UN envoy sees positive reaction to Climate Summit

Governments voluntarily agreed in Paris on terms of the agreement and now the United Nations is asking governments to step up their political will and commit, the special envoy said. By identifying some countries willing to step up will encourage others to follow, he added.

"This is a process in which every day public opinion in general is asking governments to deliver," he said. "It is an issue that has become not only in the scientific community or the environmental community, but it is a crisis that is perceived by governments in general and governments need to respond to their own citizens."

The envoy said that if he had a concern, it was not the lack of will but that "we need to step up ambitions quite radically."

"We are not talking about a small, incremental approach but rather a quite drastic increase (in ambition), because if you take all the commitments that countries made up to date, we are still in a trajectory that will bring us to over 3 degrees in increase in the temperature and that would be a disaster," he said.

"To drop it from the trajectory of 3 degrees on which we are today to less than 1.5, you need, I would say, an exponential increase in ambition, and we are counting on some countries to do it," de Alba said.

He said the key is to have clarity on the urgency of action. "We need to identify actions that can be implemented immediately and can have a really transformative impact and that are realistic."

Just calling for action, sounding the alarm and not being able to demonstrate that it is still possible to achieve the goals would not be a solution, he said.

Countries must present an actionable plan of mitigation to participate in the Sept. 23 summit, one day before the opening of the annual General Debate of the UN General Assembly.