Land use and land cover changes (LULCCs) can influence surface temperature through local and nonlocal biophysical processes. However, the local and nonlocal effects of historical LULCCs have rarely been explicitly investigated. In this study, we separate the local and nonlocal effects of historical (1985–2014) human land use activities based on a set of simulations with and without LULCCs from the Coupled Model Intercomparison Project Phase 6. We also attempt to explore the sources of the intermodel difference in the LULCC effects using a variance decomposition method. The results show that the nonlocal effects (-0.06 ℃ at the global scale) dominate the cooling effect of historical LULCCs mainly via decreases in downward longwave radiation and increases in upward shortwave radiation. The local effects are relatively small at the global scale (0.01 ℃) and manifest as warming at low latitudes (driven by weakened sensible and latent heat fluxes) and cooling in the boreal regions (driven by enhanced upward shortwave radiation). There remains a large intermodel uncertainty in the total effects of historical LULCCs, most of which is contributed by the intermodel difference in nonlocal effects. Such intermodel inconsistency in nonlocal effects is mainly attributed to the intermodel difference in changes in downward longwave radiation and surface sensible heat flux. This study highlights the importance of nonlocal effects of historical LULCCs in terms of the magnitude and the contribution to the intermodel uncertainty in the LULCC effects.

How to cite: Luo, X., Ge, J., Cao, Y., Liu, Y., Yang, L., Wang, S., and Guo, W.: Local and nonlocal biophysical effects of historical land use and land cover changes in CMIP6 models and the intermodel uncertainty, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1513, https://doi.org/10.5194/egusphere-egu24-1513, 2024.

Irrigation plays an essential role in the Earth system by changing water, energy, and carbon fluxes, and then affecting the climate. Many previous studies have been conducted to explore its impacts on near-surface climate, highlighting its cooling effects on air temperature, especially during hot extremes. However, most studies do the exploration during the historical period and only focus on temperature. Projected greenhouse gas emissions and land use datasets have made it possible to extend the investigation under future scenarios, but there are no datasets about predicted irrigation techniques shares information. To address this issue, we create a dataset containing spatial distribution of drip, sprinkler, and flood irrigation techniques, based on a simple assumption that richer and drier countries will invest more in irrigation system upgrades. Then, the Community Earth System Model version 2 (CESM2) is developed to be able to represent different irrigation techniques for one crop type in one gridcell. Finally, with the newly created dataset and modified CESM2, we detect irrigation's impacts on heat and moist-heat stress under SSP1-2.6 and SSP3-7.0. Simulation outputs indicate that irrigation will experience various changes among regions and scenarios. In irrigation hot spots, irrigation will continue to reduce the probability of high-temperature extremes under both scenarios but cannot reverse the warming signal caused by other forcings. Moreover, irrigation's impacts on apparent temperature are very small, and even increase the hours exposed to wet bulb temperature extremes in some regions. This study reveals that irrigation's cooling impacts will persist in the future, but will not be an effective solution to the global warming issue. As for moist-heat stress, irrigation's effects are much more complicated due to its enhancing impacts on air humidity.

How to cite: Yao, Y., Satoh, Y., van Maanen, N., Taranu, S., Lampe, S., Wada, Y., Lawrence, D., Sacks, B., Weider, W., Jägermeyr, J., Schleussner, C.-F., and Thiery, W.: Irrigation-induced impacts on near-surface climate under future scenarios, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6600, https://doi.org/10.5194/egusphere-egu24-6600, 2024.

Agricultural management can significantly impact biogeochemical cycles. In this study, we estimate the effect of various agricultural management practices such as grazing management, manure application, residue management, tillage, and cover crops on land use change emissions using the LPJmL dynamic vegetation model. We follow the TRENDY protocol to perform model simulations and estimate land use change emissions. Our results show that these practices mitigate a large proportion of emissions from land conversion (such as deforestation) and thus substantially determine the size of the current terrestrial carbon sink. We argue that there is substantial potential to further enhance carbon sequestration by optimizing agricultural management practices. We demonstrate that changes in agricultural management practices typically have smaller effects on albedo, surface roughness, and evapotranspiration compared to dedicated CO2 removal techniques that entail land cover changes (such as afforestation). However, due to limited global data on agricultural management practices, the actual contribution of these practices to emissions and their potential to reduce emissions remain highly uncertain. Our study highlights the need for more research in this area and the importance of considering agricultural management practices in dynamic vegetation models to estimate land use change emissions accurately.

How to cite: Heinke, J. and Müller, C.: Agricultural management determines the size of the terrestrial carbon sink, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18269, https://doi.org/10.5194/egusphere-egu24-18269, 2024.

