We face a very stark choice. Continue with business as usual, and allow the world to become an "immense pile of filth", or change our behaviour and allow future generations to inherit a planet capable of sustaining life.
But for that to happen, we need political leadership, something which this Government has so far failed to deliver.
There has been no concerted effort made to reduce energy consumption in our public building stock, despite the financial and environmental savings which would accrue. Nor has there been a real attempt to get people out of their cars and onto public transport.
The Climate Change Bill is weak, with no targets to reduce emissions. Attempts by some local authorities to build more efficient buildings have been resisted. This Government has even gone so far as to seek special treatment for our agriculture sector in EU negotiations, despite it being a primary driver of global warming.
For two decades, scientists have warned that the climate is changing and we now know that human activity is the cause. We are well aware of the environmental destruction wrought by our consumerist culture, yet politicians have shown little or no long-term vision aimed at delivering real and lasting change.
Much of this inaction is driven by tired and stale thinking. A mistaken belief that economic recovery will be hampered. But the United Nations says tackling climate change could slow global economic growth by just 0.06pc a year, a sacrifice surely worth making.
What is hampering progress is the fact that difficult choices made today will not bear fruit in the run-up to the next General Election. But as Pope Francis notes, a sign of "true statecraft" is upholding high principles and thinking of the long-term common good.
Doing the necessary will result in a legacy of "selfless responsibility". The alternative is a world of chaos and dwindling resources.