Queen Elizabeth has told world leaders at the COP26 summit in Glasgow that now is "the time for action" on climate change.
Speaking in a video message to world leaders, she called on them to create a "safer, stabler future" for the planet.
She also raised eyebrows after failing to mention Prince Harry.
In her video address, The Queen revealed she "couldn't be more proud" of her son, Prince Charles, and eldest grandson, Prince William, and also praised the environmental efforts of her late husband, Prince Philip. But Prince Harry's name was notably absent.
"It is a source of great pride to me that the leading role my husband played in encouraging people to protect our fragile planet, lives on through the work of our eldest son Charles and his eldest son William," Her Majesty said.
"I could not be more proud of them."
Speaking via video from Windsor Castle, the 95-year-old also urged leaders to "rise above the politics of the moment" and "achieve true statesmanship" through climate action.
"In the coming days, the world has the chance to join in the shared objective of creating a safer, stabler future for our people and for the planet on which we depend," she said.
"None of us underestimates the challenges ahead.
"But history has shown that when nations come together in common cause, there is always room for hope.
"Working side-by-side, we have the ability to solve the most insurmountable problems and to triumph over the greatest of adversities."
The monarch ended her speech by telling leaders "the time for words has now moved to the time for action".
"Of course, the benefits of such actions will not be there to enjoy for all of us here today: we none of us will live forever," the Queen said.
"But we are doing this not for ourselves but for our children and our children's children, and those who will follow in their footsteps.
"And so, I wish you every good fortune in this significant endeavour."
Prince Harry and wife Meghan Markle also did not attend the conference, despite being long-time supporters of climate change action.
Prince Harry spoke out about climate change as recently as late September, when he hosted Global Citizens Live in New York.
The Queen had been due to attend the COP26 event, held in Glasgow in Scotland, in person, but was forced to pull out at the last minute due to a recent health scare which saw her spend a night in hospital.
Prince Charles and his wife Camilla, and the Duke and Duchess of Cambridge, are representing the Queen at COP26.
Concerns were first raised after the Queen cancelled a planned trip to Northern Ireland.
It was later revealed she had stayed overnight at the private King Edward VII's Hospital in central London, where she was seen by specialists and underwent "preliminary" tests.
She has since been advised by doctors to stick to "light activities" for at least two weeks as she recovers, although the source of her illness remains shrouded in mystery.
"The doctors have advised that Her Majesty can continue to undertake light, desk-based duties during this time, including some virtual Audiences, but not to undertake any official visits," a Buckingham Palace statement confirmed.
However, the Queen's health problems has sparked concerns about the future, if her condition was to worsen.