The Lancet Countdown is an international, multidisciplinary collaboration, dedicated to monitoring the evolving health profile of climate change, and providing an independent assessment of the delivery of commitments made by governments worldwide under the Paris Agreement. The 2019 report presents an annual update of 41 indicators across five key domains: climate change impacts, exposures, and vulnerability; adaptation, planning, and resilience for health; mitigation actions and health co-benefits; economics and finance; and public and political engagement. The report represents the findings and consensus of 35 leading academic institutions and UN agencies from every continent. Each year, the methods and data that underpin the Lancet Countdown’s indicators are further developed and improved, with updates described at each stage of this report. The collaboration draws on the world-class expertise of climate scientists; ecologists; mathematicians; engineers; energy, food, and transport experts; economists; social and political scientists; public health professionals; and doctors, to generate the quality and diversity of data required. The science of climate change describes a range of possible futures, which are largely dependent on the degree of action or inaction in the face of a warming world. The policies implemented will have far-reaching effects in determining these eventualities, with the indicators tracked here monitoring both the present-day effects of climate change, as well as the worldwide response. Understanding these decisions as a choice between one of two pathways—one that continues with the business as usual response and one that redirects to a future that remains “well below 2°C”—helps to bring the importance of recognising the effects of climate change and the necessary response to the forefront. Evidence provided by the Intergovernmental Panel on Climate Change, the International Energy Agency, and the US National Aeronautics and Space Administration clarifies the degree and magnitude of climate change experienced today and contextualises these two pathways. The world has observed a 1°C temperature rise above pre-industrial levels, with feedback cycles and polar amplification resulting in a rise as high as 3°C in north western Canada.^, Eight of the ten hottest years on record have occurred in the past decade. Such rapid change is primarily driven by the combustion of fossil fuels, consumed at a rate of 171 000 kg of coal, 116 000 000 L of gas, and 186 000 L of oil per s.^– Progress in mitigating this threat is intermittent at best, with carbon dioxide emissions continuing to rise in 2018. Importantly, many of the indicators contained in this report suggest the world is following this “business as usual” pathway. The carbon intensity of the energy system has remained unchanged since 1990 (indicator 3.1.1), and from 2016 to 2018, total primary energy supply from coal increased by 1·7%, reversing a previously recorded downward trend (indicator 3.1.2). Correspondingly, the health-care sector is responsible for about 4·6% of global emissions, a value which is steadily rising across most major economies (indicator 3.6). Global fossil fuel consumption subsidies increased by 50% over the past 3 years, reaching a peak of almost US$430 billion in 2018 (indicator 4.4.1). A child born today will experience a world that is more than four degrees warmer than the pre-industrial average, with climate change impacting human health from infancy and adolescence to adulthood and old age. Across the world, children are among the worst affected by climate change. Downward trends in global yield potential for all major crops tracked since 1960 threaten food production and food security, with infants often the worst affected by the potentially permanent effects of undernutrition (indicator 1.5.1). Children are among the most susceptible to diarrhoeal disease and experience the most severe effects of dengue fever. Trends in climate suitability for disease transmission are particularly concerning, with nine of the ten most suitable years for the transmission of dengue fever on record occurring since 2000 (indicator 1.4.1). Similarly, since an early 1980s baseline, the number of days suitable for Vibrio (a pathogen responsible for part of the burden of diarrhoeal disease) has doubled, and global suitability for coastal Vibrio cholerae has increased by 9·9% indicator 1.4.1). Through adolescence and beyond, air pollution—principally driven by fossil fuels, and exacerbated by climate change—damages the heart, lungs, and every other vital organ. These effects accumulate over time, and into adulthood, with global deaths attributable to ambient fine particulate matter (PM_2·5) remaining at 2·9 million in 2016 (indicator 3.3.2) and total global air pollution deaths reaching 7 million. Later in life, families and livelihoods are put at risk from increases in the frequency and severity of extreme weather conditions, with women among the most vulnerable across a range of social and cultural contexts. Globally, 77% of countries experienced an increase in daily population exposure to wildfires from 2001–14 to 2015–18 (indicator 1.2.1). India and China sustained the largest increases, with an increase of over 21 million exposures in India and 17 million exposures in China over this time period. In low-income countries, almost all economic losses from extreme weather events are uninsured, placing a particularly high burden on individuals and households (indicator 4.1). Temperature rise and heatwaves are increasingly limiting