China ‘modified’ the weather as Communist Party marked centenary in Beijing

Cloud-seeding operation was launched over suburban and surrounding areas hours before the tightly choreographed event
Artificial rain reduced PM2.5 pollutants by more than two-thirds and improved air quality, Tsinghua University researchers say

Science

Stephen Chenin Beijing

Published: 5:32pm, 5 Dec 2021

Why you can trust SCMP

China used cloud seeding to control rain and pollution in the capital ahead of a major political event in July, according to scientists at Tsinghua University.

They said the government launched the large-scale operation – lacing clouds with chemicals to bring on rainfall – over suburban Beijing and some neighbouring areas hours before the Communist Party marked its centenary on July 1.

In a research paper, they estimated the artificial rain that was created reduced the level of the air pollutant PM2.5 by more than two-thirds, and improved air quality from “moderate” to “good” under the World Health Organization standards.

The team from the university in Beijing, led by Wang Can, an environmental science professor, said it was unlikely this drop in pollution had a natural cause since “artificial rain was the only disruptive event in this period”. Their research was published in Environmental Science, a peer-reviewed Chinese journal, on November 26.

Tens of thousands of people attended the tightly choreographed event in Tiananmen Square that began at 8am in overcast conditions. There was a downpour soon after the two-hour ceremony had ended.

China’s weather authorities have been trying to alter the weather for important events since 2008, when Beijing hosted the Olympic Games. But according to the Tsinghua scientists, the party centenary presented unprecedented challenges.

One of them was an unexpected increase in air pollutants in the lead-up to the anniversary, the paper said. While most industrial activities like factories and cargo trucks had been halted in Beijing and nearby provinces, air circulation had also slowed, making it harder for pollutants to dissipate.

Chinese scientists use sound waves to increase rainfall on Tibetan Plateau

The Chinese capital also recorded its wettest summer on record this year, with almost twice the average amount of rainfall. The municipal government said groundwater levels, which had been dropping for decades, had risen by nearly 5 metres (16ft) in just a few months.

It rained nearly every day in the week before the July ceremony – on the day, audience members were supplied with raincoats as part of a souvenir pack. According to the paper, a two-hour cloud-seeding operation began at 8.30pm the night before.

People living in the mountains to the southwest of the city said they saw a large number of rockets – used to send silver iodide into the sky to stimulate rainfall – on June 30.

“It was very loud, like thunder – and it went on for a very, very long time … it was like a war zone,” said one resident, who declined to be named. “Then the rain came down, it was quite heavy.”

Another resident said he found debris from the rockets that had landed near his home.

China has built some of the world’s largest, most sophisticated networks for weather modification. The government last year launched a weather modification programme covering a vast area in the west of the country, including Xinjiang and Tibet. It aims to intercept humid air at high altitude, carried by winds from the Indian Ocean over the Himalayas, which is expected to increase because of climate change.

Using satellites, planes, mobile radar stations and artificial intelligence technology, weather authorities are seeking to predict the movement of that humid air so that they can use cloud-seeding operations to control when and where it rains, according to researchers involved in the project.

There are concerns that such large-scale projects could disrupt weather patterns elsewhere in the region. But according to Xu Xiaofeng, a former deputy director at the China Meteorological Administration, Beijing is aware of the risks as well as the limitations of the weather modification technology.

“Weather modification is not only a scientific problem but also a social engineering project closely related to [a country’s] interests, environment and responsibilities,” Xu wrote in a paper published in Chinese journal Advances in Meteorological Science and Technology in October. “To deal with these problems, we need to have new laws, regulations or international treaties,” he added.