As for his question, if you use the forcings from AR5 AII Table 1.2 (which are a little higher than CO2 forcing alone), & the global numbers@359 (but assuming 0.86 W / m2 imbalance) you get an ECS = 2.8 ºC but most folk consider energy balance methods do underestimate ECS. (skepticalscience.com)
But the point is that huge changes can happen that have local causes and are totally invisible to the global energy balance method that is Webby's bread and butter and often used by climate scientists to argue about forcings. (judithcurry.com)
Tools such as the PHPP with its steady - state energy balance method are insufficient for some uncommon planning tasks. (passiv.de)