Science for policy: what the latest IPCC climate change report means for COP26

Cover artwork of IPCC AR6 Working Group 1 Report "Changing"​ by the artist Alisa Singer looms behind COP26 logo

By Joeri Rogelj
Director of Research at Grantham Institute – Climate Change & Environment Lecturer at Imperial College London

It’s Friday morning August 6th 2021. The Intergovernmental Panel on Climate Change (IPCC) has just approved the summary document of their latest climate change assessment report. Hundreds of scientists around the world have worked over three years to complete it. The first tome of the Sixth Assessment Report (AR6) is now ready for release on Monday.

As one of the lead authors, I’m tired – exhausted even – but also proud of the work the panel has delivered in unprecedented circumstances.

The IPCC is tasked with comprehensively and transparently assessing all scientific evidence relevant to the understanding of the risks of climate change. Its reports are neutral with respect to policy. So now comes the task of translating the findings for policy, and COP26 in particular.

Clearer than ever

In the strongest terms ever, the IPCC establishes that global temperature has increased, oceans have warmed, glaciers are retreating, extreme weather is getting more intense, and global sea level is rising. Human activity is behind this – unequivocally.

The scale of changes and the present state of our planet are exceptional and unprecedented in human history. Concentrations of CO2 in our atmosphere are higher than any time in the last 2 million years.

This sets the stage for COP26: a planet where the past decade was about 1.1°C warmer than before the industrial revolution as a result of human pollution.

More necessary than ever

The report uses five scenarios to understand what the future could have in play, ranging from a world where climate policy is rolled back, to a world with ambitious action in the 2020s.

Under all scenarios, the next decades will be warmer than today, but depending on how successful we are in reducing our emissions over that period we will be in very different places by mid-century. By then, we can either have halted warming around 1.5°C or have cruised through it towards much higher levels. The outcome of COP26 will play an essential role in the direction we take.

If we manage to bring CO2 emissions down to net zero, global warming can be stabilized. If we manage to draw down CO2 from the atmosphere thereafter, global temperature increase can be reversed.

But even after we have stopped warming, we will still be left with a fundamentally altered planet. Changes to the ocean, ice sheets and global sea level will stay with us or even continue to worsen for thousands of years. This continued worsening does not mean that they spiral out of control. They are simply very sluggish to respond to the global warming of today, and halting warming will still avoid worse from happening.

The importance of keeping to the Paris Agreement’s temperature target of holding warming well below 2°C and ideally 1.5°C is emphasized once more by these findings.

Updated and improved pledges at COP26 are essential to achieving this.

More urgent than ever

One of the big questions for COP26 is whether it is still possible to keep warming below 1.5°C. The answer is yes, but only just.

AR6 largely confirms the findings of the IPCC 1.5°C Special Report from 2018. Estimates of when 1.5°C would be reached or how much CO2 we can still emit while keeping warming to 1.5°C are very similar, with no fundamental update.

That means that it is now even more firmly established that warming will rise well beyond 1.5°C unless emissions in 2030 are on a clear path to net zero by mid-century.

If these reductions are achieved, our best estimate remains that warming can be held within 0.1°C of 1.5°C.

Finally, AR6 clarifies that achieving net zero CO2 and net zero greenhouse gas emissions results in different outcomes for the planet. The former stabilises the warming caused by CO2, but the latter would result in a peak followed by a gradual reversal of global warming.

These are key insights for a COP that has a Race to Zero as one of its core campaigns.

Leadership starts now

IPCC reports are no isolated scientific endeavour. Governments play key roles in defining their topics, reviewing them, and finally approving their summaries in intense week-long plenary meetings.

These meetings are microcosms of what stirs in the COP negotiations. Some countries emphasise the need for clear and actionable key messages; others aim to remove text that would weaken their negotiating positions. Bringing such an immensely complex process to a successful end is challenging, particularly in a fully virtual setting.

During last week’s plenary the UK’s IPCC Delegation­ – led by Dr Jolene Cook from the BEIS International Climate Science Team, and who is also Head of Climate Science for COP26 – impressed authors, observers, and peers in other country delegations with their leadership, integrity, and diplomatic skill. They found solutions, common ground, and defended the science. It is this leadership that needs to continue and expand in all areas of importance to COP26.

Only when built on the solid evidence of the IPCC, will a COP26 outcome be able to withstand both scrutiny and time.

This article first appeared on LinkedIn.  You can also follow Joeri on his LinkedIn page.