Sealing a lot of air in ice, or liquifying it

[Crescent Pulsar S]

If there was a source of extreme cold on the surface of the Earth, how cold would it have to be for it to start depleting the air in the atmosphere? Or to liquify the nitrogen and oxygen? Let's assume that the ice formed is (magically) as cold as the source; would that make it possible for the ice to spread its effect at an exponential rate?

Or maybe it would be better to establish the end result I'm looking for instead of assuming some way of getting there. The ice doesn't have to cover a large area of the world, but the end result should be a worldwide extinction event. I'm hoping to achieve this either by the temperature on Earth being well below freezing on average, or by any number of things caused by a thinning of the atmosphere. In regard to the latter, the effect can be achieved over many years; it doesn't have to be immediate.

[PCHeintz72]

If there was a source of extreme cold on the surface of the Earth, how cold would it have to be for it to start depleting the air in the atmosphere? Or to liquify the nitrogen and oxygen? Let's assume that the ice formed is (magically) as cold as the source; would that make it possible for the ice to spread its effect at an exponential rate?

Or maybe it would be better to establish the end result I'm looking for instead of assuming
some way of getting there. The ice doesn't have to cover a large area of the world, but the end result should be a worldwide extinction event. I'm hoping to achieve this either by the temperature on Earth being well below freezing on average, or by any number of things caused by a thinning of the atmosphere. In regard to the latter, the effect can be achieved over many years; it doesn't have to be immediate.

78Kelvin, at least according to wiki

[Spica75]

I'm hoping to achieve this either by the temperature on Earth being well below freezing on average, or by any number of things caused by a thinning of the atmosphere. In regard to the latter, the effect can be achieved over many years; it doesn't have to be immediate.

In that case you don´t need anything nearly as extreme.

If for example no place on earth is ever above freezing, well there wont be any room for most life to "function", meaning that most kinds of food will become nonexistant.
Some people can still survive by setting up sheltering buildings, burning through a lot of nuclear fuel and getting really serious about solar power and the like, but with greenhouses of one kind or another the only source of food, it will go downhill pretty soon.

Question is how far below zero you need to freeze up oceans enough that geothermal heat no longer allows plankton and other base creatures to live. Once the existence of such is diminished, global food production drops sharply right away.

If no place and time on earth goes above -50C, after a rapid descent to around that point, very few will survive.
-70C or less and only a few handfuls that have access to the very best shelters will live beyond a year.

[Crescent Pulsar S]

It need not go that far. I'm mostly concerned with the human population, with everything else being collateral. I'm looking for the best way (as in, being fairly believable) to off mankind with something that produces a significant amount of coldness. I figure flash-freezing the entire world wouldn't be all that believable, considering the source, so I'm looking for some kind of snowball effect that at least sounds scientifically possible after dismissing said source (which is supernatural).

[PCHeintz72]

Heat would actually be easier.. there are actually at least a couple sci fi movies out there that do that exact approach...

But cold is doable...

if this is by unnatural means, then something that blocks sunlight would do it... for example, if someone blew up the moon to dust, the dust would surround the planet, and would cause a lot of the sunlight to be blocked or reflected before reaching he earth... temperatures would drop, and plants would die, this would propagate through the food chain to us. You would have mass extinctions, long cold winters, massive tidal change, etc...

A less violent but equivalent way would be for an enemy to put up some filter in long range geo-synchronous orbit to absorb the energy from the sun, or block or filter it. Currently we would not have the tech to stop something like that.

[Ellen Kuhfeld]

Are you thinking about the Great Freeze? You could do worse than emulating the events that gave us The Year Without A Summer, also known as 'eighteen-hundred-and-froze-to-death'. The eruption of Mount Tambora in 1815 darkened the skies so badly that crops failed and people starved in 1816.

(Mary Shelley, huddling indoors with a literary crowd, got into the bet that led to her writing Frankenstein.)

All you really need is enough volcanic action to give a long string of years without summer, crop failures, poverty and death. There have been episodes of extreme volcanic eruption before. Perhaps one supervolcano erupting could do the job.

[PCHeintz72]

Are you thinking about the Great Freeze? You could do worse than emulating the events that gave us The Year Without A Summer, also known as 'eighteen-hundred-and-froze-to-death'. The eruption of Mount Tambora in 1815 darkened the skies so badly that crops failed and people starved in 1816.

(Mary Shelley, huddling indoors with a literary crowd, got into the bet that led to her writing Frankenstein.)

All you really need is enough volcanic action to give a long string of years without summer, crop failures, poverty and death. There have been episodes of extreme volcanic eruption before. Perhaps one supervolcano erupting could do the job.

Or multiple continuous eruptions along the entire Ring of Fire system...

It could happen, in fact, after that huge Japanese quake he other year... some feared it might...

Though in my prior post I was referring mostly to unnatural equivalents...

[Crescent Pulsar S]

Are you thinking about the Great Freeze?

