Increase In CO2 Concentration Research Articles

Multi-model effective radiative forcing of the 2020 sulfur cap for shipping

Abstract. New regulations of sulfur emissions from shipping were introduced in 2020, reducing emissions of SO2 from international shipping by ∼ 80 %. As SO2 is an aerosol precursor, this drop in emissions over the ocean will weaken the total aerosol effective radiative forcing (ERF) that has historically masked an uncertain fraction of the warming due to the increased concentration of greenhouse gases in the atmosphere. Here, we use four global climate models and a chemical transport model to calculate the ERF resulting from an 80 % reduction in SO2 emissions from international shipping relative to 2019 emission estimates. The individual model means range from 0.06 to 0.09 W m−2, corresponding to the ERF resulting from the increase in CO2 concentration over the last 2 to 3 years. The full uncertainty in the ERF due to the new regulation is not quantified but will very likely be high considering the contribution of uncertainties in shipping SO2 emissions, the sulfur cycle, the modelling of cloud adjustments and the impact of interannual variability on the method for calculating radiative forcing.

High-pressure CO2 adsorption on MCM-41: Efficiency of microwave-assisted synthesis

The rapid increase in atmospheric CO2 concentrations, driven by human activities, has become a critical factor in global climate change, posing severe risks to sustainable development. Addressing this challenge necessitates substantial CO2 removal, which demands innovative and efficient technologies. Carbon dioxide adsorption on porous materials is a promising strategy to mitigate this issue. This study investigates the synthesis of ordered mesoporous silica MCM-41 by microwave irradiation, a technique that offers significant advantages over conventional hydrothermal methods. By optimizing the synthesis conditions, we produced MCM-41 silica with superior structural properties in just 30 min. Characterization techniques, including X-ray diffraction, FTIR, N2 adsorption/desorption isotherms, and transmission electron microscopy, confirmed the formation of well-defined pores and hexagonal channels. Notably, the synthesized MCM-41 exhibited a high CO2 adsorption capacity of 12.78 mmol g−1 at 25 °C and 50 bar, outperforming silicas produced via conventional methods and comparable to amine-modified silicas. These results highlight the potential of microwave-assisted synthesis to improve CO2 capture efficiency, offering a promising approach for future carbon capture and storage applications.

Impact of modified atmospheres enriched with carbon dioxide on the survival, biological, and physiological aspects of Aleuroglyphus ovatus (Troupeau, 1878)

Aleuroglyphus ovatus (Troupeau, 1878), a prevalent mite within stored products, inflicts substantial economic and health risks. The use of fumigants and grain protectants as methods of stored grain pest management had resulted in resistance and environmental concerns, necessitating alternative strategies. This study explored the toxicity of modified atmospheres composed of CO2, as an environmentally friendly, residue-free, and viable disinfestation alternative. The mortality of A. ovatus increased significantly with an increase in either CO2 concentration or exposure duration. Complete adult mortality was recorded after 72 h of treatment with 95% CO2. The calculated LT50 value was 30.52 h under 35% CO2, and it decreased to 11.78 h under 95% CO2. Additionally, CO2 exposure led to changes in the activity of antioxidant and detoxification enzymes in A. ovatus, indicating its physiological adaptation mechanisms under varying CO2 concentrations and the impact of these changes on development and reproductive capacity. Enzymatic assays revealed a concentration-dependent decrease in superoxide dismutase activity and an increase in catalase activity. The detoxification enzymes, glutathione S-transferase, and carboxylesterase demonstrated adaptive upregulation. The development of A. ovatus was delayed, and its reproductive capacity was reduced under CO2 stress. Population parameters, including the net reproductive rate (R0) and intrinsic rate of increase (rm) were all significantly reduced under CO2 stress, with 35% CO2 showing the severer impact. The study concludes that CO2 can be an effective tool for pest management in stored products, with 35% CO2 showing potential as a more economical option for A. ovatus extermination.

