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 present

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)