People don't know what variance is.
Most people have an intuitive understanding of what an average is, but "distance from the average" is mystifying to them.
And if you're trying to sell the public on the numbers of what's concerning, those numbers should be able to communicate the changes they expect.
"This number is small but it means BAD THINGS" isn't a very good message
Ok fine I hear you, in that case how about catastrophic climate chaos? It's even alliterative.