# In order to reduce the melting of polar ice, why couldn’t we use liquid nitrogen in some ways, to freeze parts of the pole’s seas?

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In order to reduce the melting of polar ice, why couldn’t we use liquid nitrogen in some ways, to freeze parts of the pole’s seas?

In: Physics

Because we can’t “make” cold or heat, just move it around. If we wanted to freeze a large amount of something, we have to take heat out of it and put it somewhere else.

Liquid nitrogen comes from refrigerating normal air. Which uses a shitton of electricity, that a) has a CO2 footprint, b) generates more heat than the LN2 will remove.

The heat generated on the planet isn’t the problem, the sun accounts for 99.9….% of that. The problem is that the heat leaves slower because CO2 prevents it from escaping.

Cooling things takes a lot of energy (ironically). At the moment most of our energy globally still comes from fossil fuels, which means producing more CO2 to make liquid nitrogen, increasing the greenhouse effect.

Also, when you cool stuff, you’re not “adding cold”. You’re just moving some heat away to a different place to cool the original place down. That means making a whole ton of liquid nitrogen and throwing it at the poles might temporarily cool them down, but only by increasing the temperature elsewhere, and that temperature increase would spread back to the poles really quickly, leaving you worse off than you started (because of the energy requirements to freeze the nitrogen).

It’s like trying to stop a wound from bleeding by making a bigger wound higher up the artery. Sure, maybe the one wound stopped bleeding as much, but as a whole, it just makes things worse.

**Edit:** *I just realized that you can technically cool things without moving heat around, just by trapping some thermal energy as chemical energy by doing some chemical reactions. Still not an efficient or effective way to fix icecaps.*

I do recall a line from Futurama “We just drop a giant ice cube into the ocean every once in a while”

Yes theoretically we could… but the amount required would be incredible, and that energy to make the liquid nitrogen has to come from somewhere which would probably end up making the problem worse. Also it doesn’t solve the underlying cause which is too much CO2 in the atmosphere, and that’s only getting worse.

The solution to climate change isn’t to become carbon neutral, it’s to become carbon negative. In other words we have to be taking more carbon out of the air that we put in.

Becoming carbon neutral is the first step, and arguably they easier part. Stop doing more damage.

But we haven’t figured out a practical and effective way to remove excess CO2 from the atmosphere and lock it away on geologic time scales. Planting more trees is the obvious answer, but it won’t work fast enough.

Where are we getting all this liquid nitrogen? How are we getting the energy necessary to make it without heating some part of Earth more?

Global warming and the resulting climate change are baby versions of what all suffuciently advanced civilizations are likely to consider their most difficult problem: heat dissipation. How do you power all your cool things without cooking yourself?

The Earth is a huuuge thermodynamic system, and we can (mostly) only move heat around within it. We would make liquid nitrogen by extracting heat from gaseous nitrogen, but that heat would just go somewhere else. We can then move the liquid nitrogen elsewhere and (temporarily) make that place cooler, but this becomes harder to pull off the bigger the space. “The poles “is a huge area, big enough that it would require an incredible effort to cool it down by transporting cold materials into it, and that would be at the cost of heating up the rest of the Earth. Eventually the heat extracted from the liquid nitrogen would start to bleed back into the poles.

You could fix the melting ice the same way they kept all the snow on Mt Kilimanjaro from disappearing in 2015 like Al Gore said it would.

I wonder how much that would cost. Because I work at a place where liquid nitrogen is used. Every week or two it arrives in a tanker truck. It costs \$100,000 just to refill our tank. It’s maybe 1000L tank?

There are several problems. one is that in order to produce liquid nitrogen we need energy, which produces heat. We can’t create cold, we can only move it around, and even doing that creates additional heat. So anything we do will overall create *more* heat.

But aside from that, there’s a problem of scale. Over the last couple of days alone, literally *billions* of tons of ice has melted on Greenland.

You would need *a lot* of liquid nitrogen to do anything about that.