March 20, 2023

expert reaction to the AR6 synthesis report, as published by the IPCC

The Intergovernmental Panel on Climate Change (IPCC) have published it’s Sixth Assessment Report (AR6).

This Roundup accompanied an SMC Briefing.

Prof Rachel Warren, from UEA’s School of Environmental Sciences and the Tyndall Centre for Climate Change Research at UEA, said:

“The report demonstrates the increased urgency of acting to reduce greenhouse gas emissions and the large benefits of so doing. 

“Prompt action to achieve the goals of the Paris Agreement would greatly reduce risks to food security and human health and would avoid irreversible damage to coral reefs, Arctic ecosystems and forests.  It would also reduce the rate of sea level rise, allowing humans and ecosystems to adapt more easily, and avoid the complete melting of the Greenland and Antarctic ice sheets that would otherwise occur. 

“It also emphasizes how science has revealed that the risks of global warming are larger than previously thought, with high or very risks in all categories assessed with only 2C global warming.  This means that pursuing efforts to limit global warming to 1.5C is now more important and urgent than it has ever been.” 

Prof Andy Turner, a climate scientist with particular expertise in monsoon systems at University of Reading, and a Lead Author of IPCC AR6 WGI (Chapter 10 Linking Global to Regional Climate Change), said:

“The IPCC 6th Assessment Report has demonstrated clearly that every additional fraction of warming will lead to intensification of the global water cycle and larger extremes.  For the monsoon regions around the globe, most worrying is the increase in variability, associated with a greater likelihood of flood and drought, which are damaging to agricultural yields, water supply and human health. 

“As the Synthesis Report makes clear, the scale of the challenge is unprecedented, with the burden falling disproportionately on the developing world such as those in the monsoon regions and elsewhere in the tropics.

“The IPCC 6th Assessment offers a clear way forward in “climate-resilient development”, which seeks win-win solutions to reduce or avoid greenhouse gas emissions at the same time as improving quality of life.

“Just as the damaging impacts of climate change will worsen with each degree of warming, the costs of taking action will also rise, should we delay making the necessary deep and sustained cuts in greenhouse gas emissions.”

Dr Friederike Otto, Senior Lecturer in Climate Science at Grantham Institute – Climate Change and the Environment, Imperial College London, and member of the report’s core writing team, said:

“The headline message of the new Synthesis report (SYR) sounds very familiar, and of course we’ve known for decades that burning fossil fuels is the cause of rising temperatures.

“What the new SYR shows is the gravity of the problem. The very first figure shows all the human and natural systems that are already adversely affected. In other words, many more people have lost their lives and livelihoods than originally thought.

“The climate changes as much as we’ve expected for decades, but we humans and our societies are more fragile than we thought before.

“And this is only at 1.2 degrees of warming.

“Even the small changes that we are already observing are having huge impacts around the world.

“Research by the World Weather Attribution has highlighted that climate change is bringing suffering to the world’s poorest and most vulnerable countries through extreme weather events. This research is a big part of the new evidence assessed in the report.

“What this report also shows with much more clarity than ever before is the inequity of climate change – those causing the problem are not the ones that are suffering the consequences.

“If we do not reduce greenhouse gas emissions to zero rapidly and sustainably, those most vulnerable – who have emitted far less than the rich nations and people – will continue to suffer.

“Policy makers need to take science for what it is. The IPCC reports are an incredible source of the latest information in climate science.

“They show the urgency, the gravity and the reasons for hope. But it is policy makers that need to take the actions, now.

“They shouldn’t just pick out politically appropriate passages from the IPCC report that are convenient for their goals. For example, when the IPCC says something about technology, it shouldn’t be an excuse to fixate on technological solutions and ignore everything else in the report.

“Because that is the most important message that we still have time to act and that we have everything we need to act, we know which mitigation and adaptation measures work. But the sense of urgency in implementing them is currently lacking.

“We need to stop burning fossil fuels. We know there is no alternative. There is no saving future technology that would allow us to just carry on as before.

