John Rennie interviews Jeff Sachs for The Gleaming Retort:
Sachs … is also a coauthor, with climatologist James Hansen and a multidisciplinary team of other specialists, of a recent report in the journal PLOS ONE that made a plea for 1 degree Celsius, not 2 degrees, as the appropriate ceiling for permissible warming in the future.
To get his impressions of the report’s content and of its policy implications, I spoke with Sachs a few days before the paper’s publication. What follows is a summary of that conversation.
2 °C is too much
Asked to describe the PLOS ONE report, Sachs calls it “one of the best, concise, up-to-date summaries” of current scientific understanding about the state of the warming problem, drawing on paleoclimate data, climate models, and empirical tracking of global temperatures. (He is also quick to credit it primarily to Hansen, who led the work.)
All those indications, Sachs says, lead to the same conclusions: that the impacts of climate change are already being felt, that they will multiply tremendously in the future, and that feedbacks in the climate system could greatly amplify both the future warming and the consequences associated with it.
No matter whether one favors the limit for future warming to be 1 °C or 2, Sachs says, “we’re off course for either,” with current mainstream projections suggesting that future warming could be headed toward 3-4 °C. But the PLOS ONE paper argues that even the 2 °C target accepted in past global discussions is potentially far more dangerous than was realized. “That two degree figure, which is taken as optimistic by most mainstream observers, is itself wildly complacent,” Sachs says.