Plant-based and planetary-health diets, environmental burden, and risk of mortality: a prospective cohort study of middle-aged and older adults in China.

BACKGROUND: Plant-based diets (PBDs) and planetary-health diets (PHDs) are recommended for their potential health and environmental benefits, but population-based evidence in diverse cultures is scarce. METHODS: We included 9364 adults aged 45 years and older (52·3% female, 47·7% male) from the open cohort of the China Health and Nutrition Survey. Dietary intake was assessed using 3-day 24 h dietary recalls combined with weighing methods from 1997 to 2011, and mortality was documented from 1997 to 2015. We calculated the overall PBD index (PDI), healthful PBD index (hPDI), and unhealthful PBD index (uPDI; ranges 18-90), and the PHD score (range 0-140). We also estimated the related greenhouse gas emissions, land appropriation, and total water footprint and examined their associations with mortality. FINDINGS: PBD indices were inversely related to greenhouse gas emissions, land appropriation, and total water footprint, whereas higher PHD score was related to higher environmental burdens (p<0·0001). During follow-up (mean 9·2 years), 792 (8·5%) death cases were documented. PDI (HR 1·08 [95% CI 0·88-1·32]) and hPDI (0·98 [0·80-1·21]) were not significantly associated with mortality, whereas higher uPDI was related to a higher mortality risk (1·55 [1·26-1·91]). In contrast, higher PHD score was associated with lower mortality risk (0·79 [0·63-0·99]). INTERPRETATION: The PBDs showed environmental benefits, but are not necessarily associated with lower mortality risk. The PHD, developed mainly in western populations, was related to lower mortality risk but higher environmental burdens in the Chinese population. FUNDING: Fundamental Research Funds for the Central Universities, Zhejiang University Global Partnership Fund, and National Natural Science Foundation of China.

Holistic food system innovation strategies can close up to 80% of China's domestic protein gaps while reducing global environmental impacts.

China's imports of livestock feed, particularly protein-rich feeds, pose challenges to global environmental sustainability. Achieving protein self-sufficiency for food and feed in China without exceeding environmental boundaries requires integrated measures and optimization of China's food system. Here we propose holistic food system innovation strategies consisting of three components-technological innovation, integrated spatial planning and demand-side options-to reduce protein import dependency and promote global environmental sustainability. We find that food system innovations can close almost 80% of China's future protein gaps while reducing 57-85% of agricultural import-embodied environmental impacts. Deploying these innovations would also reduce greenhouse gas emissions (22-27%) and people's harmful exposure to ammonia (73-81%) compared with the baseline scenario in 2050. Technological innovations play a key role in closing protein gaps, while integrated crop-livestock spatial planning is imperative for achieving environmental and health targets.

A systematic evaluation of seven different scores representing the EAT-Lancet reference diet and mortality, stroke, and greenhouse gas emissions in three cohorts.

