Plant morphology reflects evolutionary solutions to environmental constraints. In this experiment, students use this principle to predict the climate at their site. They collect and measure a set of traits on local tree leaf samples during the first meeting. At the following meeting(s), they pool their data and are introduced to a global database of climate and leaf morphology. In groups, they create regressions across sites and use their leaf data to predict mean annual temperature, which they compare to long-term observations from a local weather station. The experiment emphasizes quantitative analysis, data synthesis, and ecological responses to climate.