Obama warns denying climate change 'betrays future generations'

US President Barack Obama warned in a farewell address to the nation on Tuesday that to deny the reality of global warming amounted to a betrayal of generations to come.

"We can and should argue about the best approach to solve the problem," he told the crowd in Chicago.

"But to simply deny the problem, not only betrays future generations, it betrays the essential spirit of this country, the essential spirit of innovation and practical problem-solving that guided our founders."