The possibility that unrestricted emissions of greenhouse gases would not do unimaginable harm to humanity has become vanishingly small. That’s because we remain near the worst-case emissions pathways, there is little prospect of national or global action any times soon (thank you, deniers), many impacts are coming faster than the models projected, and the overwhelming majority of the scientific literature in the past 5 years has been more dire than the 2007 IPCC report, which itself was more than enough motivation for the overwhelming majority of climate scientists and countries to call for urgent action to reduce emissions.
And I haven’t even discussed the many, many studies that suggest in fact carbon-cycle feedbacks (like the defrosting tundra) are almost all positive (amplifying) and yet largely ignored in most climate models — see NSIDC bombshell: Thawing permafrost feedback will turn Arctic from carbon sink to source in the 2020s, releasing 100 billion tons of carbon by 2100 and links therein.
We can’t let this happen. It is indeed humanity’s self-destruction. We must pay any price or bear any burden to stop it.
See also his “How We Know Humans Are Warming the Planet in 8 Simple Charts“.