"We’re not showing that this is a consequence of an increase in carbon dioxide and other greenhouse gases,” Hansen says.

http://www.sciencenews.org/view/generic/id/342823/title/Extreme_hot_spells_rising

"We're not showing that this is a consequence of an increase in carbon dioxide and other greenhouse gases," Hansen says. In fact, his team's analysis makes no attempt to attribute the underlying source of warming to any particular cause. He does volunteer, however, that there is "a strong consensus within the scientific community that the warming we're seeing is primarily a response to an increase in greenhouse gases."