Global eradication rates for Helicobacter pylori infection: systematic review and meta-analysis of sequential therapy.


Abstract

Objective To do a systematic review and meta-analysis of studies comparing sequential therapy for eradication of Helicobacter pylori with pre-existing and new therapies, thus providing a glimpse of eradication success worldwide.

Design Systematic review and meta-analysis.

Data sources Medline, Embase, and Cochrane Central Register of Controlled Trials up to May 2013; abstract books of major European, American, and Asian gastroenterological meetings.

Study selection Randomised controlled trials in previously untreated adults, in which sequential therapy was compared with a pre-existing or new therapy.

Results 46 randomised controlled trials were reviewed and analysed. 5666 patients were randomised to sequential therapy and 7866 to other (established and new) treatments. The overall eradication rate of sequential therapy was 84.3% (95% confidence interval 82.1% to 86.4%). Sequential therapy was superior to seven day triple therapy (relative risk 1.21, 95% confidence interval 1.17 to 1.25; I2=29.3%; number needed to treat 6 , 95% confidence interval 5% to 7%), marginally superior to 10 day triple therapy (1.11, 1.04 to 1.19; I2= 67.2%; NNT 10, 7 to 15), but not superior to 14 day triple therapy (1.00, 0.94 to 1.06; I2=54.3%), bismuth based therapy (1.01, 0.95 to 1.06; I2=21.1%), and non-bismuth based therapy (0.99, 0.94 to 1.05; I2=52.3%). Data on eradication according to pre-treatment antimicrobial susceptibility testing were available in eight studies, and sequential therapy was able to eradicate 72.8% (61.6% to 82.8%) of the strains resistant to clarithromycin.

Conclusions Eradication rates with pre-existing and new therapies for H pylori are suboptimal. Regional monitoring of resistance rates should help to guide treatment, and new agents for treatment need to be developed.

 

Source: BMJ

 

 

Half of referred Parkinson’s disease patients are appropriate candidates for deep brain stimulation therapy.


An interesting point made by US researchers in favour of early referrals for deep brain stimulation therapy:

While deep brain stimulation has gained recognition by referring physicians as a treatment for Parkinson’s disease and other movement disorders, just half of the patients they recommend are appropriate candidates to begin this relatively new therapy immediately, researchers at Cedars-Sinai Medical Center in Los Angeles and The Mount Sinai Medical Center in New York say.

 

Researchers looked back to a 2004 study, which found that just 5% of referrals then were good candidates; they compared their new figures and surmised that referring physicians have increased their awareness and acceptance of deep brain stimulation.

But physicians still often refer patients for this therapy before other treatment options have been exhausted or because they have unrealistically high expectations for it, said Michele Tagliati, director of the Movement Disorders Program at Cedars-Sinai’s Department of Neurology.
Of 197 patients referred for evaluation for deep brain stimulation, 50% were found to be good candidates for immediate therapy, 25% were possible future candidates and 24% were poor candidates because of other neurological or medical conditions.

 

Analysing the referral sources ― movement disorder specialists, primary care physicians, general neurologists, other physicians and patients ― the researchers found that movement disorder specialists referred more patients and most were good therapy candidates.

Over the four-year study period, which ended in late 2009, researchers noted that the number of patients referred for deep brain stimulation therapy at earlier stages of the disease increased. “The study does not address this change specifically and we have no proof, but we speculate that doctors became more liberal in sending patients for surgery for deep brain stimulation,” Tagliati said. “Maybe they are accepting this therapy more and sending patients earlier for it instead of at the very end stage of disease. While doctors may be sending some patients too early to be treated immediately with deep brain stimulation therapy, it is better to see these patients too early than too late. As long as they are evaluated in a responsible, reputable movement disorders centre, they can be reevaluated months or even years later and have the surgery appropriately timed. It is not always clear exactly what is the right time for this therapy, but especially for Parkinson’s disease, if the patient is amenable to medication changes, it is not appropriate to jump to the surgery right away.”

Deep brain stimulation was approved by the Food and Drug Administration for essential tremor in 1997, Parkinson’s disease in 2002, dystonia in 2003 and extreme cases of obsessive-compulsive disorder in 2009″

Source: BMJ

Strongyloides stercoralis infection.


