European scientists say the release of large amounts of methane gas from thawing Arctic permafrost could devastate the global economy.
Permafrost, or soil below the freezing point, has been thawing under rising global temperatures for many years.
The thawing is releasing the powerful greenhouse gas methane, which is concentrated in the Arctic tundra and is also found as semi-solid gas hydrates in the sea.
A study in the science journal Nature says the release of 50-gigatonnes of methane over a decade will result in flooding, sea-level rise, agriculture damage and health impacts amounting to $60 trillion - which was roughly the size of the entire global economy last year.
The researchers say the impacts will be particularly devastating in developing countries.
Separate research also shows permafrost melting at alarming rates in the Antarctic.
Meanwhile, a new study suggests that billions of years ago greenhouse gases including methane kept Earth warm and wet enough to support life, despite the Sun being much cooler than it is now.
The findings, published in the journal , solve a 40-year-old riddle first raised by famed astronomer Carl Sagan, called the "faint young Sun paradox".
During the Archean era 2.8 billion years ago, the Sun was between 20 and 30 per cent less luminous than it is today, raising questions about how life could have survived such a frozen environment.
Increases in the greenhouse gas carbon dioxide and possibly also methane are all it takes, say the study's authors Eric Wolf and Professor Brian Toon of the .
"So we have these two pieces of evidence that are at odds," Mr Wolf said.
"There's much less sunlight, but at the same time a warm surface, and this is the paradox that we are trying to solve."