Sentinel tracks ships’ dirty emissions from orbit

The new EU satellite tasked with tracking dirty air has demonstrated how it will become a powerful tool to monitor emissions from shipping.

Sentinel-5P was launched in October last year and this week completed its in-orbit commissioning phase.

But already it is clear the satellite’s data will be transformative.

This latest image reveals the trail of nitrogen dioxide left in the air as ships move in and out of the Mediterranean Sea.

The “highway” that the vessels use to navigate the Strait of Gibraltar is easily discerned by S5P’s Tropomi instrument.

“You really see a straight line because all these ships follow approximately the same route,” explained Pepijn Veefkind, Tropomi’s principal investigator from the Dutch met office (KNMI).

“In this case, we also looked into how many big ships there are in the region [at the time], and there’s really not that many – around 20 or so, we estimate – but each one is putting out a lot of NO₂.”

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    Nitrogen dioxide is a product of the combustion of fuels, in this instance from the burning of marine diesel. But it is also possible to see in the picture the emissions hanging over major urban areas on land that come from cars, trucks and a number of industrial activities. NO₂ will be a major contributor to the poorer air quality people living in those areas experience.

    Sentinel-5P is the next big step because of its greater sensitivity and sharper view of the atmosphere.

    “Shipping lanes are something we’ve seen on previous missions but only after we’ve averaged a lot of data; so, over a month or a year. But with Tropomi we see these shipping lanes with a single image,” Dr Veefkind told BBC News.

    “The resolution we got from our previous instruments was about 20km by 20km. Now, we’ve gone down to 7km by 3.5km, and we are thinking of going to even smaller pixels.”

    Eyes in the sky

    Analysis by David Shukman, BBC Science Editor

    Far beyond the horizon, steaming through the remote High Seas, the great fleets of global shipping have for years been too distant to be observed.

    Only in port can anyone catch sight of the plumes of dark smoke rising from the vessels’ engines. But added together, the greenhouse gases from the world’s 50,000 ships make this industry the world’s sixth largest emitter, and most of it is unseen. This has long fuelled suspicions among environmental campaigners.

    Exempt from the Kyoto Protocol and then the Paris Agreement, shipping acquired a reputation as a sector that dodged its responsibilities on climate change. That’s why the landmark deal earlier this month for a cut in emissions of 50% by 2050 received so much attention. But it also raised a host of questions about policing: who would keep watch, and how?

    Europe’s Sentinel programme is part of the answer. Suddenly, at just the right time, the world’s shipping lanes are in full view.

    S5P’s availability is timely. The shipping sector has just signalled its intention to make big reductions in its emissions over the next 30 years, in particular of the greenhouse gas carbon dioxide.

    At the moment, those emissions are calculated in a “bottom-up” fashion.

    By knowing the size of the global fleet, where it moves, the ships’ specifications and how much fuel they are likely consuming – it is possible to estimate how much CO₂, or indeed NO₂, is being pumped into the atmosphere from exhausts.

    But this all involves quite a few assumptions, and so the models need to be audited by some top-down analysis as well – which is where satellites come in.

    S5P-Tropomi does not see CO₂, although its NO₂ observations can act as a tracer in the sense that wherever nitrogen dioxide turns up on shipping lanes, there will be CO₂ present, too.

    But the best solution would be a dedicated carbon-monitoring satellite.

    This is why the EU has asked its technical agent on space matters, the European Space Agency, to design a Sentinel specific to the task.

    Dubbed Sentinel 7 by many people, because that is the next available number in the series, this future mission should fly in the 2020s.

    The aim is to be able track CO₂ down through the atmosphere on a scale of around 3km by 3km, but over a wide area. That would make Sentinel 7 a forceful partner for Sentinel 5.

    Jonathan.Amos-INTERNET@bbc.co.uk and follow me on Twitter: @BBCAmos

Climate change dials down Atlantic Ocean heating system

A significant shift in the system of ocean currents that helps keep parts of Europe warm could send temperatures in the UK lower, scientists have found.

They say the Atlantic Ocean circulation system is weaker now than it has been for more than 1,000 years – and has changed significantly in the past 150.

The study, in the journal Nature, says it may be a response to increased melting ice and is likely to continue.

