The Remarkable Scientific Accomplishment of the Latest IPCC Cycle

Last month, an intense diplomatic process brought to an end an unprecedented international effort to assess the state of the planet. If you haven’t heard about it, it’s no big surprise. The headline wasn’t exactly apt: National representatives release the summary for policymakers of the Intergovernmental Panel on Climate Change’s (IPCC) Sixth Assessment Report (AR6). But behind the language of diplomacy and bureaucracy, behind the initialisms and jargon of AR6, lies a remarkable scientific achievement.

After eight years of development, AR6 reflects the collective effort of scientists from around the world and scholars from an increasingly diverse collection of disciplines – systems theory, anthropology, sociology, geography, urban planning, behavioral sciences, gender studies and media studies. to name just a few. It collects and represents results from tens of thousands of peer-reviewed papers. It’s hard to think of any other academic or policy process that integrates such diversity and depth of research, learning, and policy engagement. AR6 offers the most comprehensive examination of climate change yet produced, but it also does something more by bringing so many disciplines together. Covering so many global and regional developments and trends, the authors offer a portrait—sometimes pointillist in its detail, sometimes romantic in its daunting scope and panache—of how the world works. Nothing – well, almost nothing – sits outside of it.

The big climate takeaways have gotten a lot of press coverage, but they’re worth repeating.

• Without immediate and deep reductions in greenhouse gas (GHG) emissions, global warming will exceed 2 degrees Celsius by around 2050. Even if strong policy measures are taken now to reduce emissions, cumulative CO2 emissions will still exceed 1.5 degrees Celsius over the next two decades.
• The difference between 1.1 degrees, 1.5 degrees, and 2 degrees of warming in terms of impact on human well-being, ecosystem health, and even political stability is immense.
• Factors affecting climate are becoming increasingly difficult to isolate, and risks will overlap and amplify across sectors and regions, linking rural and urban infrastructure, populations, and economic and financial systems.
• Although all regions of the world are affected, the drivers of climate impacts and the associated risks are not evenly distributed. They will be felt disproportionately by economically and socially vulnerable and marginalized communities – but make no mistake, they will also be felt by high-income countries.
• While focusing on limiting warming to 1.5 degrees, policymakers must implement adaptation strategies and plans for warming that could potentially exceed 3 degrees.
• To enable the necessary transformation, systems transitions must be enabled by good governance at multiple levels, including urban and regional planning, access to finance, redirecting investment away from fossil fuels and stranded assets, behavioral change and innovation.

Pull out any of these key messages – or the dozens of others found throughout the 8,000+ pages of analysis – and more details, numbers and debates emerge. However, the remarkable procedural and scientific achievement of AR6 also entails a special time challenge: it took a long time, at least politically. Whether your lens is geopolitics, domestic politics, epidemiology, or artificial intelligence, you probably wouldn’t describe the past eight years, let alone eight months, as uneventful.

To the best of their ability, the authors integrated new, peer-reviewed research—including on crises that occurred during the cycle, such as the coronavirus pandemic—into the ongoing analysis. As such, the assessment provides something of a roadmap for new areas of focus, in addition to the current state of climate science. These areas deserve particular attention as they point to new areas of concern for both climate research and climate diplomacy and, due to their novelty, may well pose implementation and governance challenges.

Take Simultaneous System Transitions, a new approach featured heavily in AR6 that aimed to eliminate the sectoral disparities of the previous reporting cycle while opening new avenues for transformation. The previous reports of the AR6 cycle contained four system transitions: urban, rural and infrastructure; Energy; terrestrial, marine, coastal and freshwater ecosystems; and industry. A fifth – social transitions – was added between 2018 and 2022. This late addition is one of the important developments of the AR6 cycle, offering demand-side strategies to reduce emissions and enable transformative adaptation. Think, for example, of urban consumption, much of which falls under the umbrella of societal choice. In 2015, when AR6 launched, urban emissions accounted for just over 60 percent of global emissions. By 2020, that share had reached 67 to 72 percent of global emissions, with about a hundred of the top emitting cities accounting for about 18 percent of the global carbon footprint. Changing energy consumption patterns in these cities can make significant advances in the overall emissions picture.

