Black carbon (BC) plays a vital role in Arctic warming.Extensiveinvestigations have been conducted to elucidate the source-receptorrelationships of BC between the Arctic and mid-/high-latitude sources.However, it is unclear to what extent source relocation under globalizationcould disturb Arctic BC contamination and climate forcing from anthropogenicBC emissions. Here, we show that the global supply chain (GSC) relocationfeatured by the southward shift of industries from high-latitude developedcountries to low-latitude developing countries markedly reduces theBC burden in the Arctic using a global chemical transport model (GEOS-Chem)and a multiregional input-output analysis (MRIO). We find thatArctic annual mean BC concentration associated with the GSC relocationdrops by similar to 15% from the case without the GSC relocation. Thetotal net BC level declines 7% over the entire Arctic and 16% in theEuropean Arctic. We also observed markedly declining BC depositionas well as direct and snow albedo radiative forcing in the Arctic.We show that the Arctic BC burden would be further reduced by decreasingBC emissions in China, attributable to its emission reduction andongoing shift of the GSC from China to southern and southeastern Asia. The global supply chain relocation fromhigh-latitude Europeto low mid-latitude Asian countries markedly reduces black carbonburden and snow albedo radiative forcing in the Arctic.

Given abundant energy and mineral resources in northwestern China, the west-east energy and mineral product transmission program play an increasingly important role in China's energy supply and consumption since the 2000s. Rapid growing energy and mineral products under this program might release increasing carbon emissions, causing climate and environmental consequences in northwestern China, which seems to be overlooked before. Here, a multiregional input-output analysis (MRIO) was conducted to investigate the temporal and spatial changes in black carbon (BC) emissions embodied in west-east energy and mineral product transmission from 2007 to 2012. Results were used to estimate BC's climate and environmental impact on China, focusing on northwestern China. The results show that BC emission flow patterns have been altered dramatically in China's domestic trade from 2007 through 2012. By 2012, 48%-77% of the consumption-based BC emissions from welldeveloped Beijing-Tianjin metropolises, East Coast, and South Coast regions were outsourced to other, primarily less-developed regions, of which northwestern China was the largest net BC emission outflow region at 48.8 Gg. The BC radiative forcing over China embodied in the west-east energy transmission was quantified using a compact Earth system model OSCAR. Model estimation shows that more than 30% of BC radiative forcing in northwestern China was related to the consumption from other regions across China. Central and eastern China were two significant contributors to the BC radiative forcing in northwestern China. Severe BC environmental inequality embodied in interprovincial trade was also identified in northwestern and central China provinces among 30 Chinese provinces. Inner Mongolia, Shaanxi, Ningxia, and Xinjiang in northwestern China experienced the most prominent climate and environmental losses via trade with well-developed provinces. These results provide references to alleviate trade-related pollution and climate impacts and to promote BC environmental equality in China.

Warming environmental conditions are often credited with increasing Arctic shrub growth and altering abundance and distribution, yet it is unclear whether tundra shrub expansion will continue into future decades. Water availability may begin to limit Arctic shrub growth if increasing air temperatures create drier soil conditions due to increased evapotranspiration and permafrost-thaw-induced soil drainage. However, few studies have effectively considered how dominant tundra shrub species respond to variations in both temperature and moisture. To better understand the key effects of temperature variation and soil moisture on two dominant circumpolar deciduous shrubs, we studied shrub growth along a natural landscape gradient in West Greenland, which is a region observed to be drying due to ongoing warming. We found that the growth forms of both grey willow (Salix glauca) and dwarf birch (Betula nana) were sensitive to warmer and drier conditions. For both species, increases in air temperature positively correlated with greater shrub volume, with the doubling of canopy volume due to increased woody biomass. Leaf biomass was best predicted by edaphic features including extractable ammonium, which was positively related to soil moisture, and bulk density. Warmer soils tended to be drier, suggesting that ongoing warming in the area could lead to significant water limitation. Our findings suggest that drier soil conditions might be limiting foliar production despite warming temperatures for two circumpolar dominant shrubs,Betula nanaandSalix glauca, which could have wide-ranging, biome-level consequences about ongoing and predicted shrub growth and expansion.

There exist substantial differences in top-of-atmosphere direct radiative forcing of aerosols due to a region's economic production (RFp) and consumption (RFc), in the context of economic globalization, trade and globalizing air pollution. Yet an explicit systematic analysis of all socioeconomic and atmospheric factors determining the RF difference is lacking. Here, we evaluate five socioeconomic (population, per capita output, emission intensity) and atmospheric (chemical efficiency and radiative efficiency) factors that determine a region's RFp, RFc and their difference. We consider the RF of secondary inorganic aerosols, primary organic aerosols and black carbon by 10 regions worldwide in 2007. The population size varies by a factor of nine across the regions, and per capita output by 40 times from both production- and consumption-based perspectives. The cross-regional spread reaches a factor of 181 (species dependent) for production-based emission intensity and a factor of 96 for consumption-based intensity. From one region to another, production-based chemical efficiency changes within a factor of 5 and consumption-based efficiency within a factor of 3.5. Radiative efficiency varies slightly across the regions (within 2) from both production- and consumption-based perspectives. Although socioeconomic factors are often a greater driver for the difference between a source region's RFp and RFc, the atmospheric factors are also important for many source regions and species. Our results contribute to regional attribution of climate change and establishment of effective international collaborative mitigation strategies.