the labour capacity of various populations. In 2018, 133·6 billion potential work hours were lost globally, 45 billion more than the 2000 baseline, and southern areas of the USA lost 15–20% of potential daylight work hours during the hottest month of 2018 (indicator 1.1.4). Populations aged 65 years and older are particularly vulnerable to the health effects of climate change, and especially to extremes of heat. From 1990 to 2018, populations in every region have become more vulnerable to heat and heatwaves, with Europe and the Eastern Mediterranean remaining the most vulnerable (indicator 1.1.1). In 2018, these vulnerable populations experienced 220 million heatwave exposures globally, breaking the previous record of 209 million set in 2015 (indicator 1.1.3). Already faced with the challenge of an ageing population, Japan had 32 million heatwave exposures affecting people aged 65 years and older in 2018, the equivalent of almost every person in this age group experiencing a heatwave. Finally, although difficult to quantify, the downstream risks of climate change, such as migration, poverty exacerbation, violent conflict, and mental illness, affect people of all ages and all nationalities. A business as usual trajectory will result in a fundamentally altered world, with the indicators described providing a glimpse of the implications of this pathway. The life of every child born today will be profoundly affected by climate change. Without accelerated intervention, this new era will come to define the health of people at every stage of their lives. The Paris Agreement has set a target of “holding the increase in the global average temperature to well below 2°C above pre-industrial levels and pursuing efforts to limit the temperature increase to 1·5°C.” In a world that matches this ambition, a child born today would see the phase-out of all coal in the UK and Canada by their sixth and 11th birthday; they would see France ban the sale of petrol and diesel cars by their 21st birthday; and they would be 31 years old by the time the world reaches net-zero in 2050, with the UK’s recent commitment to reach this goal one of many to come. The changes seen in this alternate pathway could result in cleaner air, safer cities, and more nutritious food, coupled with renewed investment in health systems and vital infrastructure. This second path—which limits the global average temperature rise to “well below 2°C”—is possible, and would transform the health of a child born today for the better, right the way through their life. Considering the evidence available in the 2019 indicators, such a transition could be beginning to unfold. Despite a small increase in coal use in 2018, in key countries such as China, it continued to decrease as a share of electricity generation (indicator 3.1.2). Correspondingly, renewables accounted for 45% of global growth in power generation capacity that year, and low-carbon electricity reached a high of 32% of global electricity in 2016 (indicator 3.1.3). Global per capita use of electric vehicles increased by 20·6% between 2015 and 2016, and now represents 1·8% of China’s total transportation fuel use (indicator 3.4). Improvements in air pollution seen in Europe from 2015 to 2016, could result in a reduction of Years of Life Lost (YLL) worth €5·2 billion annually, if this reduction remained constant across a lifetime (indicator 4.2). In several cases, the economic savings from a healthier and more productive workforce, with fewer health-care expenses, will cover the initial investment costs of these interventions. Similarly, cities and health systems are becoming more resilient to the effects of climate change; about 50% of countries and 69% of cities surveyed reported efforts to conduct national health adaptation plans or climate change risk assessments (indicators 2.1.1, 2.1.2, and 2.1.3). These plans are now being implemented, with the number of countries providing climate services to the health sector increasing from 55 in 2018 to 70 in 2019 (indicator 2.2) and 109 countries reporting medium to high implementation of a national health emergency framework (indicator 2.3.1). Growing demand is coupled with a steady increase in health adaptation spending, which represents 5% (£13 billion) of total adaptation funding in 2018 and has increased by 11·8% over the past 12 months (indicator 2.4). This increase is in part funded by growing revenues from carbon pricing mechanisms, with a 30% increase to US$43 billion in funds raised between 2017 and 2018 (indicator 4.4.3). However, current progress is inadequate, and despite the beginnings of the transition described, the indicators published in the Lancet Countdown’s 2019 report are suggestive of a world struggling to cope with warming that is occurring faster than governments are able, or willing to respond. Opportunities are being missed, with the Green Climate Fund yet to receive projects specifically focused on improving climate-related public health, despite the fact that in other forums, leaders of small island developing states are recognising the links between health and climate change (indicator 5.3). In response, the generation that will be most affected by climate change has led a wave of school strikes across the world. Bold new approaches to policy making, research, and business are needed in order to change course. An unprecedented challenge demands an unprecedented response, and it will take the work of the 7·5 billion people currently alive to ensure that the health of a child born today is not defined by a changing climate.