Another late addition, perhaps more theoretical and still nascent, is found in the concept of climate resilient development (CRD). The balance and relationship between adaptation and mitigation has long plagued the work of the IPCC. Despite these difficulties and the division of the IPCC process into working groups that separate adaptation and mitigation, AR6 authors are increasingly working to bridge the bureaucratic and conceptual divide, an effort best captured in political terms in the very idea of ​​CRD becomes. The framework aims to pursue climate and development goals in an integrated way that increases their effectiveness by expanding the concepts of adaptation and resilience beyond individual projects and short-term time horizons to include longer-term transformations to ensure sustainability and equity. As a group of working group authors noted, opportunities for CRD are not evenly distributed geographically and are decreasing. Cities and urban areas, the authors concluded, provide particularly critical sites for tracking adaptation and mitigation simultaneously.

In this increased attention to cities and urban areas is a third evolution of AR6. The next reporting cycle will examine cities and urban areas for its first special report. To provide an initial framework, more than forty AR6 authors, in collaboration with city officials and industry leaders, screened the entire AR6 for city-relevant material and produced summaries for city policymakers. The reports, part of the Summary for Urban Policymakers initiative, were released at COP27. The results offer a global and regional perspective on local challenges.

• Even with greatly reduced emissions, many cities and metropolitan areas will experience increasing levels of drought, flooding, extreme heat waves and storm surges, as well as more severe hurricanes.
• Sea level rise will continue to have increasing impacts even as warming stabilizes. By 2100, coastal flooding in cities due to sea level rise will affect between 158 million and 510 million people and expose between $7.9 billion to $12.7 billion in infrastructure assets in flood damage.
• In both urban and rural settings, the impact affects the marginalized. This applies in particular to the smaller and medium-sized cities of Asia, Africa and Central and South America. In Africa, for example, almost 60 percent of the population live in informal settlements and are particularly vulnerable due to limited employment opportunities and infrastructure.
• Urbanization differs by region, but transformation is required in all city typologies. Many cities in the Global South are currently in the early stages of urban development and are seeing significant infrastructure expansion. Established cities, meanwhile, have to deal with aging infrastructure. In all cases, the associated material requirements go hand in hand with potentially high levels of gray emissions.

In this increased focus on the local and regional, it is tempting to see science as a reflection of a fractured world, but the truth is quite the opposite. The increased attention to cities and urban areas and regions serves to promote the effectiveness, impact, equity and quality of scientific knowledge. It connects governance and stakeholders horizontally and vertically, bringing together city and nation-state. The systems transition approach does the same thing, looking for solutions rather than silos. These systems offer a way of thinking about a globalized planet, as sectors like manufacturing span multiple systems like city and infrastructure, and the impact of large-scale projects and local habits is felt across regions and ecosystems.

But here’s the thing about the comprehensive knowledge and planetary roadmap captured in AR6: The Summary of the Synthesis Report for Policymakers was adopted by Member States and their climate diplomats, a formal option that cities, civil society and industry, despite their extensive advocacy is not available expertise on the issues. And while the reports themselves are steeped in the ecological consequences of globalization, they take a more neutral stance on the international order. Myriad necessary actions by nation states are detailed, but no state or states are named in any scholarly way, let alone the relationships between them.

The lack of geopolitics in the IPCC assessment reports could easily be called a failure, but it’s better understood as a feature. Aside from plenary approval of the summaries for policymakers – Geopolitics in Action – the science and intelligence captured in the main reports are intended to be kept separate and protected from diplomatic and national interests, and the price of this is silence from geopolitical developments. The AR6 authors have done their job. It is now time for those who focus on foreign policy and diplomacy to pour their expertise into the remarkable assessment of the state of the planet.