It looks to me like a mixture of:
pseudo-science (the way the computer models are used, confusion between interpolation and extrapolation, consensus quoting, etc.), 
real science (data measurements of ice cores, the physics of the CO2 cycle, etc. ), 
left wing politics (hamper and destroy US industry, empower UN bureaucrats to run the world, power power power, force the US to give its wealth with other countries etc.), and 
bad logic (correlation confusion: increased CO2 may be an effect of warming not the cause, single alternative: speculated bad effects of CO2 versus known good effects, etc.)
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That being said, there are serious, honest scientists, including those who do not take the models seriously, who believe that increased CO2 is having a significant effect on climate.
But there also those who don't.