Aerosols can influence vegetation through multiple processes, yet the resulting biophysical climate feedback from the vegetation response remains poorly understood. Here, using an ensemble of Earth system models and an observation-based empirical model, we show that the vegetation response to complete removal of anthropogenic aerosols can either cool or warm the local climate by up to 0.039 ± 0.020 °C (multimodel mean ± intermodel standard deviation) through altering albedo and evapotranspiration. This feedback exhibits distinct latitudinal asymmetry, resulting, on average, in cooling (–0.0083 ± 0.0070 °C) in boreal regions, moderate cooling (–0.0036 ± 0.0017 °C) in temperate zones, and slight warming (0.0007 ± 0.0011 °C) in the tropics (excluding the Amazon). Future projections suggest that stringent aerosol control could amplify the local cooling effect of vegetation across most vegetated areas. These findings reveal a previously overlooked pathway by which aerosols influence vegetation climate effects, highlighting the need for integrated policies on air quality control and vegetation-based climate solutions.

ABSTRACT Escalating exposure to extreme heat and ozone (O3) pollution has emerged as a principal challenge for cities worldwide. While urban greening is widely advocated for mitigating extreme heat, its impacts on compound heat-O3 pollution remain poorly understood due to intricate urban meteorology-chemistry coupling. By integrating observations, reanalysis data, and urban-land-atmosphere modeling, we demonstrate that urban greenery provides a notable yet uneven cooling effect of −0.26°C to −1.08°C in Northern Hemisphere’s metropolises, shaped by greenery fraction and local climate. Furthermore, the nonlinearly weakened O3 photochemical production within a greenery-stabilized urban boundary layer is capable of decreasing O3 in populated city centers. Despite the dual positive effects in alleviating heat and O3 exposures meteorologically, greenery-boosted biogenic emissions could chemically raise urban O3 via supplementing precursors, totally by up to 7.6 µg m−3. These findings underscore the need to incorporate fully coupled urban meteorology-chemistry interactions in urban greening strategies to achieve climatic and environmental co-benefits.

Land management plays a critical role in climate mitigation and local water security. Reforestation, as a key land management strategy, is widely implemented to sequester carbon, and it also alters local water availability through biophysical effects. However, how the same reforestation activity affects water availability under different climate states remains unclear, a gap critical for adaptive land management and water policy. Here, we show that the hydrological consequences of reforestation depend on the background climate state. Using Earth system model simulations, we find that under a low-warming scenario, reforestation causes an insignificant increase in global mean water availability but increases spatial inequality (stronger wetting over wet regions). In contrast, under a high-warming scenario, reforestation reduces global water availability while weakening spatial inequality (drying over wet regions). A moisture budget analysis attributes these differences to circulation responses in wet regions. Our findings reveal that climate context shapes reforestation outcomes, providing practical insights for policymakers designing climate-adaptive land management strategies.

Land use and land cover changes (LULCCs) can influence precipitation via changes in surface energy, water flux, and large-scale atmospheric circulation, with great implications for the sustainable development of nature and society. However, the impacts and mechanisms of these contributors to extreme precipitation changes compared with mean changes still need to be investigated. Here, we used the moisture budget equation to decompose precipitation changes into three primary contributing factors (evapotranspiration, atmospheric mean circulation, and water vapor) based on CMIP6-LUMIP experiments. A global reduction in mean precipitation due to LULCCs can be attributed to relatively equal contributions of changes in evapotranspiration and atmospheric mean circulation over the historical (1995-2014) and future (2080-2099) periods. In contrast, during the top drying month, the precipitation reduction is approximately 2-3 times greater than the multi-year mean change. The dynamic contributor representing the mean circulation change surpasses evapotranspiration as the primary contributor driving the extreme precipitation decrease in the majority of the landscape. The socioeconomic impacts of LULCCs-induced extreme precipitation changes are greater than those of the mean state, especially in the future.

Forests exhibit cooling or warming effects compared to adjacent openlands through biophysical processes. The local temperature effects are predicted by earth system models to evolve in response to climate change. However, these temporal dynamic patterns remain unconstrained by observations and have not been detected in historical records. Here, we provide satellite evidence of emergent negative trends in local land surface temperature (LST) effects of European forests from 2003–2023. The daytime cooling effects have significantly intensified in both winter (-0.17 K/decade) and summer (-0.22 K/decade). The enhanced winter cooling is attributed to the reduced shortwave radiative forcing in forests due to decreasing snow cover. In the summertime, the vegetation physiological response to increased atmospheric vapor pressure deficit boosts evaporative cooling in forests. The negative trends in LST effects of European forests are roughly supported by four state-of-the-art earth system models. However, considerable biases and intermodel spread in the representation of underlying biophysical processes. Given the continued climate change, we emphasize the need to consider their impacts on biophysical effect dynamics when comprehensive forest-related climate mitigation policies are formed.

