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The offshore region of East Asia has a crucial role in recycling precipitation, especially in the current context of a warming climate. This is because the atmospheric feedback from the sea offshore East Asia directly impacts and modifies precipitation patterns by influencing the seasonal cycles of the surface energy and water budgets. We used a regional climate model incorporating sea–air coupling to investigate and better understand these climate feedback mechanisms in East Asia. We identified a reduction in precipitation caused by sea-air coupling over East Asia during the time period 1991 − 2014 under present day conditions. Specifically, we observed an average decrease in precipitation of about 0.1 ± 0.40 mm day−1 during June–July–August. This decrease in precipitation can be attributed to a combination of factors, including the effects of upward solar radiation, the asymmetry of the thermal contrast between the land and the sea, decreased evaporation in the southeastern ocean and the weakened transport of water vapor from the sea to the land. Our research suggests that the decrease triggered by sea–air coupling will be partially alleviated under future conditions, although not completely reversed, in terms of its impact on precipitation in eastern China. Although some relief is anticipated, the overall influence of sea–air coupling on patterns of precipitation in East Asia will persist, especially south of the Yellow River in eastern China. [ABSTRACT FROM AUTHOR]

Against the current climate change background, the mid–high latitudes (>23.7°N) of the Northern Hemisphere have experienced an increase in atmospheric CO2 concentrations, which is higher than the global average. An Beijing Normal University–Earth System Model was used in this study to estimate the carbon uptake in the mid–high latitudes from 2031 to 2060 under the SSP5‐8.5 future emissions scenario. Results showed that, in the high latitudes, non‐uniform CO2 led to a reduction in net ecosystem productivity (NEP) by −0.1 Pg C yr−1. This mainly resulted from a 1.5‐fold greater increase in heterotrophic respiration than in net primary productivity (NPP). In the mid‐latitudes, meanwhile, the decrease in carbon uptake was generally due to a two‐fold greater decrease in NPP than heterotrophic respiration. The decrease in precipitation was closely correlated with local carbon uptake, which could explain this decrease in NPP. It was further found that, in East Asia, changes in atmospheric circulation induced by the non‐uniform CO2 might have reduced the amount of large‐scale precipitation by −9 mm yr−1. This reduction was the primary contributor (98%) to the decrease in overall precipitation, possibly strengthening the limitation of water on plant growth, which would cause a decline in NEP. In the future, it is suggested that such spatially varying CO2 concentrations should be assessed for possible impacts on local carbon uptake. Plain Language Summary: Because spatially varying in CO2 concentrations exists in the real world, which regulates climate system and carbon cycle, understanding it's impact is important for climate prediction and understanding changes to terrestrial carbon cycle. In this work, we test assumptions about greater CO2 concentrations in the Northern Hemisphere relative to a uniform distribution of CO2 concentrations: (a) Will lead to greater carbon uptake in the Northern Hemisphere due to the CO2 fertilization effect? (b) More generally, what will determine the carbon uptake at hemispheric scales? We find that in the mid‐latitudes of the Northern Hemisphere, the decrease in carbon uptake was generally due to a two‐fold greater decrease in net primary productivity than heterotrophic respiration as impacts of spatially varying CO2 concentrations. Such a decrease could be explained by the reduction in precipitation. We further find that a decrease in net ecosystem productivity over East Asia could mainly result from a reduction in large‐scale precipitation, which could strengthen the limitation of water on plant growth. Key Points: Non‐uniform CO2 significantly decreased carbon uptake by −0.1 ± 0.1 Pg C yr−1 in East Asia during 2031–2060Net ecosystem productivity (NEP) decreased as a result of a much stronger response of heterotrophic respiration to warming in high latitudesNon‐uniform CO2 induced a stronger decrease in heterotrophic respiration, which was the main contributor to NEP in the mid‐latitudes of North America [ABSTRACT FROM AUTHOR]

