Even the most hardcore climate change denier can’t deny that the planet is warming.

And as it warms, the Arctic permafrost is giving up many of its deadly secrets.

Not just frozen mammoths but long lost aircraft and even buried smallpox victims. A frozen 300-year-old mummy, from a group found in an ornate coffin in Siberia, contained traces of the deadly smallpox virus.

But perhaps the most worrying thing emerging from a millennia-long deep freeze is a huge number of microbes, bacteria and viruses unknown to science.

NASA scientists have discovered living microbes more than 400,000 years old in thawed permafrost.

The Arctic is at its warmest since records began

Microscopic creatures from the Cenozoic to the Pleistocene eras are re-emerging, and interacting with modern lifeforms in new and unpredictable ways.

In 2016, an anthrax outbreak that killed a child and led the the deaths of some 200,000 reindeer was traced to thawing permafrost.

A “new” virus known as Alskapox that was first identified in 2015 is now believed to be a long-frozen survivor from the distant past.

Permafrost currently covers over 20% of the world’s land surface area. It’s unknown what other ancient undiscovered micro-organisms could soon be emerging as it melts.

The thaw is going on all year round

The warming Arctic is also releasing huge amounts of methane that has been held underground for thousands of years – as well as CO2, threatening to accelerate the warming process.

Observations between 2003 and 2017 revealed that in the winter months the Arctic releases some 1.66 gigatonnes of CO2 a year, more than the the 1.03 gigatonnes soaked up over the rest of the year.

Susan Natali at Woods Hole Research Center in Massachusetts says that by by 2100 the CO2 emissions from thawing permafrost in the Arctic could climb by as much as 41%.

“Given that the Arctic has been taking up carbon for tens of thousands of years, this shift to a carbon source is important because it highlights a new dynamic in the functioning of the Earth system,” she told New Scientist.

A team led by Peter Wadhams of the University of Cambridge also flagged up the danger of the the so called “methane time bomb” which threatens to release huge amounts of the greenhouse gas into the atmosphere as the Arctic melts: “A 50-gigatonne reservoir of methane, stored in the form of hydrates, exists on the East Siberian Arctic shelf,” they warned. “It is likely to be emitted as the seabed warms, either steadily over 50 years or suddenly.”