Scientific data from precipitation driver response model intercomparison project.

This data descriptor reports the main scientific values from General Circulation Models (GCMs) in the Precipitation Driver and Response Model Intercomparison Project (PDRMIP). The purpose of the GCM simulations has been to enhance the scientific understanding of how changes in greenhouse gases, aerosols, and incoming solar radiation perturb the Earth's radiation balance and its climate response in terms of changes in temperature and precipitation. Here we provide global and annual mean results for a large set of coupled atmospheric-ocean GCM simulations and a description of how to easily extract files from the dataset. The simulations consist of single idealized perturbations to the climate system and have been shown to achieve important insight in complex climate simulations. We therefore expect this data set to be valuable and highly used to understand simulations from complex GCMs and Earth System Models for various phases of the Coupled Model Intercomparison Project.

Rapid adjustments cause weak surface temperature response to increased black carbon concentrations.

We investigate the climate response to increased concentrations of black carbon (BC), as part of the Precipitation Driver Response Model Intercomparison Project (PDRMIP). A tenfold increase in BC is simulated by 9 global coupled-climate models, producing a model-median effective radiative forcing (ERF) of 0.82 (ranging from 0.41 to 2.91) Wm-2, and a warming of 0.67 (0.16 to 1.66) K globally and 1.24 (0.26 to 4.31) K in the Arctic. A strong positive instantaneous radiative forcing (median of 2.10 Wm-2 based on five of the models) is countered by negative rapid adjustments (-0.64 Wm-2 for the same five models), which dampen the total surface temperature signal. Unlike other drivers of climate change, the response of temperature and cloud profiles to the BC forcing is dominated by rapid adjustments. Low-level cloud amounts increase for all models, while higher-level clouds are diminished. The rapid temperature response is particularly strong above 400 hPa, where increased atmospheric stabilization and reduced cloud cover contrast the response pattern of the other drivers. In conclusion, we find that this substantial increase in BC concentrations does have considerable impacts on important aspects of the climate system. However, some of these effects tend to offset one another, leaving a relatively small global warming of 0.47 K per Wm-2 - about 20 % lower than the response to a doubling of CO2. Translating the tenfold increase in BC to the present-day impact of anthropogenic BC (given the emissions used in this work) would leave a warming of merely 0.07 K.

Evaluation of the aerosol vertical distribution in global aerosol models through comparison against CALIOP measurements: AeroCom phase II results.

The ability of 11 models in simulating the aerosol vertical distribution from regional to global scales, as part of the second phase of the AeroCom model intercomparison initiative (AeroCom II), is assessed and compared to results of the first phase. The evaluation is performed using a global monthly gridded data set of aerosol extinction profiles built for this purpose from the CALIOP (Cloud-Aerosol Lidar with Orthogonal Polarization) Layer Product 3.01. Results over 12 subcontinental regions show that five models improved, whereas three degraded in reproducing the interregional variability in Z α0-6 km, the mean extinction height diagnostic, as computed from the CALIOP aerosol profiles over the 0-6 km altitude range for each studied region and season. While the models' performance remains highly variable, the simulation of the timing of the Z α0-6 km peak season has also improved for all but two models from AeroCom Phase I to Phase II. The biases in Z α0-6 km are smaller in all regions except Central Atlantic, East Asia, and North and South Africa. Most of the models now underestimate Z α0-6 km over land, notably in the dust and biomass burning regions in Asia and Africa. At global scale, the AeroCom II models better reproduce the Z α0-6 km latitudinal variability over ocean than over land. Hypotheses for the performance and evolution of the individual models and for the intermodel diversity are discussed. We also provide an analysis of the CALIOP limitations and uncertainties contributing to the differences between the simulations and observations.

Outcome prediction in chronic unilateral lumbar radiculopathy: prospective cohort study.

