scientists and engineers and management matitions who made this happen -- mathematicians who made this happen. i'm brooke baldwin. thank you very much for being with me here today. "the lead with jake tapper" starts right now in washington. 300 scientists and experts warn that we're in for a climate catastrophe. president trump says he's not buying it. "the lead" starts right now. president trump moments ago saying he does not believe a scientific report about the disastrous consequences of climate change, and this isn't the only thing he's doubting, deflecting, and ignoring from experts with potential life-or-death consequences. the crisis of his choosing. president trump today capitalizing and making new threats after teargas rains on migrants and their children rushing the border. plus, mississippi voting. the state prepares to pick a senator as the incumbent stumbles over her state's ugly past and fastens herself to