Despite challenges, China will endeavor to phase out ozone depleting substances and their planet-warming alternatives as required by international conventions, a leading environmental official said.

To date, China has phased out roughly 500,000 metric tons of ozone depleting substances, said Zhao Yingmin, vice-minister of ecology and environment, addressing an event to celebrate World Ozone Day on Sept 16 and the 30th anniversary of China joining the Montreal Protocol on Substances that Deplete the Ozone Layer.

With continuous efforts to control the substances in the past 30 years, China has made great contributions to not only the recovery of the ozone layer, but also global climate mitigation, he said.

Quoting a study by scholars from China and the United States, Zhao said China's endeavor to phase out ozone depleting substances from 1995 to 2014 avoided emissions of greenhouse gases equivalent to 11 billion tons of carbon dioxide.

The nation is also working to phase out 67.5 percent of hydrochlorofluorocarbons, or HCFCs — the last type of ozone depleting substances in China — by 2025, Zhao said.

He reiterated the country's zero tolerance for ozone depleting substances violations, saying China has unearthed almost 100 cases of illegal production, consumption and sale of ozone depleting substances since 2010.

On Sept 15, the country's ratification of the Kigali Amendment to the protocol went into effect, which aims to gradually reduce the consumption and production of hydrofluorocarbons, or HFCs.

While the substances don't deplete the ozone layer and are used as alternatives for ozone depleting substances in refrigeration and air conditioning, they are more potent than carbon dioxide in warming the planet.

The task of phasing out HFCs means that the country needs to revamp industrial chains in various sectors on a large scale.

"China has to bear a huge transition cost for it," Zhao said.

While the cost of technological upgrading will be high for many enterprises, he said a lot of workers may be laid off and need to be reemployed.

However, Zhao stressed the country's determination to phase out HFCs, vowing a series of measures to address the challenges.

Aside from amending laws and regulations according to the Kigali Amendment, the country will work on the 2020-22 national statistics for HFC emissions, which will provide the benchmark for the country to phase out 10 percent of the substances' emissions as required by 2029, he said.

He said the country will establish a network to monitor controlled substances in its effort to build up an early warning system, as well as the capability to assess progress in phasing out the substances.

China will make consistent effort to enhance local governments' capabilities in supervision and law enforcement for phasing out controlled substances, he said.

Devanand Ramiah, deputy resident representative of the United Nations Development Programme in China, said the UNDP commends the Chinese government's efforts to phase out 67.5 percent of HCFCs by 2025 and "remains confident of this goal being met".

The Kigali Amendment will be critical to address the global climate crisis, which is rapidly intensifying, he said, referring to floods in Europe and China this year as examples.

"The international community must urgently accelerate measures to deal with climate change and can take inspiration from the successes of the Montreal Protocol," Ramiah said.