Stratospheric water vapor affecting atmospheric circulation.

Water vapor plays an important role in many aspects of the climate system, by affecting radiation, cloud formation, atmospheric chemistry and dynamics. Even the low stratospheric water vapor content provides an important climate feedback, but current climate models show a substantial moist bias in the lowermost stratosphere. Here we report crucial sensitivity of the atmospheric circulation in the stratosphere and troposphere to the abundance of water vapor in the lowermost stratosphere. We show from a mechanistic climate model experiment and inter-model variability that lowermost stratospheric water vapor decreases local temperatures, and thereby causes an upward and poleward shift of subtropical jets, a strengthening of the stratospheric circulation, a poleward shift of the tropospheric eddy-driven jet and regional climate impacts. The mechanistic model experiment in combination with atmospheric observations further shows that the prevailing moist bias in current models is likely caused by the transport scheme, and can be alleviated by employing a less diffusive Lagrangian scheme. The related effects on atmospheric circulation are of similar magnitude as climate change effects. Hence, lowermost stratospheric water vapor exerts a first order effect on atmospheric circulation and improving its representation in models offers promising prospects for future research.

Bronchoscopy in the emergency department.

BACKGROUND: Flexible bronchoscopy has been safely used for decades in ambulatory and critical care settings to aid in the diagnosis and treatment of tracheobronchial tree disorders. Although emergency physicians have the requisite skills to operate and interpret flexible bronchoscopy, no reports exist on the use of bronchoscopy by emergency physicians apart from endotracheal tube placement and confirmation. OBJECTIVE: The primary goal of this study was to describe the indications, outcomes and complications of flexible bronchoscopy performed by emergency physicians in an urban academic emergency department. METHODS: This was a single-center retrospective cohort study involving chart and video review of 146 patients over a 10.5-year study period. Patients of any age were included if they had been tracheally intubated or mechanically ventilated and underwent flexible bronchoscopy in the emergency department. After patients were identified, manual chart and video review was used to collect data on patient demographics, indications for intubation, indications for bronchoscopy, details of the bronchoscopy procedure, procedural findings, outcomes of the procedure, complications, provider training levels, and additional bronchoscopies performed after admission. The data was analyzed using descriptive statistics. RESULTS: 146 patients were included in the study and all bronchoscopies were performed or supervised by attending emergency physicians. After bronchoscopy, 24% of patients displayed improvement in oxygenation or lobar collapse while most patients had no change in clinical status. One patient had temporary hypoxemia after bronchoscopy. When another physician performed a subsequent bronchoscopy during admission, the findings were in agreement with the ED bronchoscopy 86% of the time. CONCLUSION: At our institution, emergency physicians can safely and effectively use flexible bronchoscopy to diagnose and treat critically ill patients.

Building a Taxonomy to Understand Health Care Worker's Response to Workplace 'Pressure' in Complex, Volatile and Emergency Situations.

This research aims to better understand performance under pressure as experienced by health and emergency staff in the workplace. Three basic questions underpin the work: (1) how do health and emergency workers experience and make sense of the 'pressures' entailed in their jobs? (2) What impacts do these pressures have on their working lives and work performance, both positively and negatively? (3) Can we develop a useful explanatory model for 'working under pressure' in complex, volatile and emergency situations? The present article addresses the first question regarding the nature of pressure; a subsequent article will address the question of its impact on performance. Using detailed interviews with workers in a range of roles and from diverse settings across Ecuador, our analysis aims to better understand the genesis of pressure, how people respond to it and to gain insights into managing it more effectively, especially with a view to reducing workplace errors and staff burnout. Rather than imposing preformulated definitions of either 'pressure' or 'performance', we took an emic approach to gain a fresh understanding of how workers themselves experience, describe and make sense of workplace pressure. This article catalogues a wide range of pressures as experienced by our participants and maps relationships between them. We argue that while individuals are often held responsible for workplace errors, both 'pressure' and 'performance' are multifactorial, involving individuals, teams, case complexity, expertise and organizational systems and these must be considered in order to gain better understandings of performing under pressure.

