 2021 onwards. This NECA regulation applies to all vessels built after 2021, requiring these to reduce NOx emissions by 80% compared to the 2016 emission level.

In practice this means that any new ships have to be equipped with catalysts or use liquefied natural gas (LNG) fuels in order to comply with the regulation. Read about more ways to cut ship NOx pollution here.

The International Maritime Organization headquarters in London (photo: IMO)

EU regulation for maritime SOx emissions, but not for NOx

As a step towards further regulation, it was decided in December 2021 that the Mediterranean is set for more stringent sulphur limits, after the littoral countries agreed to the designation of a 0.10% Sulphur Emission Control Area (SECA) in the region, coming into force in 2025.

Commenting, the European Union (EU) Commissioner for the Environment, Oceans and Fisheries, Virginijus Sinkevičius, said: ‘Our commitment today manifests the will to work with our non-EU partners to achieve high standards of environmental protection in line with our European Green Deal. I am particularly proud that all contracting parties have agreed to designate the Mediterranean as a sulphur emission control area to protect the health of millions of Mediterranean citizens and their marine environment from ship’s pollution.’

However, a regulation on nitrogen emissions from ships will not be included in the submission to the IMO – though the countries agreed to work on NOx in the next two years which could potentially bring about a NOx ECA (NECA).

‘This is disappointing, as comprehensive scientific evidence shows that only a combined sulphur and nitrogen emission control area will maximise health benefits,’ said environmental project manager Beate Klünder. ‘A combined ECA in the Mediterranean Sea could avoid 3,100 to 4,100 premature deaths annually in 2030. To have just one of two effective measures in place is like fighting a fire with just a bucket of water instead of using the fire hose.’

Klünder added: ‘After nearly ten years of successful SECA and one year of NECA regulation in the North and Baltic Sea; we will only see a sulphur regulation in the Med. This is a lost opportunity, now the leaders of the Mediterranean countries have to show ambition in the next steps and must swiftly agree on a nitrogen regulation for ships in the Mediterranean to effectively protect people’s health, the environment and the climate.’ (source)

The IMO works towards supporting the UN Sustainable Development Goals (image: IMO)

Monitoring from space can help expedite emission controls

With the launch of new generations of satellites measuring greenhouse gases and other pollutants, like Copernicus Sentinel-5P, emission sources are rapidly becoming much clearer. This article shows that maritime organisations are working to improving emission standards, but are moving at extreme slow speed, and as shown here, only solve half of the problem.

At the same time the number of ships is increasing, in addition to the fact that large cargo ships, but also cruise ships, have very long economic lives, meaning that fleet upgrades happen very slowly. Most ships built in 2022 will still largely be fitted with traditional heavy oil and diesel engines. And even the transition to the much cleaner (but not clean!) LNG is slow, and cannot be the ultimate solution.

At Groundstation.Space we will continue to report on ship pollution, a perhaps less visible and definitely lesser known source of air and water pollution.

Also read:

A city inside a city: Focus on cruise ship pollution

Remco Timmermans

Related post