Shipping’s greener fuel quest runs into climate complications

LONDON – What does going “green” actually mean? For the global shipping industry, it is a potentially fraught question. About 3½ years ago, shipping – which carries more than 80 per cent of world trade – underwent a seismic change: the cheap, dirty marine fuel it had long relied on was banned and less-polluting alternatives hit the market.

The new rule would slash ships’ sulphur emissions, curbing acid rain and preventing hundreds of thousands of premature deaths thanks to cleaner air.

Yet some scientists have linked that same regulation 

to warmer ocean temperatures,

which can ultimately kill marine life, help melt sea ice and lead to stronger hurricanes.

But establishing, and quantifying, cause and effect is not always easy when it comes to the climate. There are lots of factors that can impact ocean temperature.

Shipping is far from alone in triggering debate about actions that are supposed to help the planet.

The destruction of natural habitats – or replacement of food crops – to grow biofuel feedstock has long been controversial, as have highly questionable carbon offsets for corporate emissions.

In the case of shipping, the industry’s sulphur emissions – while causing health and environmental problems – also have a cooling effect on the climate: they both reflect sunlight and increase the formation of reflective clouds. These concepts were known before the regulation came into force.

Shipping’s pollution-cutting rule reduced the allowable sulphur content of marine fuel from 3.5 per cent to 0.5 per cent (unless a ship had installed a special onboard cleaning unit, known as a scrubber). This would translate to an overall drop of 77 per cent in sulphur oxide emissions from ships.

Beginning on Jan 1, 2020, it was expected to avert more than half a million premature deaths by 2025 from lung cancer and cardiovascular disease alone. It would also help prevent acid rain and ocean acidification, benefitting crops, forests and aquatic species.

The rule was adopted by shipping’s global regulator, the International Maritime Organisation, which currently has 175 member states. Asked how much thought was given to ocean warming, a spokesman last week said the focus had been “on the health benefits”. 

IMO 2020, as the rule became known, potentially added about 0.2 deg C to the North Atlantic region, and likely contributed to record high temperatures, according to Dr Robert Rohde, lead scientist at the non-profit Berkeley Earth.

The regulation’s impact was also raised by Dr Thomas Smith, a scientist at the London School of Economics, who said in an e-mail that “some” warming was an inevitable consequence.

Exceptional warmth in 2023 has not been limited to the North Atlantic. Marine heatwaves have hit the Mediterranean Sea this summer.

Overall, the global average sea surface temperature – defined as the global extrapolar ocean, from 60 deg south to 60 deg north – hit a record high of 20.96 deg C on July 31.

Estimating the impact of ships’ emissions on temperatures in the Atlantic has also been complicated by less Saharan dust as well as the after-effects of “massive Canadian wildfires”, according to an August report from the European Union’s Copernicus.

“There will be, no doubt, long-term impacts from the reduced SO2 emissions,” said Copernicus Atmosphere Monitoring Service deputy director Richard Engelen.

“But it will demand dedicated research to understand the impact of sulphur changes. The changes in dust or black carbon have a more tangible effect in the short term.”

Overall, the global ocean has absorbed a whopping 90 per cent of the warming that has occurred in recent decades as a result of increasing greenhouse gases. Shipping is responsible for a significant portion of those emissions, pumping out more than a billion tonnes in 2018.

In July, the IMO set new reduction goals, including hitting net-zero greenhouse gas emissions “by or around” 2050. It is also working on rules to change shippers’ behaviour. The European Union, meanwhile, is including shipping in its emissions trading scheme starting 2024.

The IMO’s 2020 sulphur rule is not the only “green” part of the shipping industry that has generated debate. Some vessels are now running on liquified natural gas. While this does release less CO2, it also emits methane, a major contributor to global warming.

Ultimately, as shipping inches toward net-zero, future debates about the work of the IMO and others probably will not focus on whether a new rule counts as truly “green”. The question will more likely be: Is it “green” enough? BLOOMBERG