Simulating potential impacts of bottom trawling on the biological carbon pump: a case study in the Benguela Upwelling System

Bottom-trawl fishery is known to cause major disturbances to marine sediments as the dragging of trawl gears across the seabed fosters sediment resuspension, which can lead to organic particle remineralization and release of benthic CO2 and nutrients into bottom waters. However, its effects on carbon cycling and biological productivity, especially in highly productive regions like the Benguela Upwelling System (BUS), are less well studied. Here, we simulated carbon (C) and nutrient pathways from the trawled coastal seabed to overlying water masses that are being upwelled into the sunlit surface within the BUS, using shipboard data on sea surface and water column characteristics and published benthic CO2 emission estimates from bottom-trawled sediments. The latter reports 4.35 and 0.64 Tg C year-1 to be released from the seabed into upwelling source waters after bottom trawling in the northern (NBUS) and southern (SBUS) subsystems, respectively. Based on these values, we estimated a corresponding nitrate (N) input of 1.39 and 0.47 µmol kg-1 year-1, enhancing source water nitrate concentrations by ~5% and ~2%. Trawl-induced nitrate input into the sunlit surface could support a new production of 3.14 and 0.47 Tg C year-1 in the NBUS and SBUS, respectively, recapturing only 2/3 of CO2 released after bottom trawling into biomass, mainly due to differences in stoichiometric C:N ratios between the sediment (~9) and surface biomass (Redfield, 6.6). The remaining benthic CO2 can thereby lead to an increase in surface CO2 concentration and its partial pressure (pCO2), impeding CO2 uptake of the biological carbon pump in the BUS by 1.3 Tg C year-1, of which 1 Tg C year-1 is emitted to the atmosphere across the northern subsystem. Our results demonstrate the extent to which bottom trawling may affect the CO2 storage potential of coastal sediments on a basin-wide level, highlighting the need to better resolve small-scale sediment characteristics and C:N ratios to refine trawl-induced benthic carbon and nutrient effluxes within the BUS.

A study of nano-micro-bubble process for CO2 absorption in water for biogas upgrading application

The work proposed a novel micro-bubble system using swirling jet flow method for improving the physical absorption of CO2 in water. The effects of operating conditions; e.g. gas flow rate (from 500 to 2000 mL/min), inlet pressure (2 and 3.5 bar) and inlet CO2 concentration (from 5 to 60 % v/v in CO2/N2 gas mixture) on the physical absorption of CO2 were studied. It was found that the CO2 absorption system reached to steady state after 30 min with the outlet CO2 concentrations of 2.9 % and 8.8 % at 40 % and 60 % of inlet CO2 concentrations, respectively. These outlet CO2 concentrations demonstrated the standard of bio-methane for replacing natural gas in vehicle use, from which <10 % CO2 is required. Moreover, the increase of gas flow rate resulted in increase of outlet CO2 concentration. The rising of inlet pressure from 2 to 3.5 bars let to reduction of the outlet CO2 concentration together with enhancing the dissolved CO2 concentration in water from 49.1 to 51.7 mg/L at gas flow rate of 2000 mL/min and 60 % of inlet CO2 concentration. The highest efficiency of CO2 removal was 98.41 % under gas flow rate at 500 mL/min with 60 % of inlet CO2 concentration. Under the optimized conditions, this system was tested with real biogas as raw material containing mainly 57.7 % of CH4 and 40.3 % of CO2 which achieved to remove the 95.1 % of CO2 removal and no significant loss of CH4. This highlight demonstrated the potential application of this technology for biogas upgrading or purification further.

