Doubling Of CO2 Concentration Research Articles

BIOCLIM Modeling for Predicting Suitable Habitat for Endangered Tree Tapiscia sinensis (Tapisciaceae) in China

Climate change jeopardizes species survival, particularly for endangered species. This risk extends to the endangered Chinese endemic tree Tapiscia sinensis. The factors underpinning T. sinensis’s habitat distribution are poorly understood, and its potential response to future climate scenarios remains unclear. With six shortlisted climate factors and 117 occurrence records, we modeled T. sinensis’s potential distribution across China using the BIOCLIM model. We applied principal component analysis to examine the primary climate factors restricting its geographical range. The findings indicate that T. sinensis’ range is principally located in China’s middle subtropical climatic zone at low–mid altitudes. The principal component analysis identified two critical factors representing temperature and precipitation. Temperature was the most critical factor limiting T. sinensis distribution, especially the effect of temperature seasonality and isothermality. The habitat suitability model generated by BIOCLIM under current climate conditions demonstrated strong concordance between the predicted suitable areas and the present actual distribution range. These results verify that the model can reliably identify habitats conducive to T. sinensis growth and survival. However, under a hypothetical future climate scenario of doubled atmospheric CO2 concentrations for 2100, the model indicates a precipitous reduction and fragmentation in the areas with excellent suitability conditions. This predicted decline highlights the considerable threats posed by climate change to the long-term survival of this endangered species in China. Our habitat modeling yields critical insights that inform the development of science-based strategies and best practices to improve conservation management plans for research, protection, nursery cultivation, and sustainable planting in China. Habitat suitability knowledge could aid introduction and cultivation efforts for T. sinensis globally in places with analogous climates.

Elevated atmospheric CO2 drove an increase in tropical cyclone intensity during the early Toarcian hyperthermal

The occurrence of sedimentary storm deposits around the Tethys Ocean during the early Toarcian hyperthermal (~183 Ma) suggests that intensified tropical cyclone (TC) activity occurred in response to CO2 rise and marked warming. However, this hypothesized linkage between extreme warmth and storm activity remains untested, and the spatial pattern of any changes in TCs is unclear. Here, model results show that there were two potential storm genesis centers over Tethys during the early Toarcian hyperthermal located around the northwestern and southeastern Tethys. The empirically determined doubling of CO2 concentration that accompanied the early Toarcian hyperthermal (~500 to ~1,000 ppmv) leads to increased probability of stronger storms over Tethys, in tandem with more favorable conditions for coastal erosion. These results match well with the geological occurrence of storm deposits during the early Toarcian hyperthermal and confirm that increased TC intensity would have accompanied global warming.

Spatial–Temporal Distribution Pattern of Ormosia hosiei in Sichuan under Different Climate Scenarios

Ormosia hosiei is an endemic plant in China listed as a national grade II key protected wild plant with important scientific, economic, and cultural values. This study was designed to predict the potential suitable distribution areas for O. hosiei under current and future climate change and to provide a reference to enhance the species’ conservation and utilization. Based on the actual geographical locations of O. hosiei in Sichuan, we applied two species distribution models (BIOCLIM and DOMAIN) to predict its current and future potential suitable areas and future change patterns. We also analyzed the major climatic variables limiting its geographical distribution with principal component analysis. The results indicated that O. hosiei was mainly distributed in the eastern region of Sichuan and concentrated in the middle subtropical climate zone at relatively low elevations. The principal component analysis identified two critical factors representing temperature and moisture. The temperature was the most critical factor limiting O. hosiei distribution in Sichuan, especially the effect of extreme low temperatures. Both models’ simulation results of potential suitable areas under the current climate scenario showed that the excellent suitable habitat was consistent with the current actual distribution, remaining in the eastern region of Sichuan. Under the future climate scenario with doubled CO2 concentration (2100), both models predicted a sharp decrease in the areas of excellent and very high suitable habitats. The findings can inform strategies and guidelines for O. hosiei research, conservation, nursery production, and cultivation in Sichuan.

Potential impacts of climate change on the productivity and soil carbon stocks of managed grasslands.

