It appears to be a reassessment of many papers on the topic published since 2008, trying to identify which of the proposed 'catastrophic' tipping points presented in those papers are most likely to occur specifically in the 1.5-2 degree range (as opposed to the 2+ degree point, which people also look at)

> We carry out the first comprehensive reassessment of all suggested tipping elements, their CTPs, and the timescales and impacts of tipping. We also highlight steps to further improve understanding of CTPs, including an expert elicitation, a model intercomparison project, and early warning systems leveraging deep learning and remotely sensed data.

I think the real answer is that doomsday studies get clicks and the capitalist engine is at work, and being worked by scientists for attention.