The central problem they are trying to tackle here is that as we don’t know the many possible biochemical permutations life might have elsewhere in the Universe, how can we be sure about claims about observations of gasses in exoplanet atmospheres. This was in the news this week with the discovery of dimethyl sulphide on the watery planet K2-18 b. By the end of the decades there may be hundreds of such observations.

The method they propose is one that has been used in climate change science - collating expert opinion from thousands of scientists and going with what is most strongly supported. It’s not a perfect solution either, but as we’re forced to operate in any environment of incomplete data ( we don’t know the full range of potential alien biology) - it may have to do for now.