Different approaches have been used for translation of the EAT-Lancet reference diet into dietary scores that can be used to assess health and environmental impact. Our aim was to compare the different EAT-Lancet diet scores, and to estimate their associations with all-cause mortality, stroke incidence, and greenhouse gas emissions. We did a systematic review (PROSPERO, CRD42021286597) to identify different scores representing adherence to the EAT-Lancet reference diet. We then qualitatively compared the diet adherence scores, including their ability to group individuals according the EAT-Lancet reference diet recommendations, and quantitatively assessed the associations of the diet scores with health and environmental outcome data in three diverse cohorts: the Danish Diet, Cancer and Health Cohort (DCH; n=52 452), the Swedish Malmö Diet and Cancer Cohort (MDC; n=20 973), and the Mexican Teachers' Cohort (MTC; n=30 151). The DCH and MTC used food frequency questionnaires and the MDC used a modified diet history method to assess dietary intake, which we used to compute EAT-Lancet diet scores and evaluate the associations of scores with hazard of all-cause mortality and stroke. In the MDC, dietary greenhouse gas emission values were summarised for every participant, which we used to predict greenhouse gas emissions associated with varying diet adherence scores on each scoring system. In our review, seven diet scores were identified (Knuppel et al, 2019; Trijsburg et al, 2020; Cacau et al, 2021; Hanley-Cook et al, 2021; Kesse-Guyot et al, 2021; Stubbendorff et al, 2022; and Colizzi et al, 2023). Two of the seven scores (Stubbendorff and Colizzi) were among the most consistent in grouping participants according to the EAT-Lancet reference diet recommendations across cohorts, and higher scores (greater diet adherence) were associated with decreased risk of mortality (in the DCH and MDC), decreased risk of incident stroke (in the DCH and MDC for the Stubbendorff score; and in the DCH for the Colizzi score), and decreased predicted greenhouse gas emissions in the MDC. We conclude that the seven different scores representing the EAT-Lancet reference diet had differences in construction, interpretation, and relation to disease and climate-related outcomes. Two scores generally performed well in our evaluation. Future studies should carefully consider which diet score to use and preferably use multiple scores to assess the robustness of estimations, given that public health and environmental policy rely on these estimates.

Environmental impact of anesthetic drugs.

PURPOSE OF REVIEW: The environmental impact of anesthesia far exceeds that of other medical specialties due to our use of inhaled anesthetic agents (which are potent greenhouse gases) and many intravenous medications. RECENT FINDINGS: Calls for reducing the carbon footprint of anesthesia are ubiquitous in the anesthesia societies of developed nations and are appearing in proposed changes for hospital accreditation and funding in the United States. The body of research on atmospheric, land and water impacts of anesthetic pharmaceuticals is growing and generally reinforces existing recommendations to reduce the greenhouse gas emissions of anesthesia care. SUMMARY: The environmental impact of anesthesia care should factor into our clinical decisions. The onus is on clinicians to safely care for our patients in ways that contribute the least harm to the environment. Intravenous anesthesia and regional techniques have less environmental impact than the use of inhaled agents; efforts to reduce and properly dispose of pharmaceutical waste are central to reducing environmental burden; desflurane should not be used; nitrous oxide should be avoided except where clinically necessary; central nitrous pipelines should be abandoned; low fresh gas flows should be utilized whenever inhaled agents are used.

The environmental impacts of anesthesia.

PURPOSE OF REVIEW: The healthcare sector has a substantial environmental footprint, and the delivery of anesthesia contributes significantly. Inhaled anesthetics themselves are potent greenhouse gases, unused intravenous medication exert toxic effects on the environment, and the increasing reliance on single-use devices has led to an ever-growing amount of solid waste produced in operating rooms. This review discusses many of these environmental impacts and suggests practices to mitigate the environmental footprint of anesthetic practice. RECENT FINDINGS: The choice of anesthesia maintenance has significant environmental implications, with nitrous oxide and desflurane having the highest carbon footprint of all anesthetic agents. Using low fresh gas flows and supplementing or replacing inhalational agents with propofol leads to a significant reduction in emissions. Many intravenous anesthetic agents pose a risk of environmental toxicity, and efforts should be made to decrease medication waste and ensure appropriate disposal of unused medications to minimize their environmental impacts. Additionally, consideration should be given to replacing single-use devices in the operating rooms with reusable alternatives that are often both environmentally and economically superior. And solid waste generated in the operating room should be segregated thoughtfully, as processing regulated medical waste is a highly energy-intensive process. SUMMARY: Significant opportunities exist to improve the environmental footprint of anesthesia practice, and with the rapidly worsening climate crisis, the importance of implementing changes is greater than ever.

Quantification of the environmental impact of radiotherapy and associated secondary human health effects: a multi-institutional retrospective analysis and simulation.

