During the weekend, the foreign ministers (and other top political brass) of 195 countries flew into Paris for the UN climate change talks to try and add the right mixture of finesse and clout needed to land one of the most complex international agreements ever conceived.

They arrived to find a “pig’s breakfast”, in the words of one long-time observer. The 48-page draft text contains 939 points of disagreement — highlighted by passages in square brackets.

And yet many observers, predisposed as they are to calamity, are whispering faint optimism five days out from the end of the talks.

Despite the existence of hundreds of points of dissent, most could be resolved by horse-trading on just a few common themes. In particular, countries will barter on the manner and degree to which rich countries will foot the bill for the crisis they have caused, and the requirements that all countries offer up transparent checks on their progress towards cutting carbon emissions.

That we are so tantalisingly close is, in part, due to the diplomatic pedigree of the French. For once, the conference is on time after the first week, and major disagreements have been contained.

Surprisingly, and cheeringly, a strong push has also emerged to limit warming to just 1.5 degrees above pre-industrial temperatures, rather than the normally discussed 2 degrees. The latter is popularly considered “safe”. But scientists and the UN agree that for atoll nations, coral reefs and anyone living within cooee of Bangladesh, 2 degrees of warming will mean danger, suffering and the loss of homelands. Traditionally the quixotic demand of the poorest and most vulnerable nations, a 1.5-degrees target has now been called for by 108 out of 195 countries at the talks — including heavy hitters France and Germany.

But in the tortured world of consensus agreements, it only takes one country to disagree for a passage to end up in square brackets. If sections of the text contain these parentheses at the end of this week, they will simply be left out.

This leaves the door open for all sorts of diplomatic bastardry. For example, the oil-dependent House of Saud has emerged as the most obstinate opponents of a number of measures, including the 1.5-degree target and the passages on human rights, which will protect indigenous tribes from being frogmarched off their lands in order to build massive hydroelectric dams. On Thursday, Saudi negotiators insisted that it include a reference to the human rights of peoples “under occupation”. This poison pill may rally other Arab nations, but it will kill support from the Israelis and screw protections for a whole bunch of tribespeople along the way.

Yet despite all the warts and schismata, it was with some pride that this ugly global lovechild was passed on by its parents to be tailored into something acceptable. It was an emotional day for the text’s negotiators, most of whom carry the responsibility of what they are doing close to their hearts and have worked on it for four years.

Laurent Fabius, France’s foreign minister who is presiding over the conference, tried to assure them, and the world, that the child was in good hands. “I intend to muster the experience of my entire life to the service of success for next Friday,” he said. “We’re talking about life itself.”

And yet, even if all these differences can be hammered out, all will be for nothing if countries cannot resolve a fundamental problem: how can countries leave with a successful Paris agreement when the whole thing was pre-engineered to miss its primary objective?

The point of the global climate process is to limit warming to within an agreed safe level. Past attempts to reel in carbon emissions have focused on a top-down approach. An international target, legally binding and determined by consensus. But this “student politics” method, says Ruth Davis of Greenpeace, is “pie in the sky”. Everybody just ignores it and goes on polluting.

The bottom-up approach relies entirely on commitments that nations, through their domestic planning, devise and make to their peers. This is founded within the economic realities of each country and stimulates national discussions about the benefits of carbon emissions reduction. But the downside is that most of the commitments made to the Paris conference are woefully inadequate and the sum of them leads us to 2.7 degrees of warming by 2100 — high enough to destabilise global civilisation.

All year, everyone in the climate process has been trotting out an official line: Paris won’t get us to 2 degrees, but it will get an agreement to build on. In five years, once we’ve had a chance to see how great the green economy is, everyone can come back and talk about how we can make even deeper cuts.

But now we are in Paris, we see India and China telling the rest of the world to get stuffed. They want as much time as possible to keep growing their economies with coal, and when they make their commitments, they say they are doing the best they can. Additionally, they have already planned their economies until 2030, so there is no way they are coming back in just five years to change the whole lot.

Unpicking the 939 square brackets, each of which potentially contains billions of dollars, or millions of lives, looks like child’s play compared to this fundamental question of economic sovereignty. But it must be resolved. Because if it isn’t, the Paris agreement, with its recipe for 2.7 degrees of warming, will be a death warrant.

“I refuse to go home to my people without a Paris agreement that allows me to look them in the eye and say that everything is going to be OK,” said Tony de Brum, the Foreign Minister of the low-lying Marshall Islands on Saturday. The stakes are intolerably high.