Predictably, the "Breakthrough Institute" is not happy about their early fossil fuel industry connections being called out in The #NewClimateWar (thread)
As of 2005, they proudly acknowledged, as one of their funders, the "Cynthia and George Mitchell Foundation"
Who is the "Cynthia and George Mitchell Foundation". They are a private foundation, founded by shale gas magnate George Mitchell ( https://en.wikipedia.org/wiki/George_P._Mitchell) that advocates for natural gas i.e. "shale sustainability" (3) https://cgmf.org/p/shale-sustainability-program.html
The Breakthrough Institute has been criticized for "touting the fracking and burning of methane gas" (see @Sourcewatch: https://www.sourcewatch.org/index.php/Breakthrough_Institute) (4)
See also this discussion of the Breakthrough Institute from University of Washington's "Conservation Magazine" https://www.conservationmagazine.org/2013/06/gas-pains/ (5)
Needless to say, we stand firmly behind what is stated in The #NewClimateWar (6).