Efficient CO2 capture by ZIF-8-derived in-situ nitrogen-doped nanoporous carbon with ultra-high selectivity and stability

Global warming and the increasing frequency of extreme weather caused by the gradual increase in CO2 concentration in the atmosphere are urgent issues that must be addressed. In this study, ZIF-8-derived in-situ nitrogen-doped porous carbon materials were prepared through one-step pyrolysis of ZIF-8. The synthesis was gradually optimized by exploring different pyrolysis temperatures to determine the optimal ZIF-8-derived porous carbon for CO2 adsorption. The CO2-adsorption capacity of ZIF-8–800 reached 5.22 and 6.19 mmol g−1 at 25 ℃ and 0 ℃ (1 bar), respectively. After five cycles, its CO2-adsorption capacity decreased by only about 1.7 %. Moreover, the CO2/N2 selectivity at 1 bar was as high as 21.2 (48.9 at 0.05 bar), and the isothermal adsorption heat was also within a moderate range (31 kJ mol−1). The superior CO2 adsorption performance was found to originate from the comprehensive effect of the three-dimensional pore structure that combined reasonably coordinated micropores, mesopores, and macropores, as well as some specific favorable N/O groups. The results indicate the broad application prospects of ZIF-8-Ts in CO2 capture and separation and provide new ideas for the sustainable application of novel MOF-derived porous carbon materials.

Multiscale simulation of water/oil displacement with dissolved CO[formula omitted]: Implications for geological carbon storage and CO[formula omitted]-enhanced oil recovery

This study combines molecular and pore-scale simulations to enhance our understanding of water, carbon dioxide (CO2), and oil flow in a porous system for high-efficiency geological carbon storage and enhanced oil recovery. We use molecular dynamics simulations to study the variation of interfacial tension (IFT), viscosity, and contact angle across varying system CO2 concentrations. The study reveals that the IFT simulation accuracy in the three-component mixture system relates positively to the volume-to-interfacial area ratio, and IFT decreases with CO2 concentration. Oil–CO2 mixture viscosity decreases and shows an intersection with water viscosity as CO2 concentration increases. The contact angle on the hydrophobic surface of kaolinite first increases and then decreases with CO2 concentration, while the hydrophilic surface contact angle is not sensitive to the CO2 concentration. Visualizing CO2 density distribution reveals its accumulation at fluid-fluid and fluid-solid interfaces and the combined effect results in the highest CO2 density at contact-line regions. Meanwhile, the elevated CO2 density at fluid-fluid interfaces reduces IFT, contributing to the initial contact angle increase, while the CO2 density increase at fluids-solid surface explains the subsequent contact angle decrease. These findings are then upscaled into a core-scale system using lattice Boltzmann simulations. The results are summarized into a phase diagram, which reveals the non-monotonic variations of the initial-residual (I-R) curves across different CO2 concentrations, and the residual saturation overall decreases with CO2 concentration for high initial saturations. These findings underscore the critical roles of system CO2 concentration and rock components, particularly kaolinite clay minerals, in subsurface multiphase seepage confronted in geological carbon storage and CO2-enhanced oil recovery, highlighting the importance of digital rock physical chemistry.

Research on Wellbore Integrity Evaluation Model of CO2 Enhanced Composite Fracturing

CO2 injection composite fracturing is an effective method for shale oil and gas well development. The downhole casing is prone to uniform corrosion, pitting, perforation, and even corrosion fracture in the CO2 environment. Therefore, it is particularly important to reveal the physical characteristics of CO2 under actual geological conditions and the impact of CO2 corrosion on the performance of casing. A mathematical model for the temperature and pressure field of CO2 in the wellbore under fracturing conditions is established in this paper, and the temperature and pressure distribution along the depth of the well is calculated. By optimizing the CO2 state equation and using the S-W equation, Lee model, and RK model to calculate the CO2 density, viscosity and compression factor, respectively, the phase distribution pattern of CO2 along the actual wellbore is obtained. Through CO2 corrosion tests on the casing, the influence of temperature and CO2 concentration on the corrosion rate of the casing is clarified. The peak corrosion rate of Q125 steel corresponds to 80 °C, and the corrosion rate increases with the increase in CO2 concentration. Finally, a prediction model for the uniform corrosion rate of casing under different temperatures and CO2 concentration conditions is obtained, which can provide technical support for the design of CO2-enhanced fracturing technology.

