Give me a break
The isotopic data pretty much rules out most credible non-human causes for the increase in concentrations of green-house gasses (vulcanism), esp CO2. We know CO2 concentrations are on the rise, we know we are spewing billions upon billions of metric tonnes out every year while removing many noted carbon sinks. We know CO2 in the atmosphere induces a warming effect. All of this is known. To say that human activity is not causing a rise in CO2 concentration requires massive thick-headedness. The time scale is too rapid, the increase is too correlated with human activity. Ockams razor, common sense, and causal data such as it is- all of that indicates the same thing. Humans are the major factor behind warming.
DL