What is the IPCC AR6 synthesis report and why does it matter?

What is the IPCC AR6 synthesis report?

The fourth and final instalment of the sixth assessment report (AR6) by the Intergovernmental Panel on Climate Change, the body of the world’s leading climate scientists, is the synthesis report, so called because it draws together the key findings of the preceding three main sections. Together, they make a comprehensive review of global knowledge of the climate.

The first three sections covered the physical science of the climate crisis, including observations and projections of global heating, the impacts of the climate crisis and how to adapt to them, and ways of reducing greenhouse gas emissions. They were published in August 2021, February and April 2022 respectively.

The synthesis report also includes three other shorter IPCC reports published since 2018, on the impacts of global heating of more than 1.5C above pre-industrial levels, climate change and land, and climate change and the oceans and cryosphere (the ice caps and glaciers).

What will the key findings be?

There is no new science in the synthesis report, just a recap of the main findings of the previous publications. Those include warnings that the world was approaching “irreversible” levels of global heating, with catastrophic impacts rapidly becoming inevitable; and that it was “now or never” to take drastic action to avoid disaster.

Much of the synthesis report is likely to focus on the future, setting out the possible policies and actions that will stave off the worst ravages of climate breakdown and warning of the impacts of further heating.

If the main findings have already been published, why is this report needed?

Its purpose is to reduce the thousands of pages of science to a shorter format, which is further condensed into a “summary for policymakers”, to provide scientific underpinning for global climate action. It is written by scientists but haggled over by representatives of the UN’s nearly 200 governments, so some argue it is subject to watering down by regimes that do not like its messages.

The report is supposed to inform the next UN climate summit, Cop28, which will be hosted by the United Arab Emirates in Dubai from 30 November. There, nations’ progress on cutting greenhouse gas emissions since the Paris climate agreement of 2015 will be assessed. It is certain to find that governments are well off track on their emissions-cutting goals.

Will this report change anything?

This is the sixth IPCC report since the body was set up in 1988, with each comprehensive assessment taking roughly six to eight years to compile. As the reports have grown in size and urgency, so have global greenhouse gas emissions. In 2018, the IPCC warned that emissions must be halved by 2030, compared with 2010 levels, to have a good chance of limiting temperature rises to 1.5C. Yet emissions continue to climb. Last year, they rose by a little under 1%, according to the International Energy Agency. That leaves a rapidly diminishing “carbon budget” for the world to stay within the IPCC’s advised limits.

What should governments do?

Reduce emissions sharply and give up fossil fuels, through investments in renewable energy and other low-carbon technologies, increase energy efficiency, rethink agriculture and restore forests and degraded natural landscapes. It may also be necessary to develop technologies that suck carbon dioxide from the air, called “direct air capture”, or explore other means of “climate repair”.

When is the next IPCC report?

Not until about 2030. That means AR6 is effectively the last IPCC report while it is still feasible – only just – to stay within 1.5C.

Now that the impacts of the climate crisis are highly visible, and the underlying science well understood, some argue that the reporting cycles should be shortened, so that policymakers can receive clearer scientific advice throughout this crucial decade.

The IPCC can also be ordered to compile shorter reports on specific subjects, in between its mammoth comprehensive assessments. The increasingly urgent question of what to do if the world overshoots 1.5C of heating could well be a candidate for such treatment.