The fundamental difference in opinion (which has not
changed since
Michaels and Hansen started debating each other in 1988) is that Hansen (and the vast majority of relevant
experts) think that climate sensitivity (how much the globe will warm under a doubling of CO2) is around 3 (+ / -1) °C, while
Michaels thinks that it is much less (< 1 °C).
Dr
Michaels is one of many people commenting on climate
change who presents himself as an independent
expert while being secretly paid for his services by fossil fuel companies.