Forests exhibit local cooling or warming effects compared to adjacent openlands through biophysical processes. These temperature effects are predicted by earth system models to evolve in response to climate change. However, such temporal patterns remain unconstrained by observations and have not been detected in historical records. Here, by comparing the satellite observations of spatially nearby forests and openlands over the last two decades, we quantify temporal trends in local land surface temperature (LST) effects of forest change in Europe. During winter, the daytime warming effect of potential forestation weakens and reverses to cooling (-0.142 K/decade) with decreasing snow cover, as forests show less pronounced surface darkening trends than openlands. During summer, the daytime cooling effect intensifies (-0.188 K/decade) because forests remain more physiologically and hydrologically resilient to increasing soil dryness. These negative trends are broadly supported by state-of-the-art earth system models, though substantial inter-model variability persists. Given continued climate change, we emphasize the need to consider the dynamics of biophysical effects when comprehensive forest-related climate policies are formed.

Drought, a marked deficiency of surface water, has a wide adverse impact on the environment, agriculture, and the socio-economy. The global impact of land use changes on drought features and associated exposures to droughts, however, remains largely unknown. In this study, the changes of drought features are estimated by using the model simulations with and without land use change. We show that historical land use changes since 1850, mainly deforestation and crop expansion, has increased the drought frequency, duration, and severity over half of the global land area. Regions with greater activity tend to experience stronger exacerbation of drought events. Owing to their increasing frequency and prolonged duration, populations, croplands and forests are increasingly exposed to drought events, which poses serious potential impacts on human health, agriculture, and forest ecosystems. The enhanced drought events could be substantially alleviated by potential reforestation activity. Our results provide useful information for land-management-related policy-making.

The climate effectiveness of forestation in Europe is debated, as it may provide more warming via solar energy absorption than evaporative cooling. Since forests play an important role in European climate policy, it is necessary to explore potential solutions to this issue in a warmer world. Here, based on experiments conducted with a regional climate model under several forest change scenarios, we find that conversion from coniferous to broadleaved trees in currently forested areas can provide cooling for summer hot extremes (e.g., reducing the monthly mean daily maximum temperature in July over Continental Europe by 0.6 °C). The conversion can also mitigate the undesired warming impacts of forestation with present-day forest composition in most of Europe, e.g., reversing effects on the monthly mean daily maximum temperature in July over Continental Europe from +0.3 °C to -0.7 °C. This study highlights the importance of considering tree species in European forest policy development and suggests that the Northern and Central regions should be prioritised for forestation over the Western and Southern parts.

Snow phenology characterizes the cyclical changes in snow and has become an important indicator of climate change in recent decades. Changes in snow phenology can significantly impact climate and hydrological conditions. Previous studies commonly employed fixed-threshold methods to extract snow phenology, which cannot represent the differences in the beginning and/or end of the snow period under different snow conditions in the Northern Hemisphere, leading to potential uncertainties in terms of snow phenology. In this study, we observe that snow phenology extracted from different snow data and methods shows significant differences but consistently underestimates snow duration at low and middle latitudes. After normalizing, the percentage snow depth curve turns significantly at the 10 % position, marking the transition between the snow and non-snow seasons. Therefore, we propose a dynamic snow phenology method with a 10 % threshold. Using the dynamic-threshold method, there is an earlier snow cover onset day (SCOD), a later snow cover end day (SCED), and a longer snow cover duration (SCD) at low and middle latitudes, especially on the Tibetan Plateau, where the SCD differences can reach 28 d. The differences in terms of snow phenology at higher latitudes are reversed. The dynamic snow phenology accounts for the spatial heterogeneity of Northern Hemisphere snow cover and excludes the influence of inter-annual variability of snow cover on snow phenology extraction, providing a novel perspective for identifying and understanding snow cover variations in the Northern Hemisphere.

The Amazon has experienced extensive deforestation in recent decades, causing substantial impacts on local and regional climate. However, the precipitation response to this recent forest cover change remains unclear. Here, we examined biophysical effects of forest cover change in the Brazilian Amazon on dry season precipitation using a regional coupled climate model with embedded water vapor tracers. We find that the 3.2% mean reduction in forest cover that occurred in Rondônia and Mato Grosso during 2002–2015 caused a 3.5 ± 0.8% reduction in evapotranspiration and a 5.4 ± 4.4% reduction in precipitation. The reduction in evapotranspiration warmed and dried the lower atmosphere reducing convection and precipitation. Reductions in incoming moisture, dominated by reduced moisture inflow in the mid‐troposphere, accounted for 25% of the total reduction in moisture and amplified the precipitation response to forest loss. The reduction in precipitation efficiency explains 84.5% of the reduction in precipitation with the remainder due to reductions in precipitable water. The reduced precipitation sourced from water vapor inflow accounts for 76.9% of the simulated precipitation reduction, with the remaining 23.1% due to reduced local evapotranspiration. Our study demonstrates substantial reductions in dry season precipitation due to recent forest cover change in the Amazon, highlighting the importance of atmospheric responses to land cover change in this region.

