COBE's temperaturesensitivity was adequate, its angular resolution was poor, so it could not distinguish the features necessary to gauge the universe's age.
Climate sensitivity is how much will the temperature change over a doubling of atmospheric CO2 (more strictly, CO2-e, taking account of methane and all the other gasses and converting them to CO2 equivalents).
For now, aeroplanes and rotors are not slathered routinely with temperature-and pressure-sensitive paints because their sensitivity needs to be improved.
Climate sensitivity is a key parameter for estimating the long-term temperature increase expected from a doubling of the concentration of greenhouse gas emissions in the atmosphere.
One major unsettled issue in climate science indeed is what this sensitivity is, and several threads of information, including the surface temperature history, and water vapor and cloud data argue Lindzen may be correct.