What's to achieve by saying we've blown it - that people spark a revolution, or give up trying ? Some of us have been trying for decades, others have been denying for decades, doubt either set gives up.

The original goal the UNFCCC (Art2) was defined in terms of concentrations, so in 1990s diplomats were arguing about 350, 450, 550ppm - 350 being the arbitrary level at the time of the first global climate conferences. I am partly responsible for pushing the shift towards a temperature target, arguing that it would reduce the uncertainty for climate impacts (although increasing it for emissions pathways), but it was extremely hard to get US, China, India to sign up even to <2ºC (COP15). As climate impacts projections got better quantified the most vulnerable countries (mostly African and small islands - together they are many in UN... ), later joined by EU, insisted on trying for a lower number, but we had already passed 1ºC, so we got 1.5º as a compromise in Paris. That 0.5ºC might make the difference as to whether we save Greenland and WAIS, or many ecosystems and food systems. Nevertheless the decimal places are still arbitrary (also influenced by choice of base period, and negotiating in ºC not ºF ), no study quantified impacts vs efforts sufficiently to distinguish a threshold at 0.1ºC accuracy. What matters is that people understand the huge inertia in the systems, in heat and carbon transfer in the ocean, ice and biosphere, also in demographics and social systems. I made an interactive model - SWIM to help explore this. We have to keep trying.