Chlorine Loading Research Articles

N-Halamine-coated cotton for antimicrobial and detoxification applications

A new N-halamine precursor, 3-(2,3-dihydroxypropyl)-7,7,9,9-tetramethyl-1,3,8-triazaspiro[4.5]decane-2,4-dione (TTDD diol), was synthesized and bonded onto cotton fabrics. Fabrics with variable amounts of chlorine loading were prepared by using several concentrations of TTDD diol. A second N-halamine precursor, 3-(3-triethoxysilylpropyl)-7,7,9,9-tetramethyl-1,3,8-triazaspiro[4.5]decane-2,4-dione (TTDD siloxane), was also synthesized and bound to cotton for comparison purposes. The coated cotton fabrics contained two types of N–Cl moieties after chlorination of the amine and amide groups. Swatches with variable chlorine loadings were challenged with Staphylococcus aureus and Escherichia coli O157:H7 as a function of contact time. The biocidal test results showed that the chlorine loadings and surface hydrophobicities influenced the antimicrobial efficacies. The chlorinated swatches have also been employed to oxidize the simulant of chemical mustard to the less toxic sulfoxide derivative.

A Review Article: Sevelamer Hydrochloride and Metabolic Acidosis in Dialysis Patients

Sevelamer hydrochloride is a phosphate binder and its effectiveness to reduce the cardiovascular mortality of dialysis patients has been tested. Sevelamer hydrochloride also contains chlorine, so a decrease in bicarbonate due to chlorine load was anticipated and metabolic acidosis thought to associate with sevelamer hydrochloride has been reported in some papers. We reported that sevelamer hydrochloride exacerbated metabolic acidosis in hemodialysis patients, depending on the dosage. Also a Japanese nationwide survey suggested that sevelamer hydrochloride usage potentially aggravates acidosis in dialysis patients. A multi-institute research study by Edmung et al. has shown that metabolic acidosis, with serum CO2 below 17.5 mmol/L, is by itself associated with increased risk of death in dialysis patients. Furthermore, the Dialysis Outcomes and Practice Patterns Study (DOPPS) revealed that both high (> 27 mmol/L) and low (< or = 17 mmol/L) serum bicarbonate (total CO2) levels were associated with increased risk for mortality and hospitalization. There has not been any significant evidence to show that sevelamer hydrochloride has reduced the cardiovascular mortality of dialysis patients compared with calcium-based binder. Clinicians should check not only the level of chlorine but also the level of total CO2 or bicarbonate during the treatment with sevelamer hydrochloride, and control metabolic acidosis.

Effect of Alkyl Derivatization on Several Properties of N-Halamine Antimicrobial Siloxane Coatings

Variation of alkyl substitution at position 5 on the hydantoin ring of a series of N-halamine siloxane derivatives has been employed to better understand the biocidal activities of these compounds for use in preparing antimicrobial coatings. The alkyl derivatization of the hydantoin ring at its 5 position, while an essentially constant chlorine loading is maintained at the 1 position, has shown that there is little dependence of the antimicrobial efficacy against Escherichia coli O157:H7 on the alkyl chain length, in contrast to reported observations for biocidal quaternary ammonium salt derivatives. The stabilities of the derivatives toward hydrolyses and ultraviolet light exposure have also been found to not be dependent upon the nature of the alkyl substituent group. These observations led to the conclusion that the 5,5-dimethyl derivative would be recommended for use, since it is the least expensive alternative.

Centrifugal bubble O2 (1Δ) gas generator with a total pressure of 100 Torr

A centrifugal bubbling singlet-oxygen gas generator is developed in which chlorine with helium are injected into the rotating layer of the alkali solution of hydrogen peroxide through cylindrical nozzles directed at an angle of 30° to the bubbler surface. The concentrations of water vapour and O2 (1Δ) and the gas temperature were determined by using the multichannel recording of the emission bands of oxygen at 634, 703, 762 and 1268 nm. For the chlorine and helium flow rates of 60 and 90 mmol s-1, respectively, the specific chlorine load of 3.2 mmol cm-2, a total pressure of 100 Torr in the working region of the gas generator and the oxygen partial pressure of 36 Torr, the chlorine utilisation was 90% and the content of O2 (1Δ) was ≈60%. For the ratio of the flow rates of chlorine and the alkali solution of hydrogen peroxide equal to 1 mol L-1, the water vapour content was ≈25%. The chemical efficiency of the oxygen—iodine laser with this gas generator achieved 23% for the specific power of 12.7 W cm per 1 cm3 s-1 per pass of the solution through the gas generator.

