Impacts of stabilized 1.5 o C and 2 o C global warming on hot extremes over China are examined based on dynamic downscaling Dynamic downscaling can significantly modify the projection of hot extreme changes in response to the 1.5 o C and 2 o C warming The downscaling induced differences in hot extremes changes are mainly attributed to the modification of shortwave radiation changes Accepted Article This article has been accepted for publication and undergone full peer review but has not been through the copyediting, typesetting, pagination and proofreading process, which may lead to differences between this version and the Version of Record. Please cite this article as

The Loess Plateau is a highland area covering approximately 640,000 km 2 in north central China. Historical longterm deforestation and crop expansion, as well as the semiarid background climate, cause severe soil erosion and land degradation (Fu et al., 2011;He et al., 2006). Moreover, the plateau serves as the ecological safety barrier of the upper reach of the Yellow River. Soil erosion augments the sediment discharge of the Yellow River, increasing the flooding risk in densely populated areas downstream (Fu et al., 2017). To address these issues, China has carried out a series of large-scale ecological programs over the plateau, including the most influential "Grain for Green Program" (GFGP) initiated in 1999 (Bryan et al., 2018). Benefiting from the GFGP, the plateau has shown a significant greening trend since then, with the vegetation fraction increasing from 31.6% in 1999 to 59.6% in 2013 (Chen et al., 2015).Greening is beneficial to soil erosion control and, on the other hand, can influence the terrestrial water balance through biophysical processes (Piao et al., 2020;Zeng et al., 2018). Greening can facilitate surface evapotranspiration due to the larger leaf area, aerodynamically rougher surface and higher canopy conductance for tran-

Afforestation can impact surface temperature through local and nonlocal biophysical effects. However, the local and nonlocal effects of afforestation in China have rarely been explicitly investigated. In this study, we separate the local and nonlocal effects of idealized afforestation in China based on a checkerboard method and the regional Weather Research and Forecasting (WRF) Model. Two checkerboard pattern–like afforestation simulations (AFF1/4 and AFF3/4) with regularly spaced afforested and unaltered grid cells are performed; afforestation is implemented in one out of every four grid cells in AFF1/4 and in three out of every four grid cells in AFF3/4. The mechanisms for the local and nonlocal effects are examined through the decomposition of the surface energy balance. The results show that the local effects dominate surface temperature responses to afforestation in China, with a cooling effect of approximately −1.00°C for AFF1/4 and AFF3/4. In contrast, the nonlocal effects warm the land surface by 0.14°C for AFF1/4 and 0.41°C for AFF3/4. The local cooling effects mainly result from 1) enhanced sensible and latent heat fluxes and 2) decreases in downward shortwave radiation due to increased low cloud cover fractions. The nonlocal warming effects mainly result from atmospheric feedbacks, including 1) increases in downward shortwave radiation due to decreased low cloud cover fractions and 2) increases in downward longwave radiation due to increased middle and high cloud cover fractions. This study highlights that, despite the unexpected nonlocal warming effect, afforestation in China still has great potential in mitigating climate warming through biophysical processes.

<p>China has shown a world-leading vegetation greening trend since 2000, which may exert biophysical effects on near-surface air temperature (SAT). However, such effects remain largely unknown because prior studies either focus on land surface temperature, which differs from SAT, or rely on simulations, which are limited by model uncertainties. As a widely used metric in climate and extremes research, SAT is more relevant to human health and terrestrial ecosystem functions. Therefore, it is necessary to explore impacts of greening on SAT and extremes based on observations. Here, we investigate the greening effects on SAT and subsequent extremes over 2003–2014 in China based on high-resolution SAT observations combined with satellite datasets. We find that greening can cause cooling effects on the mean SAT and more pronounced cooling effects on SAT extremes over semiarid regions. Such cooling effects are attributed to enhanced evapotranspiration caused by greening and strong coupling between evapotranspiration and SAT in semiarid regions. Semiarid regions in China are the transitional zone of both climate and ecosystem and deeply influenced by human agricultural and pastoral activities. These factors make the ecosystem of these regions fragile and extremely vulnerable to climate change. Our results reveal a considerable climate benefit of greening to natural and human systems in semiarid regions, and have significant implications for on-going revegetation programs implemented in these regions of China.</p>

Pielke et al., 2011). The impacts of deforestation on surface temperature vary spatially and temporally depending on the background climate (de Winckler et al., 2017). Deforestation, on the one hand, cools the surface due to increased albedo and, on the other hand, warms the surface as a result of decreased aerodynamic roughness and evapotranspiration (