Alignment and mismatch in role relations at end-of-life: A constructivist grounded theory study.

In this Australian, constructivist grounded theory study, we undertook in-depth interviews with 11 dying people and 8 caregivers to examine their perspectives on role relations at end-of-life. We found that situations of role alignment between dying people and their family and friends support positive relational and practical outcomes, whereas role mismatch can cause considerable distress. Factors contributing to role mismatch at end-of-life were: dying people and their caregivers' efforts to shield each other from emotional harm; fear of social exclusion; and unwanted focus on the dying identity. Our findings highlight a need for flexibility and adaptability in end-of-life role relations.

Spectrum and frequency of critical procedures performed at a Level I adult and pediatric trauma center.

OBJECTIVES: The primary objective of this study was to provide physician-level data about the frequency of critical procedures at a combined adult and pediatric Level I trauma center, high-acuity, high-volume academic ED. The inspiration for this study question came from a previous study by Mittiga et al. (2013) describing pediatric critical procedure data at a similar high-acuity, high-volume, pediatric-only academic ED. Our secondary objective is to compare our pediatric level procedural spectrum and frequency with those published by Mittiga et al. (2013). METHODS: This prospective observational study occurred over eleven consecutive months at an urban, Level I combined adult/pediatric trauma center with 96,000 annual visits (8500 pediatric). We recorded only procedures performed in the resuscitation bays. All data analysis is descriptive. RESULTS: Over eleven months, data on 3891 resuscitations were collected (3686 adults and 205 children); 38 faculty physicians supervised 1838 total critical procedures, 64 on children. The mean number of critical procedures per physician per month was 4.42 (0.15 on children). Additionally, ultrasound for intravenous access, extended focused assessment with sonography for trauma (e-FAST), or cardiac ultrasound were performed in 3862 resuscitations (178 pediatric). CONCLUSIONS: Emergency medicine faculty physicians at a combined Level I adult and pediatric trauma center performed and/or supervised 4.4 total (0.15 pediatric) critical procedures per month per faculty which is nearly 6 times more critical procedures monthly than faculty at a similar volume pediatric-only trauma center. However, fewer critical procedures were performed on children at the combined facility.

Non-prescription medicines may contribute to non-adherence to prescription medicines in people living with chronic health conditions.

BACKGROUND: Non-adherence to prescribed medicines is linked to adverse health outcomes in people living with chronic health conditions (CHCs). Multiple factors are known to contribute to non-adherence to medicines including polypharmacy, demographic features and disease and health systems. Both non-prescription and prescription medicines contribute to polypharmacy; however, there is limited data on the influence of non-prescription medicines to non-adherence. AIM: Therefore, the aim of the study was to investigate the influence of non-prescription medicines to non-adherence in an Australian population. METHODS: Data from the 2016 National Survey of a random sample of Australian adult residents were utilised in this study to investigate factors associated with non-adherence. Descriptive statistics, χ2 , regression and generalised linear models were used to assess the relationships between variables of interest. Narrative response and comments were used to provide further insight. RESULTS: This study recruited 1217 participants to explore factors associated with non-adherence to medicines. Weak but statistically significant correlations were identified showing the number of CHCs, patient's age, number of prescription medicines, number of non-prescription medicines and total number of medicines associated with non-adherence. DISCUSSION: The findings suggest that people living with CHCs and taking multiple medicines, including non-prescription medicines, are likely to be non-adherent to prescription medicines. This study shows the possible involvement of non-prescription medicines in contributing to non-adherence in an Australian population and suggests that future studies with a broader demographic are warranted.

Ultraviolet radiation modelling using output from the Chemistry Climate Model Initiative.