Researchers say that could have an impact on Atlantic ecosystems.

Scientists involved in the Atlas project – the largest study of deep Atlantic ecosystems ever undertaken – say the impact will not be of the order played out in the 2004 Hollywood blockbuster The Day After Tomorrow.

But they say changes to the conveyor-belt-like system – also known as the Atlantic Meridional Overturning Circulation (Amoc) – could cool the North Atlantic and north-west Europe and transform some deep-ocean ecosystems.

That could also affect temperature-sensitive species like coral, and even Atlantic cod.

Scientists believe the pattern is a response to fresh water from melting ice sheets being added to surface ocean water, meaning those surface waters “can’t get very dense and sink”.

“That puts a spanner in this whole system,” lead researcher Dr David Thornalley, from University College London, explained.

The concept of this system “shutting down” was featured in The Day After Tomorrow.

“Obviously that was a sensationalised version,” said Dr Thornally. “But much of the underlying science was correct, and there would be significant changes to climate it if did undergo a catastrophic collapse – although the film made those effects much more catastrophic, and happening much more quickly – than would actually be the case.”

Nonetheless, a change to the system could cool the North Atlantic and north-west Europe and transform some deep-ocean ecosystems.

That is why its measurement has been a key part of the Atlas project.

Scientists say understanding what is happening to Amoc will help them make much more accurate forecasts of our future climate.

Prof Murray Roberts, who co-ordinates the Atlas project at the University of Edinburgh, told BBC News: “The changes we’re seeing now in deep Atlantic currents could have massive effects on ocean ecosystems.

“The deep Atlantic contains some of the world’s oldest and most spectacular cold-water coral reef and deep-sea sponge grounds.

“These delicate ecosystems rely on ocean currents to supply their food and disperse their offspring. Ocean currents are like highways spreading larvae throughout the ocean and we know these ecosystems have been really sensitive to past changes in the Earth’s climate.”

To measure how the system has shifted over long timescales, researchers collected long cores of sediment from the sea floor.

The sediment was laid down by past ocean currents, so the size of the sediment grains in different layers provided a measure of the current’s strength over time.

The results were also backed up by another study published in the same issue of Nature, led by researchers from the Potsdam Institute for Climate Impact Research in Germany.

This work looked at climate model data to confirm that sea-surface temperature patterns can be used as an indicator of Amoc’s strength and revealing that it has been weakening even more rapidly since 1950 in response to recent global warming.

The scientists want to continue to study patterns in this crucial temperature-regulating system, to understand whether as ice sheets continue to melt, this could drive further slowdown – or even a shutdown of a system that regulates our climate.

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Lamb cawl named most polluting dish in WWF report

A farmers’ union said it was “astonished” by a report which named a traditional Welsh dish as the “most polluting” classic British meal.

A World Wide Fund for Nature report said a bowl of lamb cawl produced as much pollution as boiling a kettle 258 times because of methane from sheep.

National Farmers Union Cymru said the report did not acknowledge “benefits to biodiversity of grazed livestock”.

The report also warned climate change could risk the future of the dish.

Cawl is made with lamb, leeks, onion, swede, carrots, parsnips and potatoes.

Hedd Pugh, NFU Cymru rural affairs board chairman, said: “We are astonished at the nature of this report that draws comparisons between lamb production and the action of turning a kettle on.

“Welsh farmers take their environmental responsibilities extremely seriously and the industry is constantly striving to become more efficient and productive in line with the goal of meeting our climate change obligations.”

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    The WWF studied the impact of four classic dishes – lamb cawl, chicken tikka masala, ploughman’s and fish and chips – which could disappear or change as a result of climate change.

    Warmer seas could see populations of cod dwindle and see the fish replaced with cheaper options such as anchovies.

    Chickens could also suffer from rising temperatures, the report said, as soy production, which is used to feed them, could be hit significantly by warmer air temperatures and changes to rainfall.

    Gareth Redmond-King, head of energy and climate at WWF said: “The threat to these classic dishes just shows that climate change could impact every aspect of our lives in future if we don’t act now.

    “If each of us takes a small action, together we can combat climate change and future-proof our best-loved dishes.”