SPICE: Stratospheric Particle Injection for Climate Engineering

气候变化是对人类的一大威胁。气候系统变暖的观测证据非常有力，其基础是气温上升、海平面上升和大范围的冰雪融化。气候模型的未来预测表明，未来几十年将发生重大变化，其中大部分是区域规模的变化，将严重影响世界上已经处于压力之下的地区。近年来，政治家和普通公众对全球变暖问题的严重性质的理解有了很大提高。然而，令人非常关切的是，通过减少温室气体排放来减缓未来变化的努力，包括2009年哥本哈根国际会议的成果，进展得太慢，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，印度季风崩溃或北极冰盖融化)。这促使人们考虑通过替代手段进行干预。虽然大多数人认为这是一种应尽可能避免的“B计划”，但越来越多的人达成共识，认为这一选择的好处、风险、成本和可行性都需要考虑。人们提出了各种“地球工程”方案，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。皇家学会最近关于地球工程气候的报告认为，通过向平流层注入硫酸盐气溶胶来减少传入的太阳辐射是最快速部署、负担得起和最有效的选择。火山喷发提供了证据，表明硫酸盐颗粒注入导致全球平均地表温度下降。然而，有人担心，这将对气温、降雨量和气候的其他方面产生重大的地区性影响。关于时间尺度也存在不确定性，例如注入的速度可能有多快，它可以多快地被“关闭”，以及与火山喷发的间歇性相比，气候对持续注入气溶胶的反应是否不同。从地球工程学的角度来看，自然火山模拟的硫酸盐颗粒注入在辐射管理方面可能不是最佳的，可能会有更好的候选颗粒注入。与此相关的是，向平流层注入候选粒子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项目将调查平流层粒子注入的有效性。它将解决太阳辐射管理中的三大挑战：1.需要在哪里向大气中注入多少，才能有效和安全地管理气候系统？2.我们如何将其传递到那里？3.可能会产生什么影响？这些问题通过3个协调和相互关联的工作包来解决：评估候选粒子：什么是“完美的”粒子，它能最大限度地分散太阳辐射，最大限度地减少温室效应和对平流层臭氧层的影响，对气候、天气、生态系统和人类健康的影响最小？使用系留气球管道向平流层注入颗粒物和/或气体比其他方法更经济、更可持续的可行性是什么？气候和环境模拟：最有效的注入地点是什么？我们怎样才能最好地利用过去的火山类比呢？平流层粒子对气候和环境有何影响？

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?