In the late 1920's, a mega-drought in China resulted in widespread crop failure and famine. Sufficient evidence suggests that this drought belonged to a dry period ranging from approximately 1922 to 1932. To understand the characteristics and the cause of this persistent drought period, we combined various data, including observations, tree ring proxy data, reanalysis data, simulation results of the Fifth Phase of the Coupled Model Intercomparison Project and numerical downscaling simulations. The results show that during 1922–1932, most regions in eastern China suffered from a persistent drought that lasted for six years, and the maximum negative precipitation anomaly reached −1.5 times the standard deviation. Given its spatial coverage, duration, and strength, the 1920s drought was unique for the 20th century. The 1920s drought was primarily caused by internal variability. Strong easterlies in lower latitudes, strong monsoon circulation, and abnormally high geopotential heights at middle and upper levels were responsible for the 1920s drought conditions in eastern China; these drought conditions could be further attributed to the joint impact of the Atlantic Multidecadal Oscillation, Pacific Decadal Oscillation and Indian Ocean Basin Mode. [ABSTRACT FROM AUTHOR]

Atmospheric carbon dioxide (CO2) would be increasing much more if it were not for terrestrial carbon (C) uptake, fueling the drawdown of atmospheric CO2 in vegetation and soil on decadal to centennial time scales. Here, we used a global Earth system model (BNU‐ESM) with two different CO2 data sets (i.e., uniform CO2 vs. non‐uniform CO2 data sets) to simulate the responses of the C balance, particularly to the non‐uniform CO2 effect. Under future conditions of 2071–2100, accounting for spatial variations of CO2 concentrations resulted in 0.51 Pg C yr−1 or 19% additional global net ecosystem production (NEP) inductions relative to the uniform conditions. The reduction in NEP in the future was mostly caused by the reduction in the Northern Hemisphere, within which summer was the season that accounted for the largest fraction of this reduction. Changes in NEP under future conditions differed largely to those under present conditions, resulting from changes in the circulation caused by the non‐uniform CO2—for example, reductions in evapotranspiration limit water vapor contributions to the lower atmosphere, and substantially diminish convective precipitation, which led to decreased precipitation. Our findings call for more attention to be paid to the influence of spatial variations in CO2 concentration—particularly in the Northern Hemisphere—to better constrain the projected C uptake under future conditions. Also, it highlights the fundamental importance of non‐uniform CO2 in determining the pattern, response, and magnitude of C uptake through to 2100. Plain Language Summary: Atmospheric carbon dioxide (CO2) is the largest contributor to the carbon (C) fluxes in terrestrial ecosystems. Here, we used a global Earth system model (BNU‐ESM) with two different CO2 data sets (i.e., uniform CO2 vs. non‐uniform CO2 data sets) to simulate the responses of the C balance, particularly to the non‐uniform CO2 effect. Under the future conditions of 2071–2100, severe reductions in net ecosystem production were shown, compared with that under the present conditions. It highlights the fundamental importance of non‐uniform CO2 in determining the pattern, response, and magnitude of C uptake through to 2100. Key Points: In response to non‐uniform CO2 during 2071–2100, net ecosystem production (NEP) decreased by ∼69% in the Northern HemisphereSpatial variations of CO2 concentrations lead to a much stronger response of NEP during springtime at high latitudesEvapotranspiration reductions limit convective precipitation and then decrease gross primary production in southern North America, southern East Asia, and central Europe [ABSTRACT FROM AUTHOR]

The land use and land cover change (LULCC) presents the large-area features since the 1980s in East Asia, particularly over China, where the largely complicated LULCC has happened for the simultaneous interconversion of croplands, forests, grasslands, and urban lands. In this study, the regional coupled model AVIM-RIEMS2.0 with dynamic vegetation process is employed to examine the impacts of LULCC on regional climate over East Asia. The results show that regional climate and terrestrial surface processes exhibit significantly seasonal and interdecadal signals in East Asia. With the influences of LULCC, forest increased 33.3% and 20.3% from the 1980s to 1990s and from the 1990s to 2000s, respectively. Meanwhile, cropland decreased 17.8% in the 1990s (compared to the 1980s) and 24.8% in the 2000s (compared to the 1990s), respectively. These transitions of land surface processes are roughly coincident with the interdecadal variations in temperature and precipitation, which trigger generally opposite changes in the 1980s as compared to the 1990s, especially over eastern China. The seasonal variability of climatic components is more evident in winter than summer, except for the precipitation. The climate change is also somewhat remarkable under the non-LULCC conditions, combined with the changes in wind fields at the 850 hPa from the simulations during three decades; they together suggest that climate change is also modulated by other controlling factors, such as East Asian monsoon circulations in addition to LULCC conversions. These results highlight the importance of LULCC in regional modeling studies, which would have practical significance in climate mitigation and adaptation over East Asia. [ABSTRACT FROM AUTHOR]