It's probably the fact that you created two accounts in 30 mins to astroturf/troll a thread about climate change which is an actual, measurable phenomenon.
What would you explain? Alarmism needs exaggerated alarm, which isn't found in the earlier comment. One could project their own worries about a warming globe onto the comment, perhaps, but that alarm would stem from within oneself, not the comment. Another might see a warming globe as the best thing that could ever happen and there is nothing in said comment that would dismiss that.
It wasn’t auto censored. And you didn’t explain anything, you made a silly and provably false statement and were understandably downvoted almost immediately. Just like if you were to claim the moon landing was faked.
Suppose someone did post that the moon landing was faked. What purpose would downvoting it serve?
1. If posted in good faith, they lose an opportunity to learn. HN should not be joining the ranks of the growing anti-education establishment.
2. If it is trolling, the downvote offers a "read receipt" telling that the wanted attention was found, which only further encourages more trolling. Do not feed the trolls.
There is no situation where downvoting would be a positive contribution. Well, unless you find enjoyment in reading the "why did you downvote this?" comments that sometimes follow. But be careful with that as someday you'll start to see them as just being annoyingly repetitive.
The presence of hyperactive censors has no bearing on the truth of whatever claim they're censoring. People like to steer whether or not they know where they're going.
Your flagged comment goes beyond claiming alarmism (i.e. exaggeration) on the part of others. It's conspiratorial in tone and uses an unnecessary insult.
You are free to say whatever you want. Society is free to dismiss your factually incorrect statements. That isn’t censorship, nobody is required to listen to your nonsense or give you a platform to spout it.