Given that there will be a lagged response from the climate to the shift to low-sulphur marine fuel, it is reasonable to expect less than half of the warming resulting from the 2020 regulations to have materialised by 2023, likely only in the hundredths of a degree globally.
This is unlikely to be sufficient to explain the spike in global sea surface temperature in recent weeks, which is around 0.2C above the prior record for this time of year.
Rather, there are a number of other factors likely contributing to current record-warm ocean temperatures. These include the end of a moderate La Niña event at the start of the year and a developing El Niño, a shift which tends to result in higher global temperatures.
Stratospheric water vapour from the 2022 eruption of the Hunga Tonga-Hunga Ha’apai volcano and an unusual absence of dust from the Sahara Desert over the tropical North Atlantic may also be helping drive the ocean heatwave.
Dr. Zeke Hausfather & Prof. Piers Forster
This year was host to a range of extreme heat events: large scale wildfires in Canada – and recently Hawaii – and abnormally high ocean temperatures in the Northern hemisphere; heat waves in Chile and abnormally low ice formation in the Antarctic, despite Southern hemisphere winter. One theory that made the rounds on Twitter was how recent regulation limiting Sulphur emissions from ocean shipping has led to a reduced could cover, thus driving increased warming.
I largely scrolled past those posts, since this narrative falls neatly into the usual playbook of climate change deniers: oh look, it’s something else causing the warming, not us humans burning fossil fuels! oh, it’s just a fluke event! oh, it’s just temporary (this one applies equally to the greenhouse effect of the water vapor from the 2022 eruption of the Tonga volcano)! Circulating the Sulphur story also insinuates that policies against pollution are bad, because they’re making global warming (which is totally not happening, by the way!) worse.
I am weary of the constant noise trying to muddy the water against climate action, but fortunately scientists are continuing to push back against the non-sense. The article above is a good summary: while the 2020 Sulphur emissions rules for shipping do indeed contribute to rising temperatures, the effect is minute compared to warming caused by greenhouse gases, it was known and taken into account while the legislation was drafted as far back as 2009, and in climate modeling.
Even when the story was not shared in bad faith, it reflects a general lack of understanding of the complex issues surrounding global warming – the long-term challenge are the increasing average temperatures, not isolated anomalies – and the widespread and counterproductive lack of trust in scientific authorities – as has been the case throughout the pandemic. It’s incredibly hubristic how people assume that a random poster on Twitter knows better than the people who dedicated the better part of their lives studying these dynamics… Or maybe it’s simply denial, refusing to accept that our actions and current lifestyles can have such dramatic consequences on the planet. After all, it’s much more convenient to deny and delay than to confront and solve difficult problems.
Reading some of the coverage before this regulation came into force, it occurs to me that it might have also contributed to last year’s supply chain issues: the regulation introduced a cap of 0.5% on Sulphur content in marine fuel, which may have forced smaller shipping companies to scrap older ships, thereby reducing available freight capacity.
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