Dr. Mann appeared Monday at news conference organized by a state representative, Greg Vitali, to promote two bills that would provide subsidies for solar installations and increase the amount of electricity that the state’s electric power utilities must generate from renewable sources of energy.

Dr. Mann, director of Penn State’s Earth System Science Center and a leading contributor to the reports of the Intergovernmental Panel on Climate Change, recently wrote a book for generalists, “The Hockey Stick and The Climate Wars,” in which he explored the barrage of political attacks that climate science has faced in recent years. The “hockey stick” refers to a graph he has used in to illustrate his argument that global temperature has risen in step with industrialization and the increasing use of fossil fuels.

Appearing with Representative Vitali, Dr. Mann criticized those who would deny climate change and mankind’s responsibility for it, even in the face of recent weather extremes.

“One often hears the misleading claim that no single event, regardless of how extreme or unprecedented, can be blamed on climate change,” he said. “That is like saying that no single roll of a ‘six’ with loaded dice can be blamed on the loading of the dice.

“Just as the unusual number of ‘sixes’ rolled is due to the loading of the dice, so are the more frequent and extreme weather events we are seeing due collectively to the ‘loading’ of weather dice by increased heat-trapping greenhouse gases produced by our continued burning of fossil fuels,” he told reporters.