Thank you everyone. It seems that just putting it in my backpack is not a good idea. I've learned some squirrel tricks, so I have a ton of hiding spots inside the library. However, I'm reluctant to hide my laptop, so I wonder if anyone has work-arounds in mind. Would an air tight ziplock do the trick? My guess is no, but I don't understand the physics at play enough to reason this out.
Another trick would be to have an extra-long sleeping bag and just leave it at the foot of the sleeping bag. Then, however, while the laptop would stay warm, there would still be an increase in humidity because we sweat in sleep, and in a sleeping bag + bivy bag, breathability is compromised.