The global climate strike was inspired by weekly demonstrations held by the Swedish teen activist Greta Thunberg, and UN workers gathered in front of the Secretariat to show support for the Secretary-General's efforts to bring about a greener future for all people.

Ms. Thunberg is attending the schoolchildren-led march in New York, but millions of people of all ages have already joined children across the world in demonstrations, from the south Pacific region, to the west coast of the United States.

UN chief Antonio Guterres told students attending the annual ceremony marking the International Day of Peace, observed on 21 September, that they are making a difference.

"Like the millions who all over the world are demonstrating today in favour of peace with nature, your presence here today is very important for our work," he said.

Climate change is indeed a youth issue, as the UN's International Fund for Agricultural Development (IFAD) said in its Rural Development Report 2019.

Nearly one billion of the global population aged 15 to 24, live in developing countries, according to IFAD. Around half, or just under 500 million, live in rural areas.

"Countries with large youth populations are typically poor and still heavily agricultural, which is one of the sectors most directly affected by climate change," the report stated.

"Countries in West and Central Africa - notably the Central African Republic, Guinea Bissau and Sierra Leone - are in this position. These countries are also in the midst of post-conflict or fragile situations, making it all the more pressing to address the challenge of youth inclusion."

There is also a gender dimension to the climate crisis. As UN Women pointed out in a tweet posted on Friday: Taking #ClimateAction is also taking action to realize women's rights.

While climate change affects everyone, the agency said it is the world's poorest-especially women and girls-who suffer most following devastating storms, drought and other conditions brought on by extreme weather conditions.

"Often, they are the last to eat or be rescued; they face greater health and safety risks as water and sanitation systems become compromised; and they take on increased domestic and care work as resources dwindle," according to a recent UN Women editorial.

More than 700 young people are expected to take part in the UN Youth Climate Summit on Saturday, to showcase their solutions to address what the UN believes is the defining issue of our time.

For UN Youth Envoy Jayathma Wickramanayake, the nearly two billion young people worldwide are "crucial" to the planet's future.

"Young people want and deserve a role in what should be a participatory process and the school strikes for climate action were born out of their desire to make global leaders aware of and act on their concerns," she told ahead of the event.

"They have a stake in the future as this is the planet they will inherit; it is they who will bear the impact of a changing climate."