diminished rainfall in rio and sao paulo, severe drought in belo horizonte. [waves crash onto the shoreline] [antonio] what would you do if you know what i know? [chiwetel] the question that has haunted antonio nobre's working life has come to haunt us all. [antonio] world war ii was nothing. what is coming our way is 1,000 times worse. [chiwetel] the filming of this story began in a very different world than the one we live in today. everything has changed. coronavirus has taught us that some warnings do come true. [antonio] it's absolutely essential that humanity, uh, understands what kind of risks we are running right now. i mean losing our habitat losing the planet where we have evolved it means really losing the capacity of continuing to live on earth. [woman] more than 15,000 scientists are sounding an alarm about climate change, they call it a warning to humanity. [indistinct chatter] [newscaster] there's a frantic effort underway tonight to find survivors. [man 1] the warmest year in the earth's recorded history and it's only getting hotter. [man 2] a