Aromar Revi, the Director of the Indian Institute for Human Settlements and an author of the Intergovernmental Panel on Climate Change (IPCC)'s Fifth Assessment Report, provides a synopsis of its key findings on impacts, vulnerability and adaptation.

The Intergovernmental Panel on Climate Change (IPCC) manages one of the largest contemporary global interdisciplinary research initiatives focussed a critical 21st century challenge for all people, everywhere: climate change. Mitigation of human impact on the global climate system (Working Group III) and reducing impacts and vulnerability and enabling effective adaptation (Working Group II) are two major focus areas of the IPCC.

As one of the 60-odd Coordinating Lead Authors (CLAs) of the Working Group II report, I spent the last 36-odd  months working with an exceptional team of the world’s leading scientists, social scientists and urbanists working in urban adaptation - from Africa, Asia, Latin and North America and Europe. We systematically reviewed published evidence on urban climate adaptation from across the world over the last 5-years.

It was a back-breaking task because the literature had grown manifold and autonomous adaptation action probably faster than that. We eventually cited over 500 papers and reports, after cross-checking them to the IPCC's exactingly high standards. Three rounds of international peer review brought us over 2,000 comments from scientists, practitioners and governments. Each was examined by the author team, changes made and responses recorded to be uploaded to the web. This was all done under the watchful eyes of two senior Review Editors who ensured the highest standards of evidence and analysis were maintained.

After over three years of intense work, debate and revision a 44-page summary of the work of 679 authors (from 70 countries) of IPCC Working Group II was presented to the 195 members (country delegations) of the IPCC in a marathon plenary meeting in Yokohama, Japan in end-March 2014. A line-by-line review and debate proceeded for 5 days, going into the wee hours of the morning as a consensus on the Summary for Policymakers (SPM) report was hammered out often a few words at a time.

Unlike other great scientific initiatives of our times, for example in high energy physics, neurosciences or nanotechnology that primarily involve peer engagement between scientists; the importance of the IPCC is the process of collective learning and co-creation between scientists, social scientists and policymakers who are responsible for overseeing global and country-based implementation of climate mitigation and adaptation policies. Over the 21st century this effort could well determine the fate of and development opportunities for billions of people, especially the poor and vulnerable in Asia and Africa.

The IPCC Working Group II report evaluates how patterns of climate risks and potential benefits are shifting, how climate change impacts and risks can be reduced and managed through adaptation and mitigation. The report also critically assesses the limits to adaptation in the case we are unable to mitigate risks fast and deeply enough over the coming three decades. This report focuses on risk, especially in decision-making and opportunities for societies, economies and ecosystems around the world,

The 30-chapter report is divided into two volumes. Volume I focuses on global and sectoral question while Volume II assesses regional risks. New chapters have been added to this assessment Report to respond to socioeconomic, cultural, and regional planning themes, including: livelihoods and poverty, human security, urban and rural areas and the oceans. The SPM attempts to capture the breadth and coverage of the WGII Report in the following logical sections.

Observed Impacts in a Changing World

In recent decades, changes in climate have caused impacts on natural and human systems on all continents and across the oceans. The SPM provides evidence that in many regions, changing precipitation or melting snow and ice are altering hydrological systems, affecting water resources in terms of quantity and quality (medium confidence). Many terrestrial, freshwater, and marine species have shifted their geographic ranges, seasonal activities, migration patterns, abundances, and species interactions in response to ongoing climate change (high confidence).

The negative impacts of climate change on crop yields have been more common than positive impacts (high confidence), based on many studies covering a wide range of regions and crops,

The current world-wide burden of human ill-health from climate change is relatively small compared with effects of other stressors and is not well quantified (medium confidence), this could however rise in the future. Differences in climate vulnerability and exposure from non-climatic factors and from multidimensional inequalities are often produced by uneven development processes (very high confidence).

Impacts from recent climate-related extremes, such as heat waves, droughts, floods, cyclones, and wildfires, reveal significant vulnerability and exposure of some ecosystems and many human systems to current climate variability (very high confidence). Climate-related hazards exacerbate other stressors, often with negative outcomes for livelihoods, especially for people living in poverty (high confidence). Violent conflict also increases vulnerability to climate change (medium evidence, high agreement).

The SPM highlights a few key reasons for concern: some unique and threatened systems, including ecosystems and cultures, are already at risk from climate change (high confidence). With increasing warming, some physical systems or ecosystems may also be at risk of abrupt and irreversible changes. Risks associated with such tipping points become moderate between 0-1°C additional warming (the SPM examines scenarios where warming proceeds towards 4°C levels by late-century) with early warning signs that warm-water coral reefs and Arctic ecosystems are already experiencing irreversible regime shifts (medium confidence).

