<p>In a lesson in this issue of <em>Smithsonian in Your Classroom, s</em>tudents do the work of a team of paleontologists studying a time of rising carbon dioxide and rapid global warming during the Eocene epoch. By examining fossils of tree leaves, and then incorporating the findings into a mathematical formula, they are able to tell average annual temperatures 55 million years ago. Really!</p> <p>Click the PDF icons to download the issue and additional materials.</p>