The Lancet Countdown: tracking progress on health and climate change was established to provide an independent, global monitoring system dedicated to tracking the health dimensions of the impacts of, and the response to, climate change. The Lancet Countdown tracks 41 indicators across five domains: climate change impacts, exposures, and vulnerability; adaptation, planning, and resilience for health; mitigation actions and health co-benefits; finance and economics; and public and political engagement. This report is the product of a collaboration of 27 leading academic institutions, the UN, and intergovernmental agencies from every continent. The report draws on world-class expertise from climate scientists, ecologists, mathematicians, geographers, engineers, energy, food, livestock, and transport experts, economists, social and political scientists, public health professionals, and doctors. The Lancet Countdown’s work builds on decades of research in this field, and was first proposed in the 2015 Lancet Commission on health and climate change, which documented the human impacts of climate change and provided ten global recommendations to respond to this public health emergency and secure the public health benefits available (panel 1). 1.. Present day changes in heat waves, labour capacity, vector-borne disease, and food security provide early warning of the compounded and overwhelming impact on public health that are expected if temperatures continue to rise. Trends in climate change impacts, exposures, and vulnerabilities show an unacceptably high level of risk for the current and future health of populations across the world. 2.. A lack of progress in reducing emissions and building adaptive capacity threatens both human lives and the viability of the national health systems they depend on, with the potential to disrupt core public health infrastructure and overwhelm health services. 3.. Despite these delays, a number of sectors have seen the beginning of a low-carbon transition, and it is clear that the nature and scale of the response to climate change will be the determining factor in shaping the health of nations for centuries to come. 4.. Ensuring a widespread understanding of climate change as a central public health issue will be crucial in delivering an accelerated response, with the health profession beginning to rise to this challenge. Vulnerability to extremes of heat has steadily risen since 1990 in every region, with 157 million more people exposed to heatwave events in 2017, compared with 2000, and with the average person experiencing an additional 1·4 days of heatwaves per year over the same period (indicators 1.1 and 1.3). For national economies and household budgets, 153 billion hours of labour were lost in 2017 because of heat, an increase of more than 62 billion hours (3·2 billion weeks of work) since 2000 (indicator 1.4). The direct effects of climate change extend beyond heat to include extremes of weather. In 2017, a total of 712 extreme weather events resulted in US$326 billion in economic losses, almost triple the total losses of 2016 (indicator 4.1). Small changes in temperature and precipitation can result in large changes in the suitability for transmission of important vector-borne and water-borne diseases. In 2016, global vectorial capacity for the transmission of the dengue fever virus was the highest on record, rising to 9·1% for Aedes aegypti and 11·1% for Aedes albopictus above the 1950s baseline. Focusing on high-risk areas and diseases, the Baltic region has had a 24% increase in the coastline area suitable for epidemics of Vibrio cholerae, and in 2016, the highlands of sub-Saharan Africa saw a 27·6% rise in the vectorial capacity for the transmission of malaria from the 1950 baseline (indicator 1.8). A proxy of agricultural yield potential shows declines in every region, with 30 countries having downward trends in yields, reversing a decades-long trend of improvement (indicator 1.9.1). Decreasing labour productivity, increased capacity for the transmission of diseases such as dengue fever, malaria, and cholera, and threats to food security provide early warning of compounding negative health and nutrition effects if temperatures continue to rise. Global inertia in adapting to climate change persists, with a mixed response from national governments since the signing of the Paris Agreement in 2015. More than half of global cities surveyed expect climate change to seriously compromise public health infrastructure, either directly, with extremes of weather disrupting crucial services, or indirectly, through the overwhelming of existing services with increased burdens of disease (indicator 2.2). Globally, spending for climate change adaptation remains well below the $100 billion per year commitment made under the Paris Agreement. Within this annual spending, only 3·8% of total development spending committed through formal UN Framework Convention on Climate Change (UNFCCC) mechanisms is dedicated to human health (indicator 2.8). This low investment in adaptive capacity is magnified in specific regions around the world, with only 55% of African countries meeting International Health Regulation core requirements for preparedness for a multihazard public health emergency (indicator 2.3). Multiple examples of stagnated mitigation efforts exist, with a crucial marker of decarbonisation—the carbon intensity of total primary energy supply—remaining unchanged since 1990 (indicator 3.1). A third of the global population, 2·8 billion people, live without access to healthy, clean, and sustainable cooking fuel or technologies, which is the same number of people as in 2000 (indicator 3.4). In the transport sector, per-capita global road-transport fuel use increased by 2% from 