Increase In Atmospheric CO2 Concentration Research Articles

Daytime warming during early grain filling offsets the CO2 fertilization effect in rice

Increasing concentrations of atmospheric CO2 are projected to have positive effects on crop photosynthesis and yield (CO2 fertilization effect, CFE). High-temperature events, such as heatwaves, during sensitive periods can have significant negative impacts on crop yield and quality; however, the combined effects of elevated CO2 (EC) and short-period elevated temperature (ET) have not been determined in the open field. Here, we show a strong negative interaction between EC and ET obtained from a temperature-free-air controlled enhancement treatment embedded in a season-long free-air CO2 enrichment (FACE) experiment on a japonica rice cultivar, Koshihikari, over three seasons at the Tsukuba FACE facility in Ibaraki, Japan. CFE was 15% at ambient temperature, but it was reduced to 3% by ET, where canopy surface temperature (Tc) was elevated by ∼1.6 °C for 20 d after flowering. Reductions in CFE mainly arose from poor grain setting at Tc above ∼30 °C. High Tc also increased the percentage of chalky grains and substantially decreased the grain appearance quality, although the threshold temperature varied between the seasons. Simultaneous increases in atmospheric CO2 concentration and air temperature are expected to increase daytime canopy temperatures more than air warming alone, thereby affecting grain yield and quality. Crop models without these processes are likely to underestimate the negative impacts of climate change on crop yield and quality. The development of adaptation measures against heat stress, particularly during reproductive and grain-filling periods, needs to be enhanced and accelerated.

Effect of gradual increase of atmospheric CO2 concentration on nitrification potential and communities of ammonia oxidizers in paddy fields

Currently, the influence of elevated atmospheric CO2 concentration (eCO2) on ammonia oxidation to nitrite, the rate-limiting step of nitrification in paddy soil, is poorly known. Previous studies that simulate the effect of eCO2 on nitrification are primarily based on an abrupt increase of atmospheric CO2 concentration. However, paddy ecosystems are experiencing a gradual increase of CO2 concentration. To better understand how the nitrification potential, abundance and communities of ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB) respond to eCO2 in paddy ecosystems, a field experiment was conducted using the following two treatments: a gradual increase of CO2 (EC, increase of 40 ppm per year until 200 ppm above ambient) and ambient CO2 (CK). The results demonstrated that the EC treatment significantly (P < 0.05) stimulated the soil potential nitrification rate (PNR) at the jointing and milky stages, which increased by 127.83% and 27.35%, respectively, compared with CK. Furthermore, the EC treatment significantly (P < 0.05) stimulated the AOA and AOB abundance by 56.60% and 133.84%, respectively, at the jointing stage. Correlation analysis showed that the PNR correlated well with the abundance of AOB (R2 = 0.7389, P < 0.001). In addition, the EC treatment significantly (P < 0.05) altered the community structure of AOB, while it had little effect on that of AOA. A significant difference in the proportion of Nitrosospira was observed between CO2 treatments. In conclusion, the gradual increase of CO2 positively influenced the PNR and abundance of ammonia oxidizers, and AOB could be more important than AOA in nitrification under eCO2.

CO2 capture using in-situ polymerized amines into pore-expanded-SBA-15: Performance evaluation, kinetics, and adsorption isotherms

Over the last decades, carbon dioxide capture has attracted lots of attention and different solution have been proposed, yet the global CO2 concentration is still increasing along with its environmental impacts. Covalently tethered amines were in-situ polymerized into mesoporous silica support, namely PE-SBA-15, for the reversible temperature swing CO2 adsorption. The in-situ polymerization approach shows high loadings of amines in comparison to the grafting technique which was confirmed via thermal decomposition and CHN elemental analysis. The covalent tethering of amines, evidenced by the characteristic absorption peaks via FTIR, resulted in good thermal stability of the sorbent and constant CO2 uptake during multicycle operation. Porosimetry analysis, pore volume and BET surface area, showed a noticeable decrease upon the functionalization of support indicating that most of the pores of the support are occupied by the amines. CO2 capture of the sorbent at different concentrations and temperatures, from 400 ppm for the direct air CO2 capture to 15 % CO2 for coal-powered plants showed good performance. A reduction in CO2 uptake was noticed upon the decrease in adsorption temperature with an optimum temperature of 25 °C. Adsorption kinetics were found to be best represented by a pseudo-second order model with significant adsorption rates. Dry adsorption isotherms of CO2 and N2 were studied at different temperatures and the CO2 isotherms were found to follow Langmuir dual site (LDS) model with a very high selectivity towards CO2. This study shows that in-situ polymerization is a key route for mitigating the continuous increase in atmospheric CO2 concentration.

