HARI SREENIVASAN, PBS NEWSHOUR WEEKEND ANCHOR:

2014 was the hottest year on Earth since modern record-keeping began in 1880. That is, until 2015. And then that was replaced by the hottest year on record, 2016.

In advance of Earth Day, which occurs three weeks from today, on Saturday, April 22nd, the new edition of "National Geographic" magazine out this week, and the website, www.natgeo.com, have published "Seven Things You Need to Know About Climate Change."

To discuss that guide and related issues, I'm joined from Washington by "National Geographic" editor-in-chief Susan Goldberg.

First, why does "National Geographic" feel it's necessary to do this type of a story?