“We must act now, otherwise we will lose far too many people, livelihoods, and ecosystems.”

Dr Alison Ming, NERC Independent Research Fellow, University of Cambridge, said:

“Our understanding of the climate system has evolved rapidly over the past decade. Better observations, improved climate models and statistical techniques have all contributed to firmly linking human activity to the widespread and rapid changes seen in every region of the globe. Modelled scenarios are used to make predictions about possible near and long term future climate change. Our grasp of the mechanisms at play in our climate system has also improved. This gives us more confidence in our model predictions. This synthesis report clearly lays out the latest science for policymakers, sets out the adverse impact of climate change and emphasizes the urgent need for integrated climate action.”

Prof Lisa Schipper, Institute of Geography, University of Bonn, said:

“The Synthesis Report retains the three most important messages across the IPCC AR6. These are (1) that time is limited and the window of opportunity to act is closing quickly. That (2) actions currently being taken, and actions that governments have committed to, are not enough to ensure either reduction of emissions to stay below 1.5C or to sufficiently help people adapt to climate change. And (3) that increasingly damaging – and in some cases irreversible – impacts that we cannot adapt to are expected unless drastic cuts to emissions are taken now.”

Dr Alaa Alkhourdajie, Research Fellow at Imperial College London’s Centre for Environmental Policy – IPCC Working Group III Senior Scientist, said:

So much scientific work went into all those IPCC reports. What did they achieve “in the real world”?

What do you think are the most important implications of the Synthesis Report’s findings for policymakers and the public, and how can we act on these implications?

“The scientific advances that have been assessed throughout this IPCC 6th assessment cycle, and now synthesised in the new Synthesis report, have resulted in a better understanding of what the future will look like, depending on the choices we make today and this decade. It is clearer now more than ever that with every increment of warming, the risks, impact and related losses and damages escalate substantially across all regions and sectors, more so for the most vulnerable communities. Choices made in this decade will determine the extent to which current and future generations will experience a hotter and different world. We now have clear understanding that there are multiple feasible, effective, low-cost technological options, available now, to reduce greenhouse gas emissions and to adapt to the changing climate. These when coupled with tried and tested policy measures that can achieve deep emissions reductions, provided that they scaled up and applied widely across all regions and sectors.”

What aspect of the Synthesis Report do you believe is particularly noteworthy or significant, and why?

“The new synthesis report will continue to provide key input to the Paris Agreement ‘pledge, review and ratchet mechanism’ throughout this decade but also beyond 2030, as the report explicitly state the 2035 levels of CO2 and GHG emissions reductions that are in line with 1.5°C or 2°C in goals the Summary for Policymakers.”

What do you believe is the most pressing thing to be achieved right now to address climate change?

“Across the entire report, there are always three key words associated with almost all findings related to limiting warming to 1.5°C and 2°C: “deep, rapid and sustained” GHG emissions reductions this decade, in all sectors and across all regions. This can be achieved if climate action is embedded in the wider development context taking into account the different context and circumstances that vary across regions. Nonetheless, shared technology, know-how, suitable policy measures and adequate climate financing can bridge these differences.”

Prof Ilan Kelman, Professor of Disasters and Health at University College London and the University of Agder, said:

“The synthesis report highlights a terrifying aspect of human-caused climate change: devastating heatwaves. People are dying now from increasing heat-humidity directly attributable to climate change. Without concerted action, as the report recommends, death rates will worsen quickly. Knock-on impacts for food are expected as outdoor agricultural workers struggle with the rising temperatures while crops and livestock wilt.

“The synthesis report describes a key action: removing fossil fuel subsidies, which amount to hundreds of billions of dollars per year. Huge benefits include reducing government debts, preventing pollution, improving health, and supporting sustainability-related jobs, if managed well. Our taxes should not be supporting an industry that hurts us.”

Prof Tom Welton, former president of the Royal Society of Chemistry, said:

“The IPCC’s work to synthesise an enormous volume of research into clear guidance reminds us of the importance of science-policy interfaces. Understanding climate change and then taking action requires the best evidence and open and transparent processes. The RSC welcomes the IPCC’s AR6 synthesis report and urges further progress to deliver an equivalent intergovernmental science panel on chemicals and waste management.

