Hillary Clinton predicted Thursday the United States will become the leading 21st century “superpower” in clean energy if the nation confronts the “most consequential, urgent, sweeping collection of challenges we face.” “We shouldn’t have to state the obvious … the data is unforgiving” in demonstrating that climate change and environmental crises are at hand, Clinton said at the National Clean Energy Summit in Las Vegas.Waving off a passionate sector of Americans who believe otherwise, she cited melting ice caps and the discovery of “carbon dioxide in our atmosphere not seen in millions of years” as evidence of potentially disastrous climate change.