Summary points

  • Strongyloidiasis is endemic in the tropics and subtropics and anyone who has travelled to, or lived in, these areas is at risk
  • Unlike most other intestinal parasite infections, strongyloidiasis may be life long
  • The infection is often asymptomatic and may only be indicated by a peripheral blood eosinophilia
  • Diagnosis is important as immunosuppression in patients with chronic infection can precipitate a life threatening hyperinfection syndrome
  • Serology is the investigation of choice for diagnosis and follow-up, as stool microscopy has a low sensitivity
  • Treatment is with 2×200 μg/kg doses of oral ivermectin given two weeks apart

Strongyloides stercoralis is an intestinal helminth that infects humans through contact with soil containing the larvae. Between 30 and 100 million people are infected worldwide.1 In the United Kingdom, strongyloidiasis is seen predominantly in migrants and returning travellers from endemic areas in the tropics and subtropics. Strongyloidiasis may present with cutaneous or gastrointestinal symptoms but is asymptomatic in over 60% of cases and only indicated by a raised blood eosinophil count.2 Diagnosis is important as the infection may persist for decades.3Immunosuppressed patients with chronic strongyloidiasis are at high risk of developing strongyloides hyperinfection syndrome, a life threatening complication whereby larval proliferation leads to systemic sepsis and multiorgan failure. If strongyloidiasis is diagnosed early, however, it is easily treatable with oral antihelmintic drugs. In this article we review the epidemiology and common symptoms of strongyloidiasis and strongyloides hyperinfection syndrome, discuss the appropriate investigations, and summarise the evidence on treatment.

Source: BMJ

Preventing sexual abusers of children from reoffending: systematic review of medical and psychological interventions.


Abstract

Objective To evaluate the effectiveness of current medical and psychological interventions for individuals at risk of sexually abusing children, both in known abusers and those at risk of abusing.

Design Systematic review of interventions designed to prevent reoffending among known abusers and prevention for individuals at risk of sexually abusing children. Randomised controlled trials and prospective observational studies were eligible. Primary outcomes were arrests, convictions, breaches of conditions, and self reported sexual abuse of children after one year or more.

Results After review of 1447 abstracts, we retrieved 167 full text studies, and finally included eight studies with low to moderate risk of bias. We found weak evidence for interventions aimed at reducing reoffending in identified sexual abusers of children. For adults, evidence from five trials was insufficient regarding both benefits and risks with psychological treatment and pharmacotherapy. For adolescents, limited evidence from one trial suggested that multisystemic therapy prevented reoffence (relative risk 0.18, 95% confidence interval 0.04 to 0.73); lack of adequate research prevented conclusions about effects of other treatments. Evidence was also inadequate regarding effectiveness of treatment for children with sexual behavioural problems in the one trial identified. Finally, we found no eligible research on preventive methods for adults and adolescents who had not sexually abused children but were at higher risk of doing so (such as those with paedophilic sexual preference).

Conclusion There are major weaknesses in the scientific evidence, particularly regarding adult men, the main category of sexual abusers of children. Better coordinated and funded high quality studies including several countries are urgently needed. Until conclusive evidence is available, realistic clinical strategies might involve reduction of specific risk factors for sex crimes, such as sexual preoccupation, in abusers at risk of reoffending.

Source: BMJ

 

Perceived job insecurity as a risk factor for incident coronary heart disease: systematic review and meta-analysis.


Abstract

Objective To determine the association between self reported job insecurity and incident coronary heart disease.

Design A meta-analysis combining individual level data from a collaborative consortium and published studies identified by a systematic review.

Data sources We obtained individual level data from 13 cohort studies participating in the Individual-Participant-Data Meta-analysis in Working Populations Consortium. Four published prospective cohort studies were identified by searches of Medline (to August 2012) and Embase databases (to October 2012), supplemented by manual searches.

Review methods Prospective cohort studies that reported risk estimates for clinically verified incident coronary heart disease by the level of self reported job insecurity. Two independent reviewers extracted published data. Summary estimates of association were obtained using random effects models.

Results The literature search yielded four cohort studies. Together with 13 cohort studies with individual participant data, the meta-analysis comprised up to 174 438 participants with a mean follow-up of 9.7 years and 1892 incident cases of coronary heart disease. Age adjusted relative risk of high versus low job insecurity was 1.32 (95% confidence interval 1.09 to 1.59). The relative risk of job insecurity adjusted for sociodemographic and risk factors was 1.19 (1.00 to 1.42). There was no evidence of significant differences in this association by sex, age (<50 v ≥50 years), national unemployment rate, welfare regime, or job insecurity measure.

