You're arguing over semantics. He was skeptical in the years prior to completing the Berkeley Earth analysis and was not upon completion. He has stated this himself in numerous interviews. I personally know multiple colleagues of his so I feel quite confident in my assertion that he was skeptical about AGW and now is not.

I'm not sure that whether or not his daughter worked for him has anything to do with the empirical evidence concerning AGW.

Warming during the first half of the 20th century is likely due to a combination of natural climatic variability (namely solar irradiance and volcanism) and anthropogenic factors (burning of fossil fuels that began ramping up during the industrial revolution). Gradual warming since the dawn of the Holocene is pretty well understood as being a function of the Milankovitch cycles. Are you suggesting that because climate has changed due to natural variation in the past, it's therefore impossible that humans are causing a meaningful change in the planetary energy budget? I'm not really following your line of reasoning so just checking.

The models have generally under-estimated temperature rise rather than the reverse. Recent research suggests cloud feedback may be stronger than anticipated and in fact result in greater warming. It's also important to point out that the CH4 hydrate feedback in the East Siberian Arctic Shelf is not incorporated into models and will possibly exacerbate warming in ways that the models don't account for. So, while it's true that there is variability in processes, scientists (especially the IPCC synthetis) has tended to be demonstrably conservative in the RCP projections. Given that the 1.5C/2C RCP are already pushing the limits of what may be "safe" upper limits for human civilization, it probably makes sense to be pragmatic and take them seriously -- especially if there's even a 5% chance that warming may actually exceed those numbers given other feedbacks.

This critique of weather stations used in the instrumental temp record is pretty tired at this point. Berkeley Earth already addressed the issue of station selection bias extensively and built a new record from a complete overhaul of the station selection methodology. Dr. Muller began the instrument record reconstruction project as a climate skeptic and as a result of his own research, changed his mind about AGW. Perhaps his paper will be enough evidence to change yours: http://static.berkeleyearth.or...

If you're trying to reject the theory of AGW, at a bare minimum you need to be providing a comprehensive general circulation model that can explain even half of present warming in the absence of forcing from anthropogenic gases. Especially given the amount of negative forcing from aerosols in the troposphere and the current level of solar irradiance.

So assuming the low-end cost of $3 per ton of CO2, we're talking a mere $3,030,000,000,000 to mitigate anthropogenic CO2 emissions Sounds like just the type of pragmatic negative emissions technology we so desperately need!

It's a huge gamble. 70% of all terrestrial vertebrates ad 96% of all marine species went extinct during the Paleocene-Eocene Thermal Maximum which is postulated by many to have been triggered by sea-floor methane release due to runaway greenhouse warming. Speciation needed 100 million+ years to recover to pre-PETM biodiversity levels so it's not really a gamble we should be considering.

5 C vs. 8 C is not even a meaningful debate concerning human presence on this planet. Either one spells probable extinction of our species. Long before we hit 5C due to rising CO2 emissions alone, a positive feedback loop in the Earth system will likely be triggered by the melting of the estimated 50 Gigatons of methane frozen at the floor of the East Siberian Arctic Shelf. A methane burp of that magnitude will be the end for us, unfortunately. James Lovelock et al.'s 2007 proposal is still probably the best bet we have for actually doing anything about this. Tens of thousands of 200 meter long open-ended cylinders positioned vertically in the world's oceans to act as up-welling pumps using wave action. They would pump cold, nutrient-rich waters to the surface and trigger massive phytoplankton blooms at the surface of the oceans. The phytoplankton would uptake atmospheric carbon, die, and sink to the bottom where it would be sequestered under sediment. This would cause enormous localized extinctions in the oceans due to hypoxia, but there aren't many other good options at this point.