of both the Clinton and George W. Bush Administrations' stances on climate change. Addressing the potential effects of climate change, Hansen has stated in an interview in January 2009, "We cannot now afford to put off change any longer. We have to get on a new path within this new administration. We have only four years left for Obama to set an example to the rest of the world. America must take the lead." Climate change activism US Senate committee testimony Hansen was invited by Rafe Pomerance to testify before the United States Senate Committee on Energy and Natural Resources on June 23, 1988. Hansen testified that "Global warming has reached a level such that we can ascribe with a high degree of confidence a cause and effect relationship between the greenhouse effect and observed warming...It is already happening now" and "The greenhouse effect has been detected and it is changing our climate now...We already reached the point where the greenhouse effect is important." Hansen said that NASA was 99% confident that the warming was caused by the accumulation of greenhouse gases in the atmosphere and not a random fluctuation. According to science historian Spencer R. Weart, Hansen's testimony increased public awareness of climate change. According to Richard Besel of California Polytechnic State University, Hansen's testimony "was an important turning point in the history of global climate change." According to Timothy M. O'Donnell of the University of Mary Washington, Hansen's testimony was "pivotal," "ignited public discussion of global warming and moved the controversy from a largely scientific discussion to a full blown science policy debate," and marked "the official beginning of the global warming policy debate." According to Roger A. Pielke of the National Center for Atmospheric Research, Hansen's "call to action" "elevated the subject of global warming and the specter of associated impacts such as more hurricanes, floods, and heat waves, to unprecedented levels of attention from the public, media, and policy makers." Criticism of coal industry Hansen has been particularly critical of the coal industry, stating that coal contributes the largest percentage of anthropogenic carbon dioxide into the atmosphere. He acknowledges that a molecule of carbon dioxide emitted from burning coal has the same effect as a molecule emitted from burning oil. The difference is where the fuel originally resides. He says that most oil comes from Russia and Saudi Arabia, and that no matter how fuel-efficient automobiles