Rising sea levels and increasing temperatures caused by human activity was a key finding of a seven-year report by a UN panel on climate change released this afternoon.
In the Pacific some low-lying countries could completely disappear, meaning whole populations will have to be relocated to other countries.
One of those is the Marshall Islands, a group of 24 atolls lying just north of the equator halfway between Fiji and Hawaii.
For the 60,000 inhabitants of the country, discussion over whether climate change is real is an insult.
They've been watching their country disappear under rising seawaters for years.
Mack Joel and his wife Tilang have lived in Majuro their entire lives, and they say the island is disappearing fast.
As a child Ms Joel used to play in a park next to a cemetery, where there were trees halfway to the reef. Now, that park has now completely vanished, along with half of the graves.
The latest scientific reports suggest the world is currently heading for a one- to two-metre rise in sea levels by the end of the century. If those predictions are accurate, the Marshall Islands - like many other low lying countries - will be lost forever.
It seems the cruellest of ironies that those most affected by climate change are those who are doing the least to cause it. The Marshallese, like their neighbours in Kiribati and Tuvalu, are mostly subsistence farmers. Their carbon footprint is virtually zero, yet it'll be these people who'll suffer the most.
Vice-President of the Marshall Islands Tony de Brum is an outspoken critic of the big powers' efforts at tackling climate change and is extremely frustrated that his people have nothing to do with the rising waters, and that there is nothing they can do to control it.
"We can stop using gasoline and diesel completely but it would still not make a dent," says Mr de Brum. "It is the big countries, the big emitters that must step up."
On certain parts of the Marshall Islands, complete parts within the lagoon have just disappeared, and his government is already preparing for the worst.
"Plans must be laid down for the future," says Mr de Brum. "What happens if we get inundated? What happens to our country culture? Our language? What happens to the people?"
When talks begin about picking up and moving someplace else - en masse, without really knowing what their status is in the next country - a series of impossible issues arise.
But Mr de Drum isn't thinking about giving up.
"We think that if we [have] to proclaim that we are planning to move, then we are admitting defeat in the war on climate change," says Mr de Brum. "We cannot allow that to happen."
The 60,000 citizens of the Marshall Islands could become refugees, the first mass movement of an entire nation fleeing the consequences of man-made global warming, rather than war or famine.
Watch the video for the full report.