Rain-fed pastoral systems are tightly connected to meteorological conditions. It is, therefore, likely that climate change, including changing atmospheric CO2 concentration, temperature, precipitation and patterns of climate extremes, will greatly affect pastoral systems. However, exact impacts on the productivity and carbon dynamics of these systems are still poorly understood, particularly over longtime scales. The present study assesses the potential effects of future climatic conditions on productivity and soil organic carbon (SOC) stocks of mowed and rotationally grazed grasslands in France. We used the CenW ecosystem model to simulate carbon, water, and nitrogen cycles in response to changes in environmental drivers and management practices. We first evaluated model responses to individual changes in each key meteorological variable to get better insights into the role and importance of each individual variable. Then, we used 3 sets of meteorological variables corresponding to 3 Representative Concentration Pathways (RCP 2.6, RCP 4.5 and RCP 8.5) for long-term model runs from 1975 to 2100. Finally, we used the same three RCPs to analyze the responses of modelled grasslands to extreme climate events. We found that increasing temperature slightly increased grasslands productivities but strongly reduced SOC stocks. A reduction in precipitation led to reductions of biomass and milk production but increased SOC. Conversely, doubling CO2 concentration strongly increased biomass and milk production and marginally reduced SOC. These SOC trends were unexpected. They arose because both increasing precipitation and CO2 increased photosynthetic carbon gain, but they had an even greater effect on the proportion of biomass that could be grazed. The amount of carbon remaining on site and able to contribute to SOC formation was actually reduced under both higher precipitation and CO2. The simulations under the three RCPs indicated that grassland productivity was increased, but that required higher N fertilizer application rates and also led to substantial SOC losses. We thus conclude that, while milk productivity may continue at current rates under climate change, or even increase slightly, there could be some soil C losses over the 21st century. In addition, under the highest-emission scenario, the increasing importance of extreme climate conditions (heat waves and droughts) might render conditions at our site in some years as unsuitable for milk production. It highlights the importance of tailoring farming practices to achieve the dual goals of maintaining agricultural production while safeguarding soil C stocks.

Spatio-temporal patterns of an invasive species Mimosa bimucronata (DC.) Kuntze under different climate scenarios in China

Invasive alien plants pose a serious threat to native ecosystems and their biodiversity. To control their spread and damage, it is critical to clarify the potential distribution patterns of the invaders at the regional scale and their response to climate change. Mimosa bimucronata (DC.) Kuntze, a shrub extremely tolerant of stressful habitat conditions, is used as firewood and hedgerow in the tropics. Since its introduction to China in the 1950s, it has established a sustainable population and become an aggressive invasive species. Due to serious ecological threats in South China, it has been listed as a Key Management Invasive Alien Species. To understand its invasibility in China, two species distribution models (SDMs), BIOCLIM and DOMAIN, were employed to evaluate the main environmental factors regulating its geographical distribution under the current climate and a future climate change scenario with double CO2 concentration. We found an extensive spread of current suitability habitats in South China, concentrated mainly in the tropical-subtropical provinces of Guangdong, Guangxi, Hainan, and Fujian. The complex interplay of local bioclimatic factors shaped the species distribution. Under the current climate, the predicted range was somewhat larger than the current one. Under the climate change scenario, suitable habitats for Mimosa bimucronata would remain similar to the current one. However, its invasiveness in the current biogeographical range would be more serious. The suitability habitats would expand and shift to the Southeastern coastal and Northern parts of South China under future climate change. We suggest adopting early monitoring and eradication measures in potential invasion areas and practical measures to contain its spread. The results could provide a conceptual basis to formulate prevention and control strategies to improve future containment of its invasion.

Environmental Factors Driving the Spatial Distribution Pattern of Venerable Trees in Sichuan Province, China.

