Are shipping emissions adding to weather events in China?

Are shipping emissions adding to weather events in China?

Mon, 25/06/2018 - 16:55
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IMPACT Marine diesel emissions have a high concentration of sulphur dioxide. Photo: Shutterstock

In the 1960s, Massachusetts Institute of Technology mathematician and meteorologist Edward Lorenz constructed a model of the weather that showed how a butterfly flapping its wings in South America could potentially affect weather in New York’s Central Park.

Is it so outlandish, then, in line with his ‘chaos theory’, to think a ship in the Indian Ocean could affect the weather in China?

If, as it is widely assumed, higher pollution levels are linked to more severe weather patterns, it stands to reason the higher the emissions, the more extreme the weather.

This theory was backed by a recent study led by Pennsylvania State University professor of atmospheric science, Michael Mann.

The study examined historical atmospheric observations to identify conditions that correlated with extreme weather patterns.

“We came as close as one can to demonstrating a direct link between climate change and a large family of extreme recent weather events,” Professor Mann said.

Consider the situation in mainland China, the world’s leading source of air pollution:

• Heavy snow hitting Shanghai for the first time in decades.

• Torrential rain and flooding.

• Gale-force winds.

And that’s just in the past few months.

China knows it has a pollution problem and has set stringent guidelines, such as barring the opening of new coal plants and requiring existing plants to cut emissions, restricting the number of cars in major urban areas, and even removing coal boilers from homes.

But while China reports some improvement in air quality, there’s only so much the country can do to rein in the weather, as well as the causes of that weather.

A significant source of pollution is outside the country’s direct control. There’s evidence that extreme weather is linked to pollution generated from the shipping industry.

A paper published in the scientific journal, Geophysical Research Letters, suggests areas marked by popular shipping lanes in the Indian Ocean and South China Sea experience twice as many lightning strikes than other areas of the water.

Here’s how it happens:

Ships burning marine diesel emit exhaust high in sulphur dioxide, which results in the formation of sulphate aerosols in the atmosphere. These aerosols act as nuclei around which water vapour condenses, creating clouds.

Typically, marine clouds comprise larger droplets and do not reach higher altitudes. However, these aerosol-formed clouds consist of smaller particles, which are more easily carried upwards by convection, resulting in the increase in lightning.

So how does this relate to weather in China?

Researchers such as atmospheric scientist Daniel Rosenfeld, of Israel’s Hebrew University, believe these ship-generated aerosols can impact on weather systems in a number of ways, such as transferring precipitation (and pollution) from one area to another, potentially thousands of kilometres away.

In other words, ships in the Indian Ocean could be impacting on the weather in Beijing.

The aerosol cloud-seeding creates droplets so small they no longer band together to form rain.

Say goodbye, then, to the clearing rains China relies on to wash out air pollution and rid urban areas of the build up of smog.

Less rain, combined with stagnation of air, leads to poor air quality for China — no matter how far it cuts its own emissions from factories and cars.

“The haze-inducing conditions are 50 per cent more likely to form between 2050 and 2099 than they were from 1950 to 1999,” says climate change writer Robinson Meyer in the The Atlantic

“And once those patterns fall into place in any one episode, they are 80 per cent more likely to persist.”

Researchers James J. Winebrake, professor at Rochester (New York) Institute of Technology, and James J. Corbett, professor at the University of Delaware, say that since 2008, ship pollution exposure has contributed to more than 1.5 million premature deaths worldwide.

Other studies have found that emissions from shipping are responsible for 24,000 premature deaths annually in East Asia, with 75 per cent of those deaths occurring in China.

It’s important to note these estimates don’t include the deaths, injuries, and economic damage from pollution-generated flooding, hurricanes, and other extreme weather events.

The link is clear – a reduction in sulphur emissions from ships leads to a reduction in sulphate aerosols, which in turn cuts down not only on the direct ill effects of shipping pollution, but on the potential for catastrophic weather events as well.