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
I've been volunteering for climate change for over a decade now, and after thoroughly researching the topic, have finally settled on Citizens' Climate Lobby as the best approach to solving the problem. Based on what I've seen, if we could get ~250 active volunteer constituents in at least 2/3rds of Congressional districts, we could pass Carbon Fee & Dividend. There is actually a majority in support now in each Congressional district (http://climatecommunication.yale.edu/visualizations-data/ycom-us-2018/) and each political party (http://climatecommunication.yale.edu/wp-content/uploads/2018/05/Global-Warming-Policy-Politics-March-2018.pdf) for a revenue-neutral carbon tax. More than 2/3rds of Republicans are actually receptive (https://community.citizensclimatelobby.org/wp-content/uploads/2017/11/june-2017-meeting-analysis-1127.pdf), and that's despite the fact that the typical Republican district has just over ~50 active volunteers (though as many as 283 and as few as 2). We probably only need an additional 45k volunteers in targeted districts, and that's on the conservative side, as it could take even fewer.
Lobbying works (https://sociology.stanford.edu/sites/default/files/publications/friends_or_foes-how_social_movement_allies_affect_the_passage_of_legislation_in_the_u._s._congress.pdf), and public opinion matters (https://www.tandfonline.com/doi/abs/10.1080/09644016.2016.1116651). The biggest barrier is probably that people tend to underestimate how popular these policies are (https://earth.stanford.edu/news/public-support-climate-policy-remains-strong) and that prevents them from taking action.