Carbon dioxide fertilization enhanced carbon sink offset by climate change and land use in Amazonia on a centennial scale

The Amazon, the Earth's largest tropical forest, plays a critical role in the global carbon cycle, acting as a significant carbon sink. Recent studies, however, indicate a decline in its carbon sequestration capacity due to climate variability, intensive deforestation, and fires. This study aims to examine the impacts of these factors on the carbon dynamics of the Amazon over a centennial scale based on dynamic global vegetation models (DGVMs) of Trendy-v11. It was found that the Amazon region exhibited significant spatiotemporal variations in net land carbon (C) fluxes, and was a net C sink (40.02 ± 242.64 Tg C yr−1) during 1901–2021. The Amazonian net biome productivity (NBP) showed a 6-decades-scale shift from a decreasing trend (−3.78 Tg C yr−2) during 1901–1959 to an increasing trend (2.39 Tg C yr−2) during 1960–2021. The Amazonian NBP was negatively related to air temperature while positively related to dry-season precipitation during 1901–2021. Furthermore, the increase of atmospheric CO2 concentration during 1901–2020 enhanced Amazonian NBP by 36.40 ± 8.39 Pg C, which was largely offset by land use change (−18.84 ± 12.02 Pg C) and climate change (−10.03 ± 5.00 Pg C). Our findings underscore the critical need for sustainable management practices in the Amazon to enhance its C sink and preserve its function in the global climate system.

A review of global long-term changes in the mesosphere, thermosphere and ionosphere: A starting point for inclusion in (semi-) empirical models

The climate of the upper atmosphere, including the mesosphere, thermosphere and ionosphere, is changing. As data records are much more limited than in the lower atmosphere and solar variability becomes increasingly dominant at higher altitudes, accurate trend detection and attribution is not straightforward. Nonetheless, observations reliably indicate that, on average, the mesosphere has been cooling, the density in the thermosphere has been decreasing, and ionospheric layers have been shifting down. These global mean changes can be largely attributed to the increase in CO2 concentration, which causes cooling and thermal contraction in the middle and upper atmosphere. The decline in thermosphere density is particularly relevant from a practical viewpoint, as this reduces atmospheric drag and thereby increases orbital lifetimes and the build-up of space debris. Long-term changes in the ionosphere can have further practical implications and are not only driven by the increase in CO2 concentration, but also by changes in the Earth’s magnetic field. The empirical models that are mostly used to inform applications in industry on the state of the upper atmosphere, as well as being widely used in science, do not yet properly account for long-term trends in the mesosphere, thermosphere and ionosphere. This is problematic when long-term future projections are needed or models rely strongly on older data. This review provides an overview of the main evidence of long-term trends observed in the mesosphere, thermosphere and ionosphere, together with the latest insights on what causes these trends. It is hoped that this may serve as a starting point to include long-term trends in (semi-) empirical models to benefit all users of these models. We also offer some thoughts on how this could be approached.

Experimental investigation of hydrogen isotope fractionation during hydration of olivine-hosted melt inclusions: Implications for D/H in Baffin Island picrites