Venerable trees are important natural resources and cultural heritage, offering historical, ecological, social and economic value. However, global warming and anthropogenic activities have threatened their welfare and survival. A comprehensive understanding of their current and future spatial patterns, vis-á-vis environmental conditions, can inform the co-management of sustainable resource use and conservation. We employed the existing spatial occurrence data and environmental variables (bioclimate and elevation) to simulate the optimal habitats for venerable trees in China's Sichuan Province. We evaluated the current and future climate scenarios of 2100 with double CO2 concentration. The BIOCLIM and QGIS spatial analyses assessed the primary factors of geographical distribution. The results identified 10,720 venerable trees from 123 species, 81 genera and 42 families. Cupressus funebris dominated, with the maximum importance value, followed by Ginkgo biloba, Ficus virens var. sublanceolata, and Phoebe zhennan. The elevation distribution of tree abundance and species richness demonstrated a unimodal pattern, skewing to the low-elevation end, with a concentration in the 600-1500 m low-medium altitude. The majority of trees and excellent habitats were found in eastern Sichuan with a less harsh terrain and climate. The bio3 (isothermality) and bio7 (temperature annual range) factors significantly influenced tree occurrence. Temperature imposed a greater effect on distribution than moisture under the current climate scenario. For the future climate-change scenario, the suitable habitats were predicted to maintain an overall stable pattern, with largely contiguous expansions of better habitats. However, climate warming would shrink the excellent habitats on the plains. The findings can inform strategies and guidelines for venerable-tree conservation in Sichuan. Furthermore, vulnerable areas could be identified. The future range expansion sites could be enlisted to cultivate new trees to replenish the venerable-tree pool. Habitat patches that remain sustainable could provide refugia with the potential for protected-area designation.

Impacts of atmospheric CO2 increase and Amazon deforestation on the regional climate: A water budget modelling study

AbstractGlobal air temperature increase has caused changes in the global climate such as droughts, floods and severe events. Land cover shifts and the increase in greenhouse gas emissions can intensify these impacts. Therefore, the application of Specific Warming Level 2 (SWL2) technique has been considered to evaluate the global warming issue in various climate scales, which may induce different responses in the climate system. The objective of this study is to evaluate the impacts of a doubling of current atmospheric CO2 concentrations as well as the influence of deforestation of the Amazon Forest on the climate of South America. In this study, the CPTEC‐BAM1.2 global model was used to simulate these processes. The first scenario of simulations considered doubled atmospheric CO2 concentration (2XCO2 = 776 ppm) and the second scenario is the total conversion of the Amazon Forest to pasture (DEF). In the third scenario both CO2 and deforestation are considered simultaneously (2XCO2 + DEF). A control simulation considers the natural Amazon Forest shape and a steady CO2 concentration of 388 ppm. Results suggest that the temperature increased in all scenarios, the highest increment in the 2XCO2 + DEF experiment (5.4°C in 2XCO2 + DEF, 5.1°C in DEF and 3.2°C in 2XCO2). The model simulated drastic negative rainfall anomalies in each of three scenarios (2XCO2 + DEF: −2.1 mm day−1, 2XCO2: −1.3 mm day−1 and DEF: −0.9 mm day−1). Besides less precipitation and evapotranspiration, shifts in moisture transport were identified in each of the three scenarios. The effect of doubled atmospheric CO2 produces results similar to deforestation for hydrological water budget changes, and total pasture conversion may intensify such changes.

Growth and actual leaf temperature modulate CO2responsiveness of monoterpene emissions from holm oak in opposite ways

