The radiative forcing potential of different climate geoengineering options
The radiative forcing potential of different climate geoengineering options
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DOI：
10.5194/acp-9-5539-2009
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发表时间：
2009-01-01
影响因子：
6.3
通讯作者：
Vaughan, N. E.
中科院分区：
文献类型：
--
作者：
Lenton, T. M.;Vaughan, N. E.
气候地球工程提案寻求纠正地球当前和未来潜在的辐射不平衡，方法是减少对入射太阳（短波）辐射的吸收，或从大气中去除二氧化碳并将其转移到长期储存库，从而增加向外的长波辐射。评估地球工程方案的一个基本标准是其气候冷却效果，我们在此根据辐射强迫潜力对其进行量化。我们使用一种简单的分析方法，基于能量平衡考虑和二氧化碳扰动衰减的脉冲响应函数。与复杂数值模型的计算相比，这有助于提高透明度，但并不具有确定性。它使我们能够比较一系列提案的相对有效性。我们认为地球工程选项是大幅减少二氧化碳排放的补充。到 2050 年，一些陆地碳循环地球工程方案可能与缓解“楔子”具有相当的规模，但只有平流层气溶胶注入、海洋层积云反照率增强或太空遮阳才有可能将气候冷却回到工业化前的状态。强有力的缓解措施，加上全球范围的空气捕获和储存、植树造林和生物炭生产，即增强二氧化碳汇，可能能够在 2100 年之前将二氧化碳排放量恢复到工业化前的水平，从而消除对其他地球工程的需要。或者，通过强有力的缓解措施将二氧化碳稳定在 500 ppm，再加上通过地球工程增加海洋层状云、草原、农田和人类住区的反照率，可能会实现辐射强迫的零散消除。海洋施肥方案只有在千年的时间尺度上持续下去才有价值，并且磷的添加可能比铁或氮肥具有更大的长期潜力。增强海洋上升流或下降流对任何有意义的时间尺度都有微不足道的影响。我们的方法为评估气候地球工程提案提供了一个通用框架，我们的结果应有助于为进一步研究的优先顺序提供信息。
Climate geoengineering proposals seek to rectify the Earth's current and potential future radiative imbalance, either by reducing the absorption of incoming solar (shortwave) radiation, or by removing CO2 from the atmosphere and transferring it to long-lived reservoirs, thus increasing outgoing longwave radiation. A fundamental criterion for evaluating geoengineering options is their climate cooling effectiveness, which we quantify here in terms of radiative forcing potential. We use a simple analytical approach, based on energy balance considerations and pulse response functions for the decay of CO2 perturbations. This aids transparency compared to calculations with complex numerical models, but is not intended to be definitive. It allows us to compare the relative effectiveness of a range of proposals. We consider geoengineering options as additional to large reductions in CO2 emissions. By 2050, some land carbon cycle geoengineering options could be of comparable magnitude to mitigation 'wedges', but only stratospheric aerosol injections, albedo enhancement of marine stratocumulus clouds, or sunshades in space have the potential to cool the climate back toward its pre-industrial state. Strong mitigation, combined with global-scale air capture and storage, afforestation, and bio-char production, i.e. enhanced CO2 sinks, might be able to bring CO2 back to its pre-industrial level by 2100, thus removing the need for other geoengineering. Alternatively, strong mitigation stabilising CO2 at 500 ppm, combined with geoengineered increases in the albedo of marine stratiform clouds, grasslands, croplands and human settlements might achieve a patchy cancellation of radiative forcing. Ocean fertilisation options are only worthwhile if sustained on a millennial timescale and phosphorus addition may have greater long-term potential than iron or nitrogen fertilisation. Enhancing ocean upwelling or downwelling have trivial effects on any meaningful timescale. Our approach provides a common framework for the evaluation of climate geoengineering proposals, and our results should help inform the prioritisation of further research into them.