Olivine-hosted melt inclusions are used to investigate the hydrogen isotope compositions (D/H) of Earth's mantle reservoirs. Studies have shown, however, that hydrogen in melt inclusion can equilibrate rapidly in response to changes to the external environment via the diffusion of protons (H+) and deuterons (D+) through the host olivine. Given that protons diffuse faster than deuterons, a kinetic fractionation of hydrogen isotopes is expected to accompany both the hydration and dehydration of melt inclusions. Other volatile species in the melt inclusion may also be affected by changes to the internal pressure and/or oxygen fugacity (fO2). Here we report results from experiments designed to investigate the behaviors of volatiles and hydrogen isotopes during the hydration of olivine-hosted melt inclusions. We show that the concentration of H2O in initially H2O-poor inclusions increases rapidly (up to ∼4 wt.% within 24 h) when the host olivine is in contact with aqueous fluid at 1200 °C and 300 MPa. The extent of hydration is controlled by time, temperature, melt inclusion volume, and H+ diffusion distance. Hydrogen isotopes initially become lighter (i.e., D/H decreases) as hydration proceeds, defining a negative correlation with H2O concentration. This trend reverses with increasing hydration as the inclusions must eventually equilibrate with the external fluid. These experimental results agree well with diffusion calculations carried out using a spherical geometry and a lattice diffusivity of 10–11.2±0.2 m2/s for H+ at 1200 °C. Therefore, anomalously light hydrogen isotopes in olivine-hosted melt inclusions from Baffin Island may not be taken as representative of the composition of the mantle source unless post-entrapment hydration can be excluded as a possibility. An increase in CO2 concentration and a significant drop in sulfur concentration accompany hydration of the melt inclusions in our experiments. The former is consistent with an observed decrease in vapor bubble size and results from a hydration-induced internal pressure increase. The latter is ascribed to the exsolution of molten sulfide from the silicate melt, which might be related to a lower fO2 in the experiments as compared to the starting materials. We find no evidence for exchange of F or Cl between the melt inclusion and external fluid.

Partitioning of Evapotranspiration and Its Response to Eco‐Environmental Factors Over an Alpine Grassland on the Qinghai–Tibetan Plateau Based on the SiB2 Model

ABSTRACTPartitioning evapotranspiration (ET) is challenging but essential for understanding the exchange of energy, water, and carbon between terrestrial ecosystems and the atmosphere. In this study, we applied the simple biosphere model (SiB2) to partition ET at a typical alpine grassland site on the Qinghai–Tibet Plateau (QTP). In addition, through process‐based model scenario experiments, we quantified the effects of four environmental factors on ET components and predicted their evolution under the two future carbon emission scenarios (ssp126 and ssp585). Our findings are summarized as follows: (1) The original version of SiB2, despite its simple structure, effectively simulates ET and its components. (2) The ratios of annual total transpiration (T), soil evaporation (Es), and canopy interception evaporation (Ei) to ET in the alpine grassland ecosystem were 51%, 43%, and 6%, respectively. (3) Each 100 mm increase in annual precipitation results in a significant increase in soil evaporation (2.77%). A 1°C increase in air temperature leads to a significant increase in vegetation transpiration (5.22%) and canopy interception evaporation (5.63%). Each 100 ppm increase in CO2 concentration causes a significant decrease in T (−5.43%) and ET (−2.97%). An increase in LAI (1 m2 m−2) has the largest effect on canopy interception evaporation (4.67%). (4) Under the high carbon emission scenario (ssp585), all ET components in this ecosystem show a significant growth trend, particularly vegetation transpiration and canopy interception evaporation. These findings will facilitate more precise predictions of the water cycle dynamics, reveal land‐atmosphere interaction mechanisms, and aid in the protection of the ecological environment of the QTP.

Differential responses of soil CO2 dynamics along soil depth to rainfall patterns in the Chinese Loess Plateau

