China has succeeded in literally changing the weather, a new study claims.

As the South China Morning Post reports, researchers say that during the Chinese Communist Party’s centennial celebration over the summer, weather authorities successfully modified the weather above Beijing to clear the sky and reduce pollution for the tens of thousands gathered for a commemorative ceremony in Tiananmen Square.

They did so using cloud seeding technology, a long-studied but controversial process that involves shooting silver iodide particles into the clouds, with the idea of attracting water droplets to modify the weather.