Environmental Sciences and Energy Research, Weizmann Institute of Science, Rehovot 76100, Israel.
Science. 2010 Jan 22;327(5964):451-4. doi: 10.1126/science.1179998.
Forests both take up CO2 and enhance absorption of solar radiation, with contrasting effects on global temperature. Based on a 9-year study in the forests' dry timberline, we show that substantial carbon sequestration (cooling effect) is maintained in the large dry transition zone (precipitation from 200 to 600 millimeters) by shifts in peak photosynthetic activities from summer to early spring, and this is counteracted by longwave radiation (L) suppression (warming effect), doubling the forestation shortwave (S) albedo effect. Several decades of carbon accumulation are required to balance the twofold S + L effect. Desertification over the past several decades, however, contributed negative forcing at Earth's surface equivalent to approximately 20% of the global anthropogenic CO2 effect over the same period, moderating warming trends.
森林既能吸收二氧化碳，又能增强对太阳辐射的吸收，对全球温度有着截然相反的影响。基于对森林干燥林线的 9 年研究，我们表明，通过将光合作用的高峰期从夏季转移到早春，大量的碳封存（冷却效应）在大的干燥过渡带（降水量为 200 至 600 毫米）得以维持，而长波辐射（L）抑制（变暖效应）则与之相抵消，这使森林的短波（S）反照率效应增加了一倍。需要几十年的碳积累才能平衡这两种 S + L 效应。然而，过去几十年的荒漠化导致地球表面的负强迫作用相当于同期全球人为 CO2 排放的 20%左右，减缓了变暖趋势。
