Just an uneducated guess- I imagine that in the last 30 years the methods of measuring sea ice have changed (more satellites, better sensors), and extrapolating the data leaves some wiggle room for interpretation. I don’t know, though.

I do kow this- my car isn’t causing it. I’ve been conflicted as to whether the Earth is warming or not because I hear about record cold and snow in weird places, but we haven’t had much of a winter at all here in Denver this year. But seeing as how almost everything you see is made of Carbon, somehow I doubt thats the problem. Actually, I dont think warming is a problem at all, I think it would be nice.