Recent climate change headlines have been dominated by news of a study stating that cutting pollution from global shipping accelerates the heating of our planet and oceans.
The study concludes that UN air pollution rules introduced in 2020 aimed to cut the sulphur content in shipping fuels. This caused an “inadvertent geoengineering termination shock” with significant global warming impacts.
Many leading scientists have since realised there’s more to this story than is apparent at first glance. They argue that the extreme ocean temperatures recorded over the past year cannot be solely blamed on shipping’s sulphur reductions. Many factors likely contribute to this effect.
The real risk to our oceans comes from climate change inaction. Governments urgently need to do more to address shipping’s huge environmental, climate change, and pollution.
The crucial negotiations happening at the UN’s International Maritime Organization (IMO) this and next year are our earliest chance to make this happen.
Sulphur oxide (SOx) refers to a range of sulphur. Oxygen-based pollutants are produced by burning fossil fuels such as coal or, in shipping, heavy fuel oil.
Dangerous Shipping Pollutants and Climate Change
Exposure to SOx can cause serious illnesses such as asthma and bronchitis and has been linked to thousands of respiratory-related deaths each year. Other effects of SOx include acid rains that cause significant damage to ecosystems.
At the same time, SOx is one of the building blocks of atmospheric particles called aerosols, which are associated with cooling and heating effects on our planet.
Other types of aerosols have the opposite effect.
Burning fossil fuels emits black carbon alongside SOx. When it reaches snow and icy environments, such as the Arctic or mountain glaciers. It has a “double-whammy” warming impact, speeding up ice melting and revealing dark land surfaces that absorb further solar radiation.
With all this science in mind, the IMO–shipping’s climate regulator. They decided to gradually restrict sulphur in marine fuels to 0.5% in 2020.
This was the right decision, benefiting countries and communities most impacted by the health and environmental effects of SOx. One study estimates that if this action were delayed until 2025, it would contribute to more than 570,000 additional premature deaths globally.
However, in 2020, the IMO also hoped that addressing SOx emissions would lead to a parallel reduction in black carbon by moving ships onto cleaner distillate fuels. In reality, however, ships merely shifted onto low-sulphur fuels that reduce SOx emissions but do not reduce black carbon.
The IMO’s failure to address other dangerous pollutants like black carbon has damaged its SOx reduction success story.
Reducing pollution must not become a trade-off between human health and climate. Instead of trying to find a single cause for climate change, it is important to remember that the current crisis does not have a single source. Even if reducing SOx shipping pollution removes an artificial cooling impact, it’s just one piece of the puzzle.
Way Forward
Addressing the climate change crisis requires not backing down from useful, life-saving measures but the opposite. Stepping up efforts to cut all pollutants, like carbon, black carbon, and methane–all of which are as closely linked to shipping as SOx.
This way, we can counter the cooling loss due to reducing polluting SOx emissions.
This year and next, the IMO is revising its existing climate rules. They are deciding on new and additional policies to deliver on their historic commitment to make shipping zero emissions by 2050.
Meeting these goals will require stepping up ambition in ships’ current energy efficiency standards. These include improved operational efficiency and reduced fuel burn. In addition, the IMO needs to urgently introduce regulations for the use of cleaner fuels in and near the Arctic to address the heating impacts of black carbon adequately.
The IMO already agreed to adopt some form of emissions price (e.g., a levy) in April 2025. They would be the world’s first universal emissions price for any international industry. Also, there are strong incentives for the uptake of zero-emission fuels.
With an ambitious approach across these policies. It includes a levy of at least $150 a tonne of greenhouse gas emissions proposed by the Pacific Island states and Belize. Shipping can be held accountable for its damages. Justice and fairness are especially important to these discussions. The IMO must ensure vulnerable states that suffer the gravest climate change impacts are appropriately assisted.
