Sentinel-5P Tracks Ship Emissions
The European satellite Sentinel-5P has recently been commissioned as part of the EU Copernicus programme. It has the ability to track shipping from trails of nitrogen dioxide left from exhaust emissions whilst on their journeys. Ships generally leave a trail when they burn marine diesel in their engines. The satellite has an instrument called Tropomi which is capable of measuring nitrogen dioxide emission levels. Single images can record the data which highlights pollution, unlike previous satellite recordings where many images had to be combined to record the pollution. Shipping is important as it is the world’s sixth largest emitter of greenhouse gases. Monitoring shipping across the majority of the planet (71% of the globe is water or ocean) will enable better pollution research to be undertaken. It will enable a better understanding of where pollution hot spot problems are.
Tropomi stands for “TROPOspheric Monitoring Instrument”. The troposphere is the lowest layer of Earth’s atmosphere. It is also where nearly all weather conditions take place and contains around 75% of the atmosphere’s mass and 99% of the total mass of water vapour and aerosols. It ranges in height from around 6 kilometres to 18 kilometres above the Earth’s surface. It varies according to latitude and time of year (the polar extent may be just 6 kilometres during the winter).
The Copernicus Sentinel-5P (P for Precursor) satellite is on a seven year mission. It will record a number of chemical constituents of the troposphere as well as other physical features that include direct sunlight. The satellite instrument is also monitoring sulphur dioxide, formaldehyde, ozone, surface UV-B, aerosols, carbon monoxide and clouds. This is the first of the atmospheric composition Sentinels and will increase our understanding of the composition of the atmosphere and how it is changing or being altered by human activities. Daily global observations will be used for improving air quality forecasts as well as for monitoring the concentrations of atmospheric constituents. The instruments also allow for trend monitoring which will enable effective implementation of policies that are designed to reduce our atmospheric emissions. Monitoring will also be able to view volcanic ash clouds, detect high UV radiation levels (that could affect people’s skin) as well as improve our understanding of atmospheric chemical and dynamic processes. It will allow better monitoring of ozone, nitrogen dioxide, and clouds.
Tropomi has an ability to record the atmosphere to molecular levels. A number of high-tech innovations such as immersed grating (where direct sunlight and reflected sunlight maybe measured) and free form optics have been designed by Dutch engineers. This allows a high quality of measurement. The ability to make very detailed daily maps of global air quality to a resolution as small as a couple of city blocks gives an idea of what Tropomi has to offer.
Already maps have been created that illustrate where the nitrogen dioxide levels are high on land. Images have shown the relationship between nitrogen oxide emissions in India and where there are coal power stations (that create the emissions).
This image shows nitrogen dioxide emission concentrations over Europe in November 2017. Red and yellow areas are the higher concentrations. This picture is copyright of ESA, 2017.
Recent calibration of the instrumentation means that it is possible to measure column concentrations through the troposphere. Typically this would be from Earth’s surface up to about 10 kilometres. This ability to map through such a large height will be invaluable to measure and record emissions. The instruments go through a process to ensure that data being sent back is of the requisite high quality. There are five functionalities that the European Space Agency (ESA) mission performance centre requires:
1. Calibration – update on-board and on-ground configuration data so that product quality requirements are met.
2. Geophysical Validation – to assess, by independent means, the quality of the generated data products. Validation provides feedback to calibration and data processors corrective and perfective maintenance activities.
3. Quality Control – routinely monitor the health of the instrument, the detection of instrument degradation and to check if the derived products meet the quality requirements during the mission lifetime.
4. Data processors and tools corrective and perfective maintenance – to manage the updates of the processors, quality control and calibration tools together with all auxiliary files in order to maintain data quality requirements.
5. Communication – the objective is to provide ESA and other stakeholders with relevant information on the status, data usage and data quality of the Sentinel-5P mission.
Tropomi helps in the understanding of the biggest atmospheric pollutants (nitrogen dioxide, ozone and particulate matter (PM)). Already it is showing how beneficial the data can be. Examples of European air quality, the ability to see nitrogen dioxide from shipping and Indian power stations show how valuable this instrumentation will be to science.
International Agreement To Reduce Shipping Emissions
Global shipping has, finally, agreed to make cuts to emissions following negotiations at the United Nations International Maritime Organization (IMO) in April 2018. The IMO has adopted an initial strategy to reduce greenhouse gas emissions and “phase them out, as soon as possible in this century” (source IMO). Previously shipping emissions have been exempt from climate agreements. Now emissions are to be reduced by 50% (compared to 2008 levels) by 2050. Shipping, like aviation, is a major emitter of greenhouse gases internationally. Overall there are similar levels of emissions from international shipping as there are from Germany (according to this BBC report).
The Marshall Islands who have the second largest register of shipping in the world will, ironically, be devastated should sea levels rise as a result of continuing further emissions. The islands are, like several other Pacific atolls, low lying with an average altitude of just over two metres. They welcomed the initial agreements are require that they should go further.
Already there are IMO regulatory agreements to use low sulphur fuel from 1 January 2020. This may have an impact on global oil supplies; refining capacity will be need to be found given the huge quantities of fossil fuel being used by this sector. Further details are explained in this oil price article. As a result of this change Middle Eastern suppliers may lose out as they provide higher sulphur content crude oils.
In March 2018 the IMO agreed mandatory data collection and recording for fuel oil consumption of ships. This recording will provide information on what further changes can be adopted in the future and on how successful the policy is. Data collection will begin in January 2019 and ships will have to report on an annual basis to the IMO. Mandatory Ship Energy Efficiency Management Plans (SEEMP) will be required and will provide a methodology to report data to the ship’s flag State. The IMO is responsible for preventing marine and atmospheric pollution from ships.
The IMO agreement should be the start of big emissions cuts from this sector. There is now a need to innovate and create new designs of ships which are more streamlined and with cleaner engines. The engines could be powered by hydrogen, batteries, or the wind or perhaps a hybrid system. This initially agreed strategy is due to be revised by 2023 with the aim of reducing green house gas emissions even further.
Whilst the IMO agreement mandates a reduction in shipping emissions the Sentinel-5P Tropomi instrument enables monitoring of the emissions on a daily basis. Logged data will be comparable with satellite measured pollution information. The satellite data will improve our knowledge of a complex area of science. Each will hopefully compliment each other leading to reduced emissions and pollution from a sector that needs to act.