Anthropogenic land use and land cover changes (LULCC) have profound impacts on land water availability, defined as precipitation (P) minus evapotranspiration (ET), through biophysical pathways. However, such impacts have long been debated mostly due to either the inadequate consideration of the atmospheric feedbacks arising from the changes in circulations and background climate in observation-based studies or unrealistic representation of historical LULCC in idealized-simulation-based studies. To overcome these limitations, we use the latest simulations from multiple Earth system models to investigate the impacts of historical (1850–2014) and future (2015–2100) LULCC on P–ET. Here we show that historical LULCC caused an insignificant reduction in global P–ET, mainly in wet regions. Locally, P–ET tends to decrease (increase) in deforestation (reforestation) regions mainly due to the dominant role of precipitation. Approximately 3.8

By using model simulations, we show that historical land use and land cover change since 1850 has impacted aridity index (AI) worldwide, causing divergent responses in different regions. Locally, AI tends to increase (getting humid) in reforestation regions and most humid regions. Owing to these changes, the area of the humid zone expanded insignificantly by 0.22% of the global land area at the expense of drylands.

Large-scale revegetation on the Chinese Loess Plateau has profoundly influenced the terrestrial water cycle through biophysical processes. However, previous studies have primarily focused on the hydrological effects of revegetation averaged over specific periods, ignoring the potential influence of interannual climate variability on the revegetation effects. This study investigates the role of East Asian summer monsoon (EASM) variability}a key driver of the plateau's interannual climate}in shaping the hydrological outcomes of revegetation. Using the Weather Research and Forecasting (WRF) Model coupled with a water vapor tracer, we reveal divergent hydrological effects of revegetation due to EASM variability. In strong EASM years, revegetation increases precipitation (0.51 mm day-1), completely offsetting increased evapotranspiration (0.31 mm day-1) and yielding a net gain (0.20 mm day-1) in water yield (defined as precipitation minus evapotranspiration). Conversely, weak EASM years show precipitation reduction (-0.04 mm day-1) alongside evapotranspiration increase (0.26 mm day-1), resulting in water yield decline (-0.30 mm day-1). In normal EASM years, the hydrological effects of revegetation exhibit intermediate behavior between those observed in strong and weak EASM years. The divergent precipitation responses to revegetation primarily stem from substantial variations in precipitation derived from water vapor inflow beyond the plateau. These differences are mediated through distinct responses in both local boundary layer processes and large-scale atmospheric circulation patterns under different EASM intensity regimes. These findings underscore the importance of integrating climate variability into the hydrological assessment of revegetation, offering valuable insights for the sustainable development of ongoing revegetation projects over the Loess Plateau.

Abstract Land use and land cover changes (LULCCs) can influence surface temperature through local and nonlocal biophysical processes, which remain inadequately addressed. In this study, we separate the local and nonlocal effects of historical (1850–2014) LULCCs based on model outputs from the Coupled Model Intercomparison Project Phase 6. We also attempt to explore the sources of intermodel differences in the effects of LULCCs. The multimodel mean shows a cooling effect of −0.05°C (with an intermodel range of −0.24–0.06°C) at the global scale due to cropland and pastureland expansion, consisting of dominant nonlocal cooling of −0.06°C (with an intermodel range of −0.26–0.06°C) and slight local warming of 0.01°C (with an intermodel range of −0.01–0.05°C). The modeling results show some clear consistency in the effects of LULCCs despite considerable intermodel uncertainties. The local effects cause warming at low latitudes and cooling in boreal regions via changes in upward shortwave radiation and sensible and latent heat fluxes. The nonlocal effects mainly cause cooling via decreases in downward longwave radiation and increases in upward shortwave radiation. Intermodel differences in the total effects are dominated by those in the nonlocal effects, which are further attributed to divergent changes in downward longwave radiation and sensible heat flux across the models. This study highlights the importance of the nonlocal effects of LULCCs in terms of strength and intermodel uncertainty, with implications for designing land‐based solutions aimed at climate change mitigation.

AbstractMercury (Hg), a potent neurotoxin posing risks to human health, is cycled through vegetation uptake, which is susceptible to climate change impacts. However, the extent and pattern of these impacts are largely unknown, obstructing predictions of Hg’s fate in terrestrial ecosystems. Here, we evaluate the effects of climate change on vegetation elemental Hg [Hg(0)] uptake using a state-of-the-art global terrestrial Hg model (CLM5-Hg) that incorporates plant physiology. In a business-as-usual scenario, the terrestrial Hg(0) sink is predicted to decrease by 1870 Mg yr−1 in 2100, that is ~60% lower than the present-day condition. We find a potential decoupling between the trends of CO2 assimilation and Hg(0) uptake process by vegetation in the 21st century, caused by the decreased stomatal conductance with increasing CO2. This implies a substantial influx of Hg into aquatic ecosystems, posing an elevated threat that warrants consideration during the evaluation of the effectiveness of the Minamata Convention.