From the Sailor Moon anime? Yeah. Few ever get into the specifics of it, at least without rehashing no more than what we're already told by the canon, and I want to do something different from what's been done. (Even though I don't like that version of the series' history.) I have the catalyst, but not exactly how the catalyst will create the desired effect. All I know for sure is that it will be caused by something that can produce extremely cold temperatures.

I'm thinking, at the very least, that most or all of Tokyo will be frozen, initially. I'm not sure if I want to take it any further than that for a start, which is why I'm looking toward the temperature and its effects for how it can escalate from there (to becoming a global problem).

[PCHeintz72]

Yeah... but a lot depends upon just what is the reason for it... because the reason can be a limiter on causes.

There is far different causes if it is an entity or group (Such as the Senshi deliberately causing it, as in some darkfics, or an enemy they were fighting going out with a bang) vs. natural disaster (such as my proposed Ring of fire or other mentioned ideas) vs. some random space event (like a Shoemaker Levy level event smashing the moon to dust)

[Crescent Pulsar S]

Something along the lines of Snow Princess Kaguya, without the power to freeze the whole planet at once. It will be magic ice, so I think I can get away with the ice being the same temperature as the core of its source, which is what I'm hoping will cause the snowball effect.

[PCHeintz72]

Something along the lines of Snow Princess Kaguya, without the power to freeze the whole planet at once. It will be magic ice, so I think I can get away with the ice being the same temperature as the core of its source, which is what I'm hoping will cause the snowball effect.

Now see... had you mentioned it would be caused by an outside entity, that would have eliminated a lot of the guesswork...

But if you have a specific threat, and she already is known for such abilities, not much else is left to discuss...

If it is by a force, it nearly has to be by an off planet one... consider that most conquerers would want to rule the planet... but would not want to destroy it with them on it.

Some other possibilities...

The freeze weapon of Saffron in Ranma 1/2, in Process of elimination by Brian Randall it was used to freeze the planet.

A interesting form of fictional Ice called Ice-9 comes to mind, in a story by Kurt Vonnegut...

[Crescent Pulsar S]

That's because the entity was never in question. I was looking for at least one viable way of devastating life on the planet using a single source, which is very cold and can create magic ice. It sounds more vague than it is, and thus potentially misleading, because I don't want to reveal what the source is and how it came to be the cause.

For instance, if the ice initially covers Tokyo, and it happened to be as tall as it was wide, what kind of effect would that have on the weather? Knowing the stages leading up to the final result would be nice to have, too. I'm even wondering, in the case that some nation tries to nuke it, what the result might be.

[PCHeintz72]

That's because the entity was never in question. I was looking for at least one viable way of devastating life on the planet using a single source, which is very cold and can create magic ice.

Single devastating source? Hmmm...

Well... cooling the planets core itself as one example would devastate life on the planet, but would not really freeze it as you seem to desire.

On the other hand, that Ice-Nine seems to be a more viable idea than initially thought... while not from Sailor Moon, I would imagine if it existed, someone like her would know of and be able to use it.

You might really want to look into that one, as a potential made up attack of hers...

For instance, if the ice initially covers Tokyo, and it happened to be as tall as it was wide, what kind of effect would that have on the weather? Knowing the stages leading up to the final result would be nice to have, too. I'm even wondering, in the case that some nation tries to nuke it, what the result might be.

A block of ice as big as you describe I would imagine would be problematic, but nuking it would be bad.... sure you would vaporize most of it, but that would destroy the city.... even far worse, the rest would be contaminated water that would have just been blown into the ocean...

Not sure how it would affect weather though unless it actually physically impeded clouds.

If normal ice, I would image it creating rainfall and fog due to the fact it would melt... if it is allowed to... even if not I would imagine it would affect temperature and humidity over the entire region.

[Crescent Pulsar S]

An Ice-9-like effect, huh... If the initial formation of ice reaches the harbor, and the water continues to freeze by virtue of the ice's nature rather than needing a certain amount of magical power, that could work. That's roughly seventy percent of the Earth's surface covered in ice, which -- I imagine -- would have a quick effect on the atmosphere. With the water's expansion into ice, I wonder if it would have an effect on fault lines, moving the tectonic plates to some degree, and causing a lot of earthquakes and volcanic eruptions.

[Spica75]

An Ice-9-like effect, huh... If the initial formation of ice reaches the harbor, and the water continues to freeze by virtue of the ice's nature rather than needing a certain amount of magical power, that could work.

Just a Tokyo iced up would not cause any major changes in climate, but if the ice goes out to the Pacific and onwards to all connected oceans and seas, BIG effect yeah. Seawater turning to ice means you greatly increase the albedo effect, ie., how much of the solar energy that is reflected instead of absorbed.

This is effectively the opposite of what climate researchers are currently afraid will happen/is happening, that the large glaciers/ice covers around the poles are going away, because if they do much more energy is absorbed by the earth. Aside from potentially raising ocean water levels by anything up to 60m in the process of course...