Extensive reduction of surface UV radiation since 1750 in world's populated regions

Human activity influences a wide range of components that affect the surface UV radiation levels, among them ozone at high latitudes. We calculate the effect of human-induced changes in the surface erythemally weighted ultra-violet radiation (UV-E) since 1750. We compare results from a radiative transfer model to surface UV-E radiation for year 2000 derived by satellite observations (from Total Ozone Mapping Spectroradiometer) and to ground based measurements at 14 sites. The model correlates well with the observations; the correlation coefficients are 0.97 and 0.98 for satellite and ground based measurements, respectively. In addition to the effect of changes in ozone, we also investigate the effect of changes in SO<sub>2</sub>, NO<sub>2</sub>, the direct and indirect effects of aerosols, albedo changes and aviation-induced contrails and cirrus. The results show an increase of surface UV-E in polar regions, most strongly in the Southern Hemisphere. Furthermore, our study also shows an extensive surface UV-E reduction over most land areas; a reduction up to 20% since 1750 is found in some industrialized regions. This reduction in UV-E over the industrial period is particularly large in highly populated regions

Combined observational and modeling based study of the aerosol indirect effect

International audienceThe indirect effect of aerosols via liquid clouds is investigated by comparing aerosol and cloud characteristics from the Global Climate Model CAM-Oslo to those observed by the MODIS instrument onboard the TERRA and AQUA satellites http://modis.gsfc.nasa.gov). The comparison is carried out for 15 selected regions ranging from remote and clean to densely populated and polluted. For each region, the regression coefficient and correlation coefficient for the following parameters are calculated: Aerosol Optical Depth vs. Liquid Cloud Optical Thickness, Aerosol Optical Depth vs. Liquid Cloud Droplet Effective Radius and Aerosol Optical Depth vs. Cloud Liquid Water Path. Modeled and observed correlation coefficients and regression coefficients are then compared for a 3-year period starting in January 2001. Additionally, global maps for a number of aerosol and cloud parameters crucial for the understanding of the aerosol indirect effect are compared for the same period of time. Significant differences are found between MODIS and CAM-Oslo both in the regional and global comparison. However, both the model and the observations show a positive correlation between Aerosol Optical Depth and Cloud Optical Depth in practically all regions and for all seasons, in agreement with the current understanding of aerosol-cloud interactions. The correlation between Aerosol Optical Depth and Liquid Cloud Droplet Effective Radius is variable both in the model and the observations. However, the model reports the expected negative correlation more often than the MODIS data. Aerosol Optical Depth is overall positively correlated to Cloud Liquid Water Path both in the model and the observations, with a few regional exceptions

Halfway to doubling of CO2 radiative forcing

The “double CO2” experiment has become a standard experiment in climate science, and a convenient way of comparing the sensitivity of different climate models. Double CO2 was first used by Arrhenius in the 19th century and in the classic paper by Manabe and Wetherald, published 50 years ago, which marked the start of the modern era of climate modeling. Doubling CO2 now has an iconic role in climate research. The equilibrium climate sensitivity (ECS) is defined as the global-mean surface temperature change resulting from a doubling of CO2, which is a headline result in Intergovernmental Panel on Climate Change (IPCC) assessments. In its most recent assessment IPCC concluded that the ECS “is likely in the range 1.5 to 4.5oC”. We show that we are now halfway to doubling of CO2 since pre-industrial times in terms of radiative forcing, but not in concentration

Radiative forcing of carbon dioxide, methane, and nitrous oxide: a significant revision of the methane radiative forcing

New calculations of the radiative forcing (RF) are presented for the three main well‐mixed greenhouse gases, methane, nitrous oxide, and carbon dioxide. Methane’s RF is particularly impacted because of the inclusion of the shortwave forcing; the 1750–2011 RF is about 25% higher (increasing from 0.48 W m−2 to 0.61 W m−2) compared to the value in the Intergovernmental Panel on Climate Change (IPCC) 2013 assessment; the 100 year global warming potential is 14% higher than the IPCC value. We present new simplified expressions to calculate RF. Unlike previous expressions used by IPCC, the new ones include the overlap between CO2 and N2O; for N2O forcing, the CO2 overlap can be as important as the CH4 overlap. The 1750–2011 CO2 RF is within 1% of IPCC’s value but is about 10% higher when CO2 amounts reach 2000 ppm, a value projected to be possible under the extended RCP8.5 scenario

Data Quality of Surgery for Carotid Artery Stenosis. Are the National Vascular Registries Reliable?

AbstractObjectivesTo study completeness of reporting carotid endarterectomies, including peri-operative stroke and mortality rate, in a national vascular registry, NorKar, and a national administrative registry, The Norwegian Patient Register (NPR).DesignComparative registry-based national study.MaterialsMember hospitals of NorKar, including 89% of carotid endarterectomies in Norway, were compared with relevant data in NPR for the years 2000–2002.MethodsWe compared procedure-codes, diagnosis-codes, in-hospital death and the occurrence of peri-operative stroke after treatment for carotid artery stenosis in the two registries to evaluate completeness.ResultsCompared with the NPR numbers, 16% of carotid endarterectomies were missing in the reports from member hospitals of NorKar. Further, during this three-year period, there was an under-reporting of seven strokes and two deaths. The discrepancy was most pronounced in 2001.ConclusionsThere is an under-reporting of patients operated on for carotid artery stenosis in NorKar according to NPR numbers as well as an under-reporting of early deaths and strokes. There is a need for better quality data in the NorKar Registry. Registry quality would be likely to improve if patient identifiable data were available in both registries

A new method for normalized interpretation of antimicrobial resistance from disk test results for comparative purposes.

