Founders Pledge has recently completed a large report on climate change, which recommends two new cost-effective climate change charities - the Clean Air Task Force and Coalition for Rainforest Nations. This is on our research page here (which also has a report on mental health and will be supplemented with a number of other in-house reports over the next few months). I know some EAs are interested in climate change and it is something we are often asked about. We have been relying on old GWWC research for a while so this should be a useful update.
It may also be of interest because both charities work on policy rather than doing direct work. Finally, there is some discussion of why we do not recommend Cool Earth.
Edit: there is also a discussion of the link between nuclear power and nuclear weapons that may be of interest to ex risk people
Sorry if this is 'clutter' but i will mention CCAN (chesapeake climate action network, based near Wash DC).They do good work mostly on energy conservation, solar power, carbon taxation (which may be feasible politically in this area), , mountain top removal coal ming, and fracking and pipelines in the Appalachian mountains--all very difficult political and social issues. i have disagreed with a few of their policies (ie putting wind farms in Appalachian Mountains; i support offshore wind power rather than turning near wilderness into industrial wind farms--and I think they now mostly support my position),
Its likely CCAN because it operates in an area which has many envrionmentalists and affluent people does not really need more funding (one of the EA concepts---dont put more money where its not needed)---CCAN knows how to raise funds (eg they have a 3 day comedy show benefit this weekend). But I will just put out a plug for them as being an ok group but there may be other groups with higher priority.
This subgroup of EA i find interesting and potentially useful.