Antimicrobial efficacy and light stability of N-halamine siloxanes bound to cotton

N-halamine silane syntheses and coatings of cotton fabrics as siloxanes were addressed for a series of silanes. The coated fabrics were chlorinated by exposure to dilute sodium hypochlorite with a range of chlorine loadings from 0.20% to 0.26%. Two types of N–Cl moieties were involved in the N-halamine siloxanes, amine and amide. The siloxane-coated cotton swatches were very effective in inactivating Escherichia coli O157:H7 and Staphylococcus aureus, each in 10 min contact time. The N–Cl bond and compound stabilities under UV irradiation and ambient light exposure were also investigated. Both UV and laboratory light stability tests show that most of the chlorine on cotton coated with 3-(3-triethoxysilylpropyl)-7,7,9,9-tetramethyl-1,3,8-triazaspiro[4.5]decane-2,4-dione could be regenerated after irradiation, while most of the lost chlorine from 5,5-dimethyl-3-(3′-triethoxysilylpropyl)hydantoin and 4-[3-triethoxysilylpropoxyl]-2,2,6,6-tetramethylpiperidine could not be recovered upon rechlorination.

Impact of long‐range correlations on trend detection in total ozone

Total ozone trends are typically studied using linear regression models that assume a first‐order autoregression of the residuals [so‐called AR(1) models]. We consider total ozone time series over 60°S–60°N from 1979 to 2005 and show that most latitude bands exhibit long‐range correlated (LRC) behavior, meaning that ozone autocorrelation functions decay by a power law rather than exponentially as in AR(1). At such latitudes the uncertainties of total ozone trends are greater than those obtained from AR(1) models and the expected time required to detect ozone recovery correspondingly longer. We find no evidence of LRC behavior in southern middle‐and high‐subpolar latitudes (45°–60°S), where the long‐term ozone decline attributable to anthropogenic chlorine is the greatest. We thus confirm an earlier prediction based on an AR(1) analysis that this region (especially the highest latitudes, and especially the South Atlantic) is the optimal location for the detection of ozone recovery, with a statistically significant ozone increase attributable to chlorine likely to be detectable by the end of the next decade. In northern middle and high latitudes, on the other hand, there is clear evidence of LRC behavior. This increases the uncertainties on the long‐term trend attributable to anthropogenic chlorine by about a factor of 1.5 and lengthens the expected time to detect ozone recovery by a similar amount (from ∼2030 to ∼2045). If the long‐term changes in ozone are instead fit by a piecewise‐linear trend rather than by stratospheric chlorine loading, then the strong decrease of northern middle‐ and high‐latitude ozone during the first half of the 1990s and its subsequent increase in the second half of the 1990s projects more strongly on the trend and makes a smaller contribution to the noise. This both increases the trend and weakens the LRC behavior at these latitudes, to the extent that ozone recovery (according to this model, and in the sense of a statistically significant ozone increase) is already on the verge of being detected. The implications of this rather controversial interpretation are discussed.

Strong influence of lowermost stratospheric ozone on lower tropospheric background ozone changes over Europe

Using ozone measurements from two sounding sites and two high‐altitude stations in Central Europe, we show evidence for a dominant influence of changes in lowermost stratospheric ozone on the variability and overall upward trend of background ozone in the lower troposphere (3000–3500 m asl) during the 1992–2004 period. Numerical simulations with a stratospheric chemistry transport model suggest that changes in lower stratospheric ozone were driven by dynamics rather than by changes in stratospheric chlorine loading. In addition, Lagrangian model simulations indicate that changes in downward transport of ozone from the stratosphere into the troposphere were dominated by changes in lowermost stratospheric ozone concentrations rather than by variations of cross‐tropopause air mass transport. This suggests that the positive ozone trends and concentration anomalies in the lower free troposphere over Europe during the 1990s were likely to a large extent due to enhanced stratospheric ozone contributions, particularly in winter–spring.

