Atmospheric aerosols can scatter and absorb the incident solar radiation, and thus impact the land carbon cycle by perturbating the radiation required for photosynthesis. Atmospheric aerosols inhibit the carbon uptake by terrestrial ecosystems through reducing the total amount of incident radiation, while the increased proportion of diffuse irradiance is known to promote photosynthesis. In the past few decades, with the rapid industrialization and urbanization, China has suffered from frequent haze pollution episodes, which have brought up severe environmental problems and ecological impacts. Here, we use a regional climate model, WRF-Chem, along with the offline driven Simplified Simple Biosphere Model (SSiB4) to investigate the impact of aerosol radiation effects on land biosphere carbon uptake capacity. The results show that the current aerosol loading has led to significant decrease in the incident solar radiation in China, which severely suppresses the gross primary production (GPP) and net primary production (NPP). Then, we assessed the influences of stringent emission and pollution control policies on terrestrial ecosystem carbon fluxes. By comparing the simulation results based on China’s ambitious carbon neutrality policies with the reference scenario with negligible emission control, we found that the carbon neutrality scenario with rigorous pollution control increases the incident solar radiation and thereby enhancing the carbon uptake of land biosphere. Under the current state of aerosol loading, the decrease of total amount of incident radiation dominates the suppression of terrestrial carbon uptake, while aerosol diffuse fertilization effect can only partly offset the inhibition of decreased solar radiation on plant photosynthesis. Our findings improve the understanding of the interactions between aerosol pollution and the land carbon cycle, and suggest an appreciable ecological benefit and a potential terrestrial carbon sink enhancement of stringent emission and pollution control actions.

How to cite: Li, L., Qiu, B., Huang, X., Guo, W., Miao, X., Chen, J., Ni, Y., and Tian, X.: Aerosol-induced radiation effect and the potential influence of stringent emission control on terrestrial carbon uptake in China, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3775, https://doi.org/10.5194/egusphere-egu23-3775, 2023.

The productivity of terrestrial ecosystems is determined, among other things, by solar radiation and its degree of scattering can increase or reduce it. The intensity of scattering is determined by the optical properties of the atmosphere due to the presence of particles suspended in the atmosphere, i.e. clouds and aerosols. Additionally, the amount of these substances and also the physical properties affect the radiation transfer and thus the plants ability of CO2 absorption. In the presented research, an attempt to quantify the impact of the different types of aerosols presence in the atmosphere on the amount of gross ecosystem production (GEP) in a transitional peatland in northwestern Poland was made. Three classes of cloudiness were assumed in the simulations: cloudless, medium and full cloud conditions, and an atmosphere-ecosystem model was used to assess the peatland productivity under these conditions. It was found that changes in the physical parameters of aerosols in the atmosphere can both increase and decrease the amount of CO2 uptake by peatlands by up to 8.2% and 6%, respectively. Thus, the research is extremely relevant to the global carbon balance, as peatlands are one of the largest reservoirs of organic carbon in the biosphere.

How to cite: Harenda, K., Markowicz, K., Poczta, P., Stachlewska, I., Bojanowski, J., Czernecki, B., Mac Arthur, A., Schüttemeyer, D., and Chojnicki, B.: Can the atmospheric aerosol impact on the functioning of a peatland?, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12046, https://doi.org/10.5194/egusphere-egu23-12046, 2023.

