I'll tell you my explanation. It changed because the vast majority of the people did not care. They went back to the drawing board and created something much more alarming and this time the people did buy it. Now we have a multi billion pound industry around Global Warming. Oh and Man is to blame thrown in for added effect.
Our world is dying. Of that there is no argument. It may take many thousands of years to eradicate Man but it will happen eventually. The weakest will die first as we are seeing with birds then death and extinction will come to all species. But, that scenario, with the exception of a few lower species, is many many years in our future.
The debate over Global Warming is huge with both sides giving their all to the debate but sadly the various governments around the world have by and large succeeded in duping the masses into thinking Global Warming is happening.
Myself I strongly believe that our world is going through one of its normal phases and that what Man has done is add a tiny minute bit to it in the great scheme of things. No matter what we do to curb Mans desire for power and trinkets, no matter what our collective governments do or claim to be doing, the end will come regardless.
Right now, it suits our governments to play with our heads but sooner or later the people of the world will rise up and unite in a revolt against the lies, lies and more lies.