Increase In Atmospheric CO2 Concentration Research Articles

Effects of Elevated CO2 on the Fitness of Three Successive Generations of Lipaphis erysimi.

Simple SummaryGlobal warming caused by the increase in atmospheric CO2 concentration is becoming a major environmental issue. Lipaphis erysimi is one of the most damaging pests of cruciferous crops worldwide, and L. erysimi has strong adaptability to the environment and reproductive capacity. The age-stage, two-sex life table is currently used by many researchers in place of the traditional age-specific life table, providing many details such as fitness and potential damage. In this study, the individual fitness and population dynamics parameters of three successive generations of L. erysimi were analyzed using the age-stage, two-sex life table. The results show that a high CO2 concentration had a cumulative effect on the survival rate and fecundity of L. erysimi, and elevated CO2 had a negative effect on the individual fitness parameters of L. erysimi. The life expectancy (exj) is significantly lower in elevated CO2 than that in ambient CO2 treatment in the three successive generations, indicating that L. erysimi was more sensitive to CO2 concentration and the life of L. erysimi was shortened under elevated CO2. Additionally, we can find that elevated CO2 has a short-term effect on the population parameters, including the intrinsic rate of increase (r) and finite rate of increase (λ) in L. erysimi. Through the data from this experiment, we believe that the individual and population fitness of L. erysimi will be decreased under elevated CO2, which indicates that the damage caused by L. erysimi may be reduced in the future with increasing CO2 levels.To assess the effect of elevated CO2 on the development, fecundity, and population dynamic parameters of L. erysimi, the age-stage, two-sex life table was used to predict the individual fitness and population parameters of three successive generations of L. erysimi in this study. The results show that a significantly longer total pre-adult stage before oviposition (TPOP) was observed in the third generation compared with the first generation of L. erysimi under the 800 μL/L CO2 treatment. The fecundity is significantly lower in the 800 μL/L CO2 treatment than that in the 400 μL/L CO2 treatment in the third generation of L. erysimi, which indicates that elevated CO2 had a negative effect on the individual fitness parameters of L. erysimi. Additionally, the life expectancy (exj) is significantly lower under the 800 μL/L CO2 treatment than that under the 400 μL/L CO2 treatment in the three successive generations. A significantly higher intrinsic rate of increase (r) and finite rate of increase (λ) were found in the second generation compared with those in the first and third generations of L. erysimi under the 800 μL/L CO2 treatment. Moreover, significantly lower r and λ were observed under the 800 μL/L CO2 treatment compared with those under the 400 μL/L and 600 μL/L CO2 treatments in the first generation of L. erysimi, which indicates that elevated CO2 has a short-term effect on the population parameters (r and λ) of L. erysimi. Our experiment can provide the data for the comprehensive prevention and control of L. erysimi in the future with increasing CO2 levels.

Interaction between increased CO2 and temperature enhance plant growth but do not affect millet grain production

The intergovernmental panel on climate change predicts a progressive increase in atmospheric CO2 concentration and temperature; however, their effects on cereals have been shown for a limited number of species. This study evaluates the effects of increased CO2 concentration and temperature separately and combined on millet growth and grain production in open-top chambers where the microclimate was adjusted to the following conditions: ambient CO2 and temperature; CO2 enriched (~ 800 ppm) and ambient temperature; ambient CO2 and higher temperature (+3ºC); and CO2-enriched and higher temperature. For each treatment, two chambers were used, each containing 15 7 L pots. Each pot received five seeds at the beginning of the experiment and thinning to one plant per pot at 15 days after sowing. Ten plants were harvested from each chamber 65 days after sowing and the plant height, the number of leaves and the longest root length as well as shoot and root biomass were measured. The remaining plants were harvested 130 days after sowing to evaluate grain production. The results indicate that high CO2 levels did not affect plant growth and biomass. On the other hand, plants subjected to high temperature grew 7% taller than those grown under ambient temperature. Contrastingly, plants submitted to both elevated CO2 and temperature were 19% taller and had 22% more shoot biomass than plants under ambient CO2 and temperature. However, grain production did not change in any of the environmental conditions. We provide evidence that millets are tolerant of the predicted climate changes and that grain production potential may not be affected.

