Carbon-climate, like other environmental sciences, has been changing. Large-scale synthesis studies are becoming more common. These synthesis studies are often conducted by science teams that are geographically distributed and on data sets that are global in scale. A broad array of collaboration and data analytics tools are now available that could support these science teams. However, building tools that scientists actually use is difficult. Also, moving scientists from an informal collaboration structure to one mediated by technology often exposes inconsistencies in the understanding of the rules of engagement between collaborators. We have developed a scientific collaboration portal, called fluxdata.org, which serves the community of scientists providing and analyzing the global FLUXNET carbon-flux synthesis data set. The key things we learned or re-learned during our portal development include: minimize the barrier to entry, provide features on a just-in-time basis, development of requirements is an on-going process, provide incentives to change leaders and leverage the opportunity they represent, automate as much as possible, and you can only learn how to make it better if people depend on it enough to give you feedback. In addition, we also learned that splitting the portal roles between scientists and computer scientists improved user adoption and trust. The fluxdata.org portal has now been in operation for ∼2 years and has become central to the FLUXNET synthesis efforts. Published in 2010 by John Wiley & Sons, Ltd.