The buffering of a riverine carbonate system under the input of acid mine drainage: Example from a small karst watershed, southwest China

In a karstic area affected by acid mine drainage (AMD), hydrochemical conditions, such as temperature, salinity, alkalinity, DIC, dissolved oxygen, and nutrients, may affect the buffering capacity of carbonate systems in freshwater systems. The resulting pH fluctuation is larger than that of a marine system. Therefore, this study focuses on the buffering of a riverine carbonate system under the input of AMD and discusses the variations in a series of buffering factors, including the Revelle factor, γDIC, γAlk βDIC, βAlk, ωDIC, and ωAlk. The results revealed that the Revelle factor could reflect the buffering process effectively; in addition, the maximum value of the Revelle factor appeared at pH = 8.5. The data points for pH greater than this value indicated that the Huatan River had the ability to absorb atmospheric CO2 in spring. Conversely, the data for pH less than this value reflected the buffering of H+ during CO2 degassing in summer and autumn. In winter, the data were around the maximum value, indicating the weakest buffering capacity. As a result, the dynamics of the carbonate system caused the most sensitive response to pH. In addition, the maximum Revelle factor value did not always indicate the carbonate system had reached equilibrium; the presence of strong CO2 degassing was still a possibility. Under acidic conditions, as CO2(aq) increased, the absolute values of γDIC, βDIC, ωDIC, and γAlk increased correspondingly, indicating the enhanced buffering capacity of H+ during CO2 degassing. Under the four Representative Concentration Pathways scenarios (RCPs) included in the IPCC’s fifth assessment report, the degassing rate of the Huatan River would decrease by 5%, 15%, 26%, or 48%, depending on the scenario. Even though the Huatan River revealed CO2 degassing characteristics in winter and spring under current conditions, it will eventually become a sink for atmospheric CO2 as atmospheric CO2 concentration increases. In this light, the carbon sink effect in karst areas will become increasingly important.

Expanding the theory for reducing the CO2 disaster—Hypotheses from partial least-squares regression and machine learning

The rapid increase in atmospheric CO2 concentration has caused a climate disaster (CO2 disaster). This study expands the theory for reducing this disaster by analyzing the possibility of reinforcing soil CO2 uptake (Fx) in arid regions using partial least-squares regression (PLSR) and machine learning models such as artificial neural networks. The results of this study demonstrated that groundwater level is a leading contributor to the regulation of the dynamics of the main drivers of Fx–air temperature at 10 cm above the soil surface, the soil volumetric water content at 0–5 cm (R2=0.76, RMSE=0.435), and soil pH (R2=0.978, RMSE=0.028) in arid regions. Fx can be reinforced through groundwater source management which influences the groundwater level (R2=0.692, RMSE=0.03). This study also presents and discusses some basic hypotheses and evidence for quantitively reinforcing Fx.

Effect of gradual increase of atmospheric CO2 concentration on nitrate-dependent anaerobic methane oxidation in paddy soils

Nitrate-dependent anaerobic oxidation of methane (AOM) is a new pathway to reduce methane emissions from paddy ecosystems. The elevated atmospheric CO2 concentration can affect methane emissions from paddy ecosystems, but its impact on the process of nitrate-dependent AOM is poorly known. Based on the automatic CO2 control platform with open top chambers and the 13CH4 stable isotope experiments, the responses of the activity of nitrate-dependent AOM, abundance and community composition of Candidatus Methanoperedens nitroreducens (M. nitroreducens)-like archaea to the gradual increase of CO2 concentration were investigated in paddy fields. We set up two CO2 concentration treatments, including an ambient CO2 and a gradual increase of CO2(increase of 40 μL·L-1 per year above ambient CO2 concentration until 160 μL·L-1). The results showed the nitrate-dependent AOM rate of 0.7-11.3 nmol CO2·g-1·d-1 in the studied paddy fields, and quantitative PCR showed the abundance of M. nitroreducens-like archaeal mcrA genes of 2.2×106-8.5×106 copies·g-1. Compared to the ambient CO2 treatment, the slow elevated CO2 treatment enhanced the nitrate-dependent AOM rate and stimulated the abundance of M. nitroreducens-like archaea, particularly in 5-10 cm soil layer. The gradual increased CO2 concentration treatment did not change the community composition of M. nitroreducens-like archaea, but significantly decreased their diversity. The soil organic carbon content was an important factor influencing the nitrate-dependent AOM process. Overall, our results showed that the gradual increase of CO2 concentration could promote the nitrate-dependent AOM, suggesting its positive role in mitigating methane emissions from paddy ecosystems under future climate change.

