The Most Efficient and Environment Friendly Programming Languages (stratoflow.com)

I think a lot of the time the most eco friendly language is whichever one doesn't make a bunch of bugs and missing features, causing people to hate tech and then go use a wood stove instead of a heat pump, toss phones in the ocean, or burn down a research lab.

There is a more recent paper by Pereira et al. from 2021 (see https://www.sciencedirect.com/science/article/abs/pii/S01676... if geomean is used (which is the correct method) instead of what they apparently do in the paper, there is yet a different order (see http://software.rochus-keller.ch/Ranking_programming_languag...).