Abstract. Climate change can profoundly alter volatile organic compound (VOC) emissions from vegetation and thus influence climate evolution. Yet, the short- and long-term effects of elevated CO2 concentrations on emissions in interaction with temperature are not well enough understood, especially for VOCs other than isoprene. To gain additional insight, we conducted a study on holm oak, which is known for its strong foliar monoterpene emissions that are directly linked to their synthesis. We measured CO2-response curves of emissions, CO2–H2O gas exchanges and chlorophyll fluorescence at two assay temperatures (30 and 35 ∘C) on saplings of four populations grown under normal and double CO2 concentrations combined with two temperature growth regimes differing by 5 ∘C (day/night: 25/15 and 30/20 ∘C). A stepwise reduction in CO2 resulted in a decrease in emissions, occasionally preceded by an increase, with the overall decrease in emissions being greater at 35 ∘C than at 30 ∘C assay temperature. During ramping to high CO2, emissions remained mostly unchanged at 35 ∘C, whereas at 30 ∘C they often dropped, especially at the highest CO2 levels (≥ 1200 ppm). In addition to the actual leaf temperature, the high CO2 responsiveness of emissions was modulated by the plant's growth temperature with warm-grown plants being more sensitive than cool-grown plants. In contrast, growth CO2 had no significant effect on the CO2 sensitivity of emissions, although it promoted plant growth and the leaf emission factor. Correlation analyses suggest that the emission response to CO2 depended primarily on the availability of energetic cofactors produced by photosynthetic electron transport. This availability was likely limited by different processes that occurred during CO2 ramping including photooxidative stress and induction of protective and repair mechanisms as well as competition with CO2 fixation and photorespiration. In addition, feedback inhibition of photosynthesis may have played a role, especially in leaves whose emissions were inhibited only at very high CO2 levels. Overall, our results confirm an isoprene-analogous behavior of monoterpene emissions from holm oak. Emissions exhibit a non-linear response curve to CO2 similar to that currently used for isoprene emission in the MEGAN model, with no difference between major individual monoterpene species and plant chemotype. Simulations estimating the annual VOC releases from holm oak leaves at double atmospheric CO2 indicate that the observed high-CO2 inhibition is unlikely to offset the increase in emissions due to the predicted warming.

Mechanisms for Zonal Mean Wind Responses in the Thermosphere to Doubled CO2 Concentration

AbstractWe explored mechanisms for the thermospheric zonal mean wind responses to doubled CO2 concentration through investigating the zonal mean momentum balance in the thermosphere using GAIA model simulations in June. The analysis shows that ion drag, molecular viscosity, and meridional pressure gradient force vary 3–20 times more than the other forces due to the doubled CO2 concentration. The three forces strongly attenuate each other; consequently, the increase in zonal mean zonal ion drag dominantly strengthens the southward wind (∼15 ms−1 at maximum) in the northern (summer) hemisphere and latitudes north of 35S. This strengthened ion drag was attributed to increased ion density/relative velocity between ions and neutral particles in the northern/southern hemisphere. Southward of 35, the zonal pressure gradient force and the meridional advection of zonal wind strengthen the southward wind by 4–12 ms−1 in total. On the other hand, the zonal wind is mainly altered by increased meridional pressure gradient force (∼15 ms−1 at maximum) caused by a latitudinally asymmetric response of the thermosphere density to increasing CO2 concentration. Our results suggest that the increased ion density in the northern hemisphere is the underlying trigger for the wind responses to increasing CO2 concentration. Furthermore, we show that the meridional advection was mainly (∼70%) due to that of the DW1 tidal component.

Effects of increasing CO2 concentration and water deficit on photosynthetic performance and water use efficiency of typical green manure plants

Exploring the impacts of CO2 and soil water availability on the photosynthetic performance and water use efficiency of three green manure plants could provide theoretical basis for the adaptive management of grassland ecosystems under future climate change. An experiment was conducted in an artificial climate chamber with precisely controled CO2 concentrations of 400 (natural atmospheric) and 800 μmol·mol-1 (doubled), and four water treatments, 80% field water holding capacity (FC) (full irrigation control group), 55%-60% FC (mild water deficit), 35%-40% FC (moderate water deficit), <35% FC (severe water deficit) to investigate the impacts of increasing CO2 concentration and water deficit on chlorophyll content, gas exchange variables, and water use efficiency (WUE) of oilseed rape (Brassica napus), white clover (Trifolium repens), and alfalfa (Medicago sativa). The results showed that under the same CO2 concentration, when soil moisture was less than 40% FC, the chlorophyll content and gas exchange parameters of three plants were significantly decreased. The treatment of 55%-60% FC did not alter the total chlorophyll content of three species, but reduced the photosynthetic rate (Pn) and transpiration rate (Tr) of white clover and alfalfa by 6%-25% and did not affect their WUE. Compared with atmospheric CO2 concentration, the doubled CO2 concentration significantly decreased the Pn of oilseed rape by 21.5% under the full irrigation treatment, increased the Pn of three species under mild water deficit, increased the Pn of oilseed rape and alfalfa under moderate water deficit, but only improved the Pn of alfalfa under severe water deficit. The doubled CO2 concentration significantly increased WUE of white clover and alfalfa under all water deficit conditions, but only increased WUE of oilseed rape under mild water deficit. Increasing CO2 concentration and water deficit significantly interacted to affect Pn of three species and the WUE of oilseed rape. In summary, the three species differed in their responses to doubled atmospheric CO2 concentration and different levels of water deficit. Our results suggested that elevated CO2 concentration could improve the adverse effects of mild water deficit on photosynthetic performance and WUE of three species, but only improve the photosynthetic performance of alfalfa under severe water deficit.