Both the quantity and quality of radiation could be altered by aerosols and cloud, and thus changing ecosystem carbon and water fluxes, as well as their coupling relationship. Although the importance of radiation quantity to ecosystems has been well studied, how radiation quality (characterized by diffuse radiation fraction, the proportion of diffuse to total radiation, K_d) affects ecosystem carbon and water cycles remains unclear due to the lack of diffuse radiation observations. In this work, taking advantage of a newly derived K_d dataset, we comprehensively explored the impact of K_d on ecosystem carbon uptake (net ecosystem exchange, NEE), carbon flux (gross primary production, GPP), water flux (evapotranspiration, ET), and water-use efficiency (GPP/ET, WUE) based on measurements at 201 global FLUXNET sites. We found that diffuse radiation is more efficient to improve NEE, GPP and ET than direct radiation at the same radiation level for all vegetation types, leading to increased ecosystem carbon uptake and water loss with K_d at the low and middle K_d levels. Furthermore, the enhancement of GPP is stronger than ET, leading to improved ecosystem WUE by diffuse radiation. By separating radiation into diffuse and direct components, we found that diffuse radiation is the most important factor for GPP, while ET is more dominated by direct radiation, indicating the complex process underlying the response of WUE to changes in K_d. This research helps improve our understandings of the responses of ecosystem carbon and water cycle to aerosol/cloud changes.

How to cite: Wang, B. and Yue, X.: Relationships between radiation quality and ecosystem carbon and water fluxes, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-17190, https://doi.org/10.5194/egusphere-egu23-17190, 2023.

For over 30 years scientists and engineers have theoretically pondered whether it was possible to mitigate global warming by atomising seawater over the ocean in a bid to favourably manipulate aerosol-cloud-radiation processes. Given the current plight of the coral ecosystem of the Great Barrier Reef, marine cloud brightening is under considereation as a regional strategy to reduce environmental stress on coral reefs during marine heatwaves. Atmospheric, biogeochemical and ecological modelling suggest that the potential exists to reduce light and thermal stress during marine heatwaves causing coral bleaching. Results from recent field campaigns, the first to empirically test the concept of marine cloud brightening, support the foundational assumptions. From its inception the research program has involved consultation and participation of indigenous traditional custodians of the reef and has proceeded within the regulatory oversight of one of the world’s most actively managed marine estates. This talk will give an overview of the Australian research program including the scientific basis which underpins it and a summary of the most recent results and future directions.

How to cite: Harrison, D.: Marine cloud brightening, could it mitigate coral bleaching on the Great Barrier Reef?, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-17057, https://doi.org/10.5194/egusphere-egu23-17057, 2023.

Solar climate intervention using Stratospheric Aerosol Injection (SAI) is a proposed method of reducing global-mean temperatures to temporarily offset some of the effects of global warming while we cut greenhouse gas emissions and remove CO₂ from the atmosphere. While the scientific, moral, and ethical questions surrounding solar geoengineering are undoubtedly complex, rigorous and unbiased information on its advantages and pitfalls will help us make better decisions in the future. Recent research has shown that some of the negative physical side-effects of SAI can be moderated by designing a better intervention strategy. I will present a comparison between a previously published ensemble of climate model simulations using the Community Earth System Model 2 (CESM2) and a new ensemble using the United Kingdom Earth System Model 1 (UKESM1). This set of simulations is based on a moderate greenhouse gas emission scenario and start injection of stratospheric aerosols in year 2035 to keep the global-mean surface temperature at 1.5 degrees above preindustrial. The injection occurs at four different latitudes and a controller algorithm is used to maintain the latitudinal gradient and inter-hemispheric difference in surface temperature, thus moderating the side effects of previous injection methods. We compare the behavior of the algorithm between the two models, as well as the climate response, with a particular focus on tropical precipitation.

How to cite: Henry, M., Haywood, J., and Jones, A.: Towards a better understanding of the physical risks and tradeoffs of solar geoengineering., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12811, https://doi.org/10.5194/egusphere-egu23-12811, 2023.

