• Energy Research

Les événements extrêmes, tels que ceux causés par le changement climatique, les chocs économiques ou géopolitiques et les épidémies de ravageurs ou de maladies, menacent la sécurité alimentaire mondiale. La complexité de la causalité, ainsi que la myriade de façons dont un événement, ou une séquence d'événements, crée des impacts en cascade et systémiques, posent des défis importants à la recherche sur les systèmes alimentaires et aux politiques. Pour identifier les risques prioritaires pour la sécurité alimentaire et les opportunités de recherche, nous avons demandé à des experts de divers domaines et régions géographiques de décrire les principales menaces pour la sécurité alimentaire mondiale au cours des deux prochaines décennies et de suggérer des questions et des lacunes de recherche clés sur ce sujet. Nous présentons ici une hiérarchisation des menaces à la sécurité alimentaire mondiale résultant d'événements extrêmes, ainsi que des questions de recherche émergentes qui mettent en évidence les défis conceptuels et pratiques qui existent dans la conception, l'adoption et la gouvernance de systèmes alimentaires résilients. Nous espérons que ces résultats aideront à orienter le financement de la recherche et les ressources vers les transformations du système alimentaire nécessaires pour aider la société à faire face aux principaux risques du système alimentaire et à l'insécurité alimentaire en cas d'événements extrêmes. Los eventos extremos, como los causados por el cambio climático, las crisis económicas o geopolíticas y las epidemias de plagas o enfermedades, amenazan la seguridad alimentaria mundial. La complejidad de la causalidad, así como las innumerables formas en que un evento, o una secuencia de eventos, crea impactos en cascada y sistémicos, plantea desafíos significativos para la investigación y las políticas de los sistemas alimentarios por igual. Para identificar los riesgos prioritarios para la seguridad alimentaria y las oportunidades de investigación, pedimos a expertos de una variedad de campos y geografías que describieran las amenazas clave para la seguridad alimentaria mundial en las próximas dos décadas y que sugirieran preguntas y brechas clave de investigación sobre este tema. Aquí, presentamos una priorización de las amenazas a la seguridad alimentaria mundial derivadas de eventos extremos, así como preguntas de investigación emergentes que resaltan los desafíos conceptuales y prácticos que existen para diseñar, adoptar y gobernar sistemas alimentarios resilientes. Esperamos que estos hallazgos ayuden a dirigir la financiación de la investigación y los recursos hacia las transformaciones del sistema alimentario necesarias para ayudar a la sociedad a abordar los principales riesgos del sistema alimentario y la inseguridad alimentaria en situaciones extremas. Extreme events, such as those caused by climate change, economic or geopolitical shocks, and pest or disease epidemics, threaten global food security. The complexity of causation, as well as the myriad ways that an event, or a sequence of events, creates cascading and systemic impacts, poses significant challenges to food systems research and policy alike. To identify priority food security risks and research opportunities, we asked experts from a range of fields and geographies to describe key threats to global food security over the next two decades and to suggest key research questions and gaps on this topic. Here, we present a prioritization of threats to global food security from extreme events, as well as emerging research questions that highlight the conceptual and practical challenges that exist in designing, adopting, and governing resilient food systems. We hope that these findings help in directing research funding and resources toward food system transformations needed to help society tackle major food system risks and food insecurity under extreme events. وتهدد الأحداث المتطرفة، مثل تلك الناجمة عن تغير المناخ والصدمات الاقتصادية أو الجيوسياسية وأوبئة الآفات أو الأمراض، الأمن الغذائي العالمي. إن تعقيد السببية، فضلاً عن الطرق التي لا تعد ولا تحصى التي يخلق بها الحدث، أو سلسلة من الأحداث، تأثيرات متتالية ومنهجية، تشكل تحديات كبيرة لبحوث وسياسات النظم الغذائية على حد سواء. لتحديد مخاطر الأمن الغذائي ذات الأولوية وفرص البحث، طلبنا من خبراء من مجموعة من المجالات والمناطق الجغرافية وصف التهديدات الرئيسية للأمن الغذائي العالمي على مدى العقدين المقبلين واقتراح أسئلة وثغرات بحثية رئيسية حول هذا الموضوع. هنا، نقدم أولوية للتهديدات التي يتعرض لها الأمن الغذائي العالمي من الأحداث المتطرفة، بالإضافة إلى أسئلة البحث الناشئة التي تسلط الضوء على التحديات المفاهيمية والعملية الموجودة في تصميم وتبني وإدارة النظم الغذائية المرنة. نأمل أن تساعد هذه النتائج في توجيه تمويل البحوث والموارد نحو تحولات النظام الغذائي اللازمة لمساعدة المجتمع على معالجة المخاطر الرئيسية للنظام الغذائي وانعدام الأمن الغذائي في ظل الأحداث المتطرفة.

