TWISTA (The Wide-ranging Impacts of STratospheric smoke Aerosols)

有许多新的证据表明，野火引起的强火积雨云（pyroCb）事件引起的烟雾侵入平流层。这些事件在北半球和南半球的频率、强度和羽流高度似乎都在增加。烟雾气溶胶对气候的影响可能比偶尔注入平流层的火山气溶胶大得多，因为i)它们强烈吸收可能影响平流层动力学的阳光，ii)它们的表面特征可能增强它们在非均质化学和臭氧耗损中的作用。鉴于在2020年创纪录的持续南极臭氧空洞和创纪录的北极臭氧消耗之前，都发生了前所未有的野火，因此迫切需要了解它们在气候系统中的作用。在北半球，最强烈的平流层烟雾事件发生在过去的五年里。2017年，一系列遥感观测表明，太平洋西北事件（PNE）产生的烟雾在18-22公里高度持续了5个多月。2019-2020年，由于莱科克火山喷发产生的硫酸盐和灰烬，平流层气溶胶负荷异常高，但有证据表明，2019年8月西伯利亚野火（SIB）产生的烟雾可能对平流层气溶胶负荷有重大贡献。在2020年春季观测到创纪录的卤素催化北极臭氧消耗，北极极地涡旋寒冷到足以形成极地平流层云（PSCs），直到春季。研究表明，如果没有减少人类消耗臭氧层物质排放的《蒙特利尔议定书》，北半球就会出现与南极类似的臭氧空洞。在南半球，2020年1月澳大利亚的“黑色夏季”（ABS）野火在规模和强度上都是前所未有的，数百万吨烟雾气溶胶和相关气体被注入对流层上层和平流层下层。初始喷射高度达到16公里，烟雾最终达到36公里的高度（比商业跨大西洋喷气式飞机的飞行高度高出三倍）。上升到非常高的高度是由于烟雾中黑碳（BC）的存在引起的自我升高，黑碳吸收阳光并加热周围的空气。就像热气球一样，这种对阳光的吸收使烟雾和周围的空气上升。值得注意的是，这一单一事件似乎造成了三十年来最大的全球平均平流层温度扰动。2020年的南极臭氧空洞极其深刻和持久，极地平流层温度创历史新低，极地涡旋很强。从卫星观测中确定的几种化学指纹表明，北极严重的臭氧消耗和南极创纪录的臭氧空洞与这些野火事件有关。考虑到在未来全球变暖的情况下，预计野火的频率、强度和羽流高度都将增加，这就更令人担忧了。可以假定，在《蒙特利尔议定书》下非常成功地开展的所有艰苦工作都可能因不遵守减少消耗臭氧层物质而毁于一旦，而是由于全球变暖。如果北半球出现臭氧空洞，这可能会对人类赖以生存的脆弱的生态系统平衡造成进一步的威胁。同样，平流层吸收气溶胶的动力影响可能直接影响地球表面气候：在理想化的研究中，北大西洋涛动的正相位增强可能导致北欧洪水加剧，伊比利亚半岛可能出现毁灭性的干旱。因此，尽早将这些因素和反馈纳入全球气候模拟是至关重要的。

There is much new evidence of stratospheric intrusions of smoke from intense pyro-cumulonimbus (pyroCb) events from wildfires. These events appear to be increasing in frequency, intensity and plume height in both the northern and southern hemispheres. The impacts of smoke aerosol on climate may be disproportionately larger than volcanic aerosols that are sporadically injected into the stratosphere because i) they strongly absorb sunlight which may influence stratospheric dynamics and ii) their surface characteristics may enhance their role in heterogeneous chemistry and ozone depletion. Given that the record persistent Antarctic ozone hole and record Arctic ozone depletion of 2020 were preceded by unprecedented wildfires, there is an urgent need to understand their role in the climate system. In the northern hemisphere, the strongest stratospheric smoke events have occurred over the past five years. In 2017, a range of remote sensing observations showed that smoke from the Pacific Northwest event (PNE) persisted at 18-22 km altitude for over 5 months. In 2019-2020, stratospheric aerosol loading was anomalously high owing to sulfate and ash from the Raikoke eruption but there is evidence of a possible significant contribution from smoke from the August 2019 Siberian wildfires (SIB). Record halogen-catalysed Arctic ozone depletion was observed in spring of 2020 with a strong Arctic polar vortex cold enough for polar stratospheric clouds (PSCs) to form until well until springtime. Research has suggested that, in the absence of the Montreal Protocol which has reduced humanity's emissions of ozone depleting substances (ODSs), we would have had a northern hemisphere ozone hole, similar to that of the Antarctic. In the southern hemisphere, the January 2020 Australian 'Black Summer' (ABS) wildfires were unprecedented in scale and intensity with millions of tonnes of smoke aerosol and associated gases being injected into the upper troposphere and lower stratosphere. Initial injection altitudes reached 16 km and the smoke eventually reached altitudes of up to 36 km (three times higher than the operating altitude of commercial trans-Atlantic jet aircraft. The ascent to remarkably high altitudes resulted from the self-lofting caused by the presence of black carbon (BC) within smoke which absorbs sunlight and heats the air surrounding it. Just like a hot air-balloon, this absorption of sunlight causes the smoke and the surrounding air to rise. Significantly, it appears that this single event caused the largest global mean stratospheric temperature perturbation for three decades. The Antarctic ozone hole in 2020 was extremely deep and persistent, with record low polar stratospheric temperatures and a strong polar vortex.Several chemical fingerprints determined from satellite observations that suggest that the severe ozone depletion in the Arctic, and the record ozone hole in the Antarctic are linked to these wildfire events. This becomes even more worrying when one considers that wildfire frequency, intensity, and plume altitude are all forecast to increase under future global warming scenarios. It could be postulated that all of the hard work that has been performed very successfully under the Montreal Protocol might be undone not through lack of adherence to ODS reductions, but through global warming. If an ozone hole opens up over the northern hemisphere, this could pose a further existential threat to the delicate ecosystem balance that humanity relies upon. Similarly, the dynamical impacts of absorbing aerosols in the stratosphere may directly impact the Earth's surface climate: an enhanced positive phase of the North Atlantic Oscillation has been modelled in idealised studies which could lead to enhanced flooding in northern Europe and potentially devastating drought over the Iberian Peninsula. It is therefore critical to include these factors and feedbacks in global climate simulations at the earliest opportunity.