Rapid increases in shrubland and forest intrinsic water-use efficiency during an ongoing megadrought

Globally, intrinsic water-use efficiency (iWUE) has risen dramatically over the past century in concert with increases in atmospheric CO2 concentration. This increase could be further accelerated by long-term drought events, such as the ongoing multidecadal "megadrought" in the American Southwest. However, direct measurements of iWUE in this region are rare and largely constrained to trees, which may bias estimates of iWUE trends toward more mesic, high elevation areas and neglect the responses of other key plant functional types such as shrubs that are dominant across much of the region. Here, we found evidence that iWUE is increasing in the Southwest at one of the fastest rates documented due to the recent drying trend. These increases were particularly large across three common shrub species, which had a greater iWUE sensitivity to aridity than Pinus ponderosa, a common tree species in the western United States. The sensitivity of both shrub and tree iWUE to variability in atmospheric aridity exceeded their sensitivity to increasing atmospheric [CO2]. The shift to more water-efficient vegetation would be, all else being equal, a net positive for plant health. However, ongoing trends toward lower plant density, diminished growth, and increasing vegetation mortality across the Southwest indicate that this increase in iWUE is unlikely to offset the negative impacts of aridification.

A review of technologies for carbon capture, sequestration, and utilization: Cost, capacity, and technology readiness

AbstractThe continued rise in anthropogenic carbon dioxide (CO2) emissions and increase in atmospheric CO2 concentration has led to calls from experts, including the Intergovernmental Panel on Climate Change that has estimated that global warming needs to be limited to 1.5 °C above preindustrial levels to avoid the worst effects of climate change, and that carbon neutrality would need to be achieved globally by 2050 to meet this target. Achieving carbon neutrality by mid‐century will rely on successful implementation and widespread adoption of technologies for reducing emissions from large point sources of CO2, direct CO2 capture from the air, as well as storage and utilization technologies that would convert CO2 to a form that would ensure safety and permanency of storage. In this paper, engineering solutions for CO2 capture, utilization, and storage are reviewed with a focus on technology readiness level, and cost. © 2021 Society of Chemical Industry and John Wiley & Sons, Ltd.

The differential tolerance of C3 and C4 cereals to aluminum toxicity is faded under future CO2 climate

Industrial activities have led to a gradual and global increase in soil aluminum (Al) and atmospheric CO2 concentrations. Al bioavailability strongly depends on the soil pH, which in turn is affected by atmospheric CO2 levels. In spite of the concurrent impact which Al and elevated CO2 (eCO2) could have on plants, their interaction and how it might affect the growth of economically important crop species has not been investigated. Here, we have investigated the combined impact of soil Al and eCO2 exposure on key C3 (wheat, oat) and C4 (maize, sorghum) crops, at the physiological and biochemical level. Compared to C3 plants, C4 plants accumulated less Al by stimulating soil Al retention through exudation of root organic acids. Consequently, Al-exposed C4 plants maintained photosynthetic performance and anti-oxidative capacity. Exposure to eCO2 reduced the stress responses of C3 and C4 crops to Al exposure. Elevated CO2 decreased Al accumulation and oxidative damage in all cereals, and ameliorated C3 plant growth. This was reflected on the biochemical level, where eCO2 inhibited ROS production and restored RuBisCo activity in C3 crops only. Overall, our data suggest that, compared to C3 crops, C4 cereals are more tolerant to soil Al exposure under current ambient CO2 (aCO2) levels whereas future eCO2 levels might stimulate Al tolerance in C3 crops.