Ozone pollution and climate change are extremely likely to threaten future crop production in important agricultural regions around the World with the Mediterranean, South and East Asia and mid-West US being particularly at risk with implications for food security. Modelling methods used to assess risk of ozone pollution have developed in recent years away from empirical approaches based on dose-response relationships towards more process-based models. The DO3SE-Crop model has developed from an ozone deposition and effects model (having used flux-response relationships to assess damage) to a crop model capable of assessing the effect of ozone on photosynthesis and carbon allocation. Working within the AgMIP-ozone activity, DO3SE-Crop has been calibrated and evaluated against experimental ozone fumigation datasets for wheat cultivars from Spain (Mediterranean Europe), China and India and is able to assess the influence of climate variables on crop growth and yield as well as the effect of ozone on instantaneous photosynthesis and senescence. We find that the ozone effect on senescence is the primary determinant for yield loss in wheat. We are further developing the model to assess ozone effects on nutritional quality since we know that ozone is an important limiter of translocation of nitrogen to the grains. The establishment of DO3SE-Crop will allow assessments of the future impacts resulting form the combined effects of ozone and climate change on supply and nutritional aspects of food security. Importantly, this can include an assessment of the yield improvements between current and near- to mid-term future conditions for a range of adaptation options proposed for wheat in response to climate change including management of irrigation, growing season and development of new varieties from crop breeding with targeted physiological traits such as enhanced gas exchange and improved water use efficiency.

How to cite: Emberson, L., Bland, S., Pande, P., Cook, J., Booth, N., and Pandey, D.: Understanding the combined effects of ozone pollution and climate change on crop yield and nutritional quality, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-17374, https://doi.org/10.5194/egusphere-egu23-17374, 2023.

Air pollution is one of the most important environmental problems in China. As a major air pollutant, ozone (O₃) will endanger human health and terrestrial ecosystems. It is of great practical significance to obtain a continuous full-coverage dataset of ozone with high spatio-temporal resolution to conduct mechanism research from its causes, development, diffusion, impact and other aspects. In this study, a 3-stage machine learning model was developed through multiple data fusion, and the LightGBM method is used to obtain the hourly spatio-temporal distribution dataset of the O₃ concentration in China from 2013 to 2020, with a resolution of 0.25 °× 0.25°. We first revise the meteorological reanalysis data using ground observation and propose a data fusion algorithm to achieve the ground level distribution of ozone, which combines ground observation of pollutants, population data, revised reanalysis meteorological conditions, reanalysis of radiation, land and vegetation data, emission inventory and results of chemical transport model simulation.  In addition, due to the common phenomenon that the previous prediction models underestimate the extreme value of the pollution periods,therefore, we redefined the heavy pollution event and assimilated it into the 0.25 grid by using the synthetic minimum oversampling technique (SMOTE) method to improve the model performance during the extreme pollution periods.

Our model, with the 10-fold CV result of R² = 71% and RMSE= 25.1μg·m^-3, and our hourly O₃ concentration results are spatially and spatially continuous with a similar distribution compare to the observation, which proves the reliability of our model. With higher time resolution, various exposure response indicators can be obtained. AOT40 calculated by high-resolution hourly ozone concentration further, which is far more accurate than it when directly predicted by daily indexs modeling.

In addition, based on the distribution of AOT40, we assessed the agricultural damage and ecological damage caused by the change of surface ozone pollution during 2013-2020. Our estimation considered the planting area and phenological period of crops that the overestimation of crop RYL in the region can be avoided. The annual avrage production loss of wheat, rice and maize in China from 2013 to 2020 is 55.0, 57.4 and 23.6 Mt, respectively. Besides, The loss of gross primary productivity was also estimated. During 2013-2020, the ozone pollution in China caused an annual average loss of 2.1%, and the loss in the south was much higher than that in the north.

How to cite: Liu, L., Geng, G., Zhong, J., Liu, Y., Xiao, Q., Zhang, X., and Zhang, Q.: Near Real-Time Distribution of Ozone in China from 2013 to 2020 and Agricultural Impacts, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6562, https://doi.org/10.5194/egusphere-egu23-6562, 2023.

