Hmm... okay. If I understand the temperature mechanism correctly, changing the Base Temp would equally and evenly change the temps across the globe. So if it's set at the default of 59.5, and I changed that to 54.5, the temp would drop uniformly around the map by 5 degrees.

Which means it fakable using scripts by selecting temps 5 degrees higher than the ostensible target.

Of course, the chance that I understand the temperature mechanism is at best 50/50.

Right now I'm looking at selecting everything 48 degrees or less and below 7500 ft elevation, then lowering the roughness by .1 and elevation by 500 ft. No idea how realistic that will be yet. I still have to play with it.