What do you do as a scientist when you discover something that clearly contradicts the textbooks? The two of us faced this problem head-on when experiments we were running in 2005 showed that living vegetation produces the greenhouse gas methane. The established view held that only microbes that thrive without oxygen (anaerobic bacteria) can manufacture this gas. But our tests unexpectedly revealed that green plants also make methane--and quite a lot of it.

The first thing we did was look for errors in our experimental design and for every conceivable scenario that could have led us astray. Once we satisfied ourselves that our results were valid, though, we realized we had come across something very special, and we began to think about the consequences of our findings and how to present them to other researchers. Difficult as this discovery had been for us to accept, trying to convince our scientific peers and the public was almost impossible--in large part because we had to explain how such an important source of methane could have been overlooked for decades by the many able investigators studying methane and puzzling over climate change.