Climate change skeptic turned proponent

[Surgenator]

He did not in my view put forward a convincing argument at all. All his arguments amounts to is that "I found correlation between CO2 and climate change". So what? Sceptics acknowledge that, and sceptics also acknowledge that CO2 should have some effect on raising global temperatures. The models put forward by NASA and others have CO2 contributing at most 50% of the global warming trend since the beginning of the 20th century, with black carbon and methane mostly making up the rest. There's no computer model on the planet that proposes that CO2 is solely to blame.

I agree that CO2 cannot be the sole cause. What make his analysis impressive is it's a data vs data comparison. It is not a data vs model comparison. From his paper

Rather than adjust (homogenize) individual records for known and presumed discontinuities (e.g. from instrument changes and station moves), we split the records into portions occurring before and after such apparent discontinuities, creating essentially two records from one.
[...]
We have obtained an estimate of the Earth land surface temperature from 1753 unto the present. The limited land coverage prior to 1850 results in larger uncertainties in the behavior of the record; despite these, we see behavior that is significant. [...] Since the 1950s, we observe a rise in the average land surface temperature of 0.90 ± 0.05°C (95% confidence). This value is in the middle of the
comparable values reported by other groups, but with an estimated uncertainty approximately twice as tight as those of prior reports. Exact comparison of uncertainties is slightly complicated because each different group frames the uncertainties in slightly different ways; however, for the year 1951, we estimate an annual land average uncertainty of ± 0.06°C versus ± 0.14°C for CRUTEM and ± 0.17°Cfor NOAA [7,25]. GISS has never published a comparable land-only uncertainty statement.

Source

He was answering the question "Are the temperatures rise natural fluctuations or not." You don't need to make models when you're comparing data vs data. Since the older data becomes your model.

NASA and IPCC are focused on predictability; hense, they need to make accurate models to make predictions. IPCC generally compares data vs model. Hense, the accuracy of the model can come into question.

I don't have time today to address your other points. I'll get to them later.