Nonsense. It is not possible to nail down ECS to within 0.2C. Another misconception you guys hold is that there is "A" single value for ECS. In the past the global temperature has ranged from >10C colder than today to >18C warmer than today in just the last 700 million years. Anyone familiar with the paleoclimate history of the Earth knows that.
The past climates had different atmospherics ratios, and different amounts of input energy.
While we may not be able to tell specifically what the ECS will be, we can tell roughly what it has been.
There was roughly .2 C of warming before 1940, that did not go back down, If ECS is a feedback responce to input warming after an equalization period,
then we should see all of the amplified feedbacks of less than 75 years, in the record.
Of course we would need to subtract out the know warming inputs from the direct response of CO2.
Temp 1940 .08
CO2 1940 311.3 ppm
Temp 2014 .75
CO2 2014 400ppm
.75-.08= .67 C
1.73 X ln(400/311.3)= .43 C
.67-.43= .24 C
After considering the direct warming from the added CO2, there is only .24 C of possible amplified feeback,
but the number also include all the other unaccounted for variables like aerosol clearing, increases in TSI, ect.
So while we do not know how small ECS is, we can get a rough idea that it will not be more than
a .24 C output from a .28 C input (1880 to 1940 delta temp).
If we apply that same increase ratio to the input 1.2 C, we get a maximum of 2.22 C for ECS,
but we know there were other variables which have not been accounted for.
Some numbers out there place the warming from the TSI increase as much as .3 C for the last century,
if that number is accurate ECS could be a negative number!
I think the ECS will end up being a minor positive, based on published papers, and from my own looking at the input data.