"Our Fragile Planet - a Christian Perspective" - Are we breaking the rainbow?

Tue 28 May 2019

St Edmund's College

Prof. Euan Nisbet

Abstract

Our life is sustained by our home – a planet with a thin atmosphere above an ocean and some exposed land masses, with a surface temperature of about 15 oC. The air keeps the ocean liquid: without the natural greenhouse warming, the temperature would be about -18 oC. The air is also important in trapping water close to the surface: any vapour that rises falls back as rain. On land and in the sea, the plants control the reflectivity of the planet. Higher up, the air blocks damaging solar radiation. These subtle balances allow rainbows to exist from time to time: water vapour in the air, sunlight passing through. Without the balance of our atmosphere and the reflectivity of the surface, Earth would be dead, dehydrated like Venus or frozen like Mars.

Yet the air is a biological construction: nitrogen, oxygen, carbon dioxide and other gases except argon are biologically cycled. Even the argon is given off by continental rocks - no water, no granites, no granites, no continents. The Earth is like the Heart of Gold spacecraft in the Hitch-hiker’s guide to the Galaxy, powered by an infinite improbability drive. All is balanced by the great chain of being – the best of all possible worlds, to quote Leibnitz and Dr. Pangloss.

It works. But it is so easily disrupted. Adding only relatively small masses of CFCs or methane, or a bit more CO2, could upset the temperature structure so much as to cause food shortage for billions. We’ve been lucky: had CFC emission not been stopped, by now new leaves would be suffering worldwide. Adam and Eve were given conditional dominion, not absolute autocracy. The Rainbow is a covenant with all life, not simply to Noah. The early Christians specifically kept this covenant through their ruling not to take the lifeblood. By altering the air and chopping the forest, we assault Noah’s covenant. God may have promised not to send the flood again, but we might be bringing it on.

Cost: Free