There's also the Breakthrough Institute and Environmental Progress in the US. Plus the broader "Ecomodernist" movement: http://www.ecomodernism.org/
I think this is spot on - the fact that climate change as a cause area is saturated in aggregate terms masks the fact that there a number of both important and neglected (if not necessarily tractable) initiatives that could benefit from an increase in funding and talent. Nuclear and carbon capture advocacy are both good examples. Clean and plant-based meat has nice synergy with animal welfare. I think there's also probably a role for "better" journalism to counteract some of the less helpful, Malthusian narratives that seem to dominate the media right now, at least in the UK and US.