Scientists defend UN overshoot report after Saudi-led push to sideline it at COP31

Scientists behind a landmark UN report on overshooting the 1.5C warming limit have defended its credibility, after Saudi Arabia and other large developing countries questioned its scientific legitimacy and sought to keep it out of the main political decision expected from COP31.

The UN Environment Programme’s (UNEP) Limiting Overshoot report, published in September, examines how to minimise an almost certain breach of the Paris Agreement’s temperature goal, what crossing it will mean for people and ecosystems and how temperatures could be brought back down.

Scientists behind a landmark UN report on overshooting the 1.5C warming limit have defended its credibility, after Saudi Arabia and other large developing countries questioned its scientific legitimacy and sought to keep it out of the main political decision expected from COP31.

The UN Environment Programme’s (UNEP) Limiting Overshoot report, published in September, examines how to minimise an almost certain breach of the Paris Agreement’s temperature goal, what crossing it will mean for people and ecosystems and how temperatures could be brought back down.

The European Union, the UK, the Least Developed Countries (LDCs) and small island states are among those pushing for COP31 to make the response to overshoot of 1.5C one of the summit’s priorities.

But during closed-door consultations on the cover decision this week, the Arab Group, led by Saudi Arabia, have tried to cast doubt on the report’s scientific rigour, arguing it had not been peer-reviewed, according to sources familiar with the discussions.

Meanwhile, the bloc of Like-Minded Developing Countries (LDMCs), which included India and China, called for the cover decision to avoid references to reports produced outside the UN climate process, seen by observers as a thinly-veiled reference to the UNEP report.

Laurence Tubiana, CEO of the European Climate Foundation and one of the key architects of the Paris Agreement, said the overshoot report “tells us a truth some would rather hide”.

“We are on course to exceed 1.5C and limiting how far and for how long is a matter of survival for us all,” she told Climate Home News. “The attacks on climate science are an attempt to delay action. They target intergovernmental institutions that give countries a shared scientific basis for acting together.”

Rigorous approach

Speaking at an event in Antalya on Saturday, scientists involved in the report also pushed back.

Debra Roberts, a South African scientist who co-chaired the IPCC’s Working Group II in its last assessment cycle and was part of the UNEP report’s core coordinating team, said the authors had followed the standard process for a global assessment of existing science, in line with the practices of the Intergovernmental Panel on Climate Change (IPCC). The only difference, she said, was that governments did not review the outputs.

“It was certainly reviewed internally by the authors, external peer-reviewers were brought into the process, and UNEP also reviewed it,” she told Climate Home News.

Forty-four experts from across the globe authored the report, which largely synthesises existing literature, and their work was scrutinised by a further 44 reviewers in a year-long exercise.

“Let’s be straightforward here: the reports are being attacked because some people don’t like the conclusions and it’s fairly obvious why,” Bill Hare, CEO of Climate Analytics and one of the report’s reviewers, told Climate Home News.

“If you as a government are basing your economy on burning and selling fossil fuels, then the last thing you want to do is accept that we are overshooting 1.5C, because then obviously you will take on some responsibility for paying for the damage,” he added.

“Grey literature” debate

In Antalya, some big emerging economies have also called for “grey literature”, including the overshoot report, to be kept out of the cover decision. The term refers to scientific products that are published outside of traditional academic journals.

While that applies to the UNEP report, some of its authors said it should not mean “grey literature” is of lower quality and cannot be used to inform policy-making.

They added that other forms of “grey literature”, including the UNEP Emissions and Adaptation Gap reports or the work of the International Energy Agency (IEA), are routinely used in the IPCC climate science assessment cycles and sometimes referenced in COP decisions.

Manjeet Dhakal, a Nepalese advisor to the LDCs, told Climate Home News those reports have previously been very useful to inform policy-makers. He added that the overshoot report is comprehensive and countries should be guided by it in Antalya.

‘A distraction’ amid bigger science spat

One of the UNEP report authors said the attempts by some countries to cast doubt on the overshoot report is just “a distraction”.

Clashes over climate science and its role in policy-making have escalated over the last few years amid a long-running stand-off at the IPCC. Most governments want the panel to produce all of its key assessment reports in time to inform the next UN Global Stocktake of climate action, due to be completed in November 2028.

But a smaller group of countries, led by Saudi Arabia, India and Russia, have resisted, claiming that timeline would be too rushed for scientists and governments from developing countries to contribute to and review the reports.

The IPCC will reconvene in an online meeting in early December in a last-ditch effort to find a solution.

As well as the IPCC assessments, Tubiana said the findings of the overshoot report must also inform the next global stocktake.