Soil surface carbon dioxide (CO2) efflux not only originates from topsoils, but also significantly involves contributions from deeper soil layers. Soil surface CO2 efflux significantly fluctuated with rainfall patterns in arid and semiarid regions. However, how soil CO2 dynamics respond at different soil depths to varying rainfall patterns remains largely unclear. To address this gap, we continuously monitored soil CO2 concentrations, temperature, and moisture content at 10 cm, 50 cm, and 100 cm depths in situ under cropland and orchards located in the semiarid Loess Plateau over a full year. Rainfall events were meticulously recorded, categorizing them into light (<10 mm), moderate (10 mm–40 mm), and heavy (>40 mm) to discern their impact on soil CO2 dynamics. Specifically, soil CO2 flux was not affected during light rainfall. Moderate and heavy rainfall decreased soil CO2 flux at 0–10 cm by an average of 70% and 83%, respectively. This decrease was associated with reduced gas diffusivity across rainfall patterns. For instance, heavy rainfall reduced gas diffusivity by an average of 83% and 53% at 10 cm and 50 cm soil depths, respectively. Furthermore, soil CO2 concentrations slightly dropped as soil temperature decreased at 10 cm depth during light rainfall. Soil CO2 concentrations at 10 cm and 50 cm depths initially decreased by up to 15% and subsequently increasing by up to 52% during moderate and heavy rainfall. This response was likely influenced by temperature reductions and subsequent rises in moisture content, with a hysteretic response of soil CO2 concentrations to temperature. The rapid increase in soil CO2 concentrations was mainly due to a substantial decrease in gas diffusivity. Notably, heavy rainfall induced a delayed increase in soil moisture content at 50 cm depth and a significant decrease in CO2 concentration by 16% at 100 cm depth. A substantial decrease in soil CO2 concentrations in deep soil layers was primarily related to decreased soil temperature. Additionally, the observed soil CO2 dynamics were partly attributed to biotic factors (microbial biomass carbon and root density) mainly on cropland, but mainly abiotic factors (soil organic carbon and bulk density) under orchards. Overall, these results suggest that reduced gas diffusivity triggered by increased soil moisture content in topsoils and weakened biological processes caused by decreased soil temperature in deep soils typically drive the differential responses of soil CO2 dynamics to rainfall patterns.

Exploring carbon dioxide sequestration in desalination reject brine via NaOH reaction: A kinetics study

Seawater desalination is one of the most sustainable means of water supply in arid and semi-arid regions. Despite its undeniable potential to meet the global water demands, there are several environmental impacts associated with its operation, including the generation of reject brine and the emission of considerable amounts of CO2. Recently, the mineralization of carbon dioxide using desalination reject brine has emerged as a potential solution for simultaneous brine management and CO2 sequestration. In this study, the reaction kinetics of desalination reject brine with CO2 in the presence of NaOH are evaluated. The effect of various operating parameters, such as the temperature, CO2 concentration, NaOH dosage, brine salinity, CO2 flowrates and inert particles volume percent were investigated by varying them within the range of 15–55 °C, 3–20 %, 6–16 g/L, 5–72 g/L, 1–5 L/min and 0–20 %, respectively. The experimental data showed that the overall rate of CO2 conversion is equal to the sum of the rates observed for Ca2+ and Mg2+ carbonation reactions and increases proportionally with the increase in CO2 concentration. The addition of NaOH improved the Ca2+ carbonation reaction rate but had no effect on Mg2+ carbonation reactions within the investigated reaction conditions. Interestingly, increasing brine salinity had a negative effect on the reaction rate, while the change in temperature and inert particles had minimal effect on the overall reaction rate. Analysis of the solid products showed that Hydromagnesite and Calcite were the two major products obtained. Finally, experimental data were used to develop a rate model representing the CO2-Brine-NaOH system. The developed model will assist in successfully predicting the performance of the process and pave the way for efficient brine management and CO2 sequestration.

Solid amine adsorbent with surfactant modification for Direct Air Capture (DAC) under different temperature and humidity conditions

Direct air capture (DAC) technologies have been vigorously pursued to achieve the goal of net-zero CO2 emissions due to the dramatic increase in atmosphere CO2 concentrations and global temperatures. In practical DAC conditions, variations in temperature and humidity can lead to different CO2 adsorption outcomes. Current studies lack comprehensive information on the optimal temperature and humidity conditions for DAC. In this study, a comparison between PMSU-F (impregnating polyethyleneimine (PEI600) on MSU-F support) and PPMSU-F (co-impregnating polyethylene glycol (PEG200) with PEI600 on MSU-F support) under different temperature and relative humidity conditions were conducted. Under dry conditions, the addition of PEG200 effectively enhanced the adsorption capacity, adsorption rate, and amine efficiency and decreased the energy consumption for desorption depending on the comparison of the two absorbents. Under the popular atmospheric temperature ranges (−5 °C–45 °C), an increase in temperature favors CO2 adsorption. Under humid conditions, the presence of PEG200 had a negative effect due to its strong hydrophilicity. By comparing dry and humid conditions, the introduction of moisture generally enhanced overall CO2 adsorption performance, and the adsorption capacity interestingly further increased under low-temperature conditions. The highest CO2 adsorbing capacity of PMSU-F (3.82 mmol/g) and PPMSU-F (3.76 mmol/g) appeared at −5 °C and 75% relative humidity, indicating that low temperature and relatively high relative humidity were more favorable for DAC, which is possibly attributed to the thermodynamic control under low temperatures with moisture. The results indicate that the adsorbents chosen in this study are promising for DAC under low temperatures and relatively high humidity conditions. The performances of modified DAC adsorbents, e.g., adsorption capacity, stability, antioxidant property for industrial-grade DAC system should be evaluated in the next work.

