Even the "lukewarmer" position on anthropogenic global warming has become untenable on the basis of both observations and theory:
1. Lindzen & Choi papers based on ERBE satellite observations showed sensitivity (to doubled CO2 levels) of only ~0.18C
2. Dr. David Evans has shown, using the same flawed radiative model of the IPCC as the basis, that "The ECS might be almost zero, is likely less than 0.25 °C"
3. Kimoto has shown climate sensitivity is ~.15-.2C due to the IPCC false assumptions of a fixed lapse rate and a mathematical error in calculating the Planck feedback parameter:
4 Volokin et al have shown that planetary surface temperatures are a function of solar insolation and surface pressure only, not greenhouse gas concentrations, on all 8 planets for which we have adequate data, including Earth & Venus.
5. The surface temperature and tropospheric temperature profile can easily be derived from physical first principles including the 1st LoT, Ideal Gas Law, Poisson Equation, Newton's 2nd Law, and Stefan-Boltzmann Law for solar forcing only, and without greenhouse gas "radiative forcing," and perfectly replicates the verified 1976 US Standard Atmosphere. Thus, once again, sensitivity to CO2 is mathematically proven to be essentially zero.
6. Convection dominates radiative-convective equilibrium in the troposphere by a factor of ~8X, and increased greenhouse gases accelerate convection, thereby erasing any alleged cold-heats-hot greenhouse gas radiative effects on the surface.
7. Many other climate sensitivity estimates have concluded climate sensitivity is effectively zero, or so close to zero as to be unmeasurable and negligible.