Pope Leo XVI has lamented the failure of international leaders so far to summon the political will to tackle the climate crisis in a video-message to the bishops and cardinals of the Global South participating in the COP30 UN summit in Brazil.     "Creation is crying out in floods, droughts, storms and relentless heat", the American pontiff said, "One in three people live in great vulnerability because of these climate changes.     "As stewards of God's creation, we are called to act swiftly,