With all the talk about climate this week, it’s a good time to revisit what we do know about climate change.

Fortunately, the National Science Foundation just published an excellent Web site — To What Degree? — featuring a bunch of short videos, in which scientists explain what we know — and don’t know — about our changing climate.

Some 55 scientists discuss components of the topic, “What Science Is Telling Us About Climate Change.” They tackle how we know what we know, the Earth’s water cycle, its carbon cycle and heat balance. The videos show you how they do the research and even include data charts and graphs.

Yes, the scientists admit they don’t know everything about climate. “We don’t always come up with definitive answers, but hopefully incrementally we figure things out,” said Ray Bradley, a paleoclimatologist at the University of Massachusetts, Amherst. “And it might be two steps forward and one step back, but eventually progress is made.”

That’s the way science works: New research provides new answers — and new questions.

Scientists, however, do know a lot. As Richard Alley, a geoscientist at Penn State University, explains: “Our burning of fossil fuels does change the composition of the atmosphere, that does affect climate, and that does affect humans in ways that matter to me, to you and to your children and grandchildren.”

So, as the United Nations Climate Change Conference in Copenhagen continues through December 18 and the media and politicians talk about it, and skeptics shout that we shouldn’t worry about climate change for one reason or another — amid all the clamor you may wonder what the facts are, what we do know about climate change. That’s when you click over to the NSF’s To What Degree? site and watch and learn.