Luis Alfonso de Alba, UN Secretary-General Antonio Guterres' special envoy for the 2019 Climate Summit, speaks to journalists during a press conference at the UN headquarters in New York, on May 28, 2019. (Photo: Xinhua)

UN Secretary-General Antonio Guterres' special envoy for the upcoming Climate Summit said on Tuesday that the reaction from countries coming to the meeting is positive.

"We are quite optimistic because the reaction that we have had since the secretary-general called for this summit is quite positive," said the envoy, Luis Alfonso de Alba.

"We have 18 countries which are co-leading the coalitions and more than 40 countries which are actively participating in those coalitions identifying concrete actions which could be presented at the summit," the envoy said. "They have all agreed with the shift from negotiation to implementation."

The participating countries are all very much encouraged by the fact that the United Nations would be focusing much more on supporting implementation on the ground, said de Alba. "I think the trend is quite positive."

He explained that governments went to Paris and agreed to increase efforts to combat climate change by keeping the global temperature rise well below 2 degrees Celsius above pre-industrial levels and if possible limit the increase to 1.5 degrees.

There were 195 countries and the European Union attending and the accord was adopted unanimously in December 2015.

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.