Conclusions The modest association between perceived job insecurity and incident coronary heart disease is partly attributable to poorer socioeconomic circumstances and less favourable risk factor profiles among people with job insecurity.

Source: BMJ

Sequence-Based Discovery of Bradyrhizobium enterica in Cord Colitis Syndrome.


BACKGROUND

Immunosuppression is associated with a variety of idiopathic clinical syndromes that may have infectious causes. It has been hypothesized that the cord colitis syndrome, a complication of umbilical-cord hematopoietic stem-cell transplantation, is infectious in origin.

METHODS

We performed shotgun DNA sequencing on four archived, paraffin-embedded endoscopic colon-biopsy specimens obtained from two patients with cord colitis. Computational subtraction of human and known microbial sequences and assembly of residual sequences into a bacterial draft genome were performed. We used polymerase-chain-reaction (PCR) assays and fluorescence in situ hybridization to determine whether the corresponding bacterium was present in additional patients and controls.

RESULTS

DNA sequencing of the biopsy specimens revealed more than 2.5 million sequencing reads that did not match known organisms. These sequences were computationally assembled into a 7.65-Mb draft genome showing a high degree of homology with genomes of bacteria in the bradyrhizobium genus. The corresponding newly discovered bacterium was provisionally named Bradyrhizobium enterica. PCR identified B. enterica nucleotide sequences in biopsy specimens from all three additional patients with cord colitis whose samples were tested, whereas B. enterica sequences were absent in samples obtained from healthy controls and patients with colon cancer or graft-versus-host disease.

CONCLUSIONS

We assembled a novel bacterial draft genome from the direct sequencing of tissue specimens from patients with cord colitis. Association of these sequences with cord colitis suggests that B. enterica may be an opportunistic human pathogen.

Souirce: NEJM

 

Probable person to person transmission of novel avian influenza A (H7N9) virus in Eastern China, 2013: epidemiological investigation.


Abstract

Objective To determine whether the novel avian influenza H7N9 virus can transmit from person to person and its efficiency.

Design Epidemiological investigations conducted after a family cluster of two patients with avian H7N9 in March 2013.

Setting Wuxi, Eastern China.

Participants Two patients, their close contacts, and relevant environments. Samples from the patients and environments were collected and tested by real time reverse transcriptase-polymerase chain reaction (rRT-PCR), viral culture, and haemagglutination inhibition assay. Any contacts who became ill had samples tested for avian H7N9 by rRT-PCR. Paired serum samples were obtained from contacts for serological testing by haemagglutination inhibition assays.

Main outcomes measures Clinical data, history of exposure before the onset of illnesses, and results of laboratory testing of pathogens and further analysis of sequences and phylogenetic tree to isolated strains.

Results The index patient became ill five to six days after his last exposure to poultry. The second patient, his daughter aged 32, who provided unprotected bedside care in the hospital, had no known exposure to poultry. She developed symptoms six days after her last contact with her father. Two strains were isolated successfully from the two patients. Genome sequence and analyses of phylogenetic trees showed that both viruses were almost genetically identical. Forty three close contacts of both patients were identified. One had mild illness but had negative results for avian H7N9 by rRT-PCR. All 43 close contacts tested negative for haemagglutination inhibition antibodies specific for avian H7N9.

Conclusions The infection of the daughter probably resulted from contact with her father (the index patient) during unprotected exposure, suggesting that in this cluster the virus was able to transmit from person to person. The transmissibility was limited and non-sustainable.

Discussion

We believe that the most likely explanation for this family cluster of the two patients with novel avian influenza H7N9 virus infection is that the virus transmitted directly from the index patient to his daughter. Firstly, the diagnosis of the two patients was confirmed virologically, and the clinical features―fever, pneumonia with lymphopenia, and rapid progression to acute respiratory distress syndrome—all correspond to the cardinal features of reported cases in humans in China.17 18 Secondly, it was fortuitous for the investigation that the daughter did not visit the markets to buy foodstuffs and cook for the family and had no exposure to animals or history of visiting live poultry markets. She did, however, have prolonged, direct, and unprotected exposure to her father. Thirdly, two strains were isolated successfully from the two patients. Further sequence analysis showed that both possessed high degrees of similarity between nucleotide (99.6%-99.9%) and amino acid (99.0%-100%) sequences. Finally, before this study, A (H7N7) among H7 subtype influenza viruses and H5N1 virus was known to have the ability to transmit from person to person.19 20 21 Animal (ferrets and pigs) experiments indicated that the H7N9 virus possessed the capability to bind to both avian and human receptor and to transmit itself by droplet under certain conditions.22 23

