Tropical belt width proportionately more sensitive to aerosols than greenhouse gases

The tropical belt has widened during the last several decades, and both internal variability and anthropogenic forcings have contributed. Although greenhouse gases and stratospheric ozone depletion have been implicated as primary anthropogenic drivers of tropical expansion, the possible role of other drivers remains uncertain. Here, we analyze the tropical belt width response to idealized perturbations in multiple models. Our results show that absorbing black carbon (BC) aerosol drives tropical expansion, and scattering sulfate aerosol drives contraction. BC, especially from Asia, is more efficient per unit radiative forcing than greenhouse gases in driving tropical expansion, particularly in the Northern Hemisphere. Tropical belt expansion (contraction) is associated with an increase (decrease) in extratropical static stability induced by absorbing (scattering) aerosol. Although a formal attribution is difficult, scaling the normalized expansion rates to the historical time period suggests that BC is the largest driver of the Northern Hemisphere tropical widening but with relatively large uncertainty

Statin therapy is associated with reduced mortality across all age groups of individuals with significant coronary disease, including very elderly patients

AbstractObjectivesThis study evaluated the effect of statin therapy on mortality in individuals with significant coronary artery disease (CAD) stratified by age.BackgroundHydroxymethylglutaryl coenzyme A reductase inhibitors (statins) significantly reduce morbidity and mortality in individuals with CAD. Unfortunately, the large statin trials excluded individuals over 80 years old, and it is therefore unknown whether very elderly individuals benefit from statins as do younger individuals.MethodsA cohort of 7,220 individuals with angiographically defined significant CAD (≥70%) was included. Statin prescription was determined at hospital discharge. Patients were followed up for 3.3 ± 1.8 years (maximum 6.8). Patients were grouped by age (<65, 65 to 79, and ≥80 years) to determine whether statin therapy reduced mortality in an age-dependent manner.ResultsAverage age was 65 ± 12 years; 74% were male; and 31% had a postmyocardial infarction status. Overall mortality was 16%. Elderly patients were significantly less likely to receive statins than younger patients (≥80 years: 19.8%; 65 to 79 years: 21.1%; <65 years: 28.0%; p < 0.001). Mortality was decreased among statin recipients in all age groups: ≥80 years: 29.5% among patients not taking a statin versus 8.5% of those taking a statin (adjusted hazard ratio [HR] 0.50, p = 0.036); 65 to 79 years: 18.7% vs. 6.0% (HR 0.56, p < 0.001); and <65 years: 8.9% vs. 3.1% (HR 0.70, p = 0.097).ConclusionsStatin therapy is associated with reduced mortality in all age groups of individuals with significant CAD, including very elderly individuals. Although older patients were less likely to receive statin therapy, they received a greater absolute risk reduction than younger individuals. More aggressive statin use after CAD diagnosis may be indicated, even in older patients

Increased shear in the North Atlantic upper-level jet stream over the past four decades

Earth’s equator-to-pole temperature gradient drives westerly mid-latitude jet streams through thermal wind balance. In the upper atmosphere, anthropogenic climate change is strengthening this meridional temperature gradient by cooling the polar lower stratosphere and warming the tropical upper troposphere acting to strengthen the upper-level jet stream. In contrast, in the lower atmosphere, Arctic amplification of global warming is weakening the meridional temperature gradient acting to weaken the upper-level jet stream. Therefore, trends in the speed of the upper-level jet stream represent a closely balanced tug-of-war between two competing effects at different altitudes. It is possible to isolate one of the competing effects by analysing the vertical shear—the change in wind speed with height—instead of the wind speed, but this approach has not previously been taken. Here we show that, although the zonal wind speed in the North Atlantic polar jet stream at 250 hectopascals has not changed since the start of the observational satellite era in 1979, the vertical shear has increased by 15 per cent (with a range of 11–17 per cent) according to three different reanalysis datasets. We further show that this trend is attributable to the thermal wind response to the enhanced upper-level meridional temperature gradient. Our results indicate that climate change may be having a larger impact on the North Atlantic jet stream than previously thought. The increased vertical shear is consistent with the intensification of shear-driven clear-air turbulence expected from climate change which will affect aviation in the busy transatlantic flight corridor by creating a more turbulent flying environment for aircraft. We conclude that the effects of climate change and variability on the upper-level jet stream are being partly obscured by the traditional focus on wind speed rather than wind shear

The impact of statins on health services utilization and mortality in older adults discharged from hospital with ischemic heart disease: a cohort study

<p>Abstract</p> <p>Background</p> <p>Cardiovascular disease (CVD) carries a high burden of morbidity and mortality and is associated with significant utilization of health care resources, especially in the elderly. Numerous randomized trials have established the efficacy of cholesterol reduction with statin medications in decreasing mortality in high-risk populations. However, it is not known what the effect of the utilization of these medications in complex older adults has had on mortality and on the utilization of health services, such as physician visits, hospitalizations or cardiovascular procedures.</p> <p>Methods</p> <p>This project linked clinical and hospital data from the Improving Cardiovascular Outcomes in Nova Scotia (ICONS) database with administrative data from the Population Health Research Unit to identify all older adults hospitalized with ischemic heart disease between October 15, 1997 and March 31, 2001. All patients were followed for at least one year or until death. Multiple regression techniques, including Cox proportional hazards models and generalized linear models were employed to compare health services utilization and mortality for statin users and non-statin users.</p> <p>Results</p> <p>Of 4232 older adults discharged alive from the hospital, 1629 (38%) received a statin after discharge. In multivariate models after adjustment for demographic and clinical characteristics, and propensity score, statins were associated with a 26% reduction in all- cause mortality (hazard ratio (HR) 0.74, 95% confidence interval (CI) 0.63-0.88). However, statin use was not associated with subsequent reductions in health service utilization, including re-hospitalizations (HR, 0.98, 95% CI 0.91-1.06), physician visits (relative risk (RR) 0.97, 95% CI 0.92-1.02) or coronary revascularization procedures (HR 1.15, 95% CI 0.97-1.36).</p> <p>Conclusion</p> <p>As the utilization of statins continues to grow, their impact on the health care system will continue to be important. Future studies are needed to continue to ensure that those who would realize significant benefit from the medication receive it.</p