If you really buy off on this, then you really haven't thought things through. Yeah what he says is probably true. But if there wasn't the man made carbon in the atmosphere, then the volcanoes would have far less effect, if any at all. This article is directly pointed at someone who already has his mind made up, and not really interested in science, but something to confirm his pre-conceived notions.
The way I look at it, it is the height of man's hubris to say that he has no impact on the environment and hence weather.
On the flip side, it is the height of man's arrogance to claim that he has even the slightest inkling as to all the factors that affect the climate and how man's actions affect the climate.
There is also the greatest of ironies that without modern technology man would not have the instruments and computers to measure the climate and evaluate those measurements.
As to the "purity" of science, every scientist has an agenda. His or her research is limited in scope to either fall into line with what is politically popular to gain grant or university funding, or it is limited to what a corporation deems what is evaluated to provide a commercial profit and hence to garner R&D funding.