Tropospheric ozone (O₃) reduces plant productivity by entering leaves, generating reactive oxygen species and causing oxidative stress which in turn increases respiration, decreases photosynthesis, plant growth, biomass accumulation, and consequently reduces the land carbon sink. Tropical forests are potentially most vulnerable to future O₃ scenarios given their high productivity, generally high stomatal conductance and environmental conditions conducive to O₃ uptake (eg precursor emissions during biomass burning).

Here we present the first comprehensive set of measurements of O₃ effects on plant physiology and biomass accumulation in tropical forests. We exposed twelve tropical tree species to elevated O₃ concentrations in Open Top Chambers (OTCs) based at the James Cook University O₃ experimental facility in Cairns, Australia, from which we generate O₃ dose-response functions for each species. We test the importance of Leaf Mass per unit Area (LMA) as an indicator of O₃ sensitivity.

We use these relationships to parameterize the global land-surface model JULES, and apply the model over the pan-tropical region using contemporary near-surface O₃ concentration fields. For the first time we quantify the impact of O₃ on contemporary tropical productivity.

How to cite: Sitch, S., Cheesman, A. W., Brown, F., Artaxo, P., Cernusak, L. A., Folberth, G., Hayes, F., Hill, T., Mercado, L., and Uddling, J.: Ozone impacts on tropical forest productivity, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15707, https://doi.org/10.5194/egusphere-egu23-15707, 2023.

A major limitation in modeling global O₃ vegetation damage has long been the reliance on empirical O₃ sensitivity parameters derived from a limited number of species and applied at the level of plant functional types (PFTs), which ignore the large interspecific variations within the same PFT. Here, we present a major advance in large-scale assessments of O₃ plant injury by linking the trait leaf mass per area (LMA) and plant O₃ sensitivity in a broad and global perspective. Application of the new approach and a global LMA map in a dynamic global vegetation model reasonably represents the observed interspecific responses to O₃ with a unified sensitivity parameter for all plant species. Simulations suggest a contemporary global mean reduction of 4.8% in gross primary productivity by O₃, with a range of 1.1%-12.6% for varied PFTs. Hotspots with damages > 10% are found in agricultural areas in the eastern U.S., western Europe, eastern China, and India, accompanied by moderate to high levels of surface O₃. Furthermore, we reveal an inherent plant sensitivity spectrum for O₃ which is highly linked with plant leaf trait trade-off strategy, revealing high risks for fast-growing species with low LMA, such as crops, grasses and deciduous trees.

How to cite: Ma, Y., Yue, X., Sitch, S., Unger, N., Uddling, J., Mercado, L., Gong, C., and Feng, Z.: Trait-based ozone plant sensitivity to assess global vegetation damage risks, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3823, https://doi.org/10.5194/egusphere-egu23-3823, 2023.

The impact of elevated ozone concentration on crop yield, like wheat, plays a significant role yet is poorly studied in Asian countries like China and India. We have developed, calibrated, and tested a mechanistic photosynthetic-stomatal conductance canopy model (DO3SE-crop) with an integrated ozone module (Anet-gsto+O3) for the region of Xiaoji, China. The key component of the model development involves phenology, leaf scale processes, leaf-to-canopy upscaling, and carbon allocation. The calibrated model for Xiaoji simulated the difference in yield losses for ambient and elevated ozone treatments for the years 2008 for four cultivars (Y2, Y15, Y16, Y19), ranging from 21-24%, compared with the observed dataset, giving R2 of 0.74 and RMSE of 0.003. The model was tested for 2009 and gave yield losses of 24-27%, with R2 of 0.60 and RMSE of 0.12, against the observed dataset. Further, our findings suggest that the difference in yield loss is due to the early decline in carbon assimilation in elevated treatment.This happens because of the early senescence in elevated treatment, which brings leaf senescence forward by 9-11 days.

How to cite: Pande, P., Bland, S., Booth, N., Cook, J., and Emberson, L.: The development and application of a mechanistic photosynthetic-stomatal conductance canopy model (DO3SE-crop), EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10119, https://doi.org/10.5194/egusphere-egu23-10119, 2023.