Vulnerability and exposure around the world

Climate change over the 21st century is projected to reduce renewable surface water and groundwater resource availability significantly in most dry subtropical regions (robust evidence, high agreement).

Due to sea-level rise projected throughout the 21st century and beyond, coastal systems and low-lying areas will increasingly experience adverse impacts such as submergence, coastal flooding, and coastal erosion (very high confidence).

Due to projected climate change by the mid-21st century and beyond, global marine-species redistribution and marine biodiversity reduction in sensitive regions will challenge the sustained provision of fisheries productivity and other ecosystem services (high confidence).

Reducing and managing risks

All aspects of food security are potentially affected by climate change, including food access, utilisation, and price stability (high confidence). For the major crops (wheat, rice, and maize) in tropical and temperate regions, climate change without adaptation is projected to negatively impact production for local temperature increases of 2°C or more above late-20th-century levels, although individual locations may benefit (medium confidence).

Until the mid-21st century, projected climate change will impact human health mainly by exacerbating health problems that already exist (very high confidence). Throughout the 21st century, climate change is expected to lead to increases in ill-health in many regions and especially in developing countries with low income, as compared to a baseline without climate change (high confidence).

Global economic impacts from climate change are difficult to estimate. However, for most economic sectors, the impacts of drivers such as changes in population, age structure, income, technology, relative prices, lifestyle, regulation, and governance are projected to be large relative to the impacts of climate change (medium evidence, high agreement).

Adaptation potential

The SPM draws specific attention to steps that build resilience and enable sustainable development. These could accelerate successful climate-change adaptation globally. For instance, reducing basic service deficits, improving housing, and building resilient infrastructure systems could significantly reduce vulnerability and exposure in urban areas. Increased capacity, voice, and influence of low-income groups and vulnerable communities and their partnerships with local governments also benefit adaptation.

Similarly, adaptation in the agriculture, water, forestry and biodiversity sectors can be enabled via policies that respond to the real challenges of rural decision-making under uncertainty.

Adaptation experiences from across the world indicate that adaptation is becoming embedded in some planning processes (high confidence). Adaptation experience is accumulating across regions in the public and private sector and within communities (high confidence).

Responding to climate-related risks involves decision-making in a changing world. This is challenged by continuing uncertainty about the severity and timing of climate-change impacts and with limits to the effectiveness of adaptation (high confidence). Adaptation and mitigation choices in the near-term will affect the risks of climate change throughout the 21st century (high confidence). Uncertainties about future vulnerability, exposure & responses of interlinked human and natural systems are large (high confidence).

Climate Resilient Pathways for sustainable development are linked strongly to rapid and deep climate change mitigation over the next few decades. These can be enabled through transformations in economic, social, technological, and political decisions and effective actions over the next few decades.

Principles of successful adaptation

Adaptation is place and context specific, with no single approach to reducing risk appropriate across all settings (high confidence). Adaptation planning and implementation can be enhanced through complementary actions across levels, from individuals to governments (high confidence). A first step towards adaptation to future climate change is reducing vulnerability and exposure to present climate variability (high confidence). Adaptation planning and implementation at all levels of governance are contingent on societal values, objectives, and risk perceptions (high confidence). Existing and emerging economic instruments can foster adaptation by providing incentives for anticipating and reducing impacts (medium confidence).

And finally, the SPM states with very high confidence that significant co-benefits, synergies, and trade-offs exist between mitigation and adaptation and among different adaptation responses; while interactions occur both within and across regions.

Conclusion

The IPCC Fifth Assessment cycle (2009-14) brings together a plethora of evidence that GHG emission levels, throughputs and landuse changes continue to rise. If unchecked this could further the risk of a 4°C rise in mean global temperatures in the latter part of the 21st century. These changes in temperature and precipitation and downstream risks and impacts may not be possible to adapt to in many parts of the world, especially in high population concentration regions like South Asia as adaptation barriers are breached.

The IPCC report shows that there is both autonomous and planned mitigation and adaptation happening across all regions of the world. This indicates that sustainable development along climate resilient pathways is possible and realisable if transformative actions around ecosystems, economies and societies are initiated now. Greater clarity and innovation is required to identify an effective suite of initiatives that could connect-the-dots within each region's often unique set of choices to enable multiple transitions along future Climate resilient development pathways. This is clearly possible, it needs us to make a series of difficult collective choices, especially in the run up to the 2015 negotiations in Paris.

Aromar Revi, is the Director of the Indian Institute for Human Settlements. Follow him at @AromarRevi

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