It’s crunch time at COP21. Negotiators at the Paris-based climate talks have been told it’s time to make “crucial” choices needed to secure a new international deal.

The latest draft of the deal contained the potential for ambitious targets on curbing rising global temperatures and cutting emissions over the coming decades. But there’s also room for weaker options.

One group that doesn’t want to see countries settle for those weaker options is the “high ambition coalition”. Here’s everything you need to know about them.

Who is in the ‘high ambition coalition’?

Tuvalu flooding
Seawater flooding the very low-lying island nation of Tuvalu (AP)

It sounds like a terrible name for a student rock band. But the “high ambition coalition” is a grouping of more than 100 countries currently at the climate talks.

The coalition includes wealthy states like the European Union (including all its members), and Norway. Other countries, such as Mexico and Colombia, have also joined.

The coalition also includes some of the poorest countries, such as small island nations or arid African countries – states which will feel the impact of climate change most acutely, and are therefore keen for an ambitious solution.

There are 195 countries at the COP21 talks, so the coalition is in the majority.

What does the ‘high ambition coalition’ want?

Smog in China
The coalition is not happy to wait until 2030 before this deal is updated (Andy Wong/AP)

The coalition has warned it would not accept a minimalist or bare bones agreement. One of the key things it wants is a five-year “review and ratchet” mechanism.

This mechanism would see countries re-examining and raising their level of pledged climate action (if appropriate) every five years. Concerns have been raised that without this there were not clear enough measures to achieve emissions cuts.

Making sure ambition can be raised in this way is key to achieving a 2C limit to global temperature rises – beyond which “dangerous” climate change is expected – or the more stringent 1.5C many countries have backed.

This is because the current pledges by countries for climate action they will take up to 2030 will only put the world on a path to almost 3C.

Why might the ‘high ambition coalition’ not get its own way?

Xi Jinping of China at COP21
Large developing nations like China and India are predicted to be the biggest opponents to the coalition’s plans (Eric Feferberg/AP)

There is still a lot of room for disagreement between the coalition and other countries.

The issue of “differentiation” – the difference between the responsibilities and actions of different countries – remains a particularly thorny issue in the discussions.

Some countries, thought to include China and India, are trying to maintain the UN climate convention’s original strict split between developed and developing countries laid down in 1992, while others such as those in Europe are seeking wording that reflects the range of countries’ development and their ability to act.

What happens next?

Laurent Fabius
French foreign minister Laurent Fabius is chairing the talks (Niall Carson/PA)

We’re into the penultimate day of the official negotiations at Paris, so it really is crunch time for finding a deal.

A new version of the text is expected later today, after French foreign minister Laurent Fabius, who is chairing the talks, urged ministers to work through the night to achieve a new draft.