Our findings, however, indicated that the virus has not gained the ability for efficient sustained transmission from person to person. From 14 March, the daughter came into direct contact with the oral secretions of the index patient without any personal protective equipment, contacting the patient at a much higher rate than other individuals in contact with the patient. Similar to other available human strains, the characteristics of the two strains showed no adaptation change in the receptor binding site from the avian 2,3-linked pattern toward the human 2,6-linked pattern of sialic acid receptor.1 7 Phylogenic tree analysis of all eight genomic segments indicated that the two isolates were of avian origin and that there was no reassortment with human or swine influenza viruses.24 2526 Furthermore, no asymptomatic or subclinical infections were identified among 43 close contacts by haemagglutination inhibition testing. Recent studies also indicated that avian H7N9 tends to bind lower pulmonary epithelial cells rather than those of the upper respiratory tract, which makes it difficult to transmit between humans.7

The two patients were blood related. The index patient’s son in law also provided bedside care for the index patient in the mornings and nights between 11 and 13 March without any personal protective equipment. Both biological and serological evidence showed that he was not infected with the H7N9 virus. These findings suggest that potential genetic susceptibility might be one of determinants and that avian influenza viruses, like H5N1, are more easily transmitted between individuals with genetic connection.27 28

The possible source of infection for the index case was likely to be from the live poultry market that the patient used to visit or the six quails that he bought but were slaughtered by the seller in the market one week before illness onset. One strain of avian H7N9 was isolated from environmental samples from the live poultry markets. Visiting a wet poultry market has been identified as a risk factor for human infections.8 9

Important strengths and differences in relation to other studies

With respect to the possible infection period in the second patient, we cannot ascertain when person to person transmission occurred. The most likely period was from 11 to 15 March during the index patient’s admission to hospital before transfer to intensive care, especially the periods between the afternoon of 14 March and the morning of 15 March, when the index patient began to expectorate abundantly. The daughter had direct and close contact with the index case without any protection during this period. During 8-10 March, the daughter provided only conventional care for the index patient, such as taking his temperature. Transmission is unlikely to have occurred during this period as the patient had not yet to start expectoration. Thus, the most likely incubation period was six to seven days (range 6-13 days) based on the daughter’s unprotected exposure to her father. The putative incubation period was a relatively longer than that reported by Cowling and colleagues, who estimated the average incubation period to be around three days based on Weibull model as well as live poultry to human transmission.29 We estimated the incubation period based on person to person transmission and one case in cluster.

Implications of the study

Possible transmission routes include contact while cleaning up infected oral secretions and subsequent inoculation of mucous membranes or the respiratory tract. Some researchers suggested that the daughter might have acquired her infection during the process of washing her father’s diarrhoea-soiled underwear.11 We thought this to be unlikely. Firstly, clinical data showed that the index patient did not develop diarrhoea during course of disease. Secondly, the daughter wore gloves while washing. Thirdly, no nucleic acids specific for avian H7N9 were detected from the faecal samples from the father.

We noted that 39 healthcare workers were identified as close contacts in this cluster, which was a little unusual. Both the two hospitals where the two patients were admitted were general hospitals rather than hospitals specialising in infectious disease. The awareness of personal protection of the healthcare workers was relatively weak. They used common surgical masks instead of N95 masks while providing medical services for the two patients. Another important factor was the relatively long time between the patients’ admission to a clear diagnosis with H7N9 virus infection. After the cluster was identified, infection control measures were initiated to prevent potential nosocomial transmission. Patients were isolated. Healthcare workers were required take standard respiratory and contact protection.

Weaknesses of the study

There are several limitations to our study. Firstly, we could not interview with the two patients as they were both critically ill. Therefore, the possibility that the daughter acquired her infection from the environment or other sources could not be completely ruled out, although we believe that it is less likely. Environmental investigation discovered that in addition to two swans raised by an employee of the property management, there were no other birds or poultry in her living environment. No positive results were detected from the cloacal swab and faecal samples from the two swans. Secondly, the sensitivity of haemagglutination inhibition assay was not satisfied. Thus, subclinical or asymptomatic infections could not be excluded among close contacts. A more sensitive method such as micro-neutralisation assay should be considered in the future. Finally, whole sequence alignment showed that the two isolates from patients were not identical. It is reasonable to expect slight differences between the two strains. Variations of the viral genomes occur constantly because of the high error rate of the viral polymerase. We sequenced viral genomes from the strain from the father that underwent three successive passages using MDCK cell lines. Evolution of the strain might have occurred in vivo because of the long time interval as well as the use of antiviral drugs. A previous study showed that influenza viruses often differ from those present in clinical specimens after isolation in MDCK cell culture as adaptive changes occur during virus transmission from the human host to cells of heterologous origin.30

