Just weeks before the 2008 Beijing Olympics, Chinese authorities restricted half of all private cars from the city's roads, alternating daily bans for number plates ending in even and odd numbers.

The radical move was just one of a suite of measures aiming to curb the city's choking smog, alongside factory closures and halts on construction.

Over decades of intensive development, residents had become accustomed to smog that not only caused untold respiratory and health problems but was also threatening to derail the Games.

A view from the ABC's office in Beijing on the eve of the 2008 Olympics opening ceremony. (ABC)

Even after the haze cleared, complaints by athletes and visiting media clouded the Games' legacy, spurring a renewed campaign of pollution reduction in China.

As China's economy kept growing after 2008, its emissions of aerosols — small particles in the air, distinct from greenhouse gases — peaked and then dropped rapidly.

Aerosols can include particles emitted by burning fossil fuels, others by volcanic eruptions or bushfires — even airborne sea salt is considered an aerosol.

When enough of them are concentrated in one place, haze can become visible, and weather conditions, including temperature and rainfall, may be impacted.

Likewise, when emissions are reduced, that can cause a significant change, too.

Such has been the success of China's air-cleaning effort since the 2010s that researchers have now linked it to changes in weather far beyond its borders, including in Australia.

Researchers have also tied it to global temperature rises as the aerosols' masking effect on global warming is diminished.

Reflecting heat, changing rain

Unlike greenhouse gases, which trap heat in the atmosphere, most aerosols reflect sunlight away from Earth and produce a cooling effect.

CSIRO scientist Melita Keywood likened their effect to the colour of a roof over a home.

"[Sulphate aerosols] are like a white roof that reflects light, but a black roof absorbs heat,"

she said.

"In some countries where it's cold, you might want to have a black roof, but in Australia you probably want to have a white roof."

Many aerosols also interact with water vapour in the air, affecting clouds and rainfall both positively and negatively.

Late in 2025, a team of Chinese researchers published a paper linking Australia's hot and dry weather in the 2010s to China's aerosol reductions.

They found weather systems were impacted thousands of kilometres across the Pacific, reducing moisture across large parts of Australia and significantly raising the risk of bushfires in all states and territories.