Climate sensitivity in the northern high latitudes using the Brazilian Earth System Model

An expressive number of scientific publications including the recent IPCC-AR6 report have warned about the effects of the ongoing and the projected climate change in the northern high latitudes as response to CO2 forcing. Here we investigate the response of the Arctic region to an increase in atmospheric CO2 concentration using the Brazilian Earth System Model (BESM-OA2.5) and other three state-of-the-art Global Climate Model from the CMIP5 project. We evaluated the Arctic climate sensitivity through the Polar amplification using two numerical experiments: (i) piControl numerical experiment and (ii) abrupt 4xCO2. Our results showed that the northern high latitudes are described as the most climatically sensitive areas of the world, with strongest warming occurring in winter (DJF) and autumn (SON). The Arctic climate sensitivity is linked to changes in sea ice extent and sea ice thickness. Considering this scenario, it is expected that the Arctic will become ice-free in summer time and covered only by first-year-sea ice in the remaining months. We suggest that the projected sea ice albedo feedback will reinforce the Arctic warming with lack of understanding effects beyond the Arctic region.

Application of metal-organic frameworks in CO2 hydrogenation

The dramatic increase in atmospheric CO2 concentrations has attracted people’s attention, and many strategies have been developed to convert CO2 into high-value chemicals. Metal-organic frameworks (MOFs), as a class of versatile materials, can be used in the CO2 capture and conversion because of their unique porosity, large specific surface area, rich pore structure, multiple active centers, good stability and recyclability. Various functional nanomaterials have been designed and synthesized based on metal organic framework (MOF) of crystalline porous materials to meet these challenges. Herein, in this review, the latest processes of MOFs in field the of CO2 hydrogenation to carbon monoxide, methane, formic acid, methanol and olefins are summarized, and the synthesis methods of catalysts based on MOFs and the reasons for their high catalytic activity are analyzed. Besides, a brief introduction to improve the catalytic activity of the new MOF material and explore the feasible strategies for CO2 conversion are advised. Finally, the paper discusses the main challenges and opportunities of MOF-type catalysts in CO2 chemical conversion, and presents a brief outlook on further developments in this research area.

Seasonal trends in the Southeast Florida current and shelf CO2 fluxes

An anthropogenically driven increase in atmospheric CO2 concentrations is known to drive an increase in the globally integrated ocean carbon sink. However, there is significant regional and seasonal variability, and significant changes in seasonal cycle amplitudes have been predicted. Three decades of sea surface observations collected from the southeast Florida Current and shelf waters reveal behavior over seasonal and interannual timescales for a region important to global carbon storage and transport. The strong temperature dependence of fCO2 in the region dominates the seasonal cycle of air-sea flux, although biophysical processes are also important. The possibility of wet and dry seasonal asymmetric trends through time were evaluated, but no statistically significant trends were found. The results indicate that uptake in the region has not changed over the last three decades after accounting for sampling bias and demonstrate the importance of robust seasonally unbiased data sets in conducting climate studies. Even in this highly sampled region, data distribution biases were found, mainly in the early 1990s. Seasonally biased data are thus not only a problem for polar regions but can also affect flux calculations in sub-tropical regions. Although not statistically significant to date, different responses in different seasons with time may lead to seasonal amplification and a decoupling of the annual mean and the seasonal means in the future.

Detecting the Responses of CO2 Column Abundances to Anthropogenic Emissions from Satellite Observations of GOSAT and OCO-2