We have derived values of the Ultraviolet Index (UVI) at solar noon using the Tropospheric Ultraviolet Model (TUV) driven by ozone, temperature and aerosol fields from climate simulations of the first phase of the Chemistry-Climate Model Initiative (CCMI-1). Since clouds remain one of the largest uncertainties in climate projections, we simulated only the clear-sky UVI. We compared the modelled UVI climatologies against present-day climatological values of UVI derived from both satellite data (the OMI-Aura OMUVBd product) and ground-based measurements (from the NDACC network). Depending on the region, relative differences between the UVI obtained from CCMI/TUV calculations and the ground-based measurements ranged between -5.9% and 10.6%. We then calculated the UVI evolution throughout the 21st century for the four Representative Concentration Pathways (RCPs 2.6, 4.5, 6.0 and 8.5). Compared to 1960s values, we found an average increase in the UVI in 2100 (of 2-4%) in the tropical belt (30°N-30°S). For the mid-latitudes, we observed a 1.8 to 3.4 % increase in the Southern Hemisphere for RCP 2.6, 4.5 and 6.0, and found a 2.3% decrease in RCP 8.5. Higher increases in UVI are projected in the Northern Hemisphere except for RCP 8.5. At high latitudes, ozone recovery is well identified and induces a complete return of mean UVI levels to 1960 values for RCP 8.5 in the Southern Hemisphere. In the Northern Hemisphere, UVI levels in 2100 are higher by 0.5 to 5.5% for RCP 2.6, 4.5 and 6.0 and they are lower by 7.9% for RCP 8.5. We analysed the impacts of greenhouse gases (GHGs) and ozone-depleting substances (ODSs) on UVI from 1960 by comparing CCMI sensitivity simulations (1960-2100) with fixed GHGs or ODSs at their respective 1960 levels. As expected with ODS fixed at their 1960 levels, there is no large decrease in ozone levels and consequently no sudden increase in UVI levels. With fixed GHG, we observed a delayed return of ozone to 1960 values, with a corresponding pattern of change observed on UVI, and looking at the UVI difference between 2090s values and 1960s values, we found an 8 % increase in the tropical belt during the summer of each hemisphere. Finally we show that, while in the Southern Hemisphere the UVI is mainly driven by total ozone column, in the Northern Hemisphere both total ozone column and aerosol optical depth drive UVI levels, with aerosol optical depth having twice as much influence on the UVI as total ozone column does.

Yes to Recreational Drugs and Complementary Medicines But No to Life-Saving Medications: Beliefs Underpinning Treatment Decisions Among PLHIV.

Despite the life-preserving benefits of antiretroviral therapy (ART), some people living with HIV (PLHIV) delay, decline or diverge from recommended treatment while paradoxically being willing to use potentially dangerous substances, such as recreational drugs (RD) and complementary medicines (CM). During 2016 and 2017, interviews were conducted with 40 PLHIV, in Australia to understand drivers underpinning treatment decisions. While many believed ART to be effective, they expressed concerns about long-term effects, frustration over perceived lack of autonomy in treatment decisions and financial, emotional and physical burdens of HIV care. In contrast, they ascribed a sense of self-control over the use of RD and CM, along with multiple professed benefits. The perceived burden of ART emerged as a motivator for deviating from recommended treatment, while positive views towards RD and CM appear to justify use. This study may serve as guidance for the development of future strategies to address barriers to treatment uptake and adherence and subsequently health outcomes for PLHIV in Australia and elsewhere.

Molecular Evidence of Drug-Resistant Tuberculosis in the Balimo Region of Papua New Guinea.

Papua New Guinea (PNG) has a high burden of tuberculosis (TB), including drug-resistant TB (DR-TB). DR-TB has been identified in patients in Western Province, although there has been limited study outside the provincial capital of Daru. This study focuses on the Balimo region of Western Province, aiming to identify the proportion of DR-TB, and characterise Mycobacterium tuberculosis (MTB) drug resistance-associated gene mutations. Sputum samples were investigated for MTB infection using published molecular methods. DNA from MTB-positive samples was amplified and sequenced, targeting the rpoB and katG genes to identify mutations associated with rifampicin and isoniazid resistance respectively. A total of 240 sputum samples were collected at Balimo District Hospital (BDH). Of these, 86 were classified as positive based on the results of the molecular assays. For samples where rpoB sequencing was successful, 10.0% (5/50, 95% CI 4.4⁻21.4%) were considered rifampicin-resistant through detection of drug resistance-associated mutations. We have identified high rates of presumptive DR-TB in the Balimo region of Western Province, PNG. These results emphasise the importance of further surveillance, and strengthening of diagnostic and treatment services at BDH and throughout Western Province, to facilitate detection and treatment of DR-TB, and limit transmission in this setting.