2013 to 2015, and cycling comprises less than 10% of total journeys taken in three quarters of a global sample of cities (indicators 3.6 and 3.7). The health burden of such inaction has been immense, with people in more than 90% of cities breathing polluted air that is toxic to their cardiovascular and respiratory health. Indeed, between 2010, and 2016, air pollution concentrations worsened in almost 70% of cities around the globe, particularly in low-income and middle-income countries (LMICs; indicator 3.5.1). In 2015 alone, fine particulate matter (ie, atmospheric particulate matter with a diameter of less than 2·5 μm [PM_2·5]) was responsible for 2·9 million premature deaths, with coal being responsible for more than 460 000 (16%) of these deaths, and with the total death toll (from other causes including particulates and emissions such as nitrogen oxide) being substantially higher (indicator 3.5.2). Of concern, global employment in fossil-fuel extractive industries actually increased by 8% between 2016, and 2017, reversing the strong decline seen since 2011 (indicator 4.4). At a time when national health budgets and health services face a growing epidemic of lifestyle diseases, continued delay in unlocking the potential health co-benefits of climate change mitigation is short-sighted and damaging for human health. Despite this stagnation, progress in the power generation and transport sectors provide some cause for optimism, with many positive trends being observed in the 2017 report, and which continue in the present 2018 report. Notably, coal use continues to decline (indicator 3.2) and more renewable energy was installed in 2017 than energy from fossil fuels (indicator 3.3). However, maintaining the global average temperature rise to well below 2°C necessitates wide-reaching transformations across all sectors of society, including power generation, transport, spatial infrastructure, food and agriculture, and the design of health systems. These transformations, in turn, offer levers to help tackle the root causes of the world’s greatest public health challenges. About 712 climate-related extreme events were responsible for US$326 billion of losses in 2017, almost triple the losses of 2016 (indicator 4.1). Crucially, 99% of the losses in low-income countries remained uninsured. Indicators of investment in the low-carbon economy show that the transition is already underway, with continued growth in investment in zero-carbon energy, and growing numbers of people employed in renewable energy sectors (indicators 4.2 and 4.4). Furthermore, investment in new coal capacity in 2017, was at its lowest in at least 10 years, with 2015 potentially marking a peak in coal investment. Correspondingly, global subsidies for fossil fuels continued to decrease, and carbon pricing only covers 13·1% of global greenhouse-gas emissions, a number that is expected to increase to more than 20% when planned legislation in China is implemented in late 2018 (indicators 4.6 and 4.7). However, the rise of employment in fossil fuel industries in 2017 reversed a 5 year downward trend, and will be a key indicator to follow closely. A better understanding of the health dimensions of climate change allows for advanced preparedness, increased resilience and adaptation, and a prioritisation of mitigation interventions that protect and promote human wellbeing. To this end, coverage of health and climate change in the media has increased substantially between 2007, and 2017 (indicator 5.1). Following this trend, the number of academic journal articles published on health and climate change has almost tripled over the same period (indicator 5.2). These figures often follow internationally important events, such as the UNFCCC’s Conference of the Parties (COP), along with temporary rises in mentions of health and climate change within the UN General Debate (UNGD; indicator 5.3). The extended heatwaves across the northern hemisphere in the summer of 2018, might prove to be a turning point in public awareness of the seriousness of climate change. 2017 saw a substantial rise in the number of medical and health professional associations actively responding to climate change. In the USA, the US Medical Society Consortium on Health and Climate represents 500 000 physicians. This organisation follows the formation of the UK Health Alliance on Climate Change, which brings together many of the UK’s royal medical and nursing colleges and major health institutions. Organisations like the European Renal Association–European Dialysis and Transplant Association and the UK’s National Health Service (NHS) are committing to reducing the contributions of their clinical practice emissions. The NHS achieved an 11% reduction in emissions between 2007, and 2015. Several health organisations have divested, or are committing to divest, their holdings in fossil fuel companies, including the Royal Australasian College of Physicians, the Canadian Medical Association, the American Public Health Association, and the World Medical Association (indicator 4.5). Given that climate change is the biggest global health threat of the 21st century, responding to this threat, and ensuring this response delivers the health benefits available, is the responsibility of the health profession; indeed, such a transformation will not be possible without it. The 2015 Lancet Commission made ten global recommendations to accelerate the response to climate change and deliver the health benefits this response could offer. A summary of the progress made against these recommendations using the 2018 Lancet Countdown’s indicators is presented in panel 1. Here, global leadership is increasingly provided by China, the EU, and many of the countries that are most vulnerable to climate change.