The continuing increase in atmospheric CO2 concentration caused by anthropogenic CO2 emissions significantly contributes to climate change driven by global warming. Satellite measurements of long-term CO2 data with global coverage improve our understanding of global carbon cycles. However, the sensitivity of the space-borne measurements to anthropogenic emissions on a regional scale is less explored because of data sparsity in space and time caused by impacts from geophysical factors such as aerosols and clouds. Here, we used global land mapping column averaged dry-air mole fractions of CO2 (XCO2) data (Mapping-XCO2), generated from a spatio-temporal geostatistical method using GOSAT and OCO-2 observations from April 2009 to December 2020, to investigate the responses of XCO2 to anthropogenic emissions at both global and regional scales. Our results show that the long-term trend of global XCO2 growth rate from Mapping-XCO2, which is consistent with that from ground observations, shows interannual variations caused by the El Niño Southern Oscillation (ENSO). The spatial distributions of XCO2 anomalies, derived from removing background from the Mapping-XCO2 data, reveal XCO2 enhancements of about 1.5–3.5 ppm due to anthropogenic emissions and seasonal biomass burning in the wintertime. Furthermore, a clustering analysis applied to seasonal XCO2 clearly reveals the spatial patterns of atmospheric transport and terrestrial biosphere CO2 fluxes, which help better understand and analyze regional XCO2 changes that are associated with atmospheric transport. To quantify regional anomalies of CO2 emissions, we selected three representative urban agglomerations as our study areas, including the Beijing-Tian-Hebei region (BTH), the Yangtze River Delta urban agglomerations (YRD), and the high-density urban areas in the eastern USA (EUSA). The results show that the XCO2 anomalies in winter well capture the several-ppm enhancement due to anthropogenic CO2 emissions. For BTH, YRD, and EUSA, regional positive anomalies of 2.47 ± 0.37 ppm, 2.20 ± 0.36 ppm, and 1.38 ± 0.33 ppm, respectively, can be detected during winter months from 2009 to 2020. These anomalies are slightly higher than model simulations from CarbonTracker-CO2. In addition, we compared the variations in regional XCO2 anomalies and NO2 columns during the lockdown of the COVID-19 pandemic from January to March 2020. Interestingly, the results demonstrate that the variations of XCO2 anomalies have a positive correlation with the decline of NO2 columns during this period. These correlations, moreover, are associated with the features of emitting sources. These results suggest that we can use simultaneously observed NO2, because of its high detectivity and co-emission with CO2, to assist the analysis and verification of CO2 emissions in future studies.

East Asian CO2 level change caused by Pacific Decadal Oscillation

Accurate projection of CO2 concentration in time and space remains challenging because of complex interplay between anthropogenic emissions, biospheric responses, and climatic variabilities. While the increase of atmospheric CO2 concentration is due primarily to fossil fuel burning, natural climate variabilities are known to introduce intermittent changes in the global CO2 growth rates. Thus, understanding the correlation of climate and carbon cycling systems is important in assessing the anthropogenic and natural impacts. Here, we report decadal CO2 variabilities in western Pacific based on data from several ground-based stations in the region and Atmospheric Infrared Sounder (AIRS). In addition to the well-established El Niño–Southern Oscillation (ENSO), there exists a decadal changing CO2 trend in the datasets mentioned above. Analysis of ground-based CO2 measurements in northern Taiwan shows a decadal signal at amplitudes of ~5 ppm. In contrast, AIRS shows a similar trend but at a reduced amplitude of ~1 ppm. We attribute the decadal signal to dynamical factors related to the Pacific Decadal Oscillation (PDO). This decadal signal, however, is not reproduced by the state-of-the-art data assimilation system, CarbonTacker, suggesting a gap in our knowledge of the modulation of carbon cycling systems and climate.

Elevated atmospheric CO2 adversely affects a dung beetle's development: Another potential driver of decline in insect numbers?

Insect declines have been attributed to several drivers such as habitat loss, climate change, invasive alien species and insecticides. However, in the global context, these effects remain patchy, whereas insect losses appear to be consistent worldwide. Increases in atmospheric CO2 concentrations are known to have indirect effects on herbivorous insects, but the effects on other insects are largely unexplored. We wondered if elevated atmospheric CO2 (eCO2 ) could influence the growth and survival of insects, not via rising temperature, nor through their changes in food quality, but by other means. Rearing tunnelling dung beetle Euoniticellus intermedius (Reiche, 1848) at pre-industrial (250parts per million [ppm]), current (400ppm) and eCO2 levels (600 and 800ppm), we found that exposure to eCO2 resulted in longer developmental times and increased mortality. Elevated CO2 also caused reduction of adult size and mass which is detrimental to dung beetle fitness. Additional results showed associated increases in CO2 levels inside dung brood balls, dung pH and respiration rates of the soil surrounding the developing dung beetles (CO2 flux). We thus hypothesize that elevated CO2 increases competition for O2 and nutrients between soil microbiota and subterranean insects. Given that many insect orders spend at least part of their life underground, our findings indicate the possibility of a negative ubiquitous effect of eCO2 on a large portion of the earth's insect biota. These findings therefore suggest an important area for future research on the soil community in the context of atmospheric change.