Spatial distribution of tuberculosis in a rural region of Western Province, Papua New Guinea.

INTRODUCTION: There is a high burden of tuberculosis (TB) in the Western Province, Papua New Guinea. This study aims to describe the spatial distribution of TB in the Balimo District Hospital (BDH) catchment area to identify TB patient clusters and factors associated with high rates of TB. METHODS: Information about TB patients was obtained from the BDH TB patient register for the period 26 April 2013 to 25 February 2017. The locations of TB patients were mapped, and the spatial scan statistic was used to identify high- and low-rate TB clusters in the BDH catchment area. RESULTS: A total of 1568 patients were mapped with most being from the Balimo Urban (n = 252), Gogodala Rural (n = 1010) and Bamu Rural (n = 295) local level government (LLG) areas. In the Gogodala region (Balimo Urban and Gogodala Rural LLGs), high-rate clusters occurred closer to the town of Balimo, while low-rate clusters were located in more remote regions. In addition, closer proximity to Balimo was a predictor of high-rate clustering. DISCUSSION: There is heterogeneity in the distribution of TB in the Balimo region. Active case-finding activities indicated potential underdiagnosis of TB and the possibility of associated missed diagnoses of TB. The large BDH catchment area emphasizes the importance of the hospital in managing TB in this rural region.

The influence of mixing on stratospheric age of air changes in the 21st century.

Climate models consistently predict an acceleration of the Brewer-Dobson circulation (BDC) due to climate change in the 21st century. However, the strength of this acceleration varies considerably among individual models, which constitutes a notable source of uncertainty for future climate projections. To shed more light upon the magnitude of this uncertainty and on its causes, we analyze the stratospheric mean age of air (AoA) of 10 climate projection simulations from the Chemistry Climate Model Initiative phase 1 (CCMI-I), covering the period between 1960 and 2100. In agreement with previous multi-model studies, we find a large model spread in the magnitude of the AoA trend over the simulation period. Differences between future and past AoA are found to be predominantly due to differences in mixing (reduced aging by mixing and recirculation) rather than differences in residual mean transport. We furthermore analyze the mixing efficiency, a measure of the relative strength of mixing for given residual mean transport, which was previously hypothesized to be a model constant. Here, the mixing efficiency is found to vary not only across models, but also over time in all models. Changes in mixing efficiency are shown to be closely related to changes in AoA and quantified to roughly contribute 10% to the long-term AoA decrease over the 21st century. Additionally, mixing efficiency variations are shown to considerably enhance model spread in AoA changes. To understand these mixing efficiency variations, we also present a consistent dynamical framework based on diffusive closure, which highlights the role of basic state potential vorticity gradients in controlling mixing efficiency and therefore aging by mixing.

Examining the transitions between living and dying roles at end-of-life.

Improvements in the diagnosis and disclosure of dying mean that nowadays dying people typically live with an awareness of their status for longer than they have previously. However, little is known regarding how transitions between living and dying roles occur during this time. In this grounded theory study, we investigated role transitions at end-of-life. We found that dying people periodically foreground and background living and dying selfhoods, focus on living day-by-day and goal-by-goal and reframe dying roles with an orientation to living. We argue that with better understanding of role transitions at end-of-life more compassionate and responsive care becomes possible.

Effect of Gabapentin vs Pregabalin on Pain Intensity in Adults With Chronic Sciatica: A Randomized Clinical Trial.