Abstract Non-technical summary We identify a set of essential recent advances in climate change research with high policy relevance, across natural and social sciences: (1) looming inevitability and implications of overshooting the 1.5°C warming limit, (2) urgent need for a rapid and managed fossil fuel phase-out, (3) challenges for scaling carbon dioxide removal, (4) uncertainties regarding the future contribution of natural carbon sinks, (5) intertwinedness of the crises of biodiversity loss and climate change, (6) compound events, (7) mountain glacier loss, (8) human immobility in the face of climate risks, (9) adaptation justice, and (10) just transitions in food systems. Technical summary The Intergovernmental Panel on Climate Change Assessment Reports provides the scientific foundation for international climate negotiations and constitutes an unmatched resource for researchers. However, the assessment cycles take multiple years. As a contribution to cross- and interdisciplinary understanding of climate change across diverse research communities, we have streamlined an annual process to identify and synthesize significant research advances. We collected input from experts on various fields using an online questionnaire and prioritized a set of 10 key research insights with high policy relevance. This year, we focus on: (1) the looming overshoot of the 1.5°C warming limit, (2) the urgency of fossil fuel phase-out, (3) challenges to scale-up carbon dioxide removal, (4) uncertainties regarding future natural carbon sinks, (5) the need for joint governance of biodiversity loss and climate change, (6) advances in understanding compound events, (7) accelerated mountain glacier loss, (8) human immobility amidst climate risks, (9) adaptation justice, and (10) just transitions in food systems. We present a succinct account of these insights, reflect on their policy implications, and offer an integrated set of policy-relevant messages. This science synthesis and science communication effort is also the basis for a policy report contributing to elevate climate science every year in time for the United Nations Climate Change Conference. Social media summary We highlight recent and policy-relevant advances in climate change research – with input from more than 200 experts.

AbstractGlobally, heat stress (HS) is nearly certain to increase rapidly over the coming decades, characterized by increased frequency, severity, and spatiotemporal extent of extreme temperature and humidity. While these characteristics have been investigated independently, a holistic analysis integrating them is potentially more informative. Using observations, climate projections from the CMIP5 model ensemble, and historical and future population estimates, we apply the IPCC risk framework to examine present and projected future potential impact (PI) of summer heat stress for the contiguous United States (CONUS) as a function of non‐stationary HS characteristics and population exposure. We find that the PI of short‐to‐medium duration (1–7 days) HS events is likely to increase more than three‐fold across densely populated regions of the U.S. including the Northeast, Southeast Piedmont, Midwest, and parts of the Desert Southwest by late this century (2060–2099) under the highest emissions scenario. The contribution from climate change alone more than doubles the impact in the coastal Pacific Northwest, central California, and the Great Lakes region, implying a substantial increase in HS risk without aggressive mitigation efforts.

Abstract Climate models suggest a rapid increase of extremely hot days in coming decades. Cool marine air currently ventilates extreme heat in populous coastal regions, diminishing its impacts, but how well climate models capture this effect is uncertain. Here we conduct a comprehensive observational analysis of coastal extreme-heat ventilation—its length scale, magnitude, and regional patterns—and evaluate two ensembles of downscaled global climate models along the eastern US coast. We find that coastal areas are 2 °C–4 °C cooler than ∼60 km inland, resulting in reductions near 50% in population exposure to temperatures above 35 °C. Large seasonal and inter-regional variations are closely linked with land-sea temperature contrasts. High-resolution models underestimate coastal cooling by 50%–75%, implying that substantial and spatiotemporally varying model bias correction is necessary to create accurate projections of coastal extreme heat, which is expected to rise considerably with anthropogenic forcing. Our results underline the importance of regionally- and observationally-based perspectives for assessing future extreme heat and its impacts, and for positioning effective heat-risk management for communities and jurisdictions that span coast-to-inland areas.

Recent studies project that temperature-related mortality will be the largest source of damage from climate change, with particular concern for the elderly whom it is believed bear the largest heat-related mortality risk. We study heat and mortality in Mexico, a country that exhibits a unique combination of universal mortality microdata and among the most extreme levels of humid heat. Combining detailed measurements of wet-bulb temperature with age-specific mortality data, we find that younger people are particularly vulnerable to heat: People under 35 years old account for 75% of recent heat-related deaths and 87% of heat-related lost life years, while those 50 and older account for 96% of cold-related deaths and 80% of cold-related lost life years. We develop high-resolution projections of humid heat and associated mortality and find that under the end-of-century SSP 3–7.0 emissions scenario, temperature-related deaths shift from older to younger people. Deaths among under-35-year-olds increase 32% while decreasing by 33% among other age groups.

This study investigates the historical climatology and future projected change of atmospheric rivers (ARs) and precipitation for the Middle East and North Africa (MENA) region. We use a suite of models from the Coupled Model Intercomparison Project Phase 5 (CMIP5, historical and RCP8.5 scenarios) and other observations to estimate AR frequency and mean daily precipitation. Despite its arid-to-semi-arid climate, parts of the MENA region experience strong ARs, which contribute a large fraction of the annual precipitation, such as in the mountainous areas of Turkey and Iran. This study shows that by the end of this century, AR frequency is projected to increase (~20–40%) for the North Africa and Mediterranean areas (including any region with higher latitudes than 35 N). However, for these regions, mean daily precipitation (i.e., regardless of the presence of ARs) is projected to decrease (~15–30%). For the rest of the MENA region, including the Arabian Peninsula and the Horn of Africa, minor changes in AR frequency (±10%) are expected, yet mean precipitation is projected to increase (~50%) for these regions. Overall, the projected sign of change in AR frequency is opposite to the projected sign of change in mean daily precipitation for most areas within the MENA region.