THERE are 50 months to go. That is the predicted timescale we have, in order to avert an average global temperature-rise of two degrees - the official UN climate goal. After that, it will be too late, and the effects of our carbon emissions will have been locked in.

It is not quite an announcement of the apocalypse. But rising sea-levels and climate change will have a massive effect on the geography and geopolitics of the world. Some Pacific islands will disappear entirely. Droughts and famines will bring unimaginable misery to billions of people, prompting ever-fiercer competition over ever-scarcer resources. Some parts of the world will be permanently flooded; others will become dust bowls.

So why has this issue not been higher up the political agenda? If the politicians don't believe this to be true, then they have a duty to say so. If they do, then what are they doing about it? And the answer to that is: pretty much nothing at all.

Back in 2009, President Obama proudly declared in Copenhagen that he was committed to stopping a two-degree temperature rise. But he has done little even to try to make a difference.

The United States has now abandoned the two-degree ceiling. In August, the US Special Envoy for Climate Change, Todd Stern, announced that the treaty obligations from Copenhagen were inconsistent with "the art of the possible", and that the "old orthodoxies" of a two-degree threshold "will only lead to deadlock".

Why? Because the future is a long way off. Not only have we borrowed huge amounts of money off our children and grandchildren, in the form of vast national debts, but also, because we have to pay back these debts through continual economic growth, we are locked into a system than can make things only worse.

Economic growth is everywhere lauded as the answer to all our ills. The graph showing GDP always has to point upwards - even though the graph showing carbon emissions is, as a consequence, doing exactly the same.

The problem is not simply environmental. It is economic, and even more fundamentally spiritual. Unless we in the developing world find a way to be content with a simpler style of living, then we will drive the planet towards environmental bankruptcy.

We have 50 months to go - and we are mostly doing precious little about it. Now is the time to choose sides. Those who stick their fingers in their ears and do nothing are making a choice. They have chosen the wrong side.

Canon Giles Fraser is Priest-in-Charge of St Mary's, Newington, in the diocese of Southwark.