Spatial-Temporal Changes of Carbon Source/Sink in Terrestrial Vegetation Ecosystem and Response to Meteorological Factors in Yangtze River Delta Region (China)

As an important part and the core link of a terrestrial ecosystem, terrestrial vegetation is the main means for human to regulate climate and mitigate the increase in atmospheric CO2 concentration. The Yangtze River Delta (YRD) region is an urban agglomeration with the strongest comprehensive strength among developing countries (China). In the context of global climate change, a rapid, comprehensive, and detailed understanding of the spatio-temporal characteristics and variation tendency of the net ecosystem productivity (NEP) of vegetation and its response to climate during the rapid development of the YRD region is important for protecting ecological land, strengthening land management, and optimizing urban planning. The monthly mean temperature and rainfall data from 63 meteorological stations, the MODIS net primary productivity product, and a land cover product in the YRD region were used to estimate the NEP from 2000 to 2019 based on the soil respiration model, and the correlation between NEP and meteorological factors (such as temperature and rainfall) was analyzed. The results showed that: (1) From 2000 to 2019, the carbon sink area was much larger than the carbon source area in terrestrial vegetation in the Yangtze River Delta, the mean NEP of the vegetation ecosystem in the past 20 years was 253.2 g C·m−2·a−1, and the spatial distribution presented a trend that was higher in the south and lower in the north, higher in the east and lower in the west, and that gradually increased from northwest to southeast; moreover, the NEP of mountain areas was generally higher than that of river courses and urban surroundings. The interannual fluctuation of NEP was small, but presented a slightly increasing trend, and the interannual variation of NEP was significantly correlated with the maximum NEP in this region. (2) The carbon sink capacity of different vegetation cover types was (from strong to weak): forestlands &gt; grasslands &gt; wetlands ≈ croplands. (3) The area with the NEP change rate (θslope) &gt; 0 accounted for 69.0%; however, there was certain spatial difference, the proportions of the areas with θslope &lt; 0 were (from large to small) 14.50% (Zhejiang Province, China), 9.10% (Anhui Province, China), 6.65% (Jiangsu Province, China), and 0.79% (Shanghai, China). In terms of the individual changes of these provinces and municipalities, Shanghai &gt; Zhejiang Province &gt; Jiangsu Province ≈ Anhui Province. (4) There was a correlation between NEP and the annual mean temperature and annual precipitation in some regions.

Facet-Dependent Selectivity of Cuprous Oxide/Silver Tandem Catalysts for Promoting C2H4 Production from Electrochemical CO2 Reduction

