I think you are right that Drawdown is doing good work, and trying to compare things that are quite difficult to compare. At the same point, the HN community should be aware that the data and models are neither open nor clearly identified, which means that we essentially have to just trust their conclusions. I work in this space [1], and when I see results with five significant digits (!) for prospective assessment it makes me very curious to see how these results were generated.

For an alternative, see the Big Open Network of Sustainability Assessment Information (BONSAI [2]; disclosure: I am chair of the board) which is trying to do similar work with open data and open science.

[1] https://chris.mutel.org/ [2] https://bonsai.uno/