Large‐Scale Afforestation Over the Loess Plateau in China Contributes to the Local Warming Trend

Abstract

AbstractAfforestation is a major anthropogenic forcing to the global and regional climate. However, the biophysical impacts of large‐scale afforestation on local temperature in temperate regions remain unclear, due to the closely matched but compensating radiative and non‐radiative effects. The Grain for Green Program (GFGP) is a large‐scale afforestation program implemented over the Loess Plateau (LP) in China. The GFGP thus provides an ideal platform to explore the temperature effect of afforestation. This study investigated such a temperature effect through long‐term, high‐resolution simulations incorporating satellite observations in a coupled land‐atmosphere model. With an optimal combination of physical schemes proposed by this study, we greatly improved the accuracy of regional climate modeling. The results reveal that the afforestation caused a significant decline (−0.50% yr−1) in albedo. An increment in net shortwave radiation mainly led to an increment in net radiation (7.95 W m−2). The afforestation also led to an increment in sensible heat flux (3.78 W m−2). Consequently, the afforestation caused a warming effect (0.36°C) in 2‐meter air temperature at the inter‐annual scale. At the intra‐annual scale, there was a cooling effect in July and August, while other months demonstrated a warming effect. The radiative effect dominated local temperature change induced by the afforestation over the LP. Therefore, the large‐scale afforestation contributed to the local warming trend. Our findings highlight the temperature effect of afforestation, and imply that more attention should be paid to future revegetation to carefully assess its potential influence on regional climate.