The stability of calibration model in measuring and mapping soil organic matter in a dry climatic area

The increase of atmospheric CO2 concentration from soil organic matter (SOM) decomposition may contribute to the global warming and climate change. So, sequestering this greenhouse gas into SOM may be used to mitigate climate change. However, tedious procedures in measuring and mapping SOM need to be replaced with a method which works based on the reliability of calibration model developed. This research aimed to test the reliability of the calibration model that was built from a separate soil sample group to be used to measure and map SOM on other validation soil sample group, in the mostly dry climatic area of Kayangan Sub-district, North Lombok Indonesia. For this purpose, 300 soil samples were collected from the area using grid method, which were then dried, ground, sieved, analysed for SOM content using the Walkley and Black method, and scanned using Near Infrared Spectroscopy. The model built using calibration sample group was able to reliably measure and map the SOM content of the spectral data collected from the validation sample set. This is shown by the coefficient of determination (R2 V = 0.79), root mean square error (RMSEV = 0.246%) and the ratio prediction to deviation (RPDV = 2.09). SOM maps generated from both laboratory and near infrared method can show very low, low and medium SOM content. These maps can be further used as a reference for applying organic fertilizers, avoiding excessive use of fertilizers, and monitoring soil carbon sequestration in mitigating climate change.

A brief review of electrocatalytic reduction of CO2—Materials, reaction conditions, and devices

AbstractGlobal warming caused by the rapid increase in atmospheric CO2 concentration is regarded as one of the most serious problems faced by human being. Electrochemical CO2 reduction (ECR) is one promising strategy that can fix CO2 in a mild and clean manner combined with sustainable energies. However, the ECR performance is highly dependent on the catalysis system because of the difficulty in CO2 activation, low mass transfer, poor product selectivity, and competitive hydrogen evolution reaction (HER). The binding strength of electrocatalysts toward carbon intermediates is the crucial factor for ECR performance. Furthermore, the reaction conditions and the configurations of devices are also of significance for ECR efficiencies. Here, we briefly reviewed the effects of electrocatalyst materials, as well as the reaction conditions, coupled anodic reactions, and devices on the ECR. Moreover, challenges and some perspectives for large‐scale applications are included.

Atmospheric CO2 enrichment effect on water use efficiency in chickpea (Cicer arietinum L.)

AbstractEffect of atmospheric CO2 enrichment on crop water relations was evaluated in an open‐top chamber experiment on kabuli chickpea (Cicer arietinum L.; Pusa 1,105). Increase in atmospheric CO2 concentration (e[CO2], 580 ± 20 μmol/mol) resulted in 21%–46% increase in leaf water potential, and 7%–11% in relative leaf water content, indicating higher water content in leaves, compared to the ambient level (a[CO2], 384 ± 12 μmol/mol). Higher leaf water status was connoted through spectral indices over the growing period. A rise in CO2, however, brought increase in leaf diffusive resistance and canopy temperature by 15%–35% and 3%–11%, respectively, potentially indicating partial closure of stomata. Increase in leaf area index (13%–73%), and higher spectral vegetation index suggested improved growth of chickpea under e[CO2]. An increase in leaf area compensated the decrease in diffusive resistance, and therefore seasonal total water use was similar between enriched and ambient conditions. Although water use efficiency (WUE) increased by 30% (p < .05) due to an increase in crop biomass under e[CO2], the canopy conductance remained unaffected. Results suggest a possibility of improved plant water status, enhanced biomass production and increased WUE for chickpea, with similar crop water use under future e[CO2] levels.

