In 2007, the IPCC warned that “as global average temperature
increase exceeds about 3.5°C [relative to 1980 to 1999], model
projections suggest significant extinctions (40-70% of species
assessed) around the globe.” On our current emissions path, we
will warm far more than that this century, which suggests we
risk the high end of species loss. A new study in Science study
(subs. req’d) confirms this risk. It examines “the pace of
diversity loss leading to the Triassic-Jurassic boundary (TJB).”
It finds “the sudden diversity drop … coincided with a mere ~100
to ~350 ppmv rise in CO2 concentration,” and “CO2-induced global
warming was likely an important contributory factor to plant
species turnover at the TJB.” The study notes “The abrupt plant
diversity loss … is consistent with expected plant responses to
a catastrophically rapid rather than gradual environmental
change,” such as might be caused from a massive release of
methane Good thing homo “sapiens” sapiens isn’t doing anything
that might bring about ca