Effect of climate change and elevated CO2 on reference evapotranspiration in Varanasi, India - A case study

Evapotranspiration (ET) is the major component of hydrological cycle, and will affect the crop water requirement and future planning and management of water resources under changing climate scenarios. In the present study, an attempt was made to study the sensitivity of reference evapotranspiration (ETo) to different climatic variables, and effect of temperature and elevated CO2 on ETo using meteorological data (1973-2010) of the Banaras Hindu University (BHU), Varanasi. The FAO-56 Penman–Monteith method was used to estimate ETo, and sensitivity of ETo was studied in terms of changes in temperature, solar radiation, wind speed and vapour pressure deficit. The combined effect of temperature and elevated CO2 levels was studied by varying the temperature from 1°C to 5°C, and the CO2 level from 330 ppm to 660 ppm. The simulation results showed that the mean temperature (Tmean) influenced the annual ETo the most followed by solar radiation (Rs), vapour pressure deficit (VPD) and wind speed (U2). There are about 18.20, 13.80, 7.90 and 5.40% increase in annual ETo with 25% increase in Tmean, Rs, VPD, and U2, respectively. Simulating the combined effect of temperature and elevated CO2 indicated that the effect of 2.5 °C rise in temperature is offset by doubling of CO2 concentration. Thus, the effect of rising temperature is moderated by the increasing CO2 concentrations, and the crop water demand may not rise significantly under the climate change scenarios.

Effects of elevated CO2 on the evapotranspiration over the agricultural land in Northwest China

The increase in atmospheric carbon dioxide (CO2) concentration is changing plant physiology, thus affecting terrestrial hydrological response. A nonlinear stomatal conductance response to carbon dioxide concentration (gs-CO2) was incorporated in the VIC model for better representation of the evapotranspiration (ET) response to the elevated CO2. The annual ET of maize and wheat over the agricultural land in Northwest China was found to decrease by 0.54% and 0.21% during 1980–2010, respectively. Under doubled CO2 concentration (660 ppm), the ET reduction of maize and wheat was 23.3 mm and 8.9 mm, which accounted for 4.3% and 1.8% of the corresponding annual ET. The annual ET reduction of maize, under the four future scenarios (RCP4.5_2040s, RCP4.5_2080s, RCP8.5_2040s, and RCP8.5_2080s), was about 1.1–6.4%, resulted from an ensemble mean of eight general circulation models. The effects of elevated CO2 offset part of ET increase caused by the precipitation and temperature changes. This study has practical implications for precise irrigation. The ET response of maize should be paid more attention for its larger potential in saving irrigation water for the studied region. The elevated CO2 concentration will be beneficial for saving irrigation water to a certain degree.

Return to different climate states by reducing sulphate aerosols under future CO2 concentrations

It is generally believed that anthropogenic aerosols cool the atmosphere; therefore, they offset the global warming resulting from greenhouse gases to some extent. Reduction in sulphate, a primary anthropogenic aerosol, is necessary for mitigating air pollution, which causes atmospheric warming. Here, the changes in the surface air temperature under various anthropogenic emission amounts of sulphur dioxide (SO2), which is a precursor of sulphate aerosol, are simulated under both present and doubled carbon dioxide (CO2) concentrations with a climate model. No previous studies have conducted explicit experiments to estimate the temperature changes due to individual short-lived climate forcers (SLCFs) in different climate states with atmosphere–ocean coupled models. The simulation results clearly show that reducing SO2 emissions at high CO2 concentrations will significantly enhance atmospheric warming in comparison with that under the present CO2 concentration. In the high latitudes of the Northern Hemisphere, the temperature change that will occur when fuel SO2 emissions reach zero under a doubled CO2 concentration will be approximately 1.0 °C, while this value will be approximately 0.5 °C under the present state. This considerable difference can affect the discussion of the 1.5 °C/2 °C target in the Paris Agreement.