Effects of Elevated CO2 Concentrations on 13C Fractionation during Photosynthesis, Post-Photosynthesis and Night Respiration in Mangrove Saplings Avicennia marina and Rhizophora stylosa

Carbon fractionation (Δ13C) is well documented for various plants functional types. Yet, specific studies on Δ13C on mangroves are particularly rare although they have a key role in coastal carbon (C) cycling. In this study, we investigated the 13C exchanges between leaves and the atmosphere and between the main plant’s organs in two common mangroves species, Avicennia marina and Rhizophora stylosa subjected to two different CO2 concentrations. Two-years-old saplings were grown in mesocosms during one year under 400 ppm and 800 ppm of CO2. At the end of the experiment, the isotopic value of the night-respired CO2 was measured on six individuals for each species and CO2 treatment. Then, 60 saplings were harvested to measure the organs δ13C values, and, finally, carbon fractionation (Δ13C) during photosynthesis, post-photosynthesis and apparent Δ13C during night respiration were calculated. Results indicated that elevated CO2 reduced Δ13C during photosynthesis by 13% and during night respiration by 20%. Alongside, within-plant Δ13C was twice higher in the saplings grown under elevated CO2 concentrations. These results showed that ongoing and future increases in atmospheric CO2 concentrations have the potential to modify the δ13C values of mangrove trees. These results could have important implications in Blue Carbon sciences, and particularly in the comprehension of future carbon cycling in coastal wetlands, mangroves being an essential link in terrestrial and marine food webs along tropical and subtropical coastlines.

Carbon Accumulation in Arable Soils: Mechanisms and the Effect of Cultivation Practices and Organic Fertilizers

The organic carbon content of soils is a key parameter of soil fertility. Moreover, carbon accumulation in soils may mitigate the increase in atmospheric CO2 concentration. The principles of carbon accumulation in arable soils are well known. The inclusion of clover/alfalfa/grass within the rotation is a central instrument to increase soil organic carbon. In addition, the regular application of rotted or composted farmyard manure within the rotation can increase soil organic carbon contents much more than the separate application of straw and cattle slurry. Humic substances, as a main stable part of soil organic carbon, play a central role in the accumulation of soil carbon. A major effect of compost application on soil carbon may be the introduction of stable humic substances which may bind and stabilize labile organic carbon compounds such as amino acids, peptides, or sugars. From this point of view, a definite soil carbon saturation index may be misleading. Besides stable composts, commercially available humic substances such as Leonardite may increase soil organic carbon contents by stabilization of labile C sources in soil.

Cattle, climate and complexity: food security, quality and sustainability of the Australian cattle industries.

Marked increases in atmospheric CO2 concentrations are largely associated with the release of sequestered carbon in fossil fuels. While emissions of green-house gasses (GHG) from cattle have significant global warming potential, these are biogenic sources and substantially involve carbon in natural cycles, rather than fossil fuel. Cattle use human inedible feeds and by-products of human food production to produce nutrient-dense foods of great value to humans. Reductions in land clearing and burning of grasslands and increased carbon sequestration in soils and trees have potential to substantially reduce GHG emissions. Increased efficiencies of production through intensified feeding and enteric modification have markedly reduced intensity of GHG emissions for cattle in Australia. Genetic selection for lower emissions has modest, but cumulative potential to reduce GHG (mostly CH4 ) emissions and intensity. Improved reproductive performance can reduce intensity of GHG emissions, especially in beef production. Feeds and technologies that reduce GHG production and intensity include improved pastures, grain feeding, dietary lipids, nitrates, ionophores, seaweed, 3-NOP, hormonal growth promotants in beef, and improved diets for peri-parturient dairy cattle. There is considerable potential to further reduce emissions from cattle using the technologies reviewed. Cattle are susceptible to heat stress and ameliorating interventions include tree and shelter belts, shade, housing, cooling with fans and water and dietary manipulations. Numerous interventions can reduce GHG emissions and intensity from cattle. There are opportunities to increase carbon capture and maintain biodiversity in Australia's extensive rangelands, but these require quantification and application. We can reduce the intensity of CH4 emissions for cattle in Australia and simultaneously improve their well-being.

