Prince Charles is "proud" of his sons' work to tackle climate change.
The 73-year-old royal has been an outspoken environmental campaigner for decades and he is delighted both Princes William and Harry have launched their own initiatives to help save the planet.
In an essay for America's Newsweek magazine, he wrote: “As a father, I am proud that my sons have recognised this threat [of climate change]. Most recently, my elder son, William, launched the prestigious Earthshot Prize to incentivise change and help repair our planet over the next 10 years by identifying and investing in the technologies that can make a difference.
“And my younger son, Harry, has passionately highlighted the impact of climate change, especially in relation to Africa, and committed his charity to being net zero.”
Charles also reflected on his late father, Prince Philip's, efforts to help the planet through the World Wildlife Fund (WWF).
He wrote: "Sixty years ago, my late father identified the damage humankind was inflicting on the planet and helped to found the World Wildlife Fund. A decade later, when I first spoke publicly about the environment, many wondered if my sense of urgency was misplaced.
"That view has shifted in the intervening decades, though all too slowly, and, even today, lacks the urgency needed."
In the essay, Charles warned "the time is now" when it comes to taking action against climate change.
He added: “The eyes of our children and grandchildren are judging us. Let ours be the generation that ‘can.’ And does. As we enter a new year, there is not a moment to lose.”
The Prince of Wales believes the "world is on the brink" and urgent action is needed.
He wrote: "I have seen at first-hand the impact of false dawns. In November, I travelled to Jordan and, standing at the Baptism site of Jesus, could see the depleting levels of water in what is already one of the most water poor countries in the world.
"In Egypt, who will preside over the next C.O.P. meeting, I heard about the devastating impact of climate change on water and agriculture in the Nile Delta, now one of the most vulnerable ecosystems on Earth.
"Later that month, when I travelled to Barbados, I listened to peoples’ fears about the rising sea levels and the resulting threat posed to their country’s very existence.
"The world is on the brink and we need the mobilizing urgency of a war-like footing if we are to win."