Millennium time-scale experiments on climate-carbon cycle with doubled CO2 concentration

Earth system models (ESMs) are commonly used for simulating the climate–carbon (C) cycle and for projecting future global warming. While ESMs are most often applied to century-long climate simulations, millennium-long simulations, which have been conducted by other types of models but not by ESM because of the computational cost, can provide basic fundamental properties of climate–C cycle models and will be required for estimating the carbon dioxide (CO2) concentration and subsequent climate stabilization in the future. This study used two ESMs (the Model for Interdisciplinary Research on Climate, the Earth system model version (MIROC-ESM) and the MIROC Earth system version 2 for long-term simulation (MIROC-ES2L)) to investigate millennium-scale climate and C cycle adjustment to external forcing. The CO2 concentration was doubled abruptly at the beginning of the model simulations and kept at that level for the next 1000 or 2000 years; these model simulations were compared with transient simulations where the CO2 was increased at the rate of 1% year−1 for up to 140 years (1pctCO2). Model simulations to separate and evaluate the C cycle feedbacks were also performed. Unlike the 1pctCO2 experiment, the change in temperature–cumulative anthropogenic C emission (∆T–CE) relationship was non-linear over the millennium time-scales; there were differences in this nonlinearity between the two ESMs. The differences in ∆T–CE among existing models suggest large uncertainty in the ∆T and CE in the millennium-long climate-C simulations. Ocean C and heat transport were found to be disconnected over millennium time-scales, leading to longer time-scale of ocean C accumulation than heat uptake. Although the experimental design used here was highly idealized, this long-lasting C uptake by the ocean should be considered as part of the stabilization of CO2 concentration and global warming. Future studies should perform millennium time-scale simulations using a hierarchy of models to clarify climate-C cycle processes and to understand the long-term response of the Earth system to anthropogenic perturbations.

Climate Sensitivity and Feedbacks of BCC-CSM to Idealized CO2 Forcing from CMIP5 to CMIP6

Climate sensitivity represents the response of climate system to doubled CO2 concentration relative to the preindustrial level, which is one of the sources of uncertainty in climate projections. It is unclear how the climate sensitivity and feedbacks will change as a model system is upgraded from the Coupled Model Intercomparison Project Phase 5 (CMIP5) to CMIP6. In this paper, we address this issue by comparing two versions of the Beijing Climate Center Climate System Model (BCC-CSM) participating in CMIP6 and CMIP5, i.e., BCC-CSM2-MR and BCC-CSM1.1m, which have the same horizontal resolution but different physical parameterizations. The results show that the equilibrium climate sensitivity (ECS) of BCC-CSM slightly increases from CMIP5 (2.94 K) to CMIP6 (3.04 K). The small changes in the ECS result from compensation between decreased effective radiative forcing (ERF) and the increased net feedback. In contrast, the transient climate response (TCR) evidently decreases from 2.19 to 1.40 K, nearly the lower bound of the CMIP6 multimodel spread. The low TCR in BCC-CSM2-MR is mainly caused by the small ERF overly even though the ocean heat uptake (OHU) efficiency is substantially improved from that in BCC-CSM1.1m. Cloud shortwave feedback (λSWCL) is found to be the major cause of the increased net feedback in BCC-CSM2-MR, mainly over the Southern Ocean. The strong positive λSWCL in BCC-CSM2-MR is coincidently related to the weakened sea ice-albedo feedback in the same region. This result is caused by reduced sea ice coverage simulated during the preindustrial cold season, which leads to reduced melting per 1-K global warming. As a result, in BCC-CSM2-MR, reduced surface heat flux and strengthened static stability of the planetary boundary layer cause a decrease in low-level clouds and an increase in incident shortwave radiation. This study reveals the important compensation between λSWCL and sea ice-albedo feedback in the Southern Ocean.