Temporal decrease in upper atmospheric chlorine

We report a steady decrease in the upper stratospheric and lower mesospheric abundances of hydrogen chloride (HCl) from August 2004 through January 2006, as measured by the Microwave Limb Sounder (MLS) aboard the Aura satellite. For 60°S to 60°N zonal means, the average yearly change in the 0.7 to 0.1 hPa (∼50 to 65 km) region is −27 ± 3 pptv/year, or −0.78 ± 0.08 percent/year. This is consistent with surface abundance decrease rates (about 6 to 7 years earlier) in chlorine source gases. The MLS data confirm that international agreements to reduce global emissions of ozone‐depleting industrial gases are leading to global decreases in the total gaseous chlorine burden. Tracking stratospheric HCl variations on a seasonal basis is now possible with MLS data. Inferred stratospheric total chlorine (ClTOT) has a value of 3.60 ppbv at the beginning of 2006, with a (2‐sigma) accuracy estimate of 7%; the stratospheric chlorine loading has decreased by about 43 pptv in the 18‐month period studied here. We discuss the MLS HCl measurements in the context of other satellite‐based HCl data, as well as expectations from surface chlorine data. A mean age of air of ∼ 5.5 years and an age spectrum width of 2 years or less provide a fairly good fit to the ensemble of measurements.

Solar cycle effect delays onset of ozone recovery

Short‐ and long‐term changes of total ozone are investigated by means of an ensemble simulation with the coupled chemistry‐climate model E39/C for the period 1960 to 2020. Past total ozone changes are well simulated on both, long (decadal) and short (monthly) timescales. Even the 2002 Antarctic ozone anomaly appears in the ensemble. The model results indicate that the 11‐year solar cycle will delay the onset of a sustained ozone recovery. The lowest global mean total ozone values occur between 2005 and 2010, although stratospheric chlorine loading is assumed to decline after 2000. E39/C results exhibit a significant increase of total ozone after the beginning of the next decade, following the upcoming solar minimum. The observed ozone increase in the second half of the 1990s is reproduced by E39/C and is identified as a combined post‐Pinatubo and solar cycle effect rather than the beginning of a sustainable ozone recovery.

Oxygen—iodine ejector laser with a centrifugal bubbling singlet-oxygen generator

It is shown that if a supersonic oxygen—iodine ejector laser is fed by singlet oxygen from a centrifugal bubbling generator operating at a centrifugal acceleration of ∼400g, the laser output power achieves a value 1264 W at a chemical efficiency of 24.6% for an alkaline hydrogen peroxide flow rate of 208 cm3s-1 and a specific chlorine load of 1.34 mmol s-1 per square centimetre of the bubble layer.

A new fast stratospheric ozone chemistry scheme in an intermediate general‐circulation model. II: Application to effects of future increases in greenhouse gases

AbstractWhile chlorine loadings in the atmosphere are expected to decrease towards pre‐ozone‐hole levels by 2060, the greenhouse gases (GHGs) burden is rising continuously and may in turn significantly modify the stratospheric ozone layer.In this study, use is made of the new interactively coupled chemistry–general‐circulation model IGCMFASTOC to investigate in detail the response of stratospheric ozone to a specified increase in GHG concentrations between 1979 and 2060.The Intermediate General Circulation Model (IGCM) is a relatively fast general‐circulation model with parametrizations of an intermediate level of complexity, and the new chemistry scheme Fast STratospheric Ozone Chemistry (FASTOC) is an efficient input‐output model composed of pre‐computed nonlinear functions.A total of seven 14‐year time‐slice simulations are performed to allow for the separation of individual processes and the analysis of sensitivity to methane and stratospheric water‐vapour scenarios.In a basic scenario where all GHG concentrations increase (except stratospheric H2O) the total ozone column is found to increase at a global rate of 0.27 DU decade−1 with maxima in late winter–spring poles. This increase is merely the result of two opposing effects: (i) An increase of ozone concentration in the summer and tropical stratospheric region near 30–40 km which is passively advected into the polar‐night vortex between 40 and 20 km. This ozone increase is due to the slowing down of the NOx catalytic cycle caused by the cooling of the stratosphere resulting from increased GHG concentrations in the stratosphere. (ii) A decrease of ozone concentration in the same region which is also advected into the polar‐night vortex, due to enhanced NOx concentrations caused by the increased N2O concentrations. These two opposing effects are additive to a large degree, i.e. the sum of their individual effects is a good approximation of their total effect when the processes are acting together.A significant deviation from this additivity occurs inside the northern polar‐night vortex and to a lesser extent in the southern polar‐night vortex. Our analysis suggests that methane is mainly responsible for this feature. The impact of methane increase on ozone is confined to the high latitudes and is found to have a negative sign in the northern polar vortex when the stratospheric cooling is taken into account, and a positive sign when no stratospheric cooling is taken into account.The scenario where methane is kept at its 1979 level produces a global rate of increase of the ozone column of 9% above the basic scenario. The scenario where stratospheric H2O is increased by 50% leads to a global rate of increase of the ozone column of 70% above the basic scenario. Finally, in a scenario where CO2 is reduced to its 1979 level and the other GHGs involved in the ozone chemistry are increased as in the basic scenario, the global effect of GHGs on the ozone layer is to decrease it at a rate of 0.37 DU decade−1. Copyright © 2005 Royal Meteorological Society

