Isoprene is a molecule emitted from trees, with around 500 teragrams of carbon emitted every single year as isoprene alone. Most of the isoprene emitted originates from the tropics, including areas like the Amazon rainforest, the Congo basin in Africa, and Indonesia. However, very few measurements of isoprene have been done in the tropics, making it difficult to fully understand exactly how much isoprene is emitted and what chemistry it undergoes in the atmosphere.

Using new measurements of isoprene from space, we can pinpoint how much isoprene is above these remote tropical regions. We find that each tropical region has very different drivers of isoprene concentrations: some vary with temperature, and others with precipitation. Previous studies have shown that isoprene emissions generally increase with temperature, but very few show any relationship between isoprene emissions and rain outside of drought conditions. We hypothesize that natural sources of nitrogen oxides, a group of molecules that can alter how quickly isoprene is chemically lost in the atmosphere, may be causing some of these isoprene variations.