World leaders should redouble efforts to cut soot emissions because it is the cheapest and fastest way to combat climate change, climate scientists and advocates have told the Guardian.

Deposits of soot – unburned carbon particles – have stained parts of the Arctic black, changing the ice from a reflector of sunlight to an absorber of heat, and accelerating the melting of ice and snow, which itself is starting to alter global weather patterns.



Some scientists believe reducing the concentration of soot particles and other so-called “short-lived climate pollutants” entering the atmosphere may be easier in the short term than bringing down carbon dioxide emissions.

Such a “quick win” would be important to provide breathing space while world populations reduce their use of fossil fuels, scientists say.

Paul Bledsoe, a former White House adviser who has worked on climate science issues for a decade, said: “Limiting short-lived climate pollutants is the cheapest, fastest way to prevent ice melt globally, particularly in the Arctic.”



Durwood Zaelke, president of the Institute for Governance and Sustainable Development, said: “You can’t solve a fast-moving problem like Arctic warming without fast-moving solutions. Cutting the short lived-climate pollutants is the fastest solution we’ve got.

“Cutting these super climate pollutants can cut Arctic warming by two-thirds in the near term.”



The vast expanse of ice and snow covering the Arctic may look startlingly white from a distance, but on closer examination the glaciers and snow cover are patched by dark streaks of inky black and dusty grey and brown. Some are small and self-contained; others are miles long. All are the mark of man.

Hailong Wang, an atmospheric scientist at the US Pacific Northwest National Laboratory, said that both observational and modelling evidence showed that soot was warming the Arctic.

Torches for casing-head gas flaring in the Orenburg region of Russia. Flare stacks are primarily used for burning off flammable gas released by pressure relief valves. Photograph: Alexey Solodov

“The warming effect could be through the direct heating to the air, snow and sea ice by absorbing sunlight, and then accelerating the melting of snow and sea ice,” Wang said. “When the melting starts, there are positive feedback processes that can lead to even faster melting.”

Work by Piers Forster, a professor of physical climate change at the University of Leeds, and Maria Sands, a researcher at Norway’s Cicero institute, and their colleagues, has established that reducing soot emissions could lower Arctic temperatures by 0.2C within a few decades – a valuable contribution, considering that the commitment made in the Paris agreement was to hold temperature rises to no more than 1.5C or 2C.

The Arctic bears what could be considered more than its fair share of the world’s pollution. Industry and tourism in the region are tiny, though mining and oil companies continue to eye-up potential sites as the permafrost retreats. The dirt that scars the Arctic landscape is not local: rather, ocean and air currents carry substances – soot, heavy metals, plastic particles, and more – fromacross the globe to deposit them in this pristine environment. Chemical pollution has even been found to cause brain damage in polar bears.

Soot in the atmosphere has been calculated to be capable of causing warming of about 0.5C in the Arctic, from heating of the atmosphere and melting of snow. This amounts to about a quarter of the observed warming since pre-industrial times.

However, the picture is more complicated than these raw figures might suggest. Unburned carbon particles and gases, such as sulphur dioxide, which often accompany soot production, can have an aerosol cooling effect, because in the atmosphere they can deflect heat from the sun back into space. This process, sometimes called global dimming, makes it hard to estimate the final effects of the pollution.

Chemical pollution has been found to cause brain damage in polar bears. Photograph: Jonnie Hughes/BBC/Silverback Films

While mercury, PCBs (polychlorinated biphenyl) and other pollutants persist for decades, soot is a less permanent problem. “Unlike greenhouse gases, soot particles are relatively short-lived in the atmosphere. The average lifetime is around a week or two,” says Wang. “New snowfall [can also] cover them [the soot particles] pretty quickly.”

And this, according to Zaelke, is what makes soot so important. “Speed is the key metric here, that we haven’t paid enough attention to [in discussions over climate change],” he said. “We have been looking at slow-moving solutions [such as reducing greenhouse gases] and we need to catch up. We need to do something about near-term warming if we are going to stabilise the climate.”

Greenhouse gases are produced by a wide range of human industries: generating electricity, driving, flying, raising cattle, making cement, agricultural fertilisers, and many more. Soot comes from a smaller subset of these activities. Coal-fired power stations are a leading source, as are dirty vehicle engines, and industrial chimneys, but even in developing countries where people have little access to electricity and powered transport, soot is produced by indoor fires used for cooking and heating.

Global warming is not the only impact. Soot is behind human health problems from Beijing to Burundi, as the particles are breathed into lungs where they remain, causing and exacerbating respiratory diseases. Smoky fuels kill more than 4 million people a year, according to the World Health Organisation – a disproportionate number of them women and children, from dirty cooking fires.

Dealing with soot, therefore, is not only a win for the climate, but for people’s health. Forster and Sand have identified three measures as potentially the most effective: reducing the domestic burning of wood in Asia, cutting the flaring of gas in Russia, and reducing emissions from diesel vehicles globally.

A coal-powered plant on the outskirts of Linfen, in China’s Shanxi province. Soot produced by chimneys has been found to cause breathing problems in humans. Photograph: Peter Parks/AFP/Getty Images

The technology to do all of these is available. Gas flaring is not only unnecessary but inefficient, as captured waste gases can be used for fuel. Scrubbers can also be fitted to the chimneys of fossil fuel power stations. Car engines can be fitted with filters, as they are in many developed countries, to remove the dirt from exhausts. Cooking fires are individually harder to reach, but in many areas of the world simple solar cookers could be used that would not only reduce deaths from pollution but ease the lives of women and girls for whom the drudgery of finding fuel each day can be physically demanding, and put a brake on education and development.

History shows that while these measures can involve some upfront costs, these are quickly repaid in quality of life. Londoners, for example, took pea-soupers as a fact of life before clean air legislation was passed following the deadly smogs of the early 1950s. With the right regulation and political will, soot could be made a historical curiosity across the globe.

Forster said: “The measures [to reduce soot] would also help by reducing carbon dioxide emissions. They would also kick in faster – within 10 years of the emissions reduction – whereas CO2 emissions reductions just slow the rate of warming. You need negative [CO2] emissions for a CO2 cooling effect.”

Mike Childs, head of policy at Friends of the Earth, said: “With scientists recognising that soot ranks second only behind carbon dioxide in terms of global warming, it’s crucial that this pollution is cut to help avoid the worst impacts of climate change. Tackling soot would be a win-win, because it will bring enormous health benefits by cutting air pollution too. Governments must act now, and act fast.”

These actions will only be effective as part of a broader push to tackle carbon emissions. Although dealing with soot could be an important way of heading off one of the threats to the Arctic and the world, it cannot be a substitute for acting on warming gases more widely. “Greenhouse gases are still the major player in causing the overall melting of the Arctic,” said Wang. Stopping soot pollution could give us a vital breathing space, but an effective end to global warming – and Arctic melting – will require much more.