BACKGROUND: Identification of prognostic factors for persistent pain and disability are important for better understanding of the clinical course of chronic unilateral lumbar radiculopathy and to assist clinical decision-making. There is a lack of scientific evidence concerning prognostic factors. The aim of this study was to identify clinically relevant predictors for outcome at 52 weeks. METHODS: 116 patients were included in a sham controlled clinical trial on epidural injection of glucocorticoids in patients with chronic unilateral lumbar radiculopathy. Success at follow-up was ≤ 17.5 for visual analogue scale (VAS) leg pain, ≤ 22.5 for VAS back pain and ≤ 20 for Oswestry Disability Index (ODI). Fifteen clinically relevant variables included demographic, psychosocial, clinical and radiological data and were analysed using a logistic multivariable regression analysis. RESULTS: At follow-up, 75 (64.7%) patients had reached a successful outcome with an ODI score ≤ 20, 54 (46.6%) with a VAS leg pain score ≤ 17.5, and 47 (40.5%) with a VAS back pain score ≤ 22.5. Lower age (OR 0.94 (CI 0.89-0.99) for each year decrease in age) and FABQ Work ≥ 34 (OR 0.16 (CI 0.04-0.61)) were independent variables predicting a successful outcome on the ODI. Higher education (OR 5.77 (CI 1.46-22.87)) and working full-time (OR 2.70 (CI 1.02-7.18)) were statistically significant (P <0.05) independent predictors for successful outcome (VAS score ≤ 17.5) on the measure of leg pain. Lower age predicted success on ODI (OR 0.94 (95% CI 0.89 to 0.99) for each year) and less back pain (OR 0.94 (0.90 to 0.99)), while higher education (OR 5.77 (1.46 to 22.87)), working full-time (OR 2.70 (1.02 to 7.18)) and muscle weakness at baseline (OR 4.11 (1.24 to 13.61) predicted less leg pain, and reflex impairment at baseline predicted the contrary (OR 0.39 (0.15 to 0.97)). CONCLUSIONS: Lower age, higher education, working full-time and low fear avoidance beliefs each predict a better outcome of chronic unilateral lumbar radiculopathy. Specifically, lower age and low fear avoidance predict a better functional outcome and less back pain, while higher education and working full-time predict less leg pain. These results should be validated in further studies before being used to inform patients. TRIAL REGISTRATION: Current Controlled Trials ISRCTN12574253 . Registered 18 May 2005.

Remote sensing of aerosols in the Arctic for an evaluation of global climate model simulations.

In this study Moderate Resolution Imaging Spectroradiometer (MODIS) Aqua retrievals of aerosol optical thickness (AOT) at 555 nm are compared to Sun photometer measurements from Svalbard for a period of 9 years. For the 642 daily coincident measurements that were obtained, MODIS AOT generally varies within the predicted uncertainty of the retrieval over ocean (ΔAOT = ±0.03 ± 0.05 · AOT). The results from the remote sensing have been used to examine the accuracy in estimates of aerosol optical properties in the Arctic, generated by global climate models and from in situ measurements at the Zeppelin station, Svalbard. AOT simulated with the Norwegian Earth System Model/Community Atmosphere Model version 4 Oslo global climate model does not reproduce the observed seasonal variability of the Arctic aerosol. The model overestimates clear-sky AOT by nearly a factor of 2 for the background summer season, while tending to underestimate the values in the spring season. Furthermore, large differences in all-sky AOT of up to 1 order of magnitude are found for the Coupled Model Intercomparison Project phase 5 model ensemble for the spring and summer seasons. Large differences between satellite/ground-based remote sensing of AOT and AOT estimated from dry and humidified scattering coefficients are found for the subarctic marine boundary layer in summer. KEY POINTS: Remote sensing of AOT is very useful in validation of climate models.

Accuracy of physical examination for chronic lumbar radiculopathy.

BACKGROUND: Clinical examination of patients with chronic lumbar radiculopathy aims to clarify whether there is nerve root impingement. The aims of this study were to investigate the association between findings at clinical examination and nerve root impingement, to evaluate the accuracy of clinical index tests in a specialised care setting, and to see whether imaging clarifies the cause of chronic radicular pain. METHODS: A total of 116 patients referred with symptoms of lumbar radiculopathy lasting more than 12 weeks and at least one positive index test were included. The tests were the straight leg raising test, and tests for motor muscle strength, dermatome sensory loss, and reflex impairment. Magnetic resonance imaging (n = 109) or computer tomography (n = 7) were imaging reference standards. Images were analysed at the level of single nerve root(s), and nerve root impingement was classified as present or absent. Sensitivities, specificities, and positive and negative likelihood ratios (LR) for detection of nerve root impingement were calculated for each individual index test. An overall clinical evaluation, concluding on the level and side of the radiculopathy, was performed. RESULTS: The prevalence of disc herniation was 77.8%. The diagnostic accuracy of individual index tests was low with no tests reaching positive LR >4.0 or negative LR <0.4. The overall clinical evaluation was slightly more accurate, with a positive LR of 6.28 (95% CI 1.06-37.21) for L4, 1.74 (95% CI 1.04-2.93) for L5, and 1.29 (95% CI 0.97-1.72) for S1 nerve root impingement. An overall clinical evaluation, concluding on the level and side of the radiculopathy was also performed, and receiver operating characteristic (ROC) analysis with area under the curve (AUC) calculation for diagnostic accuracy of this evaluation was performed. CONCLUSIONS: The accuracy of individual clinical index tests used to predict imaging findings of nerve root impingement in patients with chronic lumbar radiculopathy is low when applied in specialised care, but clinicians' overall evaluation improves diagnostic accuracy slightly. The tests are not very helpful in clarifying the cause of radicular pain, and are therefore inaccurate for guidance in the diagnostic workup of the patients. The study population was highly selected and therefore the results from this study should not be generalised to unselected patient populations in primary care nor to even more selected surgical populations.