BACKGROUND: The health-care industry is a substantial contributor to global greenhouse gas emissions, yet the specific environmental impact of radiotherapy, a cornerstone of cancer treatment, remains under-explored. We aimed to quantify the emissions associated with the delivery of radiotherapy in the USA and propose a framework for reducing the environmental impact of oncology care. METHODS: In this multi-institutional retrospective analysis and simulation study, we conducted a lifecycle assessment of external beam radiotherapy (EBRT) for ten anatomical disease sites, adhering to the International Organization for Standardization's standards ISO 14040 and ISO 14044. We analysed retrospective data from Jan 1, 2017, to Oct 1, 2023, encompassing patient and staff travel, medical supplies, and equipment and building energy use associated with the use of EBRT at four academic institutions in the USA. The primary objective was to measure the environmental impacts across ten categories: greenhouse gases (expressed as kg of carbon dioxide equivalents [CO2e]), ozone depletion, smog formation, acidification, eutrophication, carcinogenic and non-carcinogenic potential, respiratory effects, fossil fuel depletion, and ecotoxicity. Human health effects secondary to these environmental impacts were also estimated as disability-adjusted life years. We also assessed the potential benefits of hypofractionated regimens for breast and genitourinary (ie, prostate and bladder) cancers on US greenhouse gas emissions using an analytic model based on the 2014 US National Cancer Database for fractionation patterns and patient commute distances. FINDINGS: We estimated that the mean greenhouse gas emissions associated with a standard 25-fraction EBRT course were 4310 kg CO2e (SD 2910), which corresponded to 0·0035 disability-adjusted life years per treatment course. Transit and building energy usage accounted for 25·73% (1110 kg CO2e) and 73·95% of (3190 kg CO2e) of total greenhouse gas emissions, respectively, whereas supplies contributed only 0·32% (14 kg CO2e). Across the other environmental impact categories, most of the environmental impact also stemmed from patient transit and energy use within facilities, with little environmental impact contributed by supplies used. Hypofractionated treatment simulations suggested a substantial reduction in greenhouse gas emissions-by up to 42% for breast and 77% for genitourinary cancer-and environmental impacts more broadly. INTERPRETATION: This comprehensive lifecycle assessment of EBRT delineates the environmental and secondary health impacts of radiotherapy, and underscores the urgent need for sustainable practices in oncology. The findings serve as a reference for future decarbonisation efforts in cancer care and show the potential environmental benefits of modifying treatment protocols (when clinical equipoise exists). They also highlight strategic opportunities to mitigate the ecological footprint in an era of escalating climate change and increasing cancer prevalence. FUNDING: Mount Zion Health Fund.

Balancing patient needs with environmental impacts for best practices in general anesthesia: Narrative review and clinical perspective.

Discussions of the environmental impacts of general anesthetics have focused on greenhouse gas (GHG) emissions from inhaled agents, with those of total intravenous anesthesia (TIVA) recently coming to the forefront. Clinical experts are calling for the expansion of research toward life cycle assessment (LCA) to comprehensively study the impact of general anesthetics. We provide an overview of proposed environmental risks, including direct GHG emissions from inhaled anesthetics and non-GHG impacts and indirect GHG emissions from propofol. A practical description of LCA methodology is also provided, as well as how it applies to the study of general anesthesia. We describe available LCA studies comparing the environmental impacts of a lower carbon footprint inhaled anesthetic, sevoflurane, to TIVA/propofol and discuss their life cycle steps: manufacturing, transport, clinical use, and disposal. Significant hotspots of GHG emission were identified as the manufacturing and disposal of sevoflurane and use (attributed to the manufacture of the required syringes and syringe pumps) for propofol. However, the focus of these studies was solely on GHG emissions, excluding other environmental impacts of wasted propofol, such as water/soil toxicity. Other LCA gaps included a lack of comprehensive GHG emission estimates related to the manufacturing of TIVA plastic components, high-temperature incineration of propofol, and gas capture technologies for inhaled anesthetics. Considering that scarce LCA evidence does not allow for a definite conclusion to be drawn regarding the overall environmental impacts of sevoflurane and TIVA, we conclude that current anesthetic practice involving these agents should focus on patient needs and established best practices as more LCA research is accumulated.

