NBCUniversal Inc. November 20, 2019 3:11 am ‘Late Night': Al Gore Calls Climate Change Most Serious Challenge Al Gore calls climate change the most serious challenge human civilization has ever faced and talks about an upcoming global event for climate change awareness. US & World Videos 1:36 Arizona Senate repeals 1864 abortion ban 2:15 Heavily-camouflaged minors charged after ‘assassins' game at Old Lyme school 2:40 7th grader brought gun to school in Hartford: police 1:40 Democrats say Big Oil misled public for decades about climate change 1:36 A student brought a gun to middle school in Hartford: police