Unanswered questions and future research

To the best of our knowledge, this is the first report of probable transmissibility of this novel virus from person to person with detailed epidemiological, clinical, and virological data. The importance of an isolated case of such transmission means there is potential for greater human to human transmission. Thus, timely detection as well as rapid investigation and risk assessments of clusters is critically important as the increase in clusters might indicate potential transmissibility of a novel virus.

What is already known on this topic

  • Most cases of novel avian H7N9 occur sporadically
  • Animal experiments indicated that the H7N9 virus can transmit itself by droplet under certain conditions
  • No definite evidence indicates that the novel virus can transmit itself from person to person
  • To our best knowledge, this is the first report of probable transmissibility of the H7N9 virus from person to person with detailed epidemiological, clinical, and virological data
  • Our findings reinforced that the novel virus possesses the potential for pandemic spread

What this study adds

 

Source: BMJ

 

Pentagon’s giant blood serum bank may provide PTSD clues.


The massive repository of genetic material is poised to advance research—just don’t bother asking for your samples back.

Nestled inside a generic-looking office building here in suburban Maryland, down the hall from cable-provider Comcast, sits the largest blood serum repository in the world.

SciAm_1.13545

Seven freezers, each roughly the size of a high school basketball court, are stacked high with row upon row of small cardboard boxes containing tubes of yellow or pinkish blood serum, a liquid rich in antibodies and proteins, but devoid of cells. The freezers hover at –30 degrees Celsius—cold enough to make my pen dry up and to require that workers wear protective jumpsuits, hats, gloves and face masks. Four more empty freezers, which are now kept at room temperature, await future samples.

The bank of massive freezers—and its contents—is maintained by the Department of Defense (DoD). The cache of government-owned serum may provide unique insights into the workings of various maladies when linked with detailed information on service members’ demographics, deployment locations and health survey data. New research projects tapping the precious serum could lead to breakthroughs in some of the hottest topics in military research—including the hunt for biomarkers for post-traumatic stress disorder and suicide risk. But DoD’s policy of keeping its samples in perpetuity—even after troops leave the force—could raise a few eyebrows.

From humble beginnings

The military started collecting serum samples 28 years ago as a by-product of its HIV surveillance. Since then serum has been routinely collected from leftover blood from HIV tests or standard post-deployment health check-ups and then frozen for future reference. Now the Department of Defense Serum Repository (DoDSR) has swelled to include 55.5 million samples of serum from 10 million individuals—mostly service members, veterans or military applicants. The armed forces use DoDSR for general health surveillance to track infectious diseases and to shape health policies. But the repository is also ripe for targeted research programs.

Annually the facility may field as many as 100 requests to use some of the serum from that icy reserve. Sixty-two requests received the green light to sample from DoDSR last year, half of them for research and half for clinical testing of an individual patient’s samples. In the past five years DoDSR has filled 278 such requests. But not all DoDSR uses are medical: they have also played a role in criminal proceedings, serving as a reference point for female victims in two rape cases, says Mark Rubertone, who oversees the DoDSR. “The value of the specimens does not go away, even after [service members] leave the military,” he says.

Even with the promise of ongoing health surveillance and potential research that would benefit the force, not all contributors to the repository are enthusiastic about—or even necessarily aware of—their participation. DoDSR does not discard serum samples, even if individual service members or military applicants request that their samples be removed. Fewer than 10 individuals have asked for the removal of their samples, according to Rubertone. But the requests are likely rare because service members and their families are not actively aware of the serum, even though they may know that their blood—in one form or another—is on file, Rubertone acknowledges. Thus far, no one has successfully retrieved his or her biological materials from the facility.

A RAND Corp. report on the facility, published in 2010 (after an earlier draft was revealed via Wikileaks), pointed out that nearly 900,000 samples in the repository were not from active duty or reservist personnel—they were from so-called “dependent beneficiaries” in service members’ families. Those numbers have since grown, to a “couple million” samples, according to the DoDSR count. The biological material from military family members often ends up in the repository after beneficiaries receive pregnancy care or visit a sexually transmitted infection clinic. The data accompanying those samples are more sparse and so the serum specimens are not as useful for studies, although they are still kept in the repository. Another 4 percent of the samples come from civilians who applied for military service but did not join.