Infectious Diseases in a Changing Climate.

This JAMA Insights in the Climate Change and Health series discusses the importance of clinicians having awareness of changes in the geographic range, seasonality, and intensity of transmission of infectious diseases to help them diagnose, treat, and prevent these diseases.

Climate Change and Stroke: A Topical Narrative Review.

The impacts of accumulating atmospheric greenhouse gases on the earth's climate are now well established. As a result, there have been increases in ambient temperatures and resultant higher frequency and duration of temperature extremes and other extreme weather events, which have been linked to a wide range of adverse health outcomes. This topical narrative review provides a summary of published evidence on the links between climate change and stroke. There is consistent evidence of associations between stroke incidence and mortality and increasing ambient temperature and air pollution. Associations have also been shown for changes in barometric pressure, wildfires, and desert dust and sandstorms, but current evidence is limited. Flooding and other extreme weather events appear to primarily cause service disruption, but more direct links to stroke may emerge. Synergies between dietary changes that reduce stroke risk and may also reduce carbon footprint are being explored. We also discuss the impact on vulnerable populations, proposed pathophysiologic mechanisms, mitigation strategies, and current research priorities. In conclusion, climate change increasingly impacts the stroke community, warranting elevated attention.

A WHO-led global strategy to control greenhouse gas emissions: a call for action.

BACKGROUND: Climate change, driven by anthropogenic greenhouse gas emissions, is among the greatest threats to human health. The World Health Organisation (WHO), has led global efforts to respond to emerging public health threats including the control of hazardous substances such as tobacco, alcohol, lead and asbestos, with remarkable health gains. BODY: Despite WHO's clear messaging on the enormous and growing health risks of climate change, greenhouse gases are not yet classified as hazardous substances, requiring control through a global strategy or framework. Additionally, WHO has not classified disease attributable to climate change as a result of the promulgation of these hazards as a Public Health Emergency of International Concern (PHEIC), despite the serious and preventable health risks it poses globally. Several historical precedents set the stage for WHO to declare excess greenhouse gases as health hazards, including the control of ozone-depleting substances and breast-milk substitutes where the public benefit of control exceeded the potential benefit of their promulgation. In addition, WHO's undertaking within the International Health Regulations to protect global health, providing imperative to declare climate change a PHEIC, with Tedros Adhanom Ghebreyesus, director-general of WHO, declaring: "The climate crisis is a health crisis, fuelling outbreaks, contributing to higher rates of noncommunicable diseases, and threatening to overwhelm our health workforce and health infrastructure". Importantly, the health sector, perhaps more than other sectors, has successfully overcome formidable, vested interests in combatting these threats to health. CONCLUSION: It is thus imperative that WHO make full use of their credibility and influence to establish a global framework for the control of greenhouse gases through the declaration of excess greenhouse gas emissions as a hazardous substance, and declaring climate change a PHEIC. Who else is better placed to drive the considerable societal transformation needed to secure a liveable future?

Seasonal advance of intense tropical cyclones in a warming climate.

Intense tropical cyclones (TCs), which often peak in autumn1,2, have destructive impacts on life and property3-5, making it crucial to determine whether any changes in intense TCs are likely to occur. Here, we identify a significant seasonal advance of intense TCs since the 1980s in most tropical oceans, with earlier-shifting rates of 3.7 and 3.2 days per decade for the Northern and Southern Hemispheres, respectively. This seasonal advance of intense TCs is closely related to the seasonal advance of rapid intensification events, favoured by the observed earlier onset of favourable oceanic conditions. Using simulations from multiple global climate models, large ensembles and individual forcing experiments, the earlier onset of favourable oceanic conditions is detectable and primarily driven by greenhouse gas forcing. The seasonal advance of intense TCs will increase the likelihood of intersecting with other extreme rainfall events, which usually peak in summer6,7, thereby leading to disproportionate impacts.

