China is investigating whether air pollution has played a part in the rapid increase in the number of people struck by lightning in some of its largest cities in recent decades.
The investigation follows a discovery by US scientist that fossil fuel exhaust fumes could double the lightning risk at sea, which raised concerns about the risk to vessels in some of the world’s busiest waters, including the South China Sea.
Lightning kills or injures nearly 4,000 people in China each year, according to government statistics, but less than 20 years ago the reported casualties were only around 400.
The cost of the damage it causes to businesses in sectors such as telecommunications, power and transport is estimated to be somewhere between 5 billion and 10 billion yuan.
Li Jing-xiao, a researcher at Beijing Lightning Protection Centre, said large quantities of polluting particles in the atmosphere could generate powerful electric fields which can be released as lightning bolts.
Li said his team had recently been asked by the government to investigate a possible link between smog and lightning-related accidents.
A total 47 people were killed and 96 injured by lightning in Beijing between 1957 to 2015, according to Li, who had access to the relevant databases.
“The majority of these cases occurred after the 1990s,” he said. Between 2000 and 2009, for instance, the number of people killed or injured was nearly seven times that in the 1960s or 1970s.
The higher number of deaths coincided with the increase of emissions.
The number of cars in Beijing increased from 130,000 in 1982 to nearly six million this year. Car exhaust fumes and industrial pollution have made Beijing one of the world’s most polluted cities in recent years.
A study last year showed that sulphate levels in Beijing’s skies could be equivalent to those caused by volcanic eruptions.
“Statistics and physics are both pointing a finger at smog. It is a suspect we can no longer ignore,” Li said.
Li and colleagues plan to set up radar and other monitoring devices that will measure the levels of air pollutants as well as their physical and chemical details before lightning strikes.
With an observation period of a year or longer they hoped to gather enough data “for clues that will possibly save lives”.
But some scientists expect a negative finding. They said that the smog caused by pollution would reduce the amount of sunlight reaching the ground by deflecting much of the solar energy back into space.
Consequently, this will reduce convection in the atmosphere and lead to fewer thunder storms, according to these critics of the theory.
Li Rui, an atmospheric physicist at the school of earth and space sciences at the University of Science and Technology of China in Hefei, Anhui said the question of whether air pollution could lead to more lightning strikes had generated a long and heated debate in the research community.
“It is quite possible considering the laws of physics, but it is also quite difficult to get hard evidence,” he said.