Half a degree Additional warming: Prognosis and Projected Impacts on Health (HAPPI-Health)

最近的《柳叶刀》气候变化和健康委员会得出结论，“气候变化是21世纪最大的全球健康威胁”。在这里，我们特别考虑了未来气候健康负担的热健康组成部分，试图首次估计世界发展中地区未来气候变化下与温度相关的死亡人数。即使有很大的误差条，这个数字也很难计算。除了气候预测的不确定性外，热应激与人类健康之间的关系在不同国家之间，甚至在同一国家的不同城市之间也存在很大差异。一些发达国家在区域范围内进行了估计。例如，在英国，根据目前约2000例死亡的年度基线估计，到2050年，热相关死亡率将增加约250%（Hajat等人，2014）。本提案旨在通过描述不同气候变化预测方法的不确定性、导致极端现象的机制及其与城市一级温度-健康负担的关系，全面了解地球仪所有区域的极端温度和与温度相关的死亡率，包括发展中国家等以前避开的区域。具体而言，对于未来气候，我们考虑巴黎协定的气候情景。《巴黎协定》旨在将全球平均气温限制在远低于工业化前水平2摄氏度的范围内，并力争将其限制在1.5摄氏度。但这一目标目前得到了相当薄弱的科学证据的支持（James et al，2016），特别是在高影响极端天气事件的相对风险方面。除了海平面上升，全球变暖1.5摄氏度的影响，以及通过将温度稳定在1.5摄氏度而不是2摄氏度而避免的影响，将在世界大多数地区受到极端天气事件风险变化的影响，因此我们提出的研究具有相关性。Fischer & Knutti（2015）估计，全球平均而言，极端高温的发生率在1.5和2 ℃之间增加一倍。就个别区域而言，大规模的平均数并不能为风险预防和复原力的决策提供充分的依据。大气动力学和温室气体以外的因素的变化也会影响高温和降雨的极端情况，在局部地区，可能会产生大于甚至与全球平均水平相反的风险变化（Szier等人，2016年）。《巴黎协定》呼吁研究特定变暖水平的影响，而不是某种可能性下预期的情景的影响，来产生一定程度的变暖。这就需要一种新的方法来估计未来的气候，这是对提供CMIP 5和CMIP 6核心的由CNOMO驱动的实验的补充。为了解决这个问题，我们采用了新开发的半度额外变暖;预测和预计影响（HAPPI; Mitchell et al，2016 a）情景集-一组有针对性的实验，专门设计用于解决与巴黎协定全球平均升温异常1. 5 C和2 C目标相关的问题。巴黎协定是国际气候界向前迈出的重要一步，并将在下一次IPCC报告（AR 6）中发挥重要作用。该提案汇集了气候专家（米切尔和艾伦）和健康专家（加斯帕里尼），对气候变化的主要影响之一，与温度有关的死亡率进行全面分析。它评估了极端温度的驱动因素，气候变化信号最大的地方，以及这些对世界各地区域和城市一级健康负担的影响。

The most recent Lancet Commissions on climate change and health concluded that "Climate change is the biggest global health threat of the 21st century". Here, we specifically consider the thermal-health component of the future climate-health burden in an attempt to estimate, for the first time, the number of temperature related deaths under future climate change in developing regions of the world. This number is surprisingly hard to calculate even with large error bars. Aside from the uncertainties in climate projections, the relationship between heat stress and human health varies significantly between countries, and even between cities within the same country. Estimates have been made on a regional scale in some developed countries. For instance, in the UK, a ~250% increase in heat related mortality by the year 2050 was estimated from an annual baseline of ~2000 current deaths (Hajat et al, 2014). This proposal aims to provide a comprehensive understanding of extreme temperatures and associated temperature-related mortality in all regions of the globe, including previously avoided regions such as developing nations, by characterising the uncertainties in different methods of climate change projections, mechanisms driving the extremes, and their relationship to the temperature-health burden at the city level. Specifically, for future climate we consider Paris Agreement climate scenarios. The Paris Agreement aims to limit globally averaged temperatures to well below 2C above pre-industrial levels, and pursue ambitions to limit it to 1.5C. But this aim is currently supported by rather thin scientific evidence (James et al, 2016), in particular with respect to relative risks of high-impact extreme weather events. Sea level rise aside, the impacts of a global warming of 1.5C, and the impacts avoided by stabilising temperatures at 1.5 instead of 2C, will be dominated, in most regions of the world, by changing risks of extreme weather events, hence the relevance of our proposed research. Fischer & Knutti (2015) estimate that, on a global average, the occurrence of heat extremes doubles between 1.5 & 2C warming. For individual regions, large-scale averages do not provide an adequate basis for decisions on risk prevention and resilience. Changes in atmospheric dynamics and factors other than greenhouse gases also affect heat and rainfall extremes, and, locally, may yield changes in risk that are either greater than or even opposed to the global average (Schaller et al, 2016).The Paris Agreement calls for research into the impacts of a given level of warming, not the impacts of a scenario that is expected, at some probability, to yield a given level of warming. This requires a new approach to estimate future climate which is complementary to the scenario-driven experiments that provide the core of CMIP5 and CMIP6. To address this, we employ the newly developed Half a degree Additional warming; Prognosis and Projected Impacts (HAPPI; Mitchell et al, 2016a) scenario set - a set of targeted experiments specifically designed to address questions related to the Paris Agreement targets of 1.5C and 2C global averaged warming anomalies.The Paris Agreement is a major step forward for the international climate community, and will play a large role in the next IPCC report (AR6) and well beyond. This proposal brings together experts in climate (Mitchell and Allen) and health (Gasparrini), to provide a comprehensive analysis of one the key impacts of climate change, temperature related mortality. It provides an assessment of what drives extreme temperatures, where the climate change signals are largest, and how these impact on the regional- and city-level health burden around the world.