Nitrous Oxide Use in Australian Health Care: Strategies to Reduce the Climate Impact.

Nitrous oxide is a useful inhaled analgesic. Due to its high global warming potential and ozone-depleting properties, the nitrous oxide emissions related to health care are being increasingly scrutinized. In this narrative review, we will discuss the clinical uses of nitrous oxide relevant to anesthetists, in addition to its contribution as a greenhouse gas. Using available data from Australia, we will explore potential strategies for reducing the impact of those emissions, which are likely to be applicable in other countries. These include destruction of captured nitrous oxide, minimizing nitrous oxide waste and reducing clinical use. Anesthesia clinicians are well placed to raise awareness with colleagues and consumers regarding the environmental impact of nitrous oxide and to promote cleaner alternatives. Reducing use is likely to be the most promising reduction strategy without large-scale changes to infrastructure and subsequent delay in action.

Future temperature extremes threaten land vertebrates.

The frequency, duration, and intensity of extreme thermal events are increasing and are projected to further increase by the end of the century1,2. Despite the considerable consequences of temperature extremes on biological systems3-8, we do not know which species and locations are most exposed worldwide. Here we provide a global assessment of land vertebrates' exposures to future extreme thermal events. We use daily maximum temperature data from 1950 to 2099 to quantify future exposure to high frequency, duration, and intensity of extreme thermal events to land vertebrates. Under a high greenhouse gas emission scenario (Shared Socioeconomic Pathway 5-8.5 (SSP5-8.5); 4.4 °C warmer world), 41.0% of all land vertebrates (31.1% mammals, 25.8% birds, 55.5% amphibians and 51.0% reptiles) will be exposed to extreme thermal events beyond their historical levels in at least half their distribution by 2099. Under intermediate-high (SSP3-7.0; 3.6 °C warmer world) and intermediate (SSP2-4.5; 2.7 °C warmer world) emission scenarios, estimates for all vertebrates are 28.8% and 15.1%, respectively. Importantly, a low-emission future (SSP1-2.6, 1.8 °C warmer world) will greatly reduce the overall exposure of vertebrates (6.1% of species) and can fully prevent exposure in many species assemblages. Mid-latitude assemblages (desert, shrubland, and grassland biomes), rather than tropics9,10, will face the most severe exposure to future extreme thermal events. By 2099, under SSP5-8.5, on average 3,773 species of land vertebrates (11.2%) will face extreme thermal events for more than half a year period. Overall, future extreme thermal events will force many species and assemblages into constant severe thermal stress. Deep greenhouse gas emissions cuts are urgently needed to limit species' exposure to thermal extremes.

Associations of daily diet-related greenhouse gas emissions with the incidence and mortality of chronic diseases: a systematic review and meta-analysis of epidemiological studies.

OBJECTIVES: Although the entire process extending from food production to dietary consumption makes a large contribution to total greenhouse gas (GHG) emissions, little and inconsistent evidence exists on the epidemiological associations of daily diet-related GHG emissions with chronic disease risk or all-cause mortality. This systematic review and meta-analysis explored the observational epidemiological relationship between daily diet-related GHG emissions and health outcomes, including the risk of chronic diseases and all-cause mortality. METHODS: Original articles published in English until May 2022 were identified by searching PubMed, Ovid-Embase, Web of Science, CINAHL, and Google Scholar. The extracted data were pooled using both fixed-effects and random-effects meta-analyses and presented as hazard and risk ratios (RRs) with 95% confidence intervals (CIs). RESULTS: In total, 7 cohort studies (21 study arms) were included for qualitative synthesis and meta-analysis. The GHG emissions of dietary consumption showed a significant positive association with the risk of chronic disease incidence and mortality in both fixed-effects and random-effects models (fixed: RR, 1.04; 95% CI, 1.03 to 1.05; random: RR, 1.04; 95% CI, 1.02 to 1.06). This positive association was robust regardless of how daily diet-related GHG emissions were grouped. More strongly animal- based diets showed higher GHG emissions. However, there were only a few studies on specific chronic diseases, and the subgroup analysis showed insignificant results. There was no evidence of publication bias among the studies (Egger test: p=0.79). CONCLUSIONS: A higher GHG-emission diet was found to be associated with a greater risk of all-cause mortality.

