Here's a moral principle: we ought not to act in a way likely to help cause the death of others.
This seems to me a pretty plausible principle and I don't expect much disagreement.
It's why you should not drink and drive.
But note the word "likely".
It is wrong to do things likely to cause death or injury even if you get lucky and death does not ensue.
Note too the principle is not a matter of helping people.
It's a matter of minimal decency, of not doing things likely to cause other people harm.
If broken glass left on the roadway by drunken idiots makes you righteously indignant you should be in favour of this principle.
Here's another principle which follows from the first: we ought not to act in a way likely to help cause the death of billions of others.
Again, I don't expect much of an argument.
Obviously if it is wrong to act in a way likely to help cause the death of a few, then it is wrong to act in a way likely to help cause the death of billions.
Furthermore, the principle still holds if the part an individual plays in the process is relatively small.
Suppose a billion individuals each acts in such a way that as a combined result of all their actions another billion is likely to die.
Their individual actions are still wrong even if they are only responsible for a billionth part of the catastrophe.
With me so far? Well, here's the kicker.
It's not a moral principle but a factual claim.
It's this: if you are not trying, both as an individual and as a citizen, to drastically reduce greenhouse gas emissions, you are acting in a way that is likely to help cause the death of billions of others.
If we combine this factual claim with the minimal moral principle we can derive a new duty: we ought to be trying both as individuals and citizens to drastically reduce greenhouse gas emissions.
As I said, I don't expect much disagreement when it comes to the moral principle.
The factual claim is more controversial.
But the basic argument is simple.
Greenhouse gases cause global warming.
Unless humanity starts cutting back drastically on greenhouse gas emissions - by something in the region of 80% over the next 40 years - then we risk catastrophic global warming which will lead to a massive decline in the world's fertility.
Deserts will spread, deltas will flood, river flows will become more erratic, there will be more droughts and more floods and some places will simply become too hot for many crops to grow.
The floods in Pakistan and the heatwave in Russia provide a foretaste of things to come.
A fifth or more of Pakistan is flooded and its infrastructure devastated. If they get away with less than a 20% drop in their food production, they will be very lucky.
Meanwhile, Russia has lost up to 25% of its wheat. What happens when not two large countries but five or six are simultaneously subject to such heatwaves and floods? The world's population is expected to expand to about nine billion by 2040, an increase of about 32%.
If, as a consequence of global warming, the world's fertility drops by a mere 10% from current levels, well, as the saying goes, "You do the math".
So if as an individual you are not cutting back drastically on your greenhouse gas emissions you are acting in a way that is likely to help cause the death of billions of others.
The comfort and convenience of a large car, the fun and profit of frequent foreign travel all add up to a small share in the catastrophe that is likely to come.
But why do I say that if as a citizen you are not acting to reduce greenhouse gas emissions, you are acting in a way likely to help cause the death of billions? Because our whole civilisation is built on fossil fuels and involves the emission of greenhouse gases.
So by shopping at the supermarket or turning on the power supply, you are participating in a set of institutions which threaten to bring about a global catastrophe.
You can reduce the greenhouse gas emissions for which you are directly responsible by cycling to work and cutting back on foreign travel.
But to minimise the emissions for which you are indirectly responsible, you must work to change the system. Unless humanity as a whole reconfigures its technology and reforms its institutions so as to cut emissions there is a serious risk billions of people will die.
And unless we as a nation reform our institutions and reconfigure our technologies we are acting in such a way as to help bring about this result.
Thus, simply by going with the flow and not doing your bit to change the system, you are acting in a way likely to help bring about the death of billions.
And this brings me back to recent events, specifically the Appeal Court decision on Project Hayes.
If I am right, then it is our duty - a matter of minimal decency, like not driving drunk - to shut down the coal-burning power plant at Huntly as soon as possible and generate the shortfall in electricity from carbon-neutral sources such as wind farms.
Furthermore, we probably need to increase our generating capacity as we work towards the elimination of the internal combustion engine and the end of coal-fired heating.
This means it is morally vital to press ahead with wind farms unless there are overpowering reasons to the contrary.
The fact that Project Hayes would spoil the view is not one of these reasons.
Thus, in delaying or halting it, its opponents have not, as they evidently suppose, done a righteous day's work.
They have helped keep Huntly operational.
And in doing this they have done their bit to help bring about a catastrophe.
When the Environment Court ruled against Project Hayes, it was not that the landscape trumped any economic benefit.
No, the look of the landscape and the pleasure a few selfish aesthetes took in it was allowed to trump the interests of the planet and the interests of humanity.
Let's hope the Environment Court changes its mind.
Dr Charles Pigden lectures in philosophy at the University of Otago.