Effects of CO2 enrichment by fermentation of CRAM on growth, yield and physiological traits of cherry tomato.

Carbon dioxide (CO2) concentration in greenhouses is sub-optimal for vegetable production. Many techniques have been used to increase CO2 concentration in greenhouses but most of them are expensive with certain limitations and drawbacks. We adopted a new strategy to elevate CO2 concentration in the greenhouse throughout the day via crop residues and animal manure composting (CRAM). During the whole cultivation period, CRAM-treated greenhouse had doubled CO2 concentration which significantly increased the yield of cherry tomatoes (Lycopersiconesculentum L.) i.e. up to 38%. The influence of CRAM procedure on cherry tomato quality was also investigated and the concentrations of total soluble solids (TSS) and soluble sugar were found to be significantly higher in cherry tomatoes grown under composting greenhouse than that of non-composting greenhouse. Additionally, CRAM-CO2 enrichment also resulted in increased concentrations of ascorbic acid (Vitamin C) and titrate acid as compared with the control. In contrast, the concentration of nitrate was considerably decreased in cherry tomato grown under CO2 enriched condition than that of control. The increase in active oxygen metabolisms such as POD, CAT and SOD while a decrease in MDA, as well as APX was observed for cherry tomatoes grown under CO2 enriched condition. Hence, CO2 fertilization by using CRAM in greenhouse significantly improved quality and increased the yield of cherry tomatoes.

A Vegetation Climatic Unit for Studying the Impact on Higher Plants of an Increased CO2 Concentration in Comparison with the Atmospheric CO2 Concentration

An experimental vegetative climatic unit (VCU) consisting of two identical climatic chambers—experimental (CC-1) and control (CC-2)—was developed. The VCU allows long-term cultivation of higher plants under various constant microclimate conditions, moisture supply, and CO2 concentration. The basic scheme of the VCU and its parameters and operation are considered. As a result of a long (50 days) vegetation experiment in the VCU, we evaluated the effect of a double atmospheric CO2 concentration on СО2/Н2О gas exchange, the water status of leaves, and the biological productivity of pea (Pisum sativum L.) plants. The water status of the plant leaves of the experimental and control variants was evaluated based on the water potential value on the surface of the apoplast of the substomatal cavity. Compared to control plants under conditions of double CO2 concentration, a 1.5-fold increase in leaf, stem, and root weight was noted. The preservation of proportional organ growth under growing conditions at a double concentration of atmospheric CO2 in pea varieties with contrasting biological productivity—the highly productive Alpha variety and the unproductive Medovik variety—indicated the absence of varietal specificity of the pea growth reaction to increased CO2. The maximum yield of chlorophyll FSII fluorescence, photosynthetic CO2/H2O-gas exchange of intact leaves, measured at normal CO2 concentration, as well as the water status of the leaves, were the same in the plants of the experimental and control variants of the Medovik variety. With other conditions being equal, a double CO2 concentration of under nonlimiting by the water regime and mineral nutrition conditions of pea plant growing formed a leaf that does not differ from the leaf formed under a normal CO2 concentration. An increase in the biological productivity of peas under these conditions was provided by an increased photosynthetic carboxylation activity under increased atmospheric CO2 concentration and the formation of higher stem and leaf phytomass. As a result, it was concluded that the reaction of the photosynthetic and growth functions of pea plants to long-term cultivation under conditions of a double atmospheric CO2 concentration at nonlimiting by mineral nutrition and water supply conditions did not cause imbalances in growth and development. The reaction of the photosynthetic and growth functions of pea plants was within the physiological norm of the reaction of a pea plant to stress.