Importance: Optimal pharmacologic treatment for chronic sciatica (CS) is currently unclear. While gabapentin (GBP) and pregabalin (PGB) are both used to treat CS, equipoise exists. Nevertheless, pharmaceutical regulation authorities typically subsidize one drug over the other. This hinders interchange wherever the favored drug is either ineffective or ill-tolerated. Objective: To assess GBP vs PGB head to head for the treatment of CS. Design, Setting, and Participants: A preplanned interim analysis of a randomized, double-blind, double-dummy crossover trial of PGB vs GBP for management of CS at half the estimated final sample size was performed in a single-center, tertiary referral public hospital. A total of 20 patients underwent randomization from March 2016 to March 2018, and 2 were excluded with 1 lost to follow-up and the other requiring urgent surgery unrelated to the study. Patients attending a specialist neurosurgery clinic with unilateral CS were considered for trial recruitment. Chronic sciatica was defined as pain lasting for at least 3 months radiating into 1 leg only to, at, or below the knee level. Imaging (magnetic resonance imaging with or without computed tomography) corroborating a root-level lesion concordant with symptoms and/or signs was determined by the trial clinician. Inclusion criteria included patients who had not used GBP and PGB and were 18 years or older. Analyses were intention to treat and began February 2018. Interventions: Randomly assigned participants received GBP (400 mg to 800 mg 3 times a day) then PGB (150 mg to 300 mg twice daily) or vice versa, each taken for 8 weeks. Crossover followed a 1-week washout. Main Outcomes and Measures: The primary outcome was pain intensity (10-point visual analog scale) at baseline and 8 weeks. Secondary outcomes included disability (using the Oswestry Disability Index) and severity/frequency of adverse events. Results: The total trial population (N = 18) consisted mostly of men (11 [61%]) with a mean (SD) age of 57 (16.5) years. A third of the cohort were smokers (5 [28%]), and more than half consumed alcohol (12 [67%]). Gabapentin was superior to PGB, with fewer and less severe adverse events. Both GBP (mean [SD], 7.54 [1.39] to 5.82 [1.72]; P < .001) and PGB (mean [SD], 7.33 [1.30] to 6.38 [1.88]; P = .002) displayed significant visual analog pain intensity scale reduction and Oswestry Disability Index reduction (mean [SD], 59.22 [16.88] to 48.54 [15.52]; P < .001 for both). Head to head, GBP showed superior visual analog pain intensity scale reduction (mean [SD], GBP: 1.72 [1.17] vs PGB: 0.94 [1.09]; P = .035) irrespective of sequence order; however, Oswestry Disability Index reduction was unchanged. Adverse events for PGB were more frequent (PGB, 31 [81%] vs GBP, 7 [19%]; P = .002) especially when PGB was taken first. Conclusions and Relevance: Pregabalin and GBP were both significantly efficacious. However, GBP was superior with fewer and less severe adverse events. Gabapentin should be commenced before PGB to permit optimal crossover of medicines. Trial Registration: anzctr.org.au Identifier: ACTRN12613000559718.

The epidemiology of tuberculosis in the rural Balimo region of Papua New Guinea.

OBJECTIVE: Papua New Guinea (PNG) has an emerging tuberculosis (TB) epidemic which has become a national public health priority. In Western Province, there are few data about TB outside Daru and the South Fly District. This study describes the epidemiology of TB diagnosed at Balimo District Hospital (BDH) in the Middle Fly District of Western Province, PNG. METHODS: All patients (n = 1614) diagnosed with TB at BDH from April 2013 to February 2017 were recorded. Incidence of reported new cases was calculated for the combined Balimo Urban and Gogodala Rural local level government areas. Analyses investigated patient demographic and clinical information, differences between pulmonary and extrapulmonary TB patients, and predictors of treatment failure. RESULTS: The average case notification rate (2014-2016) was 727 TB cases per 100 000 people per year. One-quarter of TB cases were in children, and 77.1% of all cases had an extrapulmonary TB diagnosis. There was a 1:1.1 ratio of female to male TB cases. When comparing pulmonary and extrapulmonary TB patients, extrapulmonary TB was more likely in those aged up to 14 years and over 54 years. Extrapulmonary TB was more likely in new patients, and pulmonary TB more likely in previously treated patients. Residence in rural regions was associated with treatment failure. CONCLUSION: There is a high burden of TB in the Balimo region, including a very high proportion of extrapulmonary TB. These factors emphasise the importance of BDH as the primary hospital for TB cases in the Balimo region and the Middle Fly District, and the need for resources and staff to manage both drug-susceptible and drug-resistant TB cases.

