At least the "medieval warm period" which gets cited a lot, was a regional phenomenon and global temperatures are higher today. The Wikipedia page seems to suggest the same for the Roman warm period.

I've read that most visible flames in campfires are just glowing soot

I had the same problem, but it worked after I closed all other Lemmy tabs in my browser.

but the UI is so ugly :(

Using lemmys image hosting is not good for server storage. OP doesn't want to use imgur for a different reason i'm unaware of