Like the rest of us, advocates for renewables can fail to spot their true friends. Fans of the recent blockbuster Avatar might imagine that ecosystems get rescued by dreadlocked tree-huggers while the film's bad guys are on the ecological frontline. Buzzcuts and heavy weaponry may jar with climate change aesthetics, but back on planet Earth, though, the US military is now spearheading the global assault on carbon emissions on a range of fronts, including solar power.