Pregabalin versus gabapentin in the treatment of sciatica: study protocol for a randomised, double-blind, cross-over trial (PAGPROS).

BACKGROUND: There is currently an absence of high-grade evidence regarding the treatment of chronic sciatica (CS). Whilst gabapentin (GBP) and pregabalin (PGB) are both currently used to treat CS, equipoise exists regarding their individual use. In particular, no head-to-head study of GBP and PGB in CS exists. Despite equipoise, most countries' formulary regulatory authorities typically favour one drug for subsidy over the other. This hinders interchange wherever the favoured drug is either ineffective or not tolerated. The primary aim of this study is to conduct a head-to-head comparison of the efficacy of PGB versus GBP for CS based on outcomes on a visual analogue scale (VAS) and the Oswestry Disability Index (ODI). METHODS/DESIGN: We are conducting a prospective, randomised, double-blind, double-dummy cross-over study. Included patients will be over 18 years old and have unilateral CS with radiological confirmation of corresponding neural compression/irritation. Pregnant women, those with major organ disease, or those with creatinine clearance < 60 ml/minute will be excluded. Patients will continue their current pain medication at study onset, conditional upon dosage consistency during the prior 30 days. Each drug will be titrated up to a target dose (GBP 400-800 mg three times daily, PGB 150-300 mg twice daily) and taken for 8 weeks. The first drug will then be ceased; however, cross-over will be deferred pending a 1-week washout period. Drug efficacy will be assessed using the VAS and ODI. Results of the Health Locus of Control Scale and side effect frequency/severity will be used to determine psychological functioning. Assuming the hypothesis that PGB will display a superior effect, the sample size required is n = 38 with 80% power and a 5% type I error rate. Results will be analysed via intention-to-treat methodology. DISCUSSION: This study will establish the efficacy of PGB compared with GBP in reducing pain in people with sciatica and lead to greater understanding of the treatment options available. TRIAL REGISTRATION: Australian and New Zealand Clinical Trials Registry, 12613000559718 . Registered on 17 May 2013.

Stratospheric ozone loss over the Eurasian continent induced by the polar vortex shift.

The Montreal Protocol has succeeded in limiting major ozone-depleting substance emissions, and consequently stratospheric ozone concentrations are expected to recover this century. However, there is a large uncertainty in the rate of regional ozone recovery in the Northern Hemisphere. Here we identify a Eurasia-North America dipole mode in the total column ozone over the Northern Hemisphere, showing negative and positive total column ozone anomaly centres over Eurasia and North America, respectively. The positive trend of this mode explains an enhanced total column ozone decline over the Eurasian continent in the past three decades, which is closely related to the polar vortex shift towards Eurasia. Multiple chemistry-climate-model simulations indicate that the positive Eurasia-North America dipole trend in late winter is likely to continue in the near future. Our findings suggest that the anticipated ozone recovery in late winter will be sensitive not only to the ozone-depleting substance decline but also to the polar vortex changes, and could be substantially delayed in some regions of the Northern Hemisphere extratropics.

Revisiting the mystery of recent stratospheric temperature trends.

