So, how do we determine this? There is no dissent as to global warming and its cause.
No scientific body of national or international standing has maintained a dissenting opinion; the last was the American Association of Petroleum Geologists, which in 2007 updated its 1999 statement rejecting the likelihood of human influence on recent climate with its current non-committal position.[2][3] Some other organizations, primarily those focusing on geology, also hold non-committal positions.
So, we have opinions ranging from AGW to "non-committal". Time to respond now....?