Environmental impacts and diet quality of popular diet models compared to Turkey's national nutrition guidelines.

AIMS: This study aimed to compare the environmental impacts and diet qualities of popular diet models with the recommendations of the Turkish national dietary guidelines. METHODS: Seven-day isocaloric (8368 kJ) diet models were created taking into account the Mediterranean, Atkins (20/40/100), Ornish, Zone diets, and Turkey Dietary Guidelines-2015 recommendations with different food and nutrient contents. Water footprints were evaluated using the global water footprint standards. Greenhouse gas emissions were evaluated using carbon footprint factors compiled as a result of meta-analyses of life cycle analysis studies in the literature. In addition, the quality of diets was evaluated with the Diet Quality Index-International. RESULTS: Atkins20 diet model had the most harmful environmental impact (greenhouse gas emissions 8.74 kg CO2 -eq/per/day and total water footprint 7731 L/per/day), whereas Ornish and Mediterranean diet models (greenhouse gas emissions 2.2/3.07 kg CO2 -eq/per/day and total water footprints 3184/3675 L/per/day, respectively) had less harmful environmental impact. The highest Diet Quality Index-International score was in the Ornish diet model while the lowest Diet Quality Index-International was in the Atkins20 diet model. CONCLUSION: Ornish and Mediterranean diet models had less harmful environmental impacts, which contributed to sustainable nutrition. The importance of diet quality and environmental impacts should be kept in mind when evaluating diet models to ensure sustainable nutrition.

Diet-Attributable Greenhouse Gas Emissions and Acute Myocardial Infarction in Costa Rica Heart Study.

Adopting sustainable dietary patterns is essential for planetary and human health. As data to address this issue are lacking in Latino populations, this study examined the association between diet-attributable greenhouse gas emissions (GHGEs) and myocardial infarction (MI) in a Costa Rica Heart Study. This analysis included 1817 cases of a first non-fatal acute MI during hospitalization and their matched population-based controls, by age, sex, and area of residence. A validated food frequency questionnaire was used to quantify habitual dietary intake and diet-attributable GHGEs (kg CO2 equivalent (eq.)/year). Due to the matching design, conditional logistic regression was used. Red meat consumption contributed approximately 50% to the total diet-attributable GHGEs among both cases and controls. Higher diet-attributable GHGEs were associated with increased odds of acute MI. The odds of MI were 63% higher (OR = 1.63; 95% CI 1.20-2.21) among participants in the highest quintile (median diet-attributable GHGEs = 6247 kg CO2 eq./year) compared to the lowest quintile (median diet-attributable GHGEs = 2065 kg CO2 eq./year). An increasing linear trend in the odds of acute MI and diet-attributable GHGEs was detected (p-trend 0.0012). These findings highlight the importance of reducing red meat consumption to sustainably mitigate the incidence of MI and improve planetary health.

Health and environmental impacts of plant-rich dietary patterns: a US prospective cohort study.

