It is an open question, though with the evidence mounting against a substantial anthropogenic effect.
I often write as if Anthropogenic Global Warming was disproven or obviously false. Global Warming is an open scientific issue, one which more information is needed – and in due course will be forthcoming. The position among real scientists is that Global warming is a conjecture – not a conjecture very likely to be true, but conjecture that could be true.
Over the next decade or so, the truth, or more likely the falsity, of Anthropogenic Global Warming should become more apparent. We have plenty of time to discover the actual situation before taking big dramatic actions. If human are warming the world, it is pretty obvious we are not warming it very fast.
In 2007, there seems to have been a dramatic change in the weather on the sun. The abnormally active sun of the past several decades is most likely changing its ways. If global warming is cosmogenic, the next decade or so is going to get mighty cold.