Modic type I changes and recovery of back pain after lumbar microdiscectomy.

PURPOSE: To investigate whether the presence of Modic changes type I (MC I) found on preoperative MRI scans represent a risk factor for persistent back pain 12 months after surgery amongst patients operated for lumbar disc herniation. METHODS: Cohort study of 178 consecutive patients operated with lumbar microdiscectomy. Preoperative MRI scans were evaluated by two independent neuroradiologists. Primary outcome measure was the visual analogue scale (VAS) for back pain. Secondary outcome measures were; VAS for leg pain, physical function (Oswestry disability index), and health-related quality of life (EQ-5D), self-reported benefit of the operation and employment status. The presence of MC I was used as exposition variable and adjusted for other risk factors in multivariate analyses. RESULTS: The Modic classification showed a high inter-observer reproducibility. Patients with MC I had less improvement of back pain 12 months after surgery, compared to those who had no or other types of MC, but this negative association no longer showed statistical significance when adjusted for smoking, which remained the only independent risk factor for persistent back pain. CONCLUSIONS: Patients with preoperative MC I can expect less but still significant improvement of back pain 1 year after microdiscectomy, but not if they smoke cigarettes.

Effect of caudal epidural steroid or saline injection in chronic lumbar radiculopathy: multicentre, blinded, randomised controlled trial.

OBJECTIVE: To assess the efficacy of caudal epidural steroid or saline injection in chronic lumbar radiculopathy in the short (6 weeks), intermediate (12 weeks), and long term (52 weeks). DESIGN: Multicentre, blinded, randomised controlled trial. SETTING: Outpatient multidisciplinary back clinics of five Norwegian hospitals. PARTICIPANTS: Between October 2005 and February 2009, 461 patients assessed for inclusion (presenting with lumbar radiculopathy >12 weeks). 328 patients excluded for cauda equina syndrome, severe paresis, severe pain, previous spinal injection or surgery, deformity, pregnancy, ongoing breast feeding, warfarin therapy, ongoing treatment with non-steroidal anti-inflammatory drugs, body mass index >30, poorly controlled psychiatric conditions with possible secondary gain, and severe comorbidity. INTERVENTIONS: Subcutaneous sham injections of 2 mL 0.9% saline, caudal epidural injections of 30 mL 0.9% saline, and caudal epidural injections of 40 mg triamcinolone acetonide in 29 mL 0.9% saline. Participants received two injections with a two week interval. MAIN OUTCOME MEASURES: Primary: Oswestry disability index scores. Secondary: European quality of life measure, visual analogue scale scores for low back pain and for leg pain. RESULTS: Power calculations required the inclusion of 41 patients per group. We did not allocate 17 of 133 eligible patients because their symptoms improved before randomisation. All groups improved after the interventions, but we found no statistical or clinical differences between the groups over time. For the sham group (n = 40), estimated change in the Oswestry disability index from the adjusted baseline value was -4.7 (95% confidence intervals -0.6 to -8.8) at 6 weeks, -11.4 (-6.3 to -14.5) at 12 weeks, and -14.3 (-10.0 to -18.7) at 52 weeks. For the epidural saline intervention group (n = 39) compared with the sham group, differences in primary outcome were -0.5 (-6.3 to 5.4) at 6 weeks, 1.4 (-4.5 to 7.2) at 12 weeks, and -1.9 (-8.0 to 4.3) at 52 weeks; for the epidural steroid group (n=37), corresponding differences were -2.9 (-8.7 to 3.0), 4.0 (-1.9 to 9.9), and 1.9 (-4.2 to 8.0). Analysis adjusted for duration of leg pain, back pain, and sick leave did not change this trend. CONCLUSIONS: Caudal epidural steroid or saline injections are not recommended for chronic lumbar radiculopathy. Trial registration Current Controlled Trials ISRCTN No 12574253.