Investors who bet on tropical forest conservation and reforestation to solve global warming by storing carbon in wood face huge uncertainties because the science behind predicting carbon stocks is still shaky. Even the best Earth Systems Models fail to predict how carbon stored by tropical forests varies from place to place. The New Phytologist invites scientists doing the "most-exciting, ground-breaking research" to review timely topics in a way that non-scientists can understand. Helene Muller-Landau, staff scientist at the Smithsonian Tropical Research Institute (STRI) was chosen to write the authoritative Tansley Review of carbon accounting in the tropics.