The over-exploitation of fossil fuels and the consequent increase of atmospheric CO2 concentration have aroused people's attention to energy and environmental issues.(1) In terms of reducing CO2 content, the electrocatalytic CO2 reduction reaction (CO2RR) can effectively solidify CO2 and convert it into high value-added chemicals. There are many CO2RR reduction products, including CO, HCOOH, C2H5OH, CH4,C2H4, etc.(2) However, in the CO2RR process, the hydrogen evolution reaction (HER) in the water phase has a lower reduction potential, making the CO2RR products less selective, which has become the most important problem restricting its practical application. Therefore, improving the selectivity and activity of CO2RR products has important research significance and practical application value.In this work, a series of Cu2O/Ag nanocrystals (NCs) with different crystal faces were prepared by hydrothermal method. Specifically, cubic Cu2O (c-Cu2O) enclosed with {100} facets, rhombic dodecahedral Cu2O (d-Cu2O) enclosed with {110} facets, and octahedral Cu2O (o-Cu2O) enclosed with {111} facets, are mixed with Ag nanospheres to form c-Cu2O/Ag, d-Cu2O/Ag, and o-Cu2O/Ag bimetallic tandem catalysts. The catalysts can improve the high activity and selectivity of CO2RR to produce C2H4 product by adjusting different crystal faces. We can find from Figure 1 that o-Cu2O/Ag tandem catalyst exhibits an impressive Faradaic efficiency (66.8%) and partial current density (17.8 mA cm-2) for C2H4 product at -1.2 VRHE. This result provides a new strategy for improving the selectivity of CO2RR to produce C2+ products by adjusting the crystal facet engineering. Figure 1. (a) SEM images of o-Cu2O/Ag, (b) LSV curves of three Cu2O/Ag catalysts in Ar and CO2-saturated 0.5 M KHCO3 solutions, (c) Partial current density of C2H4 formation on the three Cu2O/Ag catalysts at -1.2 V, (d) Faradaic efficiencies of C2H4 on the three Cu2O/Ag NCs. Reference [1] P. De Luna, C. Hahn, D. Higgins, S. A. Jaffer, T. F. Jaramillo and E. H. Sargent, Science, 364 (2019).[2]Y. Zheng, A. Vasileff, X. Zhou, Y. Jiao, M. Jaroniec and S. Z. Qiao, J Am Chem Soc, 141, 7646 (2019). Figure 1

Preference of carbon absorption determines the competitive ability of algae along atmospheric CO2 concentration.

Although many studies have focused on the effects of elevated atmospheric CO2 on algal growth, few of them have demonstrated how CO2 interacts with carbon absorption capacity to determine the algal competition at the population level. We conducted a pairwise competition experiment of Phormidium sp., Scenedesmus quadricauda, Chlorella vulgaris and Synedra ulna. The results showed that when the CO2 concentration increased from 400 to 760 ppm, the competitiveness of S. quadricauda increased, the competitiveness of Phormidium sp. and C. vulgaris decreased, and the competitiveness of S. ulna was always the lowest. We constructed a model to explore whether interspecific differences in affinity and flux rate for CO2 and HCO3 − could explain changes in competitiveness between algae species along the gradient of atmospheric CO2 concentration. Affinity and flux rates are the capture capacity and transport capacity of substrate respectively, and are inversely proportional to each other. The simulation results showed that, when the atmospheric CO2 concentration was low, species with high affinity for both CO2 and HCO3 − (HCHH) had the highest competitiveness, followed by the species with high affinity for CO2 and low affinity for HCO3 − (HCLH), the species with low affinity for CO2 and high affinity for HCO3 − (LCHH) and the species with low affinity for both CO2 and HCO3 − (LCLH); when the CO2 concentration was high, the species were ranked according to the competitive ability: LCHH > LCLH > HCHH > HCLH. Thus, low resource concentration is beneficial to the growth and reproduction of algae with high affinity. With the increase in atmospheric CO2 concentration, the competitive advantage changed from HCHH species to LCHH species. These results indicate the important species types contributing to water bloom under the background of increasing global atmospheric CO2, highlighting the importance of carbon absorption characteristics in understanding, predicting and regulating population dynamics and community composition of algae.

Diagnosing Instantaneous Forcing and Feedbacks of Downwelling Longwave Radiation at the Surface: A Simple Methodology and Its Application to CMIP5 Models

Abstract Climate models predict large increases in downwelling longwave radiation (DLR) at Earth’s surface as atmospheric CO2 concentrations increase. Here we introduce a novel methodology that allows these increases to be decomposed into direct radiative forcing due to enhanced CO2 and feedbacks due to subsequent changes in atmospheric properties. For the first time, we develop explicit analytic expressions for the radiative forcing and feedbacks, which are calculable from time-mean fields of near-surface air temperature, specific humidity, pressure, total column water vapor, and total cloud fraction. Our methodology captures 90%–98% of the variance in changes in clear-sky and all-sky DLR in five CMIP5 models, with a typical error of less than 10%. The longwave feedbacks are decomposed into contributions from changes in temperature, specific humidity, water vapor height scale, and cloud fraction. We show that changes in specific humidity and height scale are closely linked to changes in near-surface air temperature and therefore, in the global average, that 90% of the increase in all-sky DLR may be attributed to a feedback from increasing near-surface air temperature. Mean-state clouds play a major role in changes in DLR by masking the clear-sky longwave and enhancing the temperature feedback via increased blackbody radiation. The impact of changes in cloud cover (the cloud feedback) on the DLR is small (∼2%) in the global average, but significant in particular geographical regions.

