About this guide
The article “Mosses tell story of retreating ice” describes how radioactive carbon-14 dating of newly exposed mosses in the Arctic shows that summers are the warmest they have been in at least the last 40,000 years. This guide covers frozen mosses, carbon-14 dating and global warming, as well as related concepts. The activity invites students to explore exponential radioactive decay and half-life with a simulation using pennies, a chemical reaction using food coloring and bleach, and through students’ own calculations. The 2016 Shattered Earth’s Heat Record Educator Guide is another great resource for teaching about environmental change.