Last year, the world’s leaders converged on Glasgow for COP26, and the most significant update to global emissions policy since the 2015 Paris Agreement. Prior to the fortnight-long conference, 154 countries had updated their pledges to reduce greenhouse gas emissions, with targets of varying ambition.
Before and during COP26, a number of different analysts looked at these updated pledges. Some found that the new policies could keep the world below 2°C of warming, while others predicted that they’d still take us well above it. But none of these predictions were peer-reviewed: scientists take longer than a couple of weeks to verify information.
Now, the first peer-reviewed study based on COP26 pledges has been published in Nature, and its results are cautiously optimistic. If every country sticks to every pledge it’s made, according to the paper, then the best estimate for peak warming is 1.9-2.0°C.
“It’s the first time in the peer-reviewed literature that the sum of all the countries’ pledges ends up with a higher than 50% likelihood of staying below the two-degree mark,” says lead author Malte Meinshausen, an associate professor of climate science at the University of Melbourne.
“It is not the pre-agreed target of the Paris Agreement, because the Paris Agreement is ‘well below two degrees’ – however two degrees still is a highly symbolic temperature mark.”
But now is not the time to relax – states need to meet these targets for the lower warming to be realised. And there’s only a 6-10% chance of keeping temperatures to the much more desirable target of 1.5°C actual warming, based on current policies.
To stay within a 1.5°C peak, as the IPCC showed last week, emissions need to peak almost immediately and then fall rapidly, with significant declines by 2030. This is feasible with our existing technology, but it’s not reflected in the world’s policies yet.
“We estimate that under the current pledges, the CO2 emissions will go up by 6-13% beyond 2010 emissions levels,” says Meinshausen.
The team of researchers examined every one of the 198 member countries’ Nationally Determined Contributions (NDCs) – the pledges made at Paris. They then studied the 154 which had been updated for Glasgow.
“We look through these documents. What are their targets? What do they promise? How do we quantify it?” explains Meinshausen.
There’s no consistent way countries are supposed to update their targets, so just finding ways to combine these pledges for analysis was a tricky process. The researchers also had to account for emissions not covered by NDCs – factors such as international aviation.
“We then crunched the whole thing through a reduced complexity climate model,” says Meinshausen. The researchers also took into account pledge updates for different countries at different points, and how they might affect total warming.
“In total we made around 185,000 climate model runs.”
The next UN Climate Change Conference, COP27, will be in November this year in Sharm El Sheikh, Egypt.
Meinshausen says that COP27 is a key opportunity for countries to update their short-term emissions-reduction goals.
“We would likely exhaust the remaining carbon budgets for 1.5° if we don’t enhance the 2030 targets, and that’s really the challenge for this year,” he says.