Climate Change Affects Reproductive Phenology in Lianas of Australia’s Wet Tropics

Lianas are increasing in abundance in many tropical forests. This increase can alter forest structure and decrease both carbon storage and tree diversityviaantagonistic relationships between lianas and their host trees. Climate change is postulated as an underlying driver of increasing liana abundances,viaincreases in dry-season length, forest-disturbance events, and atmospheric CO2concentrations; all factors thought to favour lianas. However, the impact of climate change on liana reproductive phenology, an underlying determinant of liana abundance, has been little studied, particularly outside of Neotropical forests. Over a 15-year period (2000–2014), we examined the phenological patterns of a liana community in intact rainforests of the Wet Tropics bioregion of Australia; a World Heritage Area and hotspot of floral diversity. Specifically, we assessed (1) flowering and fruiting patterns of liana species; (2) potential climate drivers of flowering and fruiting activity; and (3) the influence of El Niño-related climatic disturbances on liana phenology. We found that flowering and fruiting of the studied liana species increased over time. Liana reproduction, moreover, rose in apparent response to higher temperatures and reduced rainfall. Finally, we found flowering and fruiting of the liana species increased following El Niño events. These results suggest that liana reproduction and abundance are likely to increase under predicted future climate regimes, with potentially important impacts on the survival, growth, and reproduction of resident trees and thus the overall health of Australian tropical rainforests.

Increasing water-use efficiency mediates effects of atmospheric carbon, sulfur, and nitrogen on growth variability of central European conifers

Climate controls forest biomass production through direct effects on cambial activity and indirectly through interactions with CO2, air pollution, and nutrient availability. The atmospheric concentration of CO2, sulfur and nitrogen deposition can also exert a significant indirect control on wood formation since these factors influence the stomatal regulation of transpiration and carbon uptake, that is, intrinsic water use efficiency (iWUE). Here we provide 120-year long tree-ring time series of iWUE, stem growth, climatic and combined sulfur and nitrogen (SN) deposition trends for two common tree species, Pinus sylvestris (PISY) and Picea abies (PCAB), at their lower and upper distribution margins in Central Europe. The main goals were to explain iWUE trends using theoretical scenarios including climatic and SN deposition data, and to assess the contribution of climate and iWUE to the observed growth trends. Our results showed that after a notable increase in iWUE between the 1950s and 1980s, this positive trend subsequently slowed down. The substantial rise of iWUE since the 1950s resulted from a combination of an accelerated increase in atmospheric CO2 concentrations (Ca) and a stable level of leaf intercellular CO2 (Ci). The offset of observed iWUE values above the trajectory of a constant Ci/Ca scenario was explained by trends in SN deposition (all sites) together with the variation of drought conditions (low-elevation sites only). Increasing iWUE over the 20th and 21st centuries improved tree growth at low-elevation drought-sensitive sites. In contrast, at high-elevation PCAB sites, growth was mainly stimulated by recent warming. We propose that SN pollution should be considered in order to explain the steep increase in iWUE of conifers in the 20th century throughout Central Europe and other regions with a significant SN deposition history.

Photosynthesis, growth, and distribution of plants in lowland streams—A synthesis and new data analyses of 40 years research

