The leader of the Australian Greens Senator Richard Di Natale argues it's time to review the Australian US alliance and believes climate change is the biggest threat to national security. As the second week of the Federal election campaign rolls on,  Di Natale sought to trigger debate on the merits of a 'more independent' foreign policy in a speech at the Lowy Institute in Sydney today. He said the 'unquestioning consensus' that spans the two major parties on most areas of foreign policy and defence 'does not serve us well'.  You can listen to the address in full here: