I had never met him, although we mailed once or twice in the past year. He also occasionally commented on the Arctic Sea Ice Forum, to chime in or explain one thing or other about some of the work he did.
Most of all, I increasingly used images and graphs from his wonderful personal website, for blog posts and on the Arctic Sea Ice Graphs website, that features several of his graphs on the front page.
I guess that's why the passing of this near-stranger really struck me emotionally. The fact that a scientist would spend so much of his energy and own time to freely share all that info and visualized data, not just for fellow scientists via the peer-review process, but for the lay public as well, on a website chock-full of near-real time graphs (snow cover, sea ice, model forecast)...
It's invaluable. It really says something about a person.