"The sensitivity of the ECS [Earth's climate system] to changes in radiative forcing at the top of the atmosphere is equal to 0.41±0.05 K W−1 m2."The IPCC, however, claims that a change in the top of the atmosphere [TOA] radiation of 3.7 W/m2 from a doubling of CO2 will lead to a 3°C ± 1.5°C temperature increase. The IPCC climate sensitivity is therefore 3K/(3.7W/m2) or 0.81 K/W/m2, about double the amount [0.41 K/W/m2] determined by this new paper.
Note, however, this paper calculates sensitivity on the basis of solar radiation, which is significantly different from infrared radiation from greenhouse gases. Unlike UV and visible radiation from the Sun, infrared radiation from greenhouse gases cannot heat the oceans [70% of Earth's surface area], therefore the sensitivity to greenhouse gases on the land surface is calculated to be
(1-.70)*0.41 = 0.12 K/W/m2
indicating the effect of doubling CO2 levels on Earth's climate is trivial and confirming the low sensitivities obtained by others from observations without computer gaming. Here here here as well as Lindzen & Choi, Paltridge, Spencer & Braswell, and others.