Do spotless vessels contribute to global warming?

Do unclean vessels contribute to global warming?

Giant ocean liners have been using low-sulfur fuel since 2020, making it a massive shift. This change came as a result of regulations enforced by the International Maritime Organization (IMO). These rules have some serious repercussions, which are demonstrated in a recent study. Some experts are a bit skeptical.

The considerable fall in sulfur dioxide emissions stemming from ships could be related to the significant warming of the atmosphere over particular ocean areas, according to a study by a research team published in the journal "Communications Earth & Environment." Approximately 80% of the total growth in stored heat energy on Earth may be due to this phenomenon.

Upon adopting cleaner forms of fuel, the concentration of sulfate aerosols lessened considerably, causing sea clouds to darken. Consequently, these clouds reflected less sunlight into space. The most significant decrease in aerosol concentration occurred in the North Atlantic, the Caribbean Sea, and the South China Sea—which are among the busiest shipping routes. However, independent investigators express doubts about the study. They claim that the period considered is too brief and that man-made greenhouse gas emissions are still the prime catalyst for ongoing climate change.

Ships and High Sulfur Fuel

Previously, ship fuel had much greater sulfur content than other automotive fuel. When the sulfur combusts, it releases sulfur dioxide gas. This reaction produces sulfate aerosols, which can help cool the Earth's surface by reflecting sunlight into outer space and influencing cloud formation.

Sulfate aerosols increase the number of tiny water droplets in the atmosphere, while decreasing their size. As a result, clouds cover the sky more intensely and become lighter, resulting in increased reflection of sunlight out into space, say the scientists.

IMO2020 Regulation

In 2020, IMO2020, a new regulation by IMO, was implemented, trimming the permissible limit for sulfur in ship fuel from 3.5% to 0.5%, aimed at combating air pollution. The outflow of sulfur dioxide from shipping dropped by about 80%, as per the research.

The crew at the University of Maryland in Baltimore examined the Earth's energy balance, as it's the difference between the energy received from the sun and the energy emitted by the Earth since 2020. The introduction of IMO2020 constitutes a "strong temporary shock" for the planet's overall heat influx.

As per their calculations, IMO2020 could ostensibly accelerate global temperature increases in the coming years. The model predicts an expected warming rate of approximately 0.24°C per decade from 2030-2040—more than twice the average rate since 1880.

However, other experts are wary. "Proceed with caution," Anders Levermann from the Potsdam Institute for Climate Impact Research told the German Press Agency. Studying effects spanning short periods is usually less precise than longer durations. Besides, the share of stored heat energy might be considerably lower than 80%. "The value may be exaggerated in the modeling," added Levermann. The record-breaking temperatures experienced last year could be attributed to other causes as well.

"Scientists are baffled as to why the last 12 months exhibited global average temperatures far exceeding norms," said Niklas Höhne from Wageningen University and the Newclimate Institute in Berlin. While it's undeniable that human-induced greenhouse gas emissions play a significant role in warming, a potential additional factor remains elusive.

Apart from volcanic eruptions, the reduction of sulfur in exhaust has also been thought to be another potential culprit. This latest study provides evidence of a significant connection between lowered sulfur levels and higher temperatures. This isn't surprising from a theoretical standpoint. Sulfate aerosols are briefly effective at cooling.

The study's authors also find that the influence of IMO2000 reinforces the hypothesis that adjusting marine cloud brightness through aerosol applications could be a temporary fix for the climate. Nonetheless, they emphasized that such engineering programs are not a complete solution to warming caused by greenhouse gases and come with complex, uncertain side effects.

Levermann cautions against employing this form of geoengineering. "This approach is perilous," he said. While it's relatively cost-effective and effective at cooling, it would compel humanity to constantly pump sulfate or salt into the stratosphere at approximately 12 kilometers above ground levels. "If they want to compensate for human-induced warming using this method, they're playing with fire. As soon as they cease the aerosol applications, the temperature will rise rapidly within a few years," commented Levermann. The potential global consequences of such a scenario are unimaginable.

There's also a geopolitical angle to this engineered fix. "The nation that begins such a program is expected to be held accountable when any weather catastrophe occurs elsewhere," whispered Levermann. The dilemma is more intricate if the aerosols are released into the lower atmosphere where clouds form. "Then, the weather is personally manipulated. This engenders an unfathomable risk," warned the climate researcher.

The seas serve as a massive heat absorber and, in the words of experts, they take in over ninety percent of the heat generated by human-initiated climate change. This means that a liter of water can absorb three thousand times more warmth than a liter of air.

A team of researchers have associated the decline in man-made aerosols with the rise in sea surface temperatures in the North Pacific recently. They claim that the diminishing cooling effect of fine aerosols in China has altered the atmospheric patterns in that area, as stated by a group headed by Xiao-Tong Zheng from the Ocean University of China in Qingdao within the journal "PNAS".

A tension between air purification and climate conservation?

With human-crafted air pollutants impacting human health, numerous governments have introduced measures to reduce them. A contentious issue remains - weighing the merits of cleaner air against the potential costs of further heating, if you will - as outlined by the team helmed by Tianle Yuan.

Levermann, however, opposes this perspective. "It's not a matter of choosing between climate action or cleaner air," he stresses. "The increased visibility of climate change due to improved air quality shouldn't lead to the conclusion that we must make the air dirtier again."

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While some argue that the reduction in sulfur dioxide emissions from ships due to the IMO2020 regulation could contribute to global warming by reducing the cooling effect of sulfate aerosols, others suggest that environmental pollution from marine activities, such as oil spills and chemical discharge, exacerbates climate change by increasing greenhouse gas emissions and negatively impacting marine ecosystems.
The increased use of low-sulfur fuel by ships since 2020, as a result of the IMO regulations, has led to a significant decrease in sulfate aerosols in critical shipping lanes such as the North Atlantic, the Caribbean Sea, and the South China Sea. Meanwhile, marine research continues to explore how climate change is impacting ocean health, including the effects of warming temperatures on marine life and ocean acidification.
As concerns over climate change and environmental pollution grow, there's an urgent need for education and awareness on sustainable practices across various sectors, including shipping and marine research. This could involve implementing policies for reducing emissions, promoting clean energy solutions, and educating the general public on the impacts of human activity on the environment and oceans.

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