Forest fires in Indonesia this year have emitted 1.6 gigatonnes of CO2. To put that in perspective, it has been estimated that the entire world must emit less than 1000 gigatonnes of CO2 every year from now on if we are to avoid dangerous global warming. When forest vegetation burns, the amount of CO2 released into the atmosphere can be taken back up again by the plants as they regrow. But in Indonesia it is not only the plants that are burning. Peat that has accumulated over thousands of years is also on fire, releasing buried carbon. Forest fires in Indonesia burn most fiercely in years when the region is drier, as it is this year. Rain arrived in Indonesia recently, and the number of new fires has dropped.