Climate cooperation between China and the Republic of Korea carries special significance, especially in light of the United States' withdrawal from the landmark 2015 Paris Agreement, former United Nations secretary-general Ban Ki-moon said.

Addressing the China-ROK Roundtable on Climate Change Cooperation, which was held on the sidelines of the Boao Forum for Asia on Friday, he highlighted the critical role of China and the ROK as major economic engines in Northeast Asia and key actors in the global transition toward sustainable development.

"The policies and partnerships that emerged from our collaboration can have a powerful impact, not only for the region, but the for whole world, which is undergoing tumultuous times," he said.

Indeed, climate change is a defining challenge of our time, he stressed. No nation, however powerful, resourceful or advanced, can address it alone.

"The atmosphere does not recognize national borders... Our solutions, therefore, must also transcend borders," he emphasized. "We can negotiate many difficult and thorny issues between and among the countries, but we cannot negotiate with our nature."

Recalling the role that China and the United States played in consolidating unity and laying the foundation for the Paris Agreement, he expressed strong disappointment at seeing the US withdraw from the treaty for the second time under the Donald Trump administration.

"This is very a historic issue and very, very important issue which we must not forget... I'm sure that the United States will return after his term is over. But by that time, the climate change has been moving their own course," he noted.

But the situation has underscored the importance of climate dialogue between China and the ROK.

"China and Republic of Korea have always already shown promising leadership in this regard through investment in renewable energy, green technologies and climate innovation, continued collaboration in areas such as carbon markets," he said. "Green finance and technological exchange will be essential at the same time."

Dialogue such as this helps build understanding, share best practices and inspire new partnerships, he stated. It also sends a powerful signal that regional cooperation can play a constructive role in addressing global challenges.

"The window for meaningful climate action is narrowing rapidly. We are losing our time. We must work together again. The choices we make today will determine the future we leave to our children and grandchildren and succeeding generations," he said.