Non-CO2 effects of aviation on climate

该项目将使用最先进的模型和观测来量化当前和未来飞机的航空非二氧化碳排放对气候的影响。在过去50年中，全球航空排放强劲增长，从1970-2012年期间的年平均增长率2.2%加速到2013-2018年期间的5%。虽然现有的预测预测这一趋势将继续下去，但COVID-19大流行在未来几十年的空中交通演变方面提出了新的问题（Forster等人，2020年）。航空已经贡献了全球人为二氧化碳排放总量的2.5%，其对气候的总体影响要大得多。目前的航空辐射强迫估算表明，空中交通对全球变暖的贡献约为5%（2-14%的不确定性范围），其中很大一部分（~60%）是由非二氧化碳效应造成的。在这些非二氧化碳影响中，最大的影响是由航空引起的云量（Kärcher, 2018）和氮氧化物（导致臭氧和甲烷的变化）、水蒸气和气溶胶的排放造成的。自2010年以来，航空业承诺到2050年将其全球二氧化碳排放量与2005年的水平相比减少一半。然而，如果我们要实现《巴黎协定》的长期目标，即将全球平均气温保持在远低于工业化前水平2摄氏度的水平，那么就需要更大幅度的航空减排。最近提出了实现净零碳航空系统的新目标，2020年9月，空中客车公司公布了第一架以氢为燃料的商用零排放飞机的计划，该飞机可能在2035年投入使用。尽管我们对空中交通对气候的总体影响的理解取得了重大进展，但仍存在很大的不确定性，特别是在AIC和烟灰和硫排放导致的气溶胶-云相互作用方面。随着净零碳航空成为近期目标，提供当前和未来一代飞机的航空非二氧化碳排放量的可靠估计比以往任何时候都更加重要。该项目的目的是调查标准和下一代飞机的航空非二氧化碳排放对气候的影响。该方法将结合辐射、化学传输和基于排放的气候模型，以及使用最先进的英国地球系统模型进行模拟。虽然考虑到您的兴趣，该项目相对灵活，但可能涉及：-利用卫星观测对2020年因COVID-19限制而导致的航路覆盖变化进行全面评估。-为未来的空中交通制定一系列方案，包括对飞行态度的改变所带来的长期转变的可能性。-将英国气象局气候模式（Rap et al., 2010）现有的轨迹参数化扩展到氢燃料飞机。-量化标准和氢燃料飞机的非二氧化碳航空排放（特别是AIC，以及烟尘和硫气溶胶排放）的辐射强迫。-对标准和氢燃料飞机的航线优化（纬度/高度影响）的作用的详细评估。-在Leeds-FaiR基于排放的气候模型中开发改进的航空排放分析响应函数（Smith et al., 2018）。潜在的高影响结果我们对当前航空对气候的影响以及未来如何演变的理解仍然存在很大的不确定性。有了最先进的模型和我们世界领先的研究小组的支持，该项目将解决这些不确定性，因此将对未来的气候预测产生重要影响。公众和从事气候减缓和运输部门工作的决策者都将对此感兴趣。

This project will use state-of-the-art models and observations to quantify the climatic effect of aviation non-CO2 emissions from current and future generation aircraft.Global aviation emissions have grown strongly during the past 50 years, accelerating from an annually averaged growth rate of 2.2% over 1970-2012 to 5% during 2013-2018. While existing forecasts predict a continuation of this trend, the COVID-19 pandemic has raised new questions in terms of the evolution of air traffic during the next few decades (Forster et al., 2020). Aviation already contributes about 2.5% of the total global anthropogenic CO2 emissions and its overall effect on climate is substantially larger. Current aviation radiative forcing estimates indicate that the contribution of air traffic to global warming is roughly 5% (2-14% uncertainty range), with a significant proportion (~60%) caused by non-CO2 effects. The largest of these non-CO2 effects are caused by aviation-induced cloudiness (AIC) (Kärcher, 2018) and emissions of NOx (leading to changes in ozone and methane), water vapour and aerosols. Since 2010, the aviation industry has pledged to halve its global CO2 emissions by 2050 compared to 2005 levels. However, if we are to achieve the Paris Agreement long-term temperature goal of keeping global average temperature to well below 2C above pre-industrial levels, then even stronger aviation emission cuts are needed. A new aim of reaching a net zero-carbon aviation system has recently been proposed and in September 2020 Airbus have unveiled plans for the first commercial zero-emission aircraft fuelled by hydrogen that could be in service by 2035.Despite significant progress in our understanding of the overall impact of air traffic on climate, large uncertainties remain especially in terms of AIC and aerosol-cloud interactions resulting from soot and sulphur emissions. With net zero-carbon aviation becoming a near-term target, providing reliable estimates of the aviation non-CO2 emissions from current and future generation aircraft is now more important than ever.ObjectivesThe aim of this project is to investigate the climatic effect of aviation non-CO2 emissions from standard and future generation aircraft. The approach will involve a combination of radiation, chemistry-transport and emission-based climate models, together with simulations using the state-of-the-art UK Earth System Model. While relatively flexible to allow for your interests, the project is likely to involve:- A comprehensive assessment of changes in contrail coverage due to COVID-19 restrictions during 2020 using satellite observations. - Producing a range of scenarios for future air traffic, including the potential for a long-term shift driven by changing attitudes to flying.- Extending the existing contrail parameterisation for the UK Met Office climate model (Rap et al., 2010) to hydrogen-fuelled aircraft. - Quantifying the radiative forcing of non-CO2 aviation emissions (in particular AIC, and soot & sulphur aerosol emissions) for standard and hydrogen-fuelled aircraft. - A detailed evaluation of the role of flight route optimisation (latitude/altitude effects) for standard and hydrogen-fuelled aircraft.- Developing improved analytic response functions for aviation emissions within the Leeds-FaiR emission-based climate model (Smith et al., 2018).Potential for high impact outcomeThere are still large uncertainties in our understanding of the current aviation impact on climate and how it might evolve in the future. With access to state-of-the-art models and support from our world leading research groups, this project will address these uncertainties and will therefore have important implications for future climate projections. This will be of interest to both the general public and to policy makers working in climate mitigation and the transport sector.