The Physics of the Carbon Cycle: About the Origin of CO2 in the Atmosphere

Aims: Examination of the correctness of some assumptions of IPCC regarding climate. Discussion of consequences. Methodology: Explanation of terms used by IPCC and clarification of consequences, identification of prerequisites for the validity/applicability of these terms and scrutiny of their fulfillment under real-world conditions, discussion of consequences. Results: Based on the laws of physics and logic, two central terms used by IPCC, i.e. the fixed "airborne fraction", and the constant "CO2-budget” cannot exist in reality. The first states that about 50 % of the CO2 emitted by humans (the “airborne fraction”) stay in the atmosphere for centuries or longer (the other about 50 % leaving it within maximum a few years), the latter is the maximum value of cumulative net global anthropogenic emissions that is allowed, if global warming should be kept below a given level, for example 2 °C. According to their definition, both values are independent of the temporal distribution of the anthropogenic emissions. But physics speaks against their existence. And also the “Bern Cabon Cycle Model”, used by IPCC as an alternative method to analyze the carbon cycle, cannot be correct, because it is based on incorrect physical boundary conditions. The inadmissibility of the two terms is also supported by observations of the fast decay of 14CO2 after the atomic bomb test stop agreement. Conclusion: If the considerations made here are correct, IPCC's assessment of the sharp increase in CO2 concentration being a consequence of anthropogenic releases implodes. Consequently, the assessment of global warming to be man-made is justified no more, and the necessity to terminate all anthropogenic releases of CO2 for climate protection reasons becomes superfluous. The considerations made here appear to be very reliable, but in view of the far-reaching consequences, a careful review by the scientific community seems to be urgently needed.

Tall tower observations of a northward surging gust front in central Amazon and its role in the mesoscale transport of carbon dioxide

AbstractHigh‐frequency measurements obtained at two micrometeorological towers are investigated for a rare northward surging gust front that impacted the Amazon Tall Tower Observatory (ATTO), in central Amazon. The gust front originated from a decaying mesoscale convective system (MCS) during the morning hours of 27 December 2021 near Manaus, Amazonas state, northern Brazil, and surged north‐eastward towards the ATTO site. Large temperature drops and vigorous, persistent winds were observed at the towers which lasted for over 4 h despite the gust front being detached from its parent, decaying MCS. More importantly, the gust front was responsible for drastic increases of CO2 concentrations throughout the tower depths, which suggests that the gust front winds horizontally advected CO2‐rich air from a source upstream from the ATTO site. The CO2‐rich outflow is hypothesized to originate from downward transport and/or biomass burning from forest fires in southeastern Amazon, both ideas that are supported by large increases of aerosol concentrations measured at ATTO following the gust front passage. Our results stress the need for further investigations addressing the role played by mesoscale convective circulations in the redistribution of trace gases and aerosols in the Amazon.

