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1 month ago
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Reductions in air pollution might sound like a positive thing.
But scientists now say that reductions in East Asia are actually to blame for the sudden, rapid acceleration in global warming.
While air pollution kills millions, it also whitens clouds.
In turn, this makes the clouds reflect more sunlight back into space - helping to keep our planet cool.
As China and other nations slash their emissions, they are inadvertently removing the artificial shade that has been holding back the full force of climate change, experts from the University of Reading say.
Co-author Professor Laura Wilcox, from the University of Reading, told MailOnline: 'This shading effect from air pollution has offset some of the warming we should have seen due to increasing greenhouse gases.
'As we improve air quality, we remove some of this shading effect, unmasking more warming from greenhouse gases.
'Reducing our aerosol emissions isn't causing warming directly, but revealing more of the effects of greenhouse gas emissions.'
Scientists now say that reductions in air pollution in East Asia, and especially China, have led to a rapid increase in global warming
Over the last decade, East Asia has rapidly reduced its levels of air pollution. This map shows areas of decreased pollution in green and areas of increased pollution in purple
Since 1970, the world has been warming by around 0.18°C (0.32°F) per decade, but this suddenly increased to around 0.24°C (0.43°F) starting from around 2010.
For some researchers, this led to the worrying conclusion that the planet's climate sensitivity - how much warming is produced by a given amount of CO2 - might be at the higher end of estimates.
However, Dr Wilcox and her co-authors have proposed an alternative theory.
They noticed that the sudden increase in warming coincided very closely with East Asia's rapid air pollution cleanup.
In the last few decades, countries in East Asia have undergone dramatic transformations to clean up their air.
China, where air pollution is responsible for one million premature deaths per year, was responsible for three-quarters of all global air pollution reductions in the last decade.
This has led to a 75 per cent reduction in sulphur dioxide emissions over the past 15 years.
When pollutants like sulphur dioxide are released into the atmosphere, they form a fine mist of tiny particles called sulfate aerosols, which drift up into the atmosphere.
As Chinese cities like Beijing (pictured) cut pollution, they removed the layer of reflective particles that had been shading Earth from the worst effects of climate change
With the artificial shade of air pollution removed, the planet rapidly caught up with the warming that current CO2 levels would have otherwise produced. This has led to 0.07°C (0.12°F) of additional warming since 2010
These particles reflect sunlight themselves and influence the way clouds form to make them whiter and more long-lasting.
This acts as a 'cooling sunshade' which prevents some solar radiation from reaching Earth and being trapped by the greenhouse effect.
While the cleanup is absolutely necessary to save millions of lives, it also has the unintentional consequence of producing a temporary spike in warming.
Previous studies predicted that our planet would become 0.23°C (0.37°F) warmer, but the planet actually warmed by 0.33°C (0.55°F).
Using 160 computer simulations, the researchers showed that the East Asian cleanup produced almost all of the extra warming over the last 15 years.
These simulations showed that East Asia's rapid cleanup is responsible for 0.07°C (0.12°F) of this increase.
Overall, there has been so much pollution in the air that it has kept human-caused warming in check by up to 0.5°C (0.84°F) over the last century.
While this is a very small amount compared to total human-caused warming, around 1.3°C (2.2°F) since 1850, it shows that Earth's climate sensitivity is lower than some feared.
From this, it might be tempting to conclude that climate change is not really as bad as some scientists had thought.
Although scientists say that the reduction in air pollution (illustrated) is absolutely necessary, it has produced an unexpected spike in warming. Some scientists mistook this for the planet being more sensitive to CO2
Now that air pollution has been largely reduced, CO2 will once again take over as the main driver of global warming and will not stop warming the planet on its current trend (illustrated) until CO2 levels are reduced
However, the researchers say their study proves the complete opposite.
Lead-author Dr Bjørn Samset, from the CICERO Centre for International Climate Research, told MailOnline: 'In one sense it means that global warming is worse than before.'
Air pollution has been hiding the warming that CO2 levels should have produced, and the planet is only now catching up to where it should be.
The worst of the catch-up period may now be over, but the planet will continue to warm as greenhouse gas emissions take over as the main driver of change.
'The majority of the warming is still, and will continue to be, from greenhouse gas emissions, and the planet will keep warming until we manage to reach net zero CO2 emissions,' says Dr Samset.
'We were always going to need to face up to the full effects of global warming.
'In fact, in order to keep to the targets of the Paris agreement, we now have to work even harder to rapidly cut our greenhouse gas emissions, since the acceleration has put us closer to 1.5 degrees of global warming even quicker than feared.'
The invisible dangers of poor air quality
Poor air quality is the largest environmental risk factor for early deaths leading to an estimated 8 million deaths per year globally, according to recent analysis by the World Bank and the World Economic Forum.
The World Health Organisation recently stated that almost every organ in the body can be impacted by air pollution and that due to their small size, some pollutants penetrate the bloodstream via the lungs and circulate throughout the entire body, leading to systemic inflammation and carcinogenicity.
Exposure to air pollution can lead to strokes, ischaemic heart disease, cardiovascular disease, chronic obstructive pulmonary disease, lung cancer, pneumonia, diabetes, cognitive impairment, dementia and neurological diseases.
Particulate matter, or PM, comes from a variety of sources, including vehicle exhausts, construction sites, industrial activity or even domestic stoves and ovens. PM2.5 is particulate pollutant 2.5 micrometres or smaller in size
There is also some evidence linking air pollution exposure to the increased risk for adverse pregnancy outcomes, such as low birth weight.
Estimations of future mortality in Europe from air pollution often reach hundreds of thousands per year but vary depending on the methodology used.
