“I am disappointed with the outcome of COP25,” Guterres wrote on his Twitter.

I am disappointed with the results of # COP25.

The international community lost an important opportunity to show increased ambition on mitigation, adaptation & finance to tackle the climate crisis.

But we must not give up, and I will not give up.

- António Guterres (@antonioguterres) December 15, 2019

The UN Secretary General noted that the international community has missed an opportunity to demonstrate an increase in aspirations to combat the effects of climate change.

“But we must not give up and we will not give up,” he added.

Earlier, President of the European Council Charles Michel during the Conference of the Parties to the UN Framework Convention on Climate Change, held in Madrid, said that "the time has come for a green revolution."