BACKGROUND: Diets that are rich in animal-based foods threaten planetary and human health, but plant-rich diets have varied health and environmental effects. We aimed to characterise a healthy dietary index and three plant-based indices by their environmental impacts and associations with risk of cardiovascular disease. METHODS: In this prospective cohort study, we used data from a food-frequency questionnaire in the US-based Nurses' Health Study II. Participants were categorised by quintiles of four dietary indices, including the alternative healthy eating index-2010 (AHEI), plant-based diet index (PDI), unhealthy PDI, and healthy PDI. We calculated environmental impacts (greenhouse gas emissions and irrigation water, nitrogenous fertiliser, and high-quality cropland needs), and relative risks (RRs) of cardiovascular disease from 1991-2017, comparing quintiles. FINDINGS: We included 90 884 participants in the health-impact analysis and 65 625 participants in the environmental-impact analysis. Comparing the top and bottom quintiles, higher AHEI scores were associated with a decreased cardiovascular disease risk (relative risk 0·77 [95% CI 0·66-0·89]); 30% lower greenhouse gas emissions (Q5 2·6 kg CO2 equivalent vs Q1 3·7 kg CO2 equivalent); and lower fertiliser, cropland, and water needs (all ptrends<0·0001). Similarly, the highest healthy PDI and PDI quintiles were associated with a decreased cardiovascular disease risk (healthy PDI 0·71 [0·60-0·83] and PDI 0·74 [0·63-0·85]) and lower environmental impacts (PDI water needs ptrend=0·0014; all other ptrends<0·0001). Conversely, the highest unhealthy PDI quintile had a higher cardiovascular disease risk compared with the lowest unhealthy PDI quintile (1·15 [1·00-1·33]; ptrend=0·023) and required more cropland (ptrend<0·0001) and fertiliser (ptrend=0·0008). INTERPRETATION: Dietary patterns that are associated with better health had lower greenhouse gas emissions and nitrogenous fertiliser, cropland, and irrigation water needs. Not all plant-based diets conferred the same health and environmental benefits. US dietary guidelines should include nuanced consideration of environmental sustainability. FUNDING: US National Institutes of Health.

How Should We Respond to Health Sector Emissions That Exacerbate Climate Change and Inequity?

A warming climate poses substantial risk to public health and worsens existing health inequity. As a contributor to greenhouse gas emissions and air pollution, the health sector has obligations and ample opportunities to protect health by decreasing waste and motivating more system-wide sustainable clinical practices. Such efforts will have important ethical implications for health equity.

A weakened AMOC may prolong greenhouse gas-induced Mediterranean drying even with significant and rapid climate change mitigation.

The Mediterranean region has been identified as a climate hot spot, with models projecting a robust warming and rainfall decline in response to increasing greenhouse gases. The projected rainfall decline would have impacts on agriculture and water resources. Can such changes be reversed with significant reductions in greenhouse gases? To explore this, we examine large ensembles of a high-resolution climate model with various future radiative forcing scenarios, including a scenario with substantial reductions in greenhouse gas concentrations beginning in the mid-21st century. In response to greenhouse gas reductions, the Mediterranean summer rainfall decline is reversed, but the winter rainfall decline continues. This continued winter rainfall decline results from a persistent atmospheric anticyclone over the western Mediterranean. Using additional numerical experiments, we show that the anticyclone and continued winter rainfall decline are attributable to greenhouse gas-induced weakening of the Atlantic Meridional Overturning Circulation (AMOC) that continues throughout the 21st century. The persistently weak AMOC, in concert with greenhouse gas reductions, leads to rapid cooling and sea ice growth in the subpolar North Atlantic. This cooling leads to a strong cyclonic atmospheric circulation anomaly over the North Atlantic subpolar gyre and, via atmospheric teleconnections, to the anticyclonic circulation anomaly over the Mediterranean. The failure to reverse the winter rainfall decline, despite substantial climate change mitigation, is an example of a "surprise" in the climate system. In this case, a persistent AMOC change unexpectedly impedes the reversibility of Mediterranean climate change. Such surprises could complicate pathways toward full climate recovery.

Imperatives for integrated science and policy in managing greenhouse gas risks to the Southern Polar Region.

The Southern Polar Region (Antarctica and the Southern Ocean) is threatened by climate change, and ocean warming and acidification. Reducing climate risks through direct human interventions in the region or through biological adaptation is not possible. Resilience of the region to global warming needs the establishment of climate refugia and science-based, climate-informed, ecosystem-based management, but long-term conservation will only be assured by global reduction in greenhouse gas emissions.