The Vatican was set to release a much-trailed and highly significant encyclical by Pope Francis about climate change on Thursday. Unfortunately a draft of Laudato Si ("Be praised", a line from St Francis of Assisi's Canticle of the Sun) was leaked to an Italian magazine, L'Espresso, which published it. The Vatican is incandescent, describing it as a "heinous act" and claiming it was an early draft rather than the final text. It asked journalists to "respect professional standards" and wait until the official launch on Thursday. Unfortunately, the internet is echoing to the sound of a stable door slamming while hoofbeats clatter rapidly down the road.

Still – it was embargoed. Should you really be talking about it?

A nice question of journalistic ethics. The writer who got the scoop, Sandro Magister, would say that he was playing by the rules because technically he wasn't breaking an embargo – that is, publishing a story given to journalists in advance on the understanding that they won't use it before a particular date. It's an honour system that usually works. In Magister's case, though, he got hold of an earlier version – it's suggested that it was rescued from a consignment about to be pulped – so ethically he, and we, are probably OK. Also, it'll be interesting to see the differences between his text and the final one – perhaps just typos, perhaps more significant changes. However, Magister may have done permanent damage to his relationship with the Vatican; his accreditation has been withdrawn indefinitely. 

Fair enough. What's an encyclical, anyway?

It's a letter from the Pope to Catholic bishops, usually dealing with a significant issue. The point is that the bishops are responsible for transmitting faithful teaching to their flocks, and the encyclical tells them what it is. Encyclicals aren't exactly binding, but they do express the considered teaching of the Church, conveyed through the Pope himself.

So Francis is teaching that man-made climate change is real?

Not exactly, though the encyclical does refer to the scientific consensus that humans are responsible for most of it. It is much more about what to do about the effects of it, and about pollution, waste and poverty. Francis actually says in the draft that the Church doesn't claim to be able to settle scientific questions. However, he's pretty clear about it, saying: "Humanity is called to take note of the need for changes in lifestyle and changes in methods of production and consumption to combat this warming, or at least the human causes that produce and accentuate it." He also says: "Numerous scientific studies indicate that the greater part of the global warming in recent decades is due to the great concentration of greenhouse gases...given off above all because of human activity."

I don't mean to be rude, but what does he know about it?

He studied chemistry and worked as chemist before entering the seminary to train as a priest, though he does not, as some reports say, have a Masters degree in the subject. However, a document like this is produced after consultation and discussion with several very clever and knowledgeable people. It will be launched by a Catholic cardinal, a Christian Orthodox church leader and a climate scientist the Vatican says is an atheist.

Is there any particular reason why it's being released now, or rather on Thursday?

Yes. In December another round of climate change negotiations will start. The Paris Conference will involve 190 countries in talks aiming to reach agreement on emissions control keeping warming to 2 degrees Celsius above pre-industrial levels.

So what does it actually say?

Assuming that the draft is pretty much the same as the final version – and the whole embargo thing is still a bit awkward – Francis calls for changes in lifestyles and energy consumption to avert the "unprecedented destruction of the ecosystem". He refers to human beings' responsibility as custodians of the earth, saying that the earth is "protesting for the wrong that we are doing to her, because of the irresponsible use and abuse of the goods that God has placed on her. We have grown up thinking that we were her owners and dominators, authorised to loot her. The violence that exists in the human heart, wounded by sin, is also manifest in the symptoms of illness that we see in the Earth, the water, the air and in living things."

Any practical solutions?

The draft specifically rejects carbon credits – a system which sets an overall carbon target and lets people buy and sell the right to pollute – as a solution to the problem, saying that they won't help reduce emissions and will support "super-consumption" in certain countries. It also calls for a new global authority tasked with tackling the "reduction of pollution and the development of poor countries and regions".

Ah, poor people again: that's a Francis thing, isn't it?

It is indeed. Concern for the poor is the keynote of Francis' pontificate, and climate change hits the poor hardest.

I don't want to play Devil's Advocate, but will this actually make a difference?

By all accounts, it might very well do. There are around 1 billion Catholics in the world, all of whom pay attention, to some degree, to what the Pope says. That's bound to have an impact. Forbes quotes NASA climate scientist Gavin Schmidt, who describes himself as "not a religious person at all". However, he says, "The Pope's encyclical is probably going to have a bigger impact than the Paris negotiations." Another scientist, Katharine Hayhoe of Texas Tech University, says: "Many people have this rosy view that there's this knowledge deficit, and that if we just provided more information or if we explain the science better or if we package it better, maybe with colored graphics, or write another scientific paper, that will be the one to convince [doubters]."But the reality is it's not a scientific issue [any longer]. It is an ideological issue. We have to appeal to people based on values, not just on data and facts. So from that perspective the Pope is a very effective messenger."

Face it, though, some people are never going to be convinced.

Correct, and the draft also says: "The attitudes that stand in the way of a solution, even among believers, range from negation of the problem, to indifference, to convenient resignation or blind faith in technical solutions." He might have been talking about Republican politicians in the US, who are generally sceptical about climate change; many right-wingers there see it as a liberal plot to establish a global government.

Oh, come on.

Put "climate change conspiracy" into a search engine if you don't believe me. Republican presidential candidates don't necessarily sign up to that, but they are generally climate change sceptics. Ted Cruz compared climate change activists to "flat earthers", while Rick Santorum said the Pope should "leave science to the scientists": "When we get involved with political and controversial scientific theories, then I think the Church is probably not as forceful and credible." Lindsey Graham is the exception to the Republican rule.

I thought the science was pretty settled?

Among scientists, it is. However, as I have pointed out before in these articles, democracy is a wonderful thing: the fact that you know absolutely nothing about something doesn't mean your vote doesn't count as much as an expert's – or, indeed, that you can't run for high office. 

This is still a draft. Are there likely to be any surprises on Thursday?

We'll have to wait and see, won't we?

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