Soil carbon sequestration is an important strategy for climate change mitigation. Soil carbon stocks on agricultural lands can be augmented through sustainable land management practices such as organic manures addition, cover cropping, mulching, conservation tillage and agroforestry. Soil carbon sequestration has several co-benefits, of which increased water holding capacity and infiltration are often named. However, a global scale quantification of these hydrological co-benefits for water availability is still lacking.

In this study, we aim to quantify how soil carbon sequestration impacts soil water budget and availability, to identify potential hydrological co-benefits. We use the Community Land Model (CLM) version 5.2 in land-only mode with prescribed phenology to conduct idealized experiments simulating present-day climate conditions with altered soil carbon stocks after 20 years of sequestration. Three scenarios of carbon sequestration are investigated, based on spatially explicit soil organic carbon input maps. These include two scenarios with high and medium sequestration rates focused on cropland. Additionally, an aspirational scenario with a 0.4% annual increase in soil organic carbon stocks is conducted, which follows the "4 per mille" initiative target.

Upon analyzing the simulations at subgrid level for the crop fraction of the grid cell, our findings indicate that, overall, soil carbon sequestration enhances the water holding capacity by increasing the field capacity and reducing the permanent wilting point of the soil. This increase in water holding capacity predominantly arises from augmented porosity, which in turn surpasses the rise in actual water content. Consequently, the saturated fraction of soils across most regions decreases.

Furthermore, CLM simulations consistently demonstrate that elevated carbon stocks reduce the surface runoff and subsurface drainage, and increase soil evaporation. The upper soil layers, corresponding to the layers with elevated soil carbon, exhibit increased water content, whereas lower layers indicate either negligible or slight water content reduction. This is particularly accentuated in arid regions, which leading to an overall decline in water content in these areas. Finally, water stress is found to be decreasing, which indicates improved water retention in carbon-sequestered soil and enhances the soil sponginess. Overall, despite remaining modelling uncertainties, particularly linked to soil hydrological parametrizations and their dependency on soil carbon fractions, these sensitivity experiments reveal the potential of carbon sequestration to increase water availability and counteract water scarcity.

How to cite: Vanderkelen, I., Stocker, B. D., Swenson, S., Lawrence, D., and Davin, E. L.: Investigating the hydrological co-benefits of soil carbon sequestration using a land surface model, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15336, https://doi.org/10.5194/egusphere-egu24-15336, 2024.

Understanding human-environment feedbacks is becoming increasingly important as climate change mitigation and adaptation strategies continue to diversify, target new areas, and grow in extent. Incorporating these feedbacks into models is critical for assessing the effectiveness of such strategies and how they may change in response to a changing climate. For example, projected forest expansion varies with changing climate because climate-driven changes in forest productivity affect the cost-effectiveness of reforestation strategies. Including human-environment feedbacks in models can dramatically change the projected scenario as human systems respond to the changing environment, which in turn affects the Earth system projection.

We have incorporated human-Earth feedbacks in a synchronously coupled system comprising the Global Change Analysis Model (GCAM) and the Energy Exascale Earth System Model (E3SM). GCAM is the core model in a new E3SM human component that is at the same level as the Earth model components (land, atmosphere, ocean, etc.) and interacts with them through the shared coupling software. Terrestrial productivity is passed from E3SM to GCAM to make climate-responsive land use and CO₂ emission projections for the next five-year period, which are interpolated and passed to E3SM annually. Previous experiments with a similar model have shown that the incorporation of these feedbacks affects land use/cover change, crop prices, terrestrial carbon, local surface temperature, and land carbon-atmosphere feedbacks. Preliminary results indicate that this newly coupled system is robust in relation to the previous experiments. The human scenario is altered by terrestrial feedbacks, which in turn changes the Earth system projections. Regional differences are more pronounced than global differences due to regional shifts in land use. This new coupling addresses inconsistency across models, enables a new type of scenario development, and provides a modeling framework that is more easily updated and expanded.

How to cite: Di Vittorio, A., Hao, D., Shippert, T., Singh, B., Sinha, E., and Bond-Lamberty, B.: Human-Earth feedbacks in E3SM-GCAM successfully simulate the evolution of a combined human-Earth system, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14276, https://doi.org/10.5194/egusphere-egu24-14276, 2024.

Fostering sustainable management of forests is pivotal in advancing Europe's climate resilience and achieving its short- and long-term environmental objectives. Any management strategy has multifaceted impacts, influencing carbon cycling and also leading to biogeophysical consequences arising from altered energy partitioning in the forest, for example. Modelling can offer valuable insights into these complexities, making it a beneficial tool aiding the pursuit of science-based solutions to inform policy and decision-making processes. 
 
