Among a large number of scare-scenarios related to climate change, science reporters (using the term "science" to varying degrees of accuracy here) have been speculating on the danger of how melting ice could unleash bacteria and viruses that might bring about a global plague. It's even been the subject of at least one TV series The Last Ship.
Not to mention this piece of crap:
But how likely is this scenario?
Let's start with what's certain: regardless of what you consider the cause, there are significant areas of the world where the climate certainly is changing. Ice is receding, from many glaciers and from parts of the Arctic. But perhaps more significantly, large areas of tundra and permafrost are thawing. Huge chunks of land which were previously permanently frozen are now becoming soft and potentially accessible to be dug up. Some of these areas have been frozen for centuries, others for millennia, in some cases dating back to the last Ice Age.
And there's stuff in that ice. Sometimes, big stuff. Like this ice-age bison that was uncovered:
Or this ice-age lion cub:
Or, of course, mammoths!
Those are amazing finds for scientists. But for the most part, it's not the big stuff that's worrying people. It's the little stuff:
That's a prehistoric virus. It was found in the permafrost, and it's 30000 years old. And scientists were (very carefully) able to bring it back to life. That one in particular is harmless to human beings. But the fear is that there could be other viruses in the deep ice, thousands of years old, that could be dangerous to humans and against which we have no protections.
How realistic is this fear? If you were to look at media reporting, you'd think it's a huge danger. But if you ask a real scientist, they'll answer that they don't know (because real scientists will usually be careful to claim knowing anything for sure). There's no real precedent for just how dangerous ancient bacteria or viruses could be. What we do know is that for the most part, most really old viruses and bacteria aren't likely to survive long-term freezing. The virus in the article above did because it was a special and very strange kind of 'giant virus'. And in general, the odds of 30000 year old viruses being able to unleash a global plague are likely to be very small, according to one scientist it would be "close to zero."
So we're safe, right? Well, no. Because there is a more realistic danger. Not all the stuff frozen in the ice is 30000 years old. Some of it is just centuries old. Some of it is just from 100 years ago.
That's smallpox. It's a disease that killed as many as 500 Million people in the 20th century alone. Today, it's been completely wiped out thanks to the smallpox vaccine, in one of the greatest medical miracles of our modern age. But we're really badly prepared to handle the possibility of a smallpox outbreak suddenly happening again. Most people born after 1972 are not vaccinated.
It's far more plausible that relatively recent diseases or toxins could be found buried in the melting ice. In fact, it already happened. In 2016 in Siberia, some 75-year-old reindeer corpses thawed out of the ice, and infected the local area with anthrax. One child died and 90 people were hospitalized.
Then there's the bubonic plague:
There are areas of Europe and Asia currently under permafrost where we know for a fact the plague existed, and human victims of the plague were buried. The melting of these burial grounds could potentially unleash the disease.
So there is some cause to be concerned. Especially since these melting areas are going to be drawing a lot of attention, not just from scientists or Siberian nomads, but from oil, gold and other mineral reserves that were once trapped in the permafrost. There's a huge rush in countries like Russia, Norway and Canada to take advantage of these new resources.
So lots of people are going to be routinely moving in and out of these areas, and interacting with everything coming out of the thaw. Val Kilmer did try to warn us, but we wouldn't listen. If only The Thaw had been as awesome as Tombstone!
In all seriousness though, there's a whole bunch of other consequences from climate changes that are probably a bigger risk than the odds that a supervirus will wipe out the human race. Obviously there are dangers, and precautions should be taken. But you should remember to take panicky articles about 30000 year old viruses with a grain of salt. To say nothing of crappy sci fi-horror movies from Hollywood actors who've seen better days.