“The concentration of PM2.5 Decreases “says Chanti Detyothin, an expert in the royal artificial rain aviation service.
Small by persistent pollution, Bangkok has been the subject of a surprising operation for a year: to limit the cloud that encloses the Thai capital, the country has decided to spray ice water or carbonic ice there by plane by plane or carbon dioxide .
More “There are limits” pour “Make pollution completely disappear”concedes the specialist.
AFP journalists have mounted in mid-January aboard a small Casa military plane, which has to release the millions of inhabitants of the Thai capital trapped fine particles for weeks.
From December, in what corresponds to the start of the dry season, a thick toxic cloud envelope Bangkok, mainly linked to the emissions of vehicles and industries, and agricultural burns.
More than a million Thai have fallen sick due to the “smog” since October 2023 according to the authorities, and the economic cost of air pollution could be in billion dollars in the coming years.
A unique method …
The authorities have also isolated the inversion layer phenomenon, which acts as a hot air cover above the megalopolis, preventing the exhaust at altitude of harmful gases.
It is at this level that Thai scientists want to intervene.
Faced with the vagaries of the climate, the country is used to sending planes, even if critical voices agree that this is not the most effective solution.
For decades, Thailand has had a royal aviation service in charge of artificial rain, associated with the late King Rama IX who would have had the idea in the 1950s to help farmers against drought.
Small devices spray twice a day, at 1,500 meters above sea level, products supposed to cool the inversion layer, and therefore allow the release of polluting particles blocked on the ground.
On the plane to which AFP had access, the crew filled large blue plastic cisters in ice water, for a total of one ton. Other days, planes pour carbon dioxide (CO2) in solid form, also called carbonic ice or dry ice.
According to criticism of this unique method to Thailand, there is no sufficient evidence of its effectiveness. Launched last year, it remains in the test state, and differs from that which consists in triggering showers by dropping large quantities of chemicals in the clouds, insists Chanti.
-CO2 is one of the main greenhouse gases, which contributes to global warming, and the effects on the health of the spray of carbon dioxide in the atmosphere are little known.
Carbonic ice is provided by the Thai oil giant PTT and other companies in the sector.
PTT had not immediately responded to AFP requests.
… but questionable
It's like “Add coriander to the dish”swept away Weeunarin Lulitanonda, co -founder of the Thai network for clean air. “Instead of solving the problem, (companies) are created a beautiful image” To divert attention to their greenhouse gas, she explains.
These companies can do “Much more”she said.
A spray flight can cost up to 50,000 baht (1,400 euros).
It would be more profitable for Bangkok to apply proven measures to tackle the causes of pollution, such as low -emission traffic areas, the prohibition of certain heavy vehicles and control of agricultural burns, explained Ekbordin Winijkul , from the Asian Institute of Technology, established in Thailand.
“Before trying to do something, we should first have confidence in the data” he said.
The authorities have already launched initiatives to limit the circulation of the most polluting vehicles, develop the electric bus network or promote telework.
At the same time, air pollution continues to reach alarming levels in Bangkok, which was one of the most polluted cities in the world on Thursday, at levels well higher than the thresholds recommended by the World Health Organization, According to the Swiss company Iqar.
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