Preferential cooling of hot extremes from cropland albedo management
Preferential cooling of hot extremes from cropland albedo management
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DOI：
10.1073/pnas.1317323111
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发表时间：
2014-07-08
影响因子：
11.1
通讯作者：
Wang, Tao
中科院分区：
文献类型：
--
作者：
Davin, Edouard L.;Seneviratne, Sonia I.;Wang, Tao
改变农业做法被认为是缓解气候变化的一种可能办法。特别是，减少或抑制耕作（免耕）可能有潜力将碳封存在土壤中，这可能有助于减缓全球变暖。另一方面，这种做法也通过改变陆地表面的物理性质对区域气候产生直接影响。然而，这些地球物理效应仍然知之甚少。在这里，我们表明，免耕管理增加了农田在夏季的地表覆盖度和由此产生的冷却效果在极端高温期间被放大，从而减弱了热浪期间达到的峰值温度。使用一个区域气候模型，考虑到免耕农业对地表水分的影响，以及可能减少土壤蒸发，我们调查了欧洲完全转换为免耕农业的潜在后果。我们发现，夏季冷却从农田CONDO增加强烈放大在炎热的夏季，当表面CONDO有更多的影响地球的辐射平衡，由于晴朗的天空条件。与作物残茬覆盖相关的蒸发量减少往往会抵消干旱引起的冷却，但在炎热的日子里，干旱效应是主导因素。对于热浪滚滚的夏季，免耕法的局部降温效果约为2摄氏度。确定的非对称影响的表面温度变化对夏季温度开辟了新的途径，气候工程措施，针对高影响的事件，而不是平均气候特性。
Changes in agricultural practices are considered a possible option to mitigate climate change. In particular, reducing or suppressing tillage (no-till) may have the potential to sequester carbon in soils, which could help slow global warming. On the other hand, such practices also have a direct effect on regional climate by altering the physical properties of the land surface. These biogeophysical effects, however, are still poorly known. Here we show that no-till management increases the surface albedo of croplands in summer and that the resulting cooling effect is amplified during hot extremes, thus attenuating peak temperatures reached during heat waves. Using a regional climate model accounting for the observed effects of no-till farming on surface albedo, as well as possible reductions in soil evaporation, we investigate the potential consequences of a full conversion to no-till agriculture in Europe. We find that the summer cooling from cropland albedo increase is strongly amplified during hot summer days, when surface albedo has more impact on the Earth's radiative balance due to clear-sky conditions. The reduced evaporation associated with the crop residue cover tends to counteract the albedo-induced cooling, but during hot days the albedo effect is the dominating factor. For heatwave summer days the local cooling effect gained from no-till practice is of the order of 2 degrees C. The identified asymmetric impact of surface albedo change on summer temperature opens new avenues for climate-engineering measures targeting high-impact events rather than mean climate properties.