Research payoffs

Researchers who draw on the serum bank note that the wealth of longitudinal data from DoDSR enables cutting-edge research. Take, for example, several projects that are searching for biomarkers of post-traumatic stress disorder. By matching up pre- and post-deployment DNA from individuals who developed PTSD and also comparing the genetic material with DNA from a control population, researchers are hoping to discern clues about when and how PTSD becomes apparent at a genetic level, impacting the DNA building blocks via DNA methylation and perhaps the silencing of certain genes. Related work is also focusing on microRNA—a small, noncoding RNA molecule—that helps regulate numerous biological processes and serves as a fingerprint for disease development.

Meanwhile, other researchers are studying serum to garner clues about links between traumatic brain injury (TBI) and DNA methylation among individuals who served in Iraq and Afghanistan, gleaning information from samples on 150 service members with mild to severe TBI, along with 50 control subjects. Because individuals—both on and off the battlefield—can suffer from mild TBI and not know it, identifying a biomarker could help speed up clinical care, says study investigator Jennifer Rusiecki, an epidemiologist at Uniformed Services University of the Health Sciences in Bethesda, Md.

Without the serum available through DoDSR and its accompanying information, some of this work would likely be impossible. “I’m not aware of other banks that have this data,” Rusiecki says. All told, almost 75 publications have depended on data gleaned from the samples in these freezers. Still more projects have drawn on them but did not make it into print. And because the repository’s stated purpose is health surveillance, the samples would not be chucked even if all the studies were halted, DoDSR’s Rubertone says.

 

.

The military has instituted safeguards to prevent misuse of the serum reserve. All studies conducted with DoDSR serums are required to have a military co-investigator, a policy DoD put in place to help ensure that the serum is being used for military-relevant purposes. Researchers must also receive approval from their home institutions’ institutional review boards, groups that ensure investigators will guard patients’ confidentiality and adhere to ethical research principles.

Unfortunately, despite the scale of the military repository, blood serum has its limits as a medical resource. For research and health surveillance, the serum can only tell you so much, says Capt. Kevin Russell, the director of the Armed Forces Health Surveillance Center that oversees DoDSR. Because the serum samples are not linked to very specific exposure information—such as exactly where a service member was stationed or what he or she encountered while deployed—they only stand in as a surrogate for exposure. At the moment DoD is exploring whether other materials—urine, throat cultures, blood clots—or perhaps new technologies could enhance their repository. Nevertheless, it would be “unlikely” that Defense would get rid of its serum reserve or stop adding new samples, Russell says. And so four freezers remain empty, waiting.

Source: Nature

 

 

 

 

Ozone hole could boost global warming.


The thinning of the atmosphere’s ozone layer could be contributing to warming the planet, according to a study published this week in Geophysical Research Letters.

Kevin Grise, an atmospheric scientist at Columbia University in New York, and his team modelled the weather dynamics around the ozone hole above the Antarctic. They calculated the knock-on effects of ozone depletion on cloud cover, and ultimately on radiative forcing — the balance of solar and thermal radiation absorbed, reflected or emitted by the planet and its atmosphere.

 

Previous research by Piers Forster, an atmospheric scientist at the University of Leeds, UK, and his collaborators attributed a slight cooling effect to the ozone hole. But the latest study, which focused on the Antarctic summer between December and February, found that there may be a warming effect instead.

The team’s models predicted a shift in the southern-hemisphere jet stream — the high-altitude air currents flowing around Antarctica — as a result of ozone depletion. This produced a change in the cloud distribution, with clouds moving towards the South Pole, where they are less effective at reflecting solar radiation.

The result was that the effects on the Earth’s net energy balance were opposite to what had been calculated before. “A negative radiative forcing is what you’d expect when the ozone is depleted, but our research shows that there is a positive net radiative effect during the Antarctic summer,” Grise says.

The extra net energy absorbed by the Earth would be 0.25 watts per square metre, or roughly a tenth of the greenhouse effect attributed to CO2, Grise says. The result could be a small but non-negligible contribution to global temperature rise.

“I think it’s an interesting piece of research. They are talking about a new mechanism in the world of ozone and climate change,” says Forster. “There’s quite a lot of work to be done to pin down the mechanism, but it does sound reasonable.”

Source: Nature