Thats where the physics comes in. if the temperature is halved in terms of celsius from 70° to 35°, if in your case the temperature starts at 100°, the same energy difference would only bring the temperature down to something closer to 65° than 50°.
the specific cooling capacity of the cooler in question only "halves" the temperature if you start at a very specific point.
oh of course there is
https://www.npmjs.com/package/is-even
(do take a look at the download stats)