Hi George, Good questions, thanks for the entree.
All those variables are of intense interest to climatologists, but they don't want to converse with 'laymen' about them for several reasons.
Solar: We have sunspot records since 1749, and they indicate the sun got more active in the C20th. However, there is a strong move from NASA guys to reinterpret old geomagnetic data to say the Sun hasn't varied enough to be the cause of warming in the C20th. At the same time they have to invoke the sun to explain climate change before co2 took over so they are in a contradiction, and don't like to discuss it. The only solar measure they will use is TSI, which doesn't vary much (0.1% - enough to cause a 0.07C change in surface temp over the 11 year solar cycle, without considering amplification caused by changes in humidity, cloud cover etc). They won't consider the fact that various wavelengths within the TSI (total solar irradiance) vary a lot more, especially UV. UV variation has poorly known but large effects on ozone, plankton density and etc which have poorly understood but possibly large effects on the absorbance of energy into the ocean, cloud cover, and etc.
Clouds: The elephant in the room. Simple calcs show that a 1% variation in tropical cloud cover could reverse or double the warming trend. We can't measure cloud cover (and droplet size, density etc) accurately enough, so the models assume it remains constant. The empirical data (not without its problems) says cloud cover dropped in the tropics 1979-1998. Empirical study of the satellite data shows overall cloud feedback is negative. The modelers assume it is positive.
Sea surface temp: There's a pretty flat trend in the southern hemisphere. Co2 mixes fairly quickly from where it is emitted worldwide. How is it that global warming supposedly caused by co2 has warmed the northern hemisphere more than the south? The answer would seem to be that back radiation from greenhouse gases warm the land but not the ocean so much. Since the global ocean surface temp drives atmospheric temp, they don't really want to go there.
The fixation with global average surface air temperature masks the underlying important variables:
Ocean heat content, which is only known with reasonable accuracy since 2004, and has been falling, according to people I trust who have managed to get the data.
Outgoing longwave radiation: The error in measurement is three times the claimed co2 signal.
There is a lot that those who call us deniers are in denial of.