Hoo boy. Some days a work-oriented google search gets to be "close-up images of gecko feet," but other days, like today, it's "How do I teach children about climate change without terrifying them?"
Here are three good articles about it:
The general answer is to focus on what can be done to prepare for and mitigate global warming--we know what is going to happen so we can prepare, and we know how to slow down the trend. Even small children can take control of their own live in terms of their and their families' energy use. Older children and young adults can be moved to modify not only their personal choices but their career choices.
A very important point in the Washington Post article--if people feel despair, they do not resort to action, but quite the opposite. People need to feel hope in order to act.