Satellite observations have shown evident vegetation greening in China during the last two decades. The biophysical effects of vegetation changes on near-surface air temperature (SAT) remain elusive because prior studies focused on the effects on land surface temperature (LST). SAT is more relevant to climate mitigation and adaptation, as this temperature is experienced by humans. Here, we provide the first observational evidence of the greening effects on SAT and SAT extremes in China during 2001–2018 using the ‘space-for-time’ method. The results show a negative SAT sensitivity to greening (–0.35 °C m ^2 m ^–2 ) over China and a cooling effect of −0.08 °C on SAT driven by vegetation greening during the study period. Such a cooling effect is stronger on high SAT extremes, particularly over arid/semiarid areas, where greening could bring an additional cooling of −0.04 °C on the hottest days. An attribution analysis suggests that the main driving factor for the cooling effect of greening is the evapotranspiration change for arid/semiarid regions and the aerodynamic resistance change for humid regions. This study reveals a considerable climate benefit of greening on SAT, which is more concerned with natural and human system health than the greening effects on LST.

Increasing the urban tree cover percentage (TCP) is widely recognized as an efficient way to mitigate the urban heat island effect. The cooling efficiency of urban trees can be either enhanced or attenuated on hotter days, depending on the physiological response of urban trees to rising ambient temperature. However, the response of urban trees’ cooling efficiency to rising urban temperature remains poorly quantified for China’s cities. In this study, we quantify the response of urban trees’ cooling efficiency to rising urban temperature at noontime [∼1330 LT (local time), LT=UTC+8] in 17 summers (June, July, and August) from 2003–19 in 70 economically developed cities of China based on satellite observations. The results show that urban trees have stronger cooling efficiency with increasing temperature, suggesting additional cooling benefits provided by urban trees on hotter days. The enhanced cooling efficiency values of urban trees range from 0.002 to 0.055°C

Abstract Tibetan Plateau (TP) snow cover is featured by sub‐seasonal changes, affecting weather and climate in surrounding and downstream areas. Previous studies emphasize the effect of background atmospheric circulation on rapid changes of TP snow cover as a whole. However, spatial discrepant changes of snow cover over the TP with complex topography and uneven snowfall remain unaddressed. Our research indicates that snow cover fraction dominates the rapid changes of surface albedo across the TP, and snow depth also significantly influences surface albedo changes through modulating snow albedo in central and eastern TP with shallow snow. However, the excessive snow amount and empirical snow cover fraction schemes introduce spatially divergent biases of surface albedo changes in simulations. Our research highlights the instant response of TP surface albedo to both snow coverage and depth in snow season, and provides a promising perspective for improving TP snow and surface albedo simulations.

Afforestation can influence evapotranspiration (E) and precipitation (P), thereby altering water availability (known as P - E) on land. However, such effects on P - E have rarely been examined in the context of seasonal and spatial variations in background P - E conditions. Here we show the impacts of global tree restoration on P - E under spatiotemporally varying P - E conditions. Afforestation amplifies seasonal contrasts in P - E, resulting in higher P - E in the high P - E season and/or lower P - E in the low P - E season, over approximately two-thirds of the land area. Afforestation also amplifies spatial contrasts in P - E, leading to higher P - E in the high P - E regions but lower P - E in the low P - E regions. This study underscores the importance of considering background P - E conditions when evaluating the hydrological effects of afforestation, with important implications for both forestry and water management.

The Tibetan Plateau vortices (TPVs) are mesoscale weather systems active at the near-surface of the Tibetan Plateau (TP), which are one of the major precipitation-producing systems over the TP and its surrounding areas. TPVs mainly occur in the warm season from May to September. In this paper, we investigated the interdecadal change of TPVs in the warm seasons of 1979–2020 with the six widely used reanalysis datasets. A significant change of the TPVs frequency appears around the mid-1990s, associated with less TPVs during 1979–1995 and more TPVs during 1996–2020, which is constant among the multiple reanalysis datasets. The abrupt change of TPVs is caused by a transition of the Atlantic Multi-decadal Oscillation (AMO) from a cold phase to a warm phase in the mid-1990s. The shift of AMO leads to a silk-road pattern-like wave train and a spatially asymmetric change of tropospheric temperature. It modifies the intensity of the subtropical westerly jet and the TP heating, leading to the interdecadal change of TPV activities.