There isn't any doubt that the world has warmed over the last hundred years (since the 'little Ice Age')
Some question why the recent high land temperature readings are not reflected in satellite temperature readings and question whether this represents genuine global warming.
Others question the relative contributions of the various climate inputs (or forcings)
Solar radiance is obviously one of these inputs.
No one could accuse James Hansen of being a 'Warming Denier' He has been criticised by some for being an alarmist and he campaigns strongly for CO2 reductions.
This paper is 9 years old, in it
James Hansen wrote:Although these forcings are not well-measured, it appears that the net climate forcing is probably much less than the greenhouse forcing. One implication of this is that a forcing such as solar irradiance is more important than one would surmise by simply comparing solar and greenhouse forcings.
"not well-measured", "appears" and "probably" indicate that there is legitimate reason to go and measure them better. If the new measurements show that natural forcings are higher than previously thought, the authors need to have a hearing and not be treated as pariahs.
Scafetta and West wrote:The sun played a dominant role in climate change in the early past, as several empirical studies would suggest, and is still playing a significant, even if not a predominant role, during the last decades. The impact of solar variation on climate seems significantly stronger than predicted by some energy balance models…The significant discrepancy between empirical and theoretical model estimates might arise because the secular TSI [total solar irradiance] proxy reconstructions are disputed and/or because the empirical evidence deriving from the deconstruction of the surface temperature is deceptive for reasons unknown to us. Alternatively, the models might be inadequate because of the difficulty of modeling climate in general and a lack of knowledge of climate sensitivity to solar variations in particular
Scafetta, N., and B. J. West, 2006. Phenomenological solar contribution to the 1900-2000 global surface warming. Geophysical Research Letters, doi: 1029/2005GL025539.
The other area where there are legitimate questions is whether warming will be as universally bad or catastrophic as often claimed.