“An urgent shift to renewable and low carbon sources of energy is required to minimise the devastating impacts of climate change but we must be careful that we don’t introduce new sources of pollution or deplete critical minerals. The IPCC particularly notes these risks on batteries which we must pay careful attention to but the importance of moving to a circular economy is widespread. The chemical science community will make a vital contribution in this area and many others in transforming the global economy to a sustainable basis.”

Prof Bill Collins, Professor of Climate Processes, University of Reading, said:

“This latest report sets out the exciting possibility of a sustainable future. While some have worried about the cost of this, a key finding from this report is that there will be substantial benefits to air quality (such as ground-level ozone) from moving away from fossil fuel economies. The economic returns from these immediate health benefits are assessed to be greater than the costs incurred even before accounting for all the future climate benefits.

“But we are not currently on this path. Future CO2 emissions just from the fossil fuel infrastructures currently in place will take us beyond 1.5 degrees. Time is running out. How much fossil fuel we burn this decade will determine whether warming can be limited to 1.5 or 2 degrees. The time is now to decide whether or not to take the sustainable path set out by the IPCC.”

Prof Pierre Friedlingstein, Chair in Mathematical Modelling of Climate Systems at the University of Exeter, said:

“The IPCC AR6 synthesis report perfectly summarises current and future climate change and associated impacts and the absolute necessity to reduce greenhouse gases emissions immediately to limit further warming. At current level of CO2 emissions, the 1.5°C target would be breached in the coming decade.”

“To me, the one single sentence from the report that says it all is the following: “The choices and actions implemented in this decade will have impacts now and for thousands of years.”

Dr Rob Bellamy, Lecturer in Climate and Society at the University of Manchester, said:

“Today’s IPCC Synthesis Report makes it crystal clear that taking carbon dioxide out of the air is not just an option – but a necessity. Whether to speed up mitigation, to counterbalance leftover emissions from hard-to-abate sectors like aviation and agriculture, or to bring the temperature back down in the case of overshooting 1.5 degrees; carbon removal is firmly on the climate policy agenda. But carbon removal methods, such as afforestation and bioenergy with carbon capture and storage, also bring significant risks to people and the environment. We now need a wide-ranging societal conversation about which methods to take forward, how to incentivise them, and ultimately how to govern them. Make no mistake, we need to do carbon removal; but we need to do it responsibly.”

Prof David Lee, an expert on aviation at Manchester Metropolitan University, and a Lead Author of AR6 WGIII and Contributing Author to WGI, said:

“The Synthesis Report SPM highlights that aviation is a sector with no easy answers – a “hard-to-abate” sector – noted in SPM B.6.2. Alternative fuels emerge as the best hope (SPM C3.3.3), but the SPM also notes that there likely to be residual greenhouse gas emissions such that carbon dioxide removal (CDR) methods will need to be deployed, in order to reach net zero CO2 or GHG emissions (SPM B.6.2). What needs to be understood is how hard and how demanding this is – we (as the IPCC) were very careful to define what we meant by carbon dioxide removals, that they are “anthropogenic activities”, and it means “durably storing it in geological, terrestrial, or ocean reservoirs, or in products” (see WGI, WGIII glossaries). The Synthesis Report is a very clear signal that there are significant challenges ahead for aviation and no easy answers or quick fixes.”

Prof Daniela Schmidt, Professor in Earth Sciences, University of Bristol and Cabot Institute, said:

“It is time to acknowledge that the 10% highest-emitting households contribute about ~40% of global greenhouse gas emissions. The poorest 50% contribute only a fraction but will experience hunger, droughts and floods if we not dramatically reduce emissions. 

“The burden of our lack of action is carried by those who are young today and have not caused the problem. We are accepting that children in the most vulnerability regions in the world will have a challenging future.

“Why are we not using the many technologies and instruments which we have to dramatically reduce our emissions from transport, industry, buildings and food?”

