You might be interested in the opinion of Richard Muller:
In 2010, I watched one of his talks in which he had very uncharitable things to say about some groups of climate scientists and why he did not consider them trustworthy [1].
At about 34:28 of the video, you can hear him say the following:
This is why I'm now leading a study to redo all this in a totally transparent way.
He did [2].
What was his conclusion? Global warming is real, and in all likelihood the culprit is indeed CO2.
How did he come to that conclusion? Because it's the only proposed mechanism for global warming that actually fits the data on the 250y scale.
In 2010, I watched one of his talks in which he had very uncharitable things to say about some groups of climate scientists and why he did not consider them trustworthy [1].
At about 34:28 of the video, you can hear him say the following:
This is why I'm now leading a study to redo all this in a totally transparent way.
He did [2].
What was his conclusion? Global warming is real, and in all likelihood the culprit is indeed CO2.
How did he come to that conclusion? Because it's the only proposed mechanism for global warming that actually fits the data on the 250y scale.
[1] https://www.youtube.com/watch?v=VbR0EPWgkEI
[2] http://berkeleyearth.org/