Assessing the efficiency of dimethylpyrazole-based nitrification inhibitors under elevated CO2 conditions

Nitrification inhibitors (NIs) are useful tools to reduce nitrogen (N) losses derived from fertilization in agriculture. However, it remains unclear whether a future climate scenario with elevated CO2 could affect NIs efficiency. Thus, the objective of this work was to study whether the increase of atmospheric CO2 concentration would affect the efficiency of two dimethylpyrazole-based NIs: 3,4-dimethylpyrazol phosphate (DMPP) and 3,4-dimethylpyrazol succinic acid (DMPSA) in a plant-soil microcosm. To do so, Hordeum vulgare var. Henley plants were grown in soil fertilized with ammonium sulphate (AS) with or without NIs under controlled environmental conditions at ambient CO2 (aCO2) or elevated CO2 (eCO2; 700 ppm). In the soil, mineral nitrogen and N2O emission evolution were monitored together with nitrifying and denitrifying population that were quantified by qPCR. In the plant, biomass, total amino acid content and isotopic discrimination of N and C were measured. Both NIs showed greater efficiency to maintain soil NH4+ content under eCO2 compared to aCO2, as a consequence of 80% reduction of AOB abundance in eCO2. Indeed, both inhibitors were able to lessen 53% the N2O emissions in eCO2 compared to aCO2. Regarding the plant, DMPP and DMPSA negatively affected plant biomass at aCO2 but this effect was restored at eCO2 due to a better ammonium tolerance associated with an increase in total amino acid content. Overall, DMPP and DMPSA NIs were highly efficient under eCO2, reducing N2O emissions and keeping N in the soil stable for longer while maintaining plant biomass production.

Gradual South‐North Climate Transition in the Atlantic Realm Within the Younger Dryas

AbstractThe abrupt climate event Younger Dryas (YD) has been extensively studied; however, its structure is still poorly understood. Climate in northeastern Brazil is very sensitive to the latitudinal position of the intertropical convergence zone (ITCZ) associated with abrupt climate change in the Atlantic. Here, we report changes in the ITCZ position within the YD by using precise speleothem multiproxy records from northeastern Brazil. We provide evidence for a gradual northward migration of the ITCZ preceding poleward shifts of the westerlies and the polar front in northern high latitudes within the YD. This can be attributed to gradual increase in atmospheric CO2 concentration as a consequence of the weakening Atlantic Meridional Overturning Circulation (AMOC). We suggest that a persistent increase in atmospheric CO2 might have triggered a resumption of the AMOC and reorganization of the atmosphere circulation in the Atlantic during the mid‐YD.

Feasibility of the 4 per 1000 aspirational target for soil carbon: A case study for France.

Increasing soil organic carbon (SOC) stocks is a promising way to mitigate the increase in atmospheric CO2 concentration. Based on a simple ratio between CO2 anthropogenic emissions and SOC stocks worldwide, it has been suggested that a 0.4% (4 per 1000) yearly increase in SOC stocks could compensate for current anthropogenic CO2 emissions. Here, we used a reverse RothC modelling approach to estimate the amount of C inputs to soils required to sustain current SOC stocks and to increase them by 4‰ per year over a period of 30 years. We assessed the feasibility of this aspirational target first by comparing the required C input with net primary productivity (NPP) flowing to the soil, and second by considering the SOC saturation concept. Calculations were performed for mainland France, at a 1 km grid cell resolution. Results showed that a 30%–40% increase in C inputs to soil would be needed to obtain a 4‰ increase per year over a 30‐year period. 88.4% of cropland areas were considered unsaturated in terms of mineral‐associated SOC, but characterized by a below target C balance, that is, less NPP available than required to reach the 4‰ aspirational target. Conversely, 90.4% of unimproved grasslands were characterized by an above target C balance, that is, enough NPP to reach the 4‰ objective, but 59.1% were also saturated. The situation of improved grasslands and forests was more evenly distributed among the four categories (saturated vs. unsaturated and above vs below target C balance). Future data from soil monitoring networks should enable to validate these results. Overall, our results suggest that, for mainland France, priorities should be (1) to increase NPP returns in cropland soils that are unsaturated and have a below target carbon balance and (2) to preserve SOC stocks in other land uses.