Cop27: What can the UN climate conference realistically achieve?

What is Cop27? For almost three decades, world governments have met nearly every year to forge a global response to the climate emergency. Under the 1992 UN framework convention on climate change (UNFCCC), every country is treaty-bound to "avoid dangerous climate change" and find ways to reduce greenhouse gas emissions in an equitable way.

Cop stands for conference of the parties under the UNFCCC. Meetings have swung between fractious and soporific with moments of drama and the occasional triumph (the 2015 Paris agreement) and disaster (Copenhagen in 2009). This year promises to be a difficult follow-up to Cop26 in Glasgow.

When does it finish? The conference is being hosted by the Egyptian government in Sharm el-Sheikh. The talks are scheduled to end at 6pm on Friday 18 November but they may extend by a day or two.

Why do we need a Cop-don't we already have the Paris agreement? Yes - under the landmark Paris agreement, signed in 2015, countries committed to holding global temperature rises to "well below"

2C above pre-industrial levels, while "pursuing efforts" to limit heating to 1.5C. Those goals are legally binding and enshrined in the treaty.

However, to meet those goals, countries also agreed on nonbinding national targets to cut - or in the case of developing countries, to curb - the growth of greenhouse gas emissions in the near term, by 2030 in most cases. Those targets - known as nationally determined contributions (NDCs) - were inadequate and if fulfilled would result in 3C or more of warming, which would be disastrous.

Everyone knew at Paris that the NDCs were inadequate, so the French built into the accord a "ratchet mechanism" by which countries would have to return to the table every five years with fresh commitments. Those five years ended on 31 December 2020, and at Cop26 in November 2021 countries set out new targets.

Didn't this get sorted out at Cop26?

At Cop26, countries agreed to focus on the tougher 1.5C aspirational goal of the Paris agreement, acknowledging that the 2C target would allow massive devastation. Many countries updated their NDCS, and countries responsible for about three-quarters of global greenhouse gas emissions set out long-term targets to reach net zero carbon by about mid-century.