Abstract This paper synthesises insights and offers new quantitative analyses of data gathered during 40 years of stream research by Danish researchers and international associates. Lowland Danish streams mostly drain fertile cropland and contain high nutrient concentrations saturating maximum yield and growth rate of plants. Concentrations of carbon dioxide (CO2) are variable, although usually high, supporting a range of wetland and permanently submerged species. All terrestrial and most amphibious species are obligate CO2 users, while the majority of permanently submerged species can supplement their inorganic carbon demand with bicarbonate. In lake outlets, the average CO2 concentration was close to air saturation during summer, whereas sites with no lake influence were 9‐fold supersaturated. The 20% increase of atmospheric CO2 concentrations over the past 40 years has marginal influence on CO2 concentrations in the streams. In lake outlets with low CO2 concentrations, calculations on 33 stream species showed essentially no underwater photosynthesis by temporarily submerged terrestrial species, low rates by amphibious species, and high rates by permanently submerged bicarbonate users. Underwater photosynthetic rates increased at sites with high CO2 concentrations (no lake influence): they were lowest for terrestrial wetland species (mean 1.8 mg O2 g dry weight−1 hr−1), followed by homophyllous (3.0) and heterophyllous amphibious species (5.6), and highest among permanently submerged species (15.0). Terrestrial and amphibious species grew very slowly when CO2 levels were low, but rapidly in CO2 rich water, or when in contact with air above the water's surface. Decreasing CO2 concentrations from upstream to downstream caused lower photosynthesis rates of amphibious species, while photosynthesis by bicarbonate users was consistently high. The relative abundance of terrestrial and amphibious species decreased significantly as CO2 resources decline from upstream to downstream, while the abundance of permanently submerged species increased as streams progressed. However, plant abundance as a function of CO2 concentrations did not differ markedly among the plant groups. We conclude that photosynthesis and growth of species of different plant types under controlled experimental conditions resembling high in situ nutrient availability are closely related to inorganic carbon supplies, while their representation in plant assemblages is influenced by the spatially and temporally highly diverse ecological conditions from upstream to downstream in the mostly CO2‐rich lowland streams. Submerged terrestrial and amphibious species restricted to CO2 use for photosynthesis can partly escape the slow gas diffusion under water by growing in very CO2‐rich streams and having apical leaves in contact with air. Thus, strong restrictions on their growth and existence should be identified at sites where CO2 concentrations are consistently low and no air contact is possible, while co‐limitation by nutrients is likely to be marginal. Generally, rising atmospheric CO2 is irrelevant to photosynthesis of permanently submerged plants because of their ability to use bicarbonate and the high CO2 supersaturation in most stream sites. In contrast, photosynthesis and growth of amphibious and terrestrial plants under water are highly dependent on CO2 concentrations varying from close to air saturation in lake outlets to supersaturation in headwaters.

Enhanced Carbonate Counter Pump and upwelling strengths in the Indian sector of the Southern Ocean during MIS 11

While numerous studies have highlighted the central role of Southern Ocean (SO) dynamics in modulating rapid increases in atmospheric CO2 concentrations during deglaciations, fewer studies have yet focused on the impact of the Biological Carbon Pump - and more specifically the Carbonate Counter Pump (CCP) - in contributing to increase the CO2 concentration in oceanic surface waters and thus, in the atmosphere. Here, we present micropaleontological (coccolith, planktonic foraminifera) and geochemical (CaCO3, CaXRF, δ13CN. pachyderma) constraints from sediment core MD04-2718 retrieved in the Polar Front Zone of the Indian Ocean covering the time interval spanning Marine Isotope Stage (MIS) 12 to MIS 10 (440,000–360,000 years). We compare our results with published records from the SO to reconstruct past changes in CCP and upwelling dynamics and understand their leverage on the ocean-atmosphere portioning of CO2. We demonstrate that the sharp increase in atmospheric pCO2 during Termination V was likely associated with enhanced deep-water ventilation in the SO, that promoted the release of previously sequestered CO2 to the ocean surface as the westerly wind belt and the frontal system migrated southwards. Enhanced CCP is observed later, during MIS 11, and is likely the consequence of higher sea surface temperature and higher nutrient availability due to the reinvigoration of SO upwelling leading to increased coccolith (and to a lesser degree, planktonic foraminifera) production and export. The low eccentricity signal recorded during MIS 11 might have additionally strengthened the CCP, exerting a specific control on Gephyrocapsa morphotypes. In addition to the strong global biological productivity and higher carbon storage on land, these synergistic mechanisms may have permitted to shape the distinctive 30 ka-long pCO2 plateau characteristic of MIS 11.

