Solar geoengineering may not prevent strong warming from direct effects of CO 2 on stratocumulus cloud cover
Solar geoengineering may not prevent strong warming from direct effects of CO 2 on stratocumulus cloud cover
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太阳能地球工程可能无法阻止 CO 2 对层积云层直接影响造成的强烈变暖
DOI：
10.1073/pnas.2003730117
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发表时间：
2020
期刊：
影响因子：
--
通讯作者：
Pressel, Kyle G.
中科院分区：
文献类型：
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作者：
Schneider, Tapio;Kaul, Colleen M.;Pressel, Kyle G.
关于利用太阳能地球工程应对全球变暖的讨论假设，温室气体浓度上升导致的变暖可以通过人为减少地球吸收的阳光量来补偿。然而，太阳能地球工程可能无法防止全球变暖，因为二氧化碳可以直接影响云层：它通过调节大气中的长波辐射冷却来减少云层。太阳能地球工程并不能减轻这种影响。在这里，我们使用理想化的高分辨率云模拟来表明，即使在最初只有适度变暖的持续太阳地球工程情景下，亚热带层积云也会逐渐变薄，最终可能会分解成分散的积云，浓度超过百万分之1,700（ppm）。由于层积云覆盖了大片的亚热带海洋，并通过反射入射的阳光使地球降温，因此它们的消失将引发强烈的（约5 K）全球变暖。因此，研究结果强调，至少在这种极端和理想化的情况下，太阳能地球工程可能不足以应对温室气体驱动的全球变暖。
Discussions of countering global warming with solar geoengineering assume that warming owing to rising greenhouse-gas concentrations can be compensated by artificially reducing the amount of sunlight Earth absorbs. However, solar geoengineering may not be fail-safe to prevent global warming because CO2can directly affect cloud cover: It reduces cloud cover by modulating the longwave radiative cooling within the atmosphere. This effect is not mitigated by solar geoengineering. Here, we use idealized high-resolution simulations of clouds to show that, even under a sustained solar geoengineering scenario with initially only modest warming, subtropical stratocumulus clouds gradually thin and may eventually break up into scattered cumulus clouds, at concentrations exceeding 1,700 parts per million (ppm). Because stratocumulus clouds cover large swaths of subtropical oceans and cool Earth by reflecting incident sunlight, their loss would trigger strong (about 5 K) global warming. Thus, the results highlight that, at least in this extreme and idealized scenario, solar geoengineering may not suffice to counter greenhouse-gas-driven global warming.