Climate sensitivity revisited

The commonly used energy balance model from Gregory et al. (2002) that underlies many published estimates of Equilibrium Climate Sensitivity (ECS) and Transient Climate Response (TCR) to anthropogenic forcing requires only four parameters for calculation of ECS and three for TCR. Both estimates require a value for the increase in global mean surface air temperature (ΔT) over a period of time, the increment in forcing driving the temperature change over that period (ΔF), and knowledge of the radiative forcing resulting from a doubling in CO2 concentration (F2×CO2). For ECS a value for the associated global heating rate (ΔQ) is also required. Each of these parameters has a best estimate available from the IPCC’s Fifth Assessment Report, but the authors did not provide best estimates for ECS and TCR within the broad uncertainty ranges quoted, 1.5–4.5 K for ECS and 1.0–2.5 K for TCR. Best estimates for ECS and TCR consistent with AR5 best estimates for ΔF and F2×CO2 are provided here. A well-known heuristic model was modified and applied to seven observation-based global temperature datasets to isolate temperature trend due to anthropogenic forcing from confounding effects of variability due to volcanism, cycles in solar irradiance and internal climate variability. The seven estimates of ECS and TCR were remarkably similar despite very large differences in time-base of the datasets analysed, yielding best estimates of 2.36 ± 0.13 K and 1.58 ± 0.09 K respectively at 95% confidence based on the AR5 best estimates for ΔF, F2×CO2 and ΔQ from Wijffels et al. (2016). The ECS and TCR best estimates here are tied to those AR5 and ΔQ best estimates, but can be simply scaled were those best estimate values to be refined in the future.

Effect of Elevated CO2 Concentration on the Disease Severity of Compatible and Incompatible Interactions of Brassica napus-Leptosphaeria maculans Pathosystem.

Global warming by increased atmospheric CO2 concentration has been widely accepted. Yet, there has not been any consistent conclusion on the doubled CO2 concentration that in the future will affect plant disease incidence and severity. Blackleg disease, mainly caused by Leptosphaeria maculans, is a major disease on canola production globally. Brassica napus and L. maculans have a gene-for-gene interaction, which causes an incompatible reaction between canola plants carrying resistance genes and L. maculans isolates carrying corresponding avirulence genes. In this study, B. napus varieties and lines inoculated with different Leptosphaeria isolates were subjected to simulated growth conditions, namely, growth chambers with normal environments and with controlled CO2 concentrations of 400, 600, and 800 ppm. The results indicated that the elevated CO2 concentrations have no noticeable effect on the inferred phenotypes of the canola–blackleg interactions. However, the disease severity decreased in most of the B. napus–L. maculans interactions at extremely high CO2 concentration (800 ppm). The varied pathogenicity changes of the B. napus–L. maculans pathosystem under elevated CO2 concentrations at 400 or 600 ppm may be due to the genetic background or physiological differences in plants and pathogenicity differences in L. maculans isolates having different Avr gene profiles. The mechanisms by which elevated CO2 concentrations affect the B. napus–L. maculans pathosystem will help us understand how climate change will impact crops and diseases.

Quantifying Phosphorus and Water Demand to Attain Maximum Growth of Solanum tuberosum in a CO2-Enriched Environment.

Growth promotion by ambient CO2 enrichment may be advantageous for crop growth but this may be influenced by soil nutrient availability. Therefore, we quantified potato (Solanum tuberosum L.) growth responses to phosphorus (P) supply under ambient (a[CO2]) and elevated (doubled) CO2 concentration (e[CO2]). A pot experiment was conducted in controlled-environment chambers with a[CO2] and e[CO2] combined with six P supply rates. We obtained response curves of biomass against P supply rates under a[CO2] and e[CO2] (R2 = 0.996 and R2 = 0.992, respectively). A strong interaction between [CO2] and P was found. Overall, e[CO2] enhanced maximum biomass accumulation (1.5-fold) and water-use efficiency (WUE) (1.5-fold), but not total water use. To reach these maxima, minimum P supply rate at both [CO2] conditions was similar. Foliar critical P concentration (i.e., minimum [P] to reach 90% of maximum growth) was also similar at nearly 110 mg P m−2. Doubling [CO2] did not increase P and water demand of potato plants, thus enabling the promotion of maximum growth without additional P or water supply, but via a significant increase in WUE (9.6 g biomass kg−1 water transpired), presumably owing to the interaction between CO2 and P.