Midlatitude ClO during the maximum atmospheric chlorine burden: in situ balloon measurements and model simulations

Abstract. Chlorine monoxide (ClO) plays a key role in stratospheric ozone loss processes at midlatitudes. We present two balloon-borne in situ measurements of ClO conducted in northern hemisphere midlatitudes during the period of the maximum of total inorganic chlorine loading in the atmosphere. Both ClO measurements were conducted on board the TRIPLE balloon payload, launched in November 1996 in León, Spain, and in May 1999 in Aire sur l'Adour, France. For both flights a ClO daylight and night-time vertical profile was derived over an altitude range of approximately 15-35 km. ClO mixing ratios are compared to model simulations performed with the photochemical box model version of the Chemical Lagrangian Model of the Stratosphere (CLaMS). Simulations along 24-hour backward trajectories were performed to study the diurnal variation of ClO in the midlatitude lower stratosphere. Model simulations for the flight launched in Aire sur l'Adour 1999 show an excellent agreement with the ClO measurements. For the flight launched in León 1996, an overall good agreement is found, whereas the flight is characterized by a more complex dynamical situation due to a possible mixture of vortex and non-vortex air. We note that for both flights at solar zenith angles greater than 86°-87° simulated ClO mixing ratios are higher than observed ClO mixing ratios. However, the present findings indicate that no substantial uncertainties exist in midlatitude chlorine chemistry of the stratosphere.

Spectroscopic and Structural Characterization of Chlorine Loading Effects on Mo/Si:Ti Catalysts in Oxidative Dehydrogenation of Ethane

The structural changes induced in a silica-titania mixed-oxide support (1:1 molar ratio) by chlorine addition at different loading levels, their relation to the structural characteristics of supported MoOx species over the support, and their correlation with ethane oxidative dehydrogenation (ODH) activity have been examined. The molybdenum and chlorine precursors are incorporated into the Si/Ti support network as it forms during gelation by using a "one-pot" modified sol-gel/coprecipitation technique. In situ X-ray diffraction during calcination shows the Si/Ti 1:1 mixed-oxide support is in a state of nanodispersed anatase titania over amorphous silica. With the addition of molybdenum and chlorine modifier, this anatase feature becomes more pronounced, indicating a decreased dispersion of titania. The effective titania surface area on the chlorine-doped Si:Ti support obtained from 2-propanol temperature-programmed reaction supports this observation. Raman spectra of dehydrated samples point to an enhanced interaction of MoOx species with silica at the expense of titania. X-ray photoelectron spectroscopic results show that, without forming a molybdenum chloride, the presence of chlorine significantly alters the relative surface concentration of Si vs Ti, the electronic structure of the surface MoOx species, and the oxygen environment around supported MoOx species in the Si/Ti network. Secondary ion mass spectrometry detected the existence of SiCl fragments from the mass spectra, which provides molecular insight into the location of chlorine in Mo/Si:Ti catalysts. The observed increase in ethane ODH selectivity with chlorine modification may be ascribed to the MoOx species sharing more complex ligands with silica and titania with the indirect participation of chlorine. Steady-state isotopic transient kinetic analysis (SSITKA) is used to to examine the oxygen insertion and exchange mechanisms. The catalysts show very little oxygen exchange with the gas phase in the absence of a reaction medium. During the steady-state ODH reaction, lattice oxygen appears to be the primary source of oxygen in the formation of water and CO2.