This work introduces improvements in the representation of wood harvesting and different forest management scenarios in JSBACH4, the current version of the land component of the ICOsahedral Nonhydrostatic Earth System Model (ICON-ESM) framework. The previously established forest age class scheme of JSBACH 4 and the extensive forest parameters and harvesting schemes from the model G4M-X (by the International Institute for Applied Systems Analysis) are utilised in the development.  This combination of a detailed forestry model integrated into decision-making frameworks, coupled with an advanced land surface model intricately linking to the entirety of key climate processes, holds great potential to enhance our understanding for the management of ecosystems. The objective of this effort is to enhance the sophistication of the related forest parameters in JSBACH4, enabling a more comprehensive simulation of various forest management scenarios.  This will allow capturing the nuanced carbon cycling and biogeophysical effects associated with different types of forest management and wood harvesting practices.

How to cite: Räty, M., Lessa Derci Augustynczik, A., and Pongratz, J.: Refining the Representation of Forest Management Practices in JSBACH4 , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17965, https://doi.org/10.5194/egusphere-egu24-17965, 2024.

Afforestation affects the earth’s climate system by changing the biogeochemical and biogeophysical characteristics of the land surface. While the regional effects of afforestation are well understood in the tropics and the high-latitudes, its climate impact on the mid-latitudes is still subject of scientific discussions. The general impact of afforestation on the regional climate conditions in Europe during the last decades is investigated in this study. For this purpose, regional climate simulations are performed with different forest cover fractions over Europe. In a first simulation, afforestation in Europe is considered, while this is not the case for a second simulation.  We focus on the years 1986-2015, a period in which the forest cover in Europe increased comparatively strong, accompanied by a strong general warming over the continent.

Results show that afforestation has both local and non-local effects on the regional climate system in Europe. Due to an increased transport of turbulent heat (latent + sensible) into the atmosphere, afforestation leads to a significant reduction of the mean local surface temperatures in summer. In northern Europe, mean local surface temperatures were reduced about -0.3 K with afforestation, in central Europe about -0.5 K and in southern Europe about -0.8 K. During heat periods, this local cooling effect can reach to -1.9 K. In winter, afforestation results in a slight local warming both in northern and southern Europe, because of the albedo effect of forests. However, this effect is rather small and the mean temperature changes are not significant. In downwind direction, locally increased evapotranspiration rates with afforestation increase the general cloud cover, which results in a slight non-local warming in winter in several regions of Europe, particularly during cold spells. Thus, afforestation had a discernible impact on the climate change signal in Europe during the period 1986-2015, which may have mitigated the general warming trend in Europe, especially on the local scale in summer.

How to cite: Breil, M., Schneider, V., and Pinto, J.: The effect of forest cover changes on the regional climate conditions in Europe during the period 1986-2015, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17272, https://doi.org/10.5194/egusphere-egu24-17272, 2024.

Dryland ecosystems worldwide face substantial degradation due to adverse climatic conditions and unsustainable land practices. This is particularly evident in Africa's Sahel region, where extensive land degradation and desertification pose significant challenges to local livelihoods and socio-economic stability. To address this issue, the Great Green Wall Initiative (GGW) aims to restore over 100 million hectares of degraded land to counter desertification and support rural communities.

Here we assess how land use changes have altered ecosystem services within GGW implementation areas. We analyzed the spatiotemporal characteristics of land use change using the MODIS-Global Land Cover product from 2007 to 2019. Based on remote sensing data and established geospatial models, we evaluated five ecosystem services, namely carbon sequestration, soil conservation, sand fixation, water regulation, and food provision. We explored trends in ecosystem service changes, identified spatial clusters of high and low values, and evaluated synergies and trade-offs among these services by Pearson's coefficient and the bivariate Moran’s I method. The result showed that the level of various ecosystem services in GGW areas is heterogeneous, with a large spatial distribution. High values of ecosystem services are found in Burkina Faso, southern Nigeria and eastern Ethiopia. Synergies between ecosystem services are dominant, with the strongest synergies between carbon sequestration and soil conservation. Carbon sequestration and water regulation were clustered, but there were trade-offs with food provision. We quantified the contribution of land use to the changes in ecosystem services through the calculation of the Ecosystem Service Contribution Index (ESCI). The expansion of farmland and desertification have had significant negative impacts on ecosystem services and grassland conversion. This assessment provides critical insights into the efficacy of restoration efforts and aims to offer guidance for informed decision-making in sustainable management practices for dryland ecosystems.