Prof Ed Hawkins, climate scientist at the University of Reading, said: 

“The use of the warming stripes in the IPCC’s Assessment Report is a haunting reminder of the consequences we are facing if we fail to act on climate change now. These stripes portray a stark picture of the different and dangerous worlds that future generations could inherit, depending on our actions today. The deepening red stripes are an urgent warning of the adverse effects of rising temperatures. If we don’t take rapid action by lowering emissions, our children and grandchildren will be left to bear the brunt of extreme weather, such as more intense heatwaves, droughts, floods, and storms. This is not just about rising numbers on a chart, this is about the genuine impact on people’s lives, businesses and communities. Every bit of warming avoided makes the consequences less severe.”

Dr Chris Jones, Met Office Hadley Centre, and member of the report’s core writing team, said:

“Today’s report reveals the sheer scale of the ambition required to avoid the worst consequences of climate change. We know that climate change is already happening, and the world has already witnessed extreme events associated with the relatively modest warming we have seen so far. In fact, the world now is the coolest it is going to be, at least for many decades.

“The report underscores the need for urgent action – today’s decisions have implications for future generations. Without immediate and equitable mitigation and adaptation, climate change increasingly threatens societies and human wellbeing. But the report also shows the range of currently available and cost effective mitigation and adaptation options. Renewed efforts to invest in sustainable development give us the best chance of a climate-resilient future.”

Prof Joeri Rogelj, Professor of Climate Science & Policy, Imperial College London, said:

“The most recent IPCC Synthesis Report presents a comprehensive overview of the causes, consequences, and potential solutions to climate change – drawing from other major IPCC publications from the past two years. The release of the report couldn’t be more timely, as the UN is currently evaluating the adequacy of climate action under the Paris Agreement. Serving as a vital benchmark, it will enable measurement of progress and identification of gaps in emissions reductions and adaptation efforts.

“The Synthesis Report is the culmination of the IPCC’s sixth assessment cycle, which began in 2015. Despite facing significant obstacles, this cycle has produced some of the most influential climate reports to date. Among these are the 2018 Special Report on Global Warming of 1.5 Degrees, which helped to mobilize climate movements and drove countries and companies to set net-zero targets, and the 2021 Climate Report, which unequivocally demonstrated that human activities are responsible for almost all of the more than 1.1 degrees of global warming that we have experienced thus far.

“Taken together, these reports provide the most solid evidence of the causes, impacts, and potential solutions to climate change, and underscore the urgent need for action. While our understanding of the problem has never been clearer, it is essential that this knowledge is now translated into meaningful and effective action that addresses the crisis.”

Prof Richard Allan, Professor of Climate Science, University of Reading, said:

“As human activities continue to pump greenhouse gases into the atmosphere, the only way Earth can cool to space is becoming further compromised which is increasing global warming and intensifying the severity of wet, dry and hot extremes. This comprehensive synthesis of the state of knowledge on climate science assessed by many hundreds of scientists across three weighty reports is clear that greenhouse gas emissions must be rapidly cut across all sectors of society until net emissions are zero. Every bit of warming avoided due to the collective actions pulled from our growing, increasingly effective toolkit of options is less worse news for societies and the ecosystems upon which we all depend.”

Declared interests

Prof Daniela Schmidt was a WGII Coordinating Lead Author

Prof Joeri Rogelj: In the IPCC Sixth Assessment Cycle, Joeri Rogelj served as a Coordinating Lead Author on the Special Report on Global Warming of 1.5°C, a Lead Author on the AR6 Working Group 1 Contribution on the Physical Science Basis, and a Contributing Author on the AR6 Working Groups 2 and 3 Reports.

Prof Bill Collins: Lead author on AR6 WGI chapter 7 and Technical Summary/

Prof Allan: Lead author on AR6 WGI chapter 8, Technical Summary and Summary for Policy Makers, contributing author on AR6 WGI Chapters 2 and 11

For all other experts, no reply to our request for DOIs was received.