It is a threat to health, since a warmer world is one in which infectious diseases such as malaria and yellow fever will spread further and faster. It could imperil the world's food supply, as rising temperatures and prolonged drought render fertile areas unfit for grazing or crops.

It could endanger the very ground on which nearly half the worlds population Iive -  coastal cities such as Lagos or Cape Town, which face inundation from sea levels rising as a result of inciting icecaps and glaciers.

All this and more lies ahead.