Doubled CO2‐induced cooling in the middle atmosphere: Photochemical analysis of the ozone radiative feedback

Simple radiative arguments predict that the impact of CO2 increases on the stratosphere and mesosphere should be a cooling and that the magnitude of the temperature change should be significantly larger than in the troposphere. Considering the temperature dependence of middle atmospheric gas‐phase ozone photochemistry, it is expected that the ozone response will generate a radiative feedback that mitigates the CO2‐induced cooling. The magnitude and vertical structure of this signal need to be characterised in order to distinguish the impact of future CO2 changes from other processes affecting the temperature evolution, such as changes in chlorine loading and water vapour trends. The Canadian Middle Atmosphere Model (CMAM) has been used in a process oriented study to examine the details of radiative and photochemical feedbacks under current and doubled CO2 conditions at low and middle latitudes. The model was run both with and without interactive chemistry in order to determine the importance of the radiative feedback through ozone changes on the CO2‐induced cooling signal. Changes in other greenhouse gases, ozone depleting substances, or SST's and sea ice coverage were not considered. The interactive model results show a substantial temperature decrease throughout most of the middle atmosphere with a maximum cooling of 10–12 K at the stratopause. In association with this temperature change, the ozone mixing ratio increases by 15–20% in the upper stratosphere and by 10–15% in the lower mesosphere. Results from the non‐interactive simulations show that the magnitude of the cooling is overestimated by up to ∼4.5 K when the ozone radiative feedback is not considered. In spite of the complexity of the ozone chemistry, the ozone increase at 30–70 km can be understood primarily as a result of the negative temperature dependence of the O + O2 + M → O3 + M reaction that controls odd oxygen partitioning. Additional partial contributions to the ozone increase below 60 km are provided by a decrease in the reaction rate coefficient of the Chapman reaction O + O3 → 2O2 and by a decrease in the NO2 abundance.

A temperature-programmed X-ray photoelectron spectroscopy (TPXPS) study of chlorine adsorption and diffusion on Ag(1 1 1)

Synchrotron-based temperature programmed X-ray photoelectron spectroscopy (TPXPS) has been used to investigate the surface chloridation of Ag(1 1 1) to monolayer coverages. At 100 K both atomic and molecular chlorine species are present on the surface; adsorption at 300 K or annealing the adlayer at 100 K to this temperature generates adsorbed Cl atoms. As the surface is heated from 300 to 600 K, chlorine atoms diffuse below the surface, as demonstrated by attenuation of the Cl2p signals in TPXPS experiments. Quantitative analysis of the extent of attenuation is consistent with chlorine diffusion below the topmost silver layer. For coverages in the monolayer and sub-monolayer regime, chlorine diffusion to and from the bulk appears not to be significant, in contrast to previous results obtained at higher chlorine loadings. Chlorine is removed from the surface at 650–780 K by desorption as AgCl. These results demonstrate that chlorine diffusion beneath the surface does occur at coverages and temperatures relevant to olefin epoxidation processes carried out on silver catalysts with chlorine promoters. The surface sensitivity advantages of synchrotron-based XPS experiments were critical to observing Cl diffusion to the sub-surface at low coverages.

Rapid growth of hydrofluorocarbon 134a and hydrochlorofluorocarbons 141b, 142b, and 22 from Advanced Global Atmospheric Gases Experiment (AGAGE) observations at Cape Grim, Tasmania, and Mace Head, Ireland

An update of in situ Advanced Global Atmospheric Gases Experiment (AGAGE) hydrofluorocarbon (HFC)/hydrochlorofluorocarbon (HCFC) measurements made at Mace Head, Ireland, and Cape Grim, Tasmania, from 1998 to 2002 are reported. HCFC‐142b, HCFC‐141b, HCFC‐22 and HFC‐134a show continued rapid growth in the atmosphere at mean rates of 1.1, 1.6, 6.0, and 3.4 ppt/year, respectively. Emissions inferred from measurements are compared to recent estimates from consumption data. Minor updates to the industry estimates of emissions are reported together with a discussion of how to best determine OH concentrations from these trace gas measurements. In addition, AGAGE measurements and derived emissions are compared to those deduced from NOAA‐Climate Monitoring and Diagnostics Laboratory flask measurements (which are mostly made at different locations). European emission estimates obtained from Mace Head pollution events using the Nuclear Accident Model (NAME) dispersion model and the best fit algorithm (known as simulated annealing) are presented as 3‐year rolling average emissions over Europe for the period 1999–2001. Finally, the measurements of HCFC‐141b, HCFC‐142b, and HCFC‐22 discussed in this paper have been combined with the Atmospheric Lifetime Experiment (ALE)/Global Atmospheric Gases Experiment (GAGE)/AGAGE measurements of CFC‐11, CFC‐12, CFC‐113, CCl4, and CH3CCl3 to produce the evolution of tropospheric chlorine loading.

