Often when teaching the principles of climate change in the classroom, I've encountered students (and their parents!) who think climate change is not happening at all. What kinds of data, graphs, or evidence are there that I can present that even naive learners can understand? Which CLEAN activities present this evidence in a concise and impactful way?

Jeff:

Sometimes data, graphs, evidence don't convince people, especially if their family and friends have opinions that run counter to science. Some of the teachers we've worked with suggest focusing on how scientists know what they know, explaining the peer review process, and expecting students to master certain scientific skills even if they have an alternative opinion can help prevent students (or their parents) from disrupting the teaching of the science, which can be very technical and complex. Also, weaving in science with solutions can help minimize the sense of overwhelm that climate change science can lead to.

Here's what I run up against: often, people confront me with arguements they say are from real climate scientists that "prove" the climate is simply exhibiting a "natural" pendulum swing right now. Like the evolution/intelligent design debate, there are certain anti-climate fallacies that are frequently quoted from leading nay-sayers. What would help me would be for a climate scientist who can communicate to list some of those frequently-quoted statements against climate change and then answer them with references to data and/or clear, concise reasons why they don't hold water.

It seems that we could make use of some of the approaches used by those teaching about evolution. The National Center for Science Education has a very nice page that talks about how to address skepticism about evolution in the schools or in public debates.
http://ncse.com/resources/teachers

Or see here for a nice list of "primers" to answer common questions (or skeptical comments) about evolution.
http://ncse.com/evolution/science/evolution-primers

Does something like this exist for climate? Should it?

I agree with Mark; sometimes it's worth paying as much attention to how the message is delivered as is paid to the content. I've found this booklet very helpful for that: http://www.cred.columbia.edu/guide/

That said, I also agree with Roberta and Stephanie and have used this page for point-by-point analyses/arguments: http://www.skepticalscience.com/argument.php

I'm trying to figure out how to turn the latter into a lesson to use with high-school students.