Originally Posted by Fram

There are natural periods of warming and cooling, noone here denies that (I hope). Variance in solar activity, earthly influences (like ocean currents, volcanoes, ...), ... and for those days according to some scientists already human influence (although that would have been, in my view, truly minimal), all combine to change the climate. All these factors have to be taken in account while studying the current climate change, and many serious studies do so. Most of those still end up with a part (around 50%) of the warming which they cannot explain except by human influence (greenhouse gases).