Reducing air pollution could push the Gulf Stream towards a COLLAPSE

Reducing air pollution could push the Gulf Stream towards a COLLAPSE,

Reducing air pollution could have an unintended, and potentially disastrous side effect, a new study has found.

While lowering aerosol emissions helps humans breathe easier, it could push the Gulf Stream closer to the brink of a catastrophic collapse.

Researchers found that measures aimed at cutting sulphur dioxide and black carbon emissions are weakening the Atlantic Meridional Overturning Circulation (AMOC).

This is a vast network of global ocean currents, of which the Gulf Stream is just one part, that is critical for keeping the climate stable.

If AMOC were to collapse, studies have shown that temperatures in Northern Europe would plummet – plunging the UK into a ‘new Ice Age’.

Researchers found that cutting back air pollution will cause this key current to weaken by about six per cent by 2050.

That is on top of the weakening already being caused by human–caused climate change and greenhouse gas emissions.

However, co–author Professor Laura Wilcox, a climate scientist from the University of Reading, told the Daily Mail: ‘While reducing air pollution weakens AMOC, the effect of continued increases in greenhouse gases is larger.’

Scientists have shown that cutting air pollution could lead to a key ocean current, of which the Gulf Stream is a part, being pushed closer to collapse. Pictured: Graphs showing the weakening of the AMOC in response to reduced aerosol emissions 

AMOC functions like an enormous ocean conveyor belt, carrying heat, carbon, and nutrients around the world.

The engine driving this system is the formation of very cold, dense salty water in the Arctic.

As this water cools and sinks to the bottom of the ocean, it pulls in more warm water from the Atlantic after it and ensures that the whole network keeps moving.

That process has been keeping global ocean currents relatively stable for around the last 6,000 years, but human activity is now pushing AMOC to the edge of collapse.

As the climate warms, melting glaciers in the Greenland ice sheet are dumping millions of tonnes of fresh water into the oceans every year.

That is diluting the salty water around the poles, making it less dense and weakening AMOC.

Since this process is being driven by human–caused climate change, it might seem counterintuitive that cleaning up air pollution would make the situation worse.

However, this climate change paradox is actually a well–known problem.

The tiny particles that make up aerosol pollutants hang in the atmosphere, reflecting radiation from the sun back into space and keeping Earth cool.

This means that air pollution has actually been cushioning the full impact of climate change, holding back some of the warming we might have otherwise felt.

Critically, without those aerosols, more energy can reach the Atlantic Ocean to weaken the temperature balance that has kept AMOC going.

Professor Wilcox says: ‘As aerosol emissions are reduced, the Northern Hemisphere warms, and this warming is stronger at higher latitudes.

‘This reduces the temperature imbalance between the Equator and the Pole, so the AMOC doesn’t need to transfer as much heat to maintain balance, and weakens.’

The researchers ran 80 different simulations of the climate between 2015 and 2050, testing how different air pollution measures affected AMOC’s function.

They compared a situation in which certain regions implemented strong air pollution controls against a situation in which these rules remained lax.

This revealed that stronger controls on air pollution actually resulted in the AMOC becoming weaker at a faster rate.

Reducing aerosol emissions globally or in various regions around the world leads to more solar radiation reaching the surface of the North Atlantic, disrupting the temperature balance that drives AMOC. Pictured effects of solar radiation on global reductions globally, in North America and Europe, Africa, East Asia, and South Asia (top to bottom) 

While AMOC did weaken faster, the researchers point out that none of their simulations showed that the current would collapse by 2050.

However, researchers also found that the effect varied depending on where emissions were cut.

The strongest impacts occurred when aerosol emissions fell over North America and Europe.

This is because most of these regions’ aerosol emissions occur at mid to high latitudes, where they have a big impact on solar radiation over the waters around Greenland and west of the UK.

Emissions cutting in Africa had the second strongest effect, followed by the Middle East and East Asia.

In contrast, reducing aerosol emissions in South Asia had almost no impact on the strength of AMOC.

The researchers suggest this is because those particles are so far from the North Atlantic, where AMOC’s critical water circulation begins.

However, even when the entire world reduced aerosol emissions, the effect was still only a third of the weakening produced by greenhouse gases emitted over the same period of time.

The effects varied depending on where emissions were cut, with the most pronounced impact on AMOC coming from aerosol reductions in North America and Europe (top)

That means there is no reason to avoid reducing harmful air pollution for fear of damaging AMOC when carbon dioxide and methane are a much bigger threat.

Professor Wilcox says: ‘Poor air quality due to aerosol pollution is one of the leading causes of premature mortality worldwide, and is associated with many negative health impacts, such as respiratory illnesses and cardiovascular disease.

‘We find that, although reducing aerosol does weaken AMOC, the effect is smaller than the effect of increased greenhouse gases.

‘This suggests that making large, rapid reductions in our greenhouse gas emissions is the best thing we can do to minimise AMOC weakening.’