A novel N-halamine monomer for preparing biocidal polyurethane coatings

A novel N-halamine monomer has been prepared which can be copolymerised with a commercial water-borne acrylic polyol and a commercial isocyanate to produce a polyurethane coating which can be applied to a broad variety of surfaces. After curing, the coating can be chlorinated with a source of free chlorine, such as bleach, to render it biocidal. Once the coating loses its chlorine loading, and hence its biocidal activity, regeneration is possible by further exposure to free chlorine. In one experimental observation a coating on a wall retained its biocidal activity for more than six months. The biocidal coating should have many applications, for example, in medical facilities, in food preparation areas, in the prevention of biofouling in aqueous and humid environments, etc.

Changes in stratospheric composition, chemistry, radiation and climate caused by volcanic eruptions

Abstract The primary effect of a volcanic eruption is to alter the composition of the stratosphere by the direct injection of ash and gases. On average, there is a stratospherically significant volcanic eruption about every 5.5 years. The principal effect of such an eruption is the enhancement of stratospheric sulphuric acid aerosol through the oxidation and condensation of the oxidation product H 2 SO 4 . Following the formation of the enhanced aerosol layer, observations have shown a reduction in the amount of direct radiation reaching the ground and a concomitant increase in diffuse radiation. This is associated with an increase in stratospheric temperature and a decrease in global mean surface temperature (although the spatial pattern of temperature changes is complex). In addition, the enhanced aerosol layer increases heterogeneous processing, and this reduces the levels of active nitrogen in the lower stratosphere. This in turn gives rise to either a decrease or an increase in stratospheric ozone levels, depending on the level of chlorine loading.

Temporal development of total chlorine in the high‐latitude stratosphere based on reference distributions of mean age derived from CO2 and SF6

We present balloon‐borne observations of CO2 and SF6 and derived vertical profiles of mean age for polar winter (inside vortex) and for midlatitude (nonwinter) conditions. For SF6‐derived mean ages above 5 years a mesospheric SF6 sink may lead to an overestimation of mean age, while for younger mean ages (below 2 years) the seasonal cycle of CO2 may influence the mean age determination based on CO2. We suggest that SF6 be used as an age tracer in the lower part of the stratosphere (i.e., for low mean age), whereas CO2 will be the better age tracer for older air. The mean age distributions together with an estimate of the width of the age spectrum are used to estimate the stratospheric chlorine loading. On the basis of an emission scenario and the lifetimes of chlorine‐containing compounds we estimate the future stratospheric chlorine loading. Inside the polar vortex, at an altitude of 20 km, we expect total chlorine to return to the values present in this region in 1980, when the ozone hole first appeared, around the year 2060. This estimate is based on the assumption that the general transport characteristics will not change over the period of the analysis and can thus be regarded as a best estimate based on stationary transport, the assumed set of lifetimes and emissions, and the mean age distribution derived from our measurements. As other factors influencing ozone may undergo temporal changes, this does not mean that ozone will necessarily recover at this time. While total chlorine is probably a good proxy for inorganic chlorine at altitudes above 20 km inside the polar vortex, the changing halocarbon mix may actually lead to an earlier return of inorganic chlorine to pre‐ozone‐hole values at lower altitudes.

Future development of the ozone layer calculated by a general circulation model with fully interactive chemistry

The future development of stratospheric ozone is estimated using an atmospheric general circulation model that includes a fully interactive chemistry module. Two transient integrations considering the anthropogenic chlorine emission trend were performed. One calculated with a carbon dioxide increase and a sea surface temperature (SST) variation between 1986 and 2050, and the other without the increase or the variation. In the Southern Hemisphere polar region, a 10 day‐averaged column ozone takes its minimum of 140 Dobson Unit (DU) around 2000 and recovers above 220 DU after the late 2030s. Such temporal evolution of ozone is not greatly influenced by the carbon dioxide increase and SST variation but seems to be maintained by simulated chlorine loading in the lower stratosphere. In the integration with carbon dioxide increase and SST variation, the Northern Hemisphere polar column ozone decreases until 2010, but massive depletion such as that causing the Antarctic ozone‐hole (less than 200 DU) does not occur.