Hurtling through space, far above the Antarctic, the Sentinel-2 satellite beamed back infrared images of something thrilling to scientists on Earth: penguin droppings. The extensive staining of large patches of sea ice indicated that there were eight new colonies no one had known about - and confirmed the existence of three others that had only been suspected.

The discovery means that there are up to 10% more Emperor penguins than was previously thought, giving a new total of over half a million birds. For lovers of a species classified as "Near Threatened" by the International Union for Conservation of Nature, it was hugely significant.

The largest penguin species lives on the world's shrinking supply of sea ice - and the fate of the penguins gives humanity a clear warning about the planetary effects of burning fossil fuels.

Theirs is an extraordinary story. The penguins congregate at their breeding sites on the edge of the Antarctic in March or April each year, taking up residence on the ice which has formed during the winter. To thrive, they need what is known as a "Goldilocks zoneIn the orbit of each star lies a "habitable zone", in which planets could theoretically be found that support life. The main requirement is that it is neither too hot nor too cold. Just like the fairytale, in other words, the temperature must be "just right".": ice which is thick and flat enough to provide a stable platform for raising their chicks, but thin enough to create openings through which the birds can dive in search of food.

It also has to remain stable for at least eight months, so that the young have time to lose the down they are born with, and grow the waterproof feathers they need to survive in the sea. There is a risk too for the adults, who moult dramatically in summer and need time for their new feathers to grow - without them, they could drown.

The worry about the newly discovered breeding sites is that they are in areas which are likely to lose their sea ice if global warming continues. Scientists warn that if the climate crisis continues at its present rate, Emperors could virtually disappear by the year 2100, so delicate is their relationship with the environment.

Emperor penguins have long fascinated scientists. They were once believed to be the most primitive birds in existence, providing a missing link to the reptiles from which birds evolved.

It was in search of eggs that might prove this theory that three men set out for a penguin colony on Ross Island in 1911. When one of them - Apsley Cherry-Garrard - wrote a book about their experiences, he called it The Worst Journey In The World.

The men were part of Captain Scott's ill-fated expedition to the South Pole. Leaving the rest of the party at the expedition's base, the three hauled their sledges 60 miles in almost total darkness and temperatures as low as -61C. It took them 19 days to reach the colony, where they managed to collect five eggs - two of which broke.

On the way back, they were caught in a blizzard so severe that it ripped their tent away, forcing them to build an igloo, which the wind also destroyed. Cherry-Garrard lost most of his teeth when they splintered in the cold.

"If you march your Winter Journeys," his book concludes, "you will have your reward, so long as all you want is a penguin's egg."

Some say yes. One scientist has compared them to a canary in a coal mineIn the early days of coal mining, miners took a caged canary with them. If there was a leak of gas, the canary would be affected first, warning the miners that they were in danger.: their survival has a direct link to ours. While the exciting discovery of more birds clearly does not mean that Earth is healing itself, it does put more high-profile pressure on national leaders to take urgent action on global temperatures.

Others are more pessimistic. Even if we reach no more than 1.5% above pre-industrial temperature levels - the best-case scenario under the Paris AgreementAn agreement signed by 196 countries to try to limit global warming. - the resulting destruction of the sea ice means numbers of Emperor penguins are likely to drop by 30%. The discovery of a few more penguins will make no difference to this.

Goldilocks zone - In the orbit of each star lies a "habitable zone", in which planets could theoretically be found that support life. The main requirement is that it is neither too hot nor too cold. Just like the fairytale, in other words, the temperature must be "just right".

Canary in a coal mine - In the early days of coal mining, miners took a caged canary with them. If there was a leak of gas, the canary would be affected first, warning the miners that they were in danger.

Paris Agreement - An agreement signed by 196 countries to try to limit global warming.