I think not. The 2C target is pretty arbitrary, nobody really knows the impacts of lesser changes, even half the rate of increase promises risk of enormous problems.
I would agree that knowing more about the actual rate of increase is important in making policy decisions. And I would agree that lower-than-previously-believed climate sensitivity would indeed be good news.
But all these estimates have huge uncertainties. RealClimate has two commentaries on some of the research you present. Michael Mann's remarks conclude
However, it remains true that we do not have a precise number for the ECS (equilibrium climate sensitivity). Sherwood et al’s results give weight to higher values than some other recent estimates based on transient estimates (e.g. Otto et al. (2013)), but it should be kept in mind that there is a great asymmetry in risk between the high and low end estimates. Uncertainty cuts both ways and is not our friend. If the climate indeed turns out to have the higher-end climate sensitivity suggested by here, the impacts of unmitigated climate change are likely to be considerably greater than suggested by current best estimates.
In a similar vein, Oxford's Richard Millar concludes his
commentary on the Lewis and Curry paper by pointing out
While of some scientific interest, the impact for real-world mitigation policy of the range of conceivable values for the TCR (transient climate response) is small (see also this discussion in Sci. Am.). For targets like the 2 K guide-rail, a TCR on the lower end of the Lewis and Curry and IPCC ranges might just be the difference between a achievable rate of emissions reduction and an impossible one…
It would appear that we're working with the boundary between "doomers are right" and "we can maybe just manage this problem with urgent action," rather than the boundary between the latter and taking our sweet time to figure out what to do...
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