"It is very important to put maximum pressure on governments to accept our goal of carbon neutrality," Gueterres told mayors and youth climate representatives.

"Today we see business, cities and society changing faster than governments," he insisted.

The mayors of the C40, who have declared a "global climate emergency", have announced that they will include a youth council in local decision-making to develop their "New Green Agreement".

"All leaders have two choices: to join us, to adopt the New Green Agreement for themselves (...) or stay out", summarized a 17-year old American activist, Jamie Margolin, who founded the ZeroHour organization.

For the mayor of Paris, Anne Hidalgo, who presided over the C40, the mobilization of young people was the salvation for the fight against climate change.

Mayors from 94 global cities, including Lisbon, on Wednesday called for a "New Global Green Pact" to tackle the "current climate emergency".

The alliance of local authorities known as C40, which includes the Portuguese capital, is now presided over by the mayor of the US city of Los Angeles, Eric Garcetti, who was elected at the organisation's summit in Copenhagen, which was also attended by activists, trade unions, businesses and other civil society movements.

"We recognize the global climate emergency," said the mayors, committing themselves to reducing greenhouse gas emissions "in the sectors that contribute most to the climate crisis: transport, industry, buildings and waste.

They commit to "protecting work, helping to end poverty" and to ensuring "a fair transition for those working in the most polluting industries".

The mayors point out that this delay in the climate response "is already having devastating consequences" and argue that it is necessary to abandon fossil fuels.

For their part, they say that "the C40 cities are already reducing emissions at a pace consistent with the limits set by science, which means "reaching the peak of emissions by 2020 and halving them by 2030".

Eric Garcetti said that when it comes to climate action, "no one is doing more than cities, but no one is doing enough yet.