Temporal and Spatial Variation of Wetland CH4 Emissions from the Qinghai–Tibet Plateau under Future Climate Change Scenarios

Wetlands are an important natural source of methane (CH4), so it is important to quantify how their emissions may vary under future climate change conditions. The Qinghai–Tibet Plateau contains more than a third of China’s wetlands. Here, we simulated temporal and spatial variation in CH4 emissions from natural wetlands on the Qinghai–Tibet Plateau from 2008 to 2100 under Representative Concentration Pathways (RCP) 2.6, 4.5, and 8.5. Based on the simulation results of the TRIPLEX-GHG model forced with data from 24 CMIP5 models of global climate, we predict that, assuming no change in wetland distribution on the Plateau, CH4 emissions from natural wetlands will increase by 35%, 98% and 267%, respectively, under RCP 2.6, 4.5 and 8.5. The predicted increase in atmospheric CO2 concentration will contribute 10–28% to the increased CH4 emissions from wetlands on the Plateau by 2100. Emissions are predicted to be majorly in the range of 0 to 30.5 g C m−2·a−1 across the Plateau and higher from wetlands in the southern region of the Plateau than from wetlands in central or northern regions. Under RCP8.5, the methane emissions of natural wetlands on the Qinghai–Tibet Plateau increased much more significantly than that under RCP2.6 and RCP4.5.

Projected global warming-induced terrestrial ecosystem carbon across China under SSP scenarios

Terrestrial ecosystem carbon sequestration is one of the most economically feasible and important ways to mitigate the increase of atmospheric CO2 concentration. China's terrestrial ecosystems have a huge carbon sequestration potential. Therefore, the study on the carbon sequestration potential of vegetation ecosystems is related to the smooth implementation of China's carbon neutrality strategy in 2060. Based on the CMIP6 shared socioeconomic pathways (SSPs) scenarios, changes in the vegetation aboveground biomass carbon (ABC) were estimated using the Lund–Potsdam–Jena Dynamic Global Vegetation Model (LPJ) model (1981–2060) for China. Subsequently, the vegetation ABC dynamics were analyzed under three future scenarios based on the traditional Multi-Model Ensemble Mean (MME) method for different eco-regions in China. We found that the vegetation ABC density was 32.38 Mg/ha in China with an increasing trend of 53.99% from 1981 to 2014. The vegetation ABC density was higher in sub-regions I, II, V, and VI. Due to the main forest carbon sinks was appeared in Southwest, Northeast and Southeast of China. However, the water conditions are poor in sub-regions III, VII, and VIII, and mostly covered by desert and steppe vegetation where the productivity level is low. Under SSP1-2.6 and SSP2-4.5 scenarios, the vegetation ABC would show a decreasing trend from 2015 to 2040 with a reduction rate of 4.34% and 4.60%, but exhibit an increasing trend from 2041 to 2060 with a growth rate of 1.46% and 0.97%. While the vegetation ABC would show a decreasing trend during 2015 to 2060 with a reduction rate of 14.78% under SSP5-8.5 scenarios. Additionally, temperature and precipitation are main factors influencing the vegetation ABC. In the future scenario, due to higher temperatures resulted in the decrease of vegetation ABC in the cold temperate humid and temperate humid/sub-humid regions. However, in the northwestern arid region and Qinghai-Tibet Plateau region may have been due to relatively low temperatures in the region, warming may address this limitation and lead to a general increase in ABC.

Alumina‐Supported Alpha‐Iron(III) Oxyhydroxide as a Recyclable Solid Catalyst for CO2 Photoreduction under Visible Light

AbstractPhotocatalytic conversion of CO2 into transportable fuels such as formic acid (HCOOH) under sunlight is an attractive solution to the shortage of energy and carbon resources as well as to the increase in Earth's atmospheric CO2 concentration. The use of abundant elements as the components of a photocatalytic CO2 reduction system is important, and a solid catalyst that is active, recyclable, nontoxic, and inexpensive is strongly demanded. Here, we show that a widespread soil mineral, alpha‐iron(III) oxyhydroxide (α‐FeOOH; goethite), loaded onto an Al2O3 support, functions as a recyclable catalyst for a photocatalytic CO2 reduction system under visible light (λ&gt;400 nm) in the presence of a RuII photosensitizer and an electron donor. This system gave HCOOH as the main product with 80–90 % selectivity and an apparent quantum yield of 4.3 % at 460 nm, as confirmed by isotope tracer experiments with 13CO2. The present work shows that the use of a proper support material is another method of catalyst activation toward the selective reduction of CO2.

Alumina-Supported Alpha-Iron(III) Oxyhydroxide as a Recyclable Solid Catalyst for CO2 Photoreduction under Visible Light.

