I think the "stuns scientists" is, you know, a headline. Not a true statement. Maybe "stunned" in the sense that seeing the reality of it is still terrible, even if it was expected, but I doubt many climatologists are surprised by this as such.
Or as the end of the article puts it,
"'It is heartbreaking to see it all playing out as we have predicted for so long,' [a climatologist] said. 'The changes we have teed up for ourselves are going to be catastrophic.'”