All I would say is that all global climate change, up until the industrial revolution, was 'natural'... and that natural background change will always be with us and needs to be taken into account. But never before has the 'total global climate change' ever been dependent upon anything other than 'natural' causes.... however, now it is. Human activity can (whether or not it actually does) affect global climate. In other words, we now must incorporate this additional influence upon global climate change... to say that human activity has no effect is highly debatable (and arguably (ultimately) has to be wrong - we do have some influence.... we just don't know exactly how much...) The point being, however, that our influence must be a consideration, and not merely disregarded as totally insignificant...
The pattern of global climate change can (and is increasingly being) deciphered from scientific evidence available to us.... the mean temperature increase over the past century, in itself, is not unprecedented... however, the rate of temperature increase since the mid 1970's is.... the concentration of CO2 (and other greenhouse gases) in the atmosphere is now much higher than at any other point in human civilisation, and it just so happens to coincide with an unprecedented (again, in the context of human influence) level of global warming... and I don't believe in coincidences.