Photocatalytic conversion of CO2 into transportable fuels such as formic acid (HCOOH) under sunlight is an attractive solution to the shortage of energy and carbon resources as well as to the increase in Earth's atmospheric CO2 concentration. The use of abundant elements as the components of a photocatalytic CO2 reduction system is important, and a solid catalyst that is active, recyclable, nontoxic, and inexpensive is strongly demanded. Here, we show that a widespread soil mineral, alpha‐iron(III) oxyhydroxide (α‐FeOOH; goethite), loaded onto an Al2O3 support, functions as a recyclable catalyst for a photocatalytic CO2 reduction system under visible light (λ>400 nm) in the presence of a RuII photosensitizer and an electron donor. This system gave HCOOH as the main product with 80–90 % selectivity and an apparent quantum yield of 4.3 % at 460 nm, as confirmed by isotope tracer experiments with 13CO2. The present work shows that the use of a proper support material is another method of catalyst activation toward the selective reduction of CO2.

Changing Sensitivity of Diverse Tropical Biomes to Precipitation Consistent with the Expected Carbon Dioxide Fertilization Effect

Abstract Global environmental changes have implications for the terrestrial ecosystem functioning, but disentangling individual effects remains elusive. The impact of vegetation responses to increasing atmospheric CO2 concentrations is particularly poorly understood. As the atmospheric CO2 concentration increases, the CO2 acts as a fertilizer for plant growth. An increase in atmospheric CO2 reduces the amount of water needed to produce an equivalent amount of biomass due to closing or a narrowing of the stomata that reduces the amount of water that is transpired by plants. To study the impacts of climate change and CO2 fertilization on plant growth, we analyzed the growing season sensitivity of plant growth to climatic forcing from alpine to semi-desert eco-climatic zones of Ethiopia for various plant functional types over the period of 1982–2011. Growing season 3rd generation Normalized Difference Vegetation Index of Global Inventory Modeling and Mapping Studies (NDVI) was used as a proxy of plant growth, while mean growing season precipitation (prec), temperature (temp), and solar radiation (sr) as the climate forcing. The sensitivities of plant growth are calculated as a partial correlation, and a derivative of NDVI with respect to prec, temp and sr for earliest and recent 15-year periods of the satellite records, and using a moving window of 15-year. Our results show increasing trends of plant growth that are not explained by any climate variables. We also find that an equivalent increase in prec leads to a larger increase in NDVI since the 1980s. This result implies a given amount of prec has sustained greater amounts of plant foliage materials over time due to decreasing transpiration with increasing CO2 concentration as expected from the CO2 fertilization effect on water use efficiency and plant growth. Increasing trends of growth in shallow-rooted vegetation tend to be associated with woody vegetation encroachment.

Effects of CO2 adsorption on molecular structure characteristics of coal: Implications for CO2 geological sequestration

With a series of global problems such as greenhouse effect caused by the gradual increase of atmospheric CO2 concentration, CO2 geological storage has become one of the effective measures. To study the influence of the interaction between CO2 and coal on the molecular structure characteristics of coal, three coals of different ranks were selected for CO2 adsorption and were subjected to X-ray diffraction, Raman spectroscopy and Fourier transform infrared spectroscopy experiments. The results indicate that with increasing of CO2 pressure: 1) Due to the solubility differences of different minerals, the contents of quartz in the coal samples gradually increases, while the contents of calcite, pyrite and kaolinite decreases; 2) The average number of the aromatic layers gradually decreased indicates that some aromatic layers are destroyed and order degree is lowered in the coal microcrystalline structure, resulting in a gradual increase of the inter-layer spacing between aromatic layers, the stacking of aromatic layers; 3) The concentration of aromatic rings gradually decreases leading to the intermolecular structural defects are obvious and the gradual evolution of the microcrystalline structure into the more disordered crystal structure; 4) The hydroxyl groups are predominated by oxidation reactions in long-flame coal and lean coal, while they are mainly governed by swelling in anthracite; 5) The ratio between aliphatic and total hydrogen atoms (Hal/H), aliphatic structure (I1) and ‘A’ factor values of the anthracite reveal a slight increase, while the aromaticity 2 (AR2) and degree of condensation 2 (DOC2) values display a decreasing trend. These values of long-flame coal and lean coal only slightly change. The influence of CO2 intrusion on coal properties due to the changes of molecular structure and CO2 trapping mechanisms are discussed. Our research contributes to understand deeply the geological sequestration of CO2 in coal seams and higher CO2 injection pressures should be adopted.