SPICE: Stratospheric Particle Injection for Climate Engineering

气候变化是对人类的重大威胁。根据气温上升、海平面上升和冰雪大面积融化，气候系统变暖的观测证据非常有力。气候模型对未来的预测表明，未来几十年将发生重大变化，其中大部分是区域性的，将严重影响世界上已经处于压力之下的地区。近年来，政治家和公众对全球变暖问题的严重性有了更好的认识。然而，人们非常担心，通过减少温室气体排放来缓解未来变化的努力，包括2009年哥本哈根国际会议的成果，进展太慢，无法避免危险的气候变化风险和达到某些“临界点”的可能性（例如印度季风的崩溃或北极冰盖的融化）。这促使人们考虑以其他方式进行干预。虽然大多数人认为这是“计划B”，应该尽可能避免，但越来越多的人认为，这一选择的好处、风险、成本和可行性需要进一步研究。已经提出了各种“地球工程”选择，包括太阳辐射管理（SRM），它涉及通过使地球吸收更少的太阳辐射来抵消温室气体增加的影响。皇家学会最近关于气候地球工程的报告认为，通过向平流层注入硫酸盐气溶胶来减少入射太阳辐射是部署最迅速、负担得起和最有效的办法。火山爆发提供的证据表明，硫酸盐颗粒注入导致全球平均表面温度降低。然而，人们担心，这将对气温、降雨量和气候的其他方面产生重大的区域影响。关于时间尺度也存在不确定性，例如喷射可能多快起作用，它可能多快被“关闭”，以及与火山爆发的偶发性质相比，气候对气溶胶持续喷射的反应是否不同。在地球工程方面，硫酸盐颗粒喷射的天然火山模拟物在辐射管理方面可能不是最佳的，并且可能存在用于注射的更好的候选颗粒。与此相关的是，将候选粒子注入平流层的成本和可行性以及特定注入技术的可持续性等重大问题需要进一步研究，SPICE项目将研究平流层粒子注入的有效性。它将解决太阳辐射管理的三大挑战：1。为了有效和安全地管理气候系统，需要向大气中注入多少？2.我们怎么把它送到那里？3.可能的影响是什么？这些问题通过三个协调和相互关联的工作包来解决：评价候选粒子：什么是“完美”粒子，它能最大限度地增加太阳辐射散射，最大限度地减少温室效应和对平流层臭氧层的影响，并对气候、天气、生态系统和人类健康的影响最小？输送系统：输送颗粒的各种选择是什么？使用系留气球管道以比其他方法更具成本效益和可持续性的方式将颗粒和/或气体注入平流层的可行性如何？气候和环境建模：最有效的注射位置是什么？我们如何最好地利用过去的火山类似物？平流层颗粒物对气候和环境有什么影响？

Climate change is a major threat to humankind. Observational evidence for warming of the climate system is very strong, based on increased temperatures, sea level rise and widespread melting of snow and ice. Future projections by climate models indicate substantial changes in future decades, much of which is on a regional scale that will severely impact regions of the world that are already under stress.There has been much improved understanding of the serious nature of the global warming problem both by politicians and the general public in recent years. However, there is great concern that efforts to mitigate future change by reduced greenhouse gas (GHG) emissions, including the outcome of the international meeting in Copenhagen 2009, are proceeding too slowly to avoid the risk of dangerous climate change and the possibility of certain 'tipping points' (such as the collapse of the Indian Monsoon of melting of the Artic ice sheet) being reached. This has prompted consideration of intervention by alternative means. Although considered by the majority to be the 'Plan B' that should be avoided if at all possible, there is increased consensus that the benefits, risks, costs and feasibility of this as an option requires consideration.A variety of 'geoengineering' options have been proposed, including solar radiation management (SRM) which involves offsetting the effects of GHG increases by causing the Earth to absorb less radiation from the Sun. Reducing incoming solar radiation by injecting sulphate aerosol into the stratosphere was considered the most rapidly deployable, affordable and effective option by the recent Royal Society report on Geoengineering the Climate. Volcanic eruptions provide evidence that sulphate particle injection leads to reductions in globally-averaged surface temperatures. However, there are concerns that there will be substantial regional impacts, on temperatures, rainfall and other aspects of climate. There are also uncertainties concerning timescales e.g. how rapidly injection might act, how quickly it could be 'turned off' and whether the climate responds differently to continued injection of aerosols compared with the episodic nature of volcanic eruptions.In terms of geo-engineering, the natural volcanic analogue of sulphate particle injection may not be optimum in terms of radiation management, and there may be better candidate particles for injection. Related to this, there are significant issues of cost and feasibility of injecting candidate particles into the stratosphere and the sustainability of particular injection technologies that require much further investigation.The SPICE project will investigate the effectiveness of stratospheric particle injection. It will address the three grand challenges in solar radiation management: 1. How much, of what, needs to be injected where into the atmosphere to effectively and safely manage the climate system? 2. How do we deliver it there? 3. What are the likely impacts? These questions are addressed through 3 coordinated and inter-linked work packages:Evaluating candidate particles: What is the 'perfect' particle, that maximizes solar radiation scattering, minimizes the greenhouse effect and the impact on the stratospheric ozone layer and has minimal impact on climate, weather, ecosystems and human health?Delivery Systems: What are the various options for delivery of particles? What is the feasibility of using a tethered-balloon pipe to inject particles and/or gases into the stratosphere in a more cost-effective and sustainable way than alternative methods?Climate and environmental modelling: What are the most effective locations for injection? How can we best use past volcanic analogues? What are the climate and environmental impacts of stratospheric particles?