Experimental study on the desorption behavior of high-volatile bituminous coals following CO2 and CH4 injection at various compositional ratios

CO2-ECBM (Enhanced Coalbed Methane recovery) offers the dual benefits of increasing methane production and reducing carbon emissions through sequestration. Previous studies have primarily focused on the competitive adsorption effects of different gas compositions during the CO2-ECBM. However, the dynamic changes in desorption volume, desorption strain, and gas composition for different compositional ratios of CO2/CH4 after injecting CO2 remain unclear. Therefore, high-volatile bituminous coals from the southern margin of the Junggar Basin are chosen for desorption experiments with five different compositional ratios of CO2/CH4. Desorption volume, desorption strain, and gas composition of the coal samples are monitored during the desorption process. Finally, the mechanism influencing the dynamic changes in gas composition during desorption is analyzed. The results indicate that as CO2 concentration increases, both desorption volume and desorption strain correspondingly increase. At the same desorption volume, a higher CO2 concentration results in greater desorption strain. For different compositional ratios of CO2/CH4, CH4 concentration gradually decreases while CO2 concentration gradually increases over desorption time. The concentration of the desorption gas is influenced by the initial CO2 concentration and the pore structure. Specifically, higher initial CO2 concentrations, better pore opening, and more developed mesopores and macropores lead to greater changes in composition concentrations during desorption. Different concentrations of CO2 all promote CH4 production, with higher CO2 concentrations enhancing CH4 production efficiency more significantly, especially for samples that are more difficult to produce. The research findings can provide guidance for the efficient production of CBM after CO2 injection.

The Freshwater Cyanobacterium Synechococcus elongatus PCC 7942 Does Not Require an Active External Carbonic Anhydrase.

Under standard laboratory conditions, Synechococcus elongatus PCC 7942 lacks EcaASyn, a periplasmic carbonic anhydrase (CA). In this study, a S. elongatus transformant was created that expressed the homologous EcaACya from Cyanothece sp. ATCC 51142. This additional external CA had no discernible effect on the adaptive responses and physiology of cells exposed to changes similar to those found in S. elongatus natural habitats, such as fluctuating CO2 and HCO3- concentrations and ratios, oxidative or light stress, and high CO2. The transformant had a disadvantage over wild-type cells under certain conditions (Na+ depletion, a reduction in CO2). S. elongatus cells lacked their own EcaASyn in all experimental conditions. The results suggest the presence in S. elongatus of mechanisms that limit the appearance of EcaASyn in the periplasm. For the first time, we offer data on the expression pattern of CCM-associated genes during S. elongatus adaptation to CO2 replacement with HCO3-, as well as cell transfer to high CO2 levels (up to 100%). An increase in CO2 concentration coincides with the suppression of the NDH-14 system, which was previously thought to function constitutively.

Resistance of grassland productivity to drought and heatwave over a temperate semi-arid climate zone

Drought and heatwave are the primary climate extremes for vegetation productivity loss in the global temperate semi-arid grassland, challenging the ecosystem productivity stability in these areas. Previous studies have indicated a significant decline in the resistance of global grassland productivity to drought, but we still lack a systematic understanding of the mechanisms determining the spatiotemporal variations in grassland resistance to drought and heatwave. In this study, we focused on temperate semi-arid grasslands of China (TSGC) to assess the spatiotemporal variations of grassland productivity resistance to different climate extremes: compound dry-hot events, individual drought events, and individual heatwave events that occurred during 2000–2019. Based on the explainable machine learning model, we explored the resistance to the interaction of drought and heatwave and identify the dominant factors determining the spatiotemporal variations in resistance. The results revealed that grassland resistance to climate extremes had decreased in Xilingol Grassland and Mu Us Sandy Land, and had a not significant increase in Otindag Desert during 2000–2019. Human activities and the increase in CO2 concentration causes a decline in resistance in Mu Us Sandy Land, and the increase of VPD and shift of vegetation loss event timing caused a decline in resistance in Xilingol Grassland, while the weakening of climate extremes, especially the shortening of drought duration, increase the resistance in Otindag Desert. Mean annual temperature dominates the spatial differences in resistance among different grasslands. When drought and heatwave occur simultaneously, there is an additive effect on resistance and causes lower resistance to compound dry-hot events compared to individual drought and heatwave events. Our analysis provides crucial insights into understanding the impact of climate extremes on the temperate semi-arid grasslands of China.