Simulated stratospheric temperatures over the period 1979-2016 in models from the Chemistry-Climate Model Initiative (CCMI) are compared with recently updated and extended satellite observations. The multi-model mean global temperature trends over 1979- 2005 are -0.88 ± 0.23, -0.70 ± 0.16, and -0.50 ± 0.12 K decade-1 for the Stratospheric Sounding Unit (SSU) channels 3 (~40-50 km), 2 (~35-45 km), and 1 (~25-35 km), respectively. These are within the uncertainty bounds of the observed temperature trends from two reprocessed satellite datasets. In the lower stratosphere, the multi-model mean trend in global temperature for the Microwave Sounding Unit channel 4 (~13-22 km) is -0.25 ± 0.12 K decade-1 over 1979-2005, consistent with estimates from three versions of this satellite record. The simulated stratospheric temperature trends in CCMI models over 1979-2005 agree with the previous generation of chemistry-climate models. The models and an extended satellite dataset of SSU with the Advanced Microwave Sounding Unit-A show weaker global stratospheric cooling over 1998-2016 compared to the period of intensive ozone depletion (1979-1997). This is due to the reduction in ozone-induced cooling from the slow-down of ozone trends and the onset of ozone recovery since the late 1990s. In summary, the results show much better consistency between simulated and satellite observed stratospheric temperature trends than was reported by Thompson et al. (2012) for the previous versions of the SSU record and chemistry-climate models. The improved agreement mainly comes from updates to the satellite records; the range of simulated trends is comparable to the previous generation of models.

Tropospheric ozone in CCMI models and Gaussian process emulation to understand biases in the SOCOLv3 chemistry-climate model.

Previous multi-model intercomparisons have shown that chemistry-climate models exhibit significant biases in tropospheric ozone compared with observations. We investigate annual-mean tropospheric column ozone in 15 models participating in the SPARC/IGAC (Stratosphere-troposphere Processes and their Role in Climate/International Global Atmospheric Chemistry) Chemistry-Climate Model Initiative (CCMI). These models exhibit a positive bias, on average, of up to 40-50% in the Northern Hemisphere compared with observations derived from the Ozone Monitoring Instrument and Microwave Limb Sounder (OMI/MLS), and a negative bias of up to ~30% in the Southern Hemisphere. SOCOLv3.0 (version 3 of the Solar-Climate Ozone Links CCM), which participated in CCMI, simulates global-mean tropospheric ozone columns of 40.2 DU - approximately 33% larger than the CCMI multi-model mean. Here we introduce an updated version of SOCOLv3.0, "SOCOLv3.1", which includes an improved treatment of ozone sink processes, and results in a reduction in the tropospheric column ozone bias of up to 8 DU, mostly due to the inclusion of N2O5 hydrolysis on tropospheric aerosols. As a result of these developments, tropospheric column ozone amounts simulated by SOCOLv3.1 are comparable with several other CCMI models. We apply Gaussian process emulation and sensitivity analysis to understand the remaining ozone bias in SOCOLv3.1. This shows that ozone precursors (nitrogen oxides (NOx), carbon monoxide, methane and other volatile organic compounds) are responsible for more than 90% of the variance in tropospheric ozone. However, it may not be the emissions inventories themselves that result in the bias, but how the emissions are handled in SOCOLv3.1, and we discuss this in the wider context of the other CCMI models. Given that the emissions data set to be used for phase 6 of the Coupled Model Intercomparison Project includes approximately 20% more NOx than the data set used for CCMI, further work is urgently needed to address the challenges of simulating sub-grid processes of importance to tropospheric ozone in the current generation of chemistry-climate models.

No Robust Evidence of Future Changes in Major Stratospheric Sudden Warmings: A Multi-model Assessment from CCMI.

Major stratospheric sudden warmings (SSWs) are the largest instance of wintertime variability in the Arctic stratosphere. Due to their relevance for the troposphere-stratosphere system, several previous studies have focused on their potential response to anthropogenic forcings. However, a wide range of results have been reported, from a future increase in the frequency of SSWs to a decrease. Several factors might explain these contradictory results, notably the use of different metrics for the identification of SSWs, and the impact of large climatological biases in single-model studies. Here we revisit the question of future SSWs changes, using an identical set of metrics applied consistently across 12 different models participating in the Chemistry Climate Model Initiative. From analyzing future integrations we find no statistically significant change in the frequency of SSWs over the 21st century, irrespective of the metric used for the identification of SSWs. Changes in other SSWs characteristics, such as their duration and the tropospheric forcing, are also assessed: again, we find no evidence of future changes over the 21st century.