CPU/GPU temps of your PC depends on your surface

So I've had a lenovo Y50 for about an year and I realized that I've been having really high cpu/gpu temps (thermal throttling). I decided to repaste it with arctic silver 5 and it worked flawlessly. All was good until yesterday I was playing some Rainbow 6 siege with my friends and my temps got high again!  My gpu was reaching 93 degs and was throttling! I thought it hasn't even been a week since I reapplied tp and the problem is back again. So the next day (today) I saw my temps were good again but this time I was in an AC room and was on a different surface. So I performed an experiment to figure out what the matter was:

Stress test were done using Furmark. I only noted gpu temps but cpu temps were affected in the same way.

Test 1:
Surface:

Some sort of study table to use on bed

Temps:

Ambient: 27 degs
GPU temps: 79 degs

Test 2:
Surface:

Dining room's main table with plastic cover on

Temps:

Ambient: 32 degs

GPU temps: 93 degs (Thermal throttles here. That's where I was playing R6S)

After reaching 93 degs I, for some reason, lifted my laptop. This made my temps to rush down to 82 degs. That's when I figured out there's not much to do with ambient temps and made me conduct this experiment.

Test 3:
Surface:

A light plastic table

Temps:
Ambient: 32degs
GPU temps: 82 degs

That's where I suspected that it's not my laptop's ventilation but the surface.

Test 4:
Surface:

A table with glass base covered with some cloth and that same plastic cover as test 2

Temps:
Ambient: 32 degs
GPU temps: 93 degs (Throttled again)

Now I was certain that its the plastic cover which made temps go so high.

Test 5:
Surface:

Same table as test 2 but without that plastic cover

Temps:

Ambient: 32 degs

GPU temps: 77 degs

Conclusion: Keeping your laptop on a table with that type of plastic cover somehow 'chokes?' the vents and makes your temps skyrocket. So, don't keep your laptop on them.

I still don't know why this happens. If you know why this happens then please comment that below.

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Lets discuss below!