The Lancet Countdown: tracking progress on health and climate change is an international, multidisciplinary research collaboration between academic institutions and practitioners across the world. It follows on from the work of the 2015 Lancet Commission, which concluded that the response to climate change could be "the greatest global health opportunity of the 21st century". The Lancet Countdown aims to track the health impacts of climate hazards; health resilience and adaptation; health co-benefits of climate change mitigation; economics and finance; and political and broader engagement. These focus areas form the five thematic working groups of the Lancet Countdown and represent different aspects of the complex association between health and climate change. These thematic groups will provide indicators for a global overview of health and climate change; national case studies highlighting countries leading the way or going against the trend; and engagement with a range of stakeholders. The Lancet Countdown ultimately aims to report annually on a series of indicators across these five working groups. This paper outlines the potential indicators and indicator domains to be tracked by the collaboration, with suggestions on the methodologies and datasets available to achieve this end. The proposed indicator domains require further refinement, and mark the beginning of an ongoing consultation process-from November, 2016 to early 2017-to develop these domains, identify key areas not currently covered, and change indicators where necessary. This collaboration will actively seek to engage with existing monitoring processes, such as the UN Sustainable Development Goals and WHO's climate and health country profiles. The indicators will also evolve over time through ongoing collaboration with experts and a range of stakeholders, and be dependent on the emergence of new evidence and knowledge. During the course of its work, the Lancet Countdown will adopt a collaborative and iterative process, which aims to complement existing initiatives, welcome engagement with new partners, and be open to developing new research projects on health and climate change.

This review analyses global or near-global estimates of population exposure to sea-level rise (SLR) and related hazards, followed by critically examining subsequent estimates of population migration due to this exposure. Our review identified 33 publications that provide global or near-global estimates of population exposure to SLR and associated hazards. They fall into three main categories of exposure, based on definitions in the publications: (i) the population impacted by specified levels of SLR; (ii) the number of people living in floodplains that are subject to coastal flood events with a specific return period; and (iii) the population living in low-elevation coastal zones. Twenty of these 33 publications discuss connections between population migration and SLR. In our analysis of the exposure and migration data, we consider datasets, analytical methods, and the challenges of estimating exposure to SLR followed by potential human migration. We underscore the complex connections among SLR, exposure to its impacts, and migration. Human mobility to and from coastal areas is shaped by diverse socioeconomic, demographic, institutional, and political factors; there may be ‘trapped’ populations as well as those who prefer not to move for social, cultural, and political reasons; and migration can be delayed or forestalled through other adaptive measures. While global estimates of exposed and potentially migrating populations highlight the significant threats of SLR for populations living in low-lying areas at or near coastlines, further research is needed to understand the interactions among localised SLR and related hazards, social and political contexts, adaptation possibilities, and potential migration and (im)mobility decision-making.

The Ganges–Brahmaputra delta enables Bangladesh to sustain a dense population, but it also exposes people to natural hazards. This article presents findings from the Gibika project, which researches livelihood resilience in seven study sites across Bangladesh. This study aims to understand how people in the study sites build resilience against environmental stresses, such as cyclones, floods, riverbank erosion, and drought, and in what ways their strategies sometimes fail. The article applies a new methodology for studying people’s decision making in risk-prone environments: the personal Livelihood History interviews (N = 28). The findings show how environmental stress, shocks, and disturbances affect people’s livelihood resilience and why adaptation measures can be unsuccessful. Floods, riverbank erosion, and droughts cause damage to agricultural lands, crops, houses, and properties. People manage to adapt by modifying their agricultural practices, switching to alternative livelihoods, or using migration as an adaptive strategy. In the coastal study sites, cyclones are a severe hazard. The study reveals that when a cyclone approaches, people sometimes choose not to evacuate: they put their lives at risk to protect their livelihoods and properties. Future policy and adaptation planning must use lessons learned from people currently facing environmental stress and shocks.