Stratospheric Ozone Loss in Mid-latitudes in Summer - a Potential Risk of Climate Engineering? (CE-O3)

最近，科学界讨论了在人口稠密地区臭氧损失的新机制，警告夏季由于对流注入到中纬度平流层低层的水蒸气而增加臭氧消耗的风险。在该区域，增加水蒸气和低温加速了二元硫酸盐-水气溶胶（H2SO4/H2O）上的非均相反应，从而产生氯诱导的催化臭氧损失。假设在未来几十年里，由于人为的气候变化，对流注入的水蒸气的强度和频率会增加，那么地球表面人口稠密地区的紫外线辐射（UV）水平也会相应增加。然而，这种新的臭氧损失机制的细节尚不清楚，因此无法准确量化由此产生的臭氧损失及其对平流层低层硫和水蒸气的敏感性。此外，将硫酸盐气溶胶注入平流层作为减缓全球变暖的一种气候工程方法，可能会加剧中纬度平流层下层的臭氧损失。由于目前对中纬度夏季低空平流层中水汽和硫酸盐气溶胶增强条件下的臭氧损失过程缺乏了解，我们在DFG优先计划“气候工程”的框架内提出了一个基于三维化学传输模型（CLaMS）不同模拟的项目。我们的目标是了解和量化这种新的臭氧损失机制的细节，并在气候工程条件下可靠地模拟可能的臭氧损失。将向气候工程界提供一种将中纬度臭氧损失与平流层硫酸盐增加的依赖关系联系起来的算法，作为进一步经济分析的基础。我们的研究结果将有助于评估未来可能的气候工程决策，以最大限度地提高全球福利，最大限度地降低社会成本。

Recently, a new mechanism for ozone loss over populated areas is discussed in the scientific community warning of an increasing risk of ozone depletion in summer from convectively injected water vapour into the mid-latitude lower stratosphere. In this region, enhanced water vapour can yield chlorine-induced catalytic ozone loss caused by heterogeneous reactions on binary sulphate-water aerosol (H2SO4/H2O) sped up by increasing water vapour and low temperatures. Assuming that the intensity and frequency of convectively injected water vapour would increase in the next decades caused by anthropogenic climate change, a related increase in levels of ultraviolet radiation (UV) on Earth's surface over populated areas would follow. However, the details of this new ozone loss mechanism are not yet clear preventing an accurate quantification of the resulting ozone loss and its sensitivity on lower stratospheric sulphur and water vapour. Moreover, the injection of sulphate aerosol into the stratosphere proposed as one method of climate engineering to mitigate global warming could in addition intensify ozone loss in the mid-latitude lower stratosphere. Motivated by the lack of current understanding of ozone loss processes under conditions of enhanced water vapour and sulphate aerosol in the mid-latitude lower summer stratosphere, we propose a project in the frame of the DFG Priority Program `Climate Engineering' based on different simulations with the three-dimensional chemistry transport model (CLaMS). Our objectives are to understand and quantify the details of this new ozone loss mechanism and to simulate reliably possible ozone loss under climate engineering conditions. An algorithm linking the dependency of mid-latitude ozone loss on increased stratospheric sulphate will be provided to the climate engineering community as basis for further economic analysis. Our findings will help possible future decisions about climate engineering to be assessed in order to maximize global welfare and minimize costs for the society.