You have already decided that what appears to be the position of a majority of experts (a large climate sensitivity to GHGs and catastrophic scenarios for the future) must be right. (illconsidered.blogspot.ru)
Knutti et al. (2006), using a different, perturbed physics ensemble, showed that models with a strong seasonal cycle in surface temperature tended to have larger climate sensitivity. (ipcc.ch)
The reason they returned to the 1.5 to 4.5 range is because there was virtually no global warming since 2000 (the so called «hiatus»), which is embarrassingly inconsistent with a large climate sensitivity. (sciencebits.com)