How to cite: Wang, Y., Dallimer, M., and Scott, C.: Effects of land use change on ecosystem services in Africa's Great Green Wall Initiative (GGW) for dryland restoration, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13862, https://doi.org/10.5194/egusphere-egu24-13862, 2024.

Forests play an important role in regulating land-atmosphere interactions, e.g., the temperature difference (δT) between land surface and air. However, previous studies have primarily focused on analyzing spatial characteristics of δT at global or regional scales, with limited research on its diurnal variations especially using observational data. In this research, we investigated the diurnal changes of δT, using air temperature from large numbers of meteorological stations and surface temperature data from ERA5-Land, for forested areas in China. Results revealed that the diurnal variations in δT (2.18°C) were greater than the observation across seasons (0.8°C), highlighting the importance of considering diurnal scale in understanding δT dynamics. The hourly δT exhibited strong positive correlations with Bowen ratio albeit with a 2-3 hour time lag. Obvious relations also detected between δT and precipitation at daytime, while nighttime relationships remained uncertain when considering the influence of elevation. Simulations from Community Earth System Model (CESM) agree well with the δT-precipitation relations during the daytime, but it overemphasizes the role of elevation in controlling hydrothermal process. We remain hopeful for further enhancement of relevant physical processes in CESM can improve its ability in simulating such interactions.

How to cite: Xu, R., Li, Y., and Davin, É.: The diurnal variation of the difference between surface skin temperature and in-situ 2 m air temperature of forests in China, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9576, https://doi.org/10.5194/egusphere-egu24-9576, 2024.

The distribution and composition of forests worldwide are primarily influenced by geographical factors, latitude, and prevailing climatic conditions. These conditions also govern how various types of forests respond to changes in climate. Understanding the feedback loop between vegetation and climate is complex due to regional variations, making it a challenging study area. Previous studies have predominantly focused on the biogeochemical processes, assessing the forest's carbon sequestration potential, while the role of biogeophysical mechanisms- such as evapotranspiration and latent heat flux, apart from albedo- in this relationship remains poorly understood.
The present study aims to comprehensively explore both the biogeochemical and biogeophysical mechanisms operating within Indian forests and their influence on climate by utilizing finer-resolution observational datasets. India, characterized by diverse geographical features, harbors 16 distinct forest types. My initial findings indicate an overall increase in forest cover except in wet evergreen and montane wet temperate forests within India. Additionally, evidence suggests heightened gross primary productivity, suggesting the forests' ability to mitigate warming effects. The study will explore the intricate dynamics of evapotranspiration and other related factors, aiming to unravel their synergistic impact on the regional climate. The findings will contribute to a more comprehensive understanding of the complex dynamics shaping forest-climate interactions, providing valuable information for sustainable forest management and climate change mitigation strategies.

How to cite: Sharma, J. and Kumar, P.: Exploring the Dynamics of Forests and Climate: A Case Study of India, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8311, https://doi.org/10.5194/egusphere-egu24-8311, 2024.

Global continual logging activities have modified the regional landscape and disrupted the energy balance through changing the surface albedo, evapotranspiration and roughness length in both current location (local) and nearby areas through feedback to the atmospheric circulation (non-local). Compared to land use change, less attention has been given to understanding the local biogeophysical effect of the different land use management practices, e.g., wood harvest (logging). Uncertainties from the reconstructed global wood harvest rate forcing data, simplified land heterogeneity and processes representation in the classic big-leaf models largely changed the outcomes. We apply a next generation dynamic vegetation model (Functionally Assembled Terrestrial Ecosystem Simulator, FATES), coupled with the land component (ELM) of DOE’s earth system model E3SM to study the local biogeophysical effect and the redistribution of energy after accounting the continuous logging activity on a global scale. In order to account for the uncertainties from forcing data and modeling approaches, we designed 9 parallel experiments with 4 different sets of global wood harvest rates derived from LUH2 reconstructed historical harvest rates combined with 2 different wood harvest methods: area-based harvest and carbon-based harvest. The results highlighted a divergent pattern of the local biogeophysical impact from logging under two dominant stages: regrowth dominant and logging dominant. We found the continuous logging causing up to 5% of the reduction of global canopy coverage and 2% of the increase of albedo. The study also highlighted the uncertainty from the forcing of data sources and modeling approach can lead to a several times difference in the magnitude of local biogeophysical effect.  

How to cite: Shu, S., Holm, J., Di Vittorio, A., Koven, C., Knox, R., and Lemieux, G.: Estimation of local biogeophysical effects of the continuous logging using a dynamic vegetation model forced by C-based wood harvest, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17255, https://doi.org/10.5194/egusphere-egu24-17255, 2024.