Objective To evaluate a calibration method for disk diffusion antibiotic susceptibility tests, using zone diameter values generated in the individual laboratory as the internal calibrator for combinations of antibiotic and bacterial species. Methods The high-zone side of zone histogram distributions was first analyzed by moving averages to determine the peak position of the susceptible population. The accumulated percentages of isolates for the high zone diameter values were calculated and converted into probit values. The normal distribution of the ideal population of susceptible strains was then determined by using the least-squares method for probit values against zone diameters, and the ideal population was thereby defined, including mean and standard deviation. Zone diameter values were obtained from laboratories at the Karolinska Hospital (KS) and Växjö Hospital (VX), and from two laboratories (LabA, LabB) in Argentina. The method relies on well standardized disk tests, but is independent of differences in MIC limits and zone breakpoints, and does not require the use of reference strains. Resistance was tentatively set at below 3 SD from the calculated, ideal mean zone diameter of the susceptible population. Results The method, called normalized interpretation of antimicrobial resistance, was tested on results from the KS and VX clinical microbiology laboratories, using the disk diffusion method for antimicrobial susceptibility tests, and for two bacterial species, Staphylococcus aureus and Escherichia coli. In total, 114 217 test results were included for the clinical isolates, and 3582 test results for control strains. The methodology at KS and VX followed the standard of the Swedish Reference Group for Antibiotics (SRGA). Zone diameter histograms for control strains were first analyzed to validate the procedure, and a comparison of actual means with the calculated means showed a correlation coefficient of r = 0.998. Results for clinical isolates at the two laboratories showed an excellent agreement for 54 of 57 combinations of antibiotic and bacterial species between normalized interpretations and the interpretations given by the laboratories. There were difficulties with E. coli and mecillinam, and S. aureus and tetracycline and rifampicin. The method was also tested on results from two laboratories using the NCCLS standard, and preliminary results showed very good agreement with quality-controlled laboratory interpretations. Conclusions The normalized resistance interpretation offers a new approach to comparative surveillance studies whereby the inhibition zone diameter results from disk tests in clinical laboratories can be used for calibration of the test

Emerging Asian aerosol patterns

Anthropogenic aerosol emissions over Asia are changing rapidly, both in composition and spatial distribution1. The Shared Socioeconomic Pathways (SSPs), potential narratives of development used by the Intergovernmental Panel for Climate Change in future projections, span a range of influences of aerosols on climate over the next decades. Several of these narratives project the continuation of a trend manifested in observations since 2010, with a clear dipole between South and East Asia. The patterns of radiative forcing that result from these distributions of aerosols will differ from those of the late 20th century. They may instigate large-scale atmospheric responses that could have wide ranging impacts on climate and society well beyond the aerosol source regions. South and East Asia are particularly vulnerable to climate change because of strong seasonal variations in precipitation, high average temperature, and very high population density. Therefore, any aerosol impacts on the strength or seasonal variations in monsoon rainfall, freshwater availability, or climate extremes, will incur large societal costs. We urge the scientific community to make definite progress towards understanding and quantifying the impacts of Asian aerosols and to tackle the potentially large regional and hemispheric implications of these emerging trends

Regional Aerosol Optical Properties and Radiative Impact of the Extreme Smoke Event in the European Arctic in Spring 2006

In spring 2006 a special meteorological situation occurred in the European Arctic region giving record high levels of air pollution. The synoptic situation resulted in extensive transport of pollution predominantly from agricultural fires in Eastern Europe into the Arctic region and record high air-pollution levels were measured at the Zeppelin observatory at Ni-Alesun(78deg 54'N, 11deg 53'E) in the period from 25 April to 12 May. In the present study we investigate the optical properties of the aerosols from this extreme event and we estimate the radiative forcing of this episode. We examine the aerosol optical properties from the source region and into the European Arctic and explore the evolution of the episode and the changes in the optical properties. A number of sites in Eastern Europe, Northern Scandinavia and Svalbard are included in the study. In addition to AOD measurements, we explored lidar measurements from Minsk, ALOMAR (Arctic Lidar Observatory for Middle Atmosphere Research at Andenes) and Ny-Alesund. For the AERONET sites included (Minsk, Toravere, Hornsund) we have further studied the evolution of the aerosol size. Importantly, at Svalbard it is consistency between the AERONET measurements and calculations of single scattering albedo based on aerosol chemical composition. We have found strong agreement between the satellite dally MODIS AOD and the ground-based AOD observations. This agreement is crucial for the radiative forcing calculations. We calculate a strong negative radiative forcing for the most polluted days employing the analysed ground based data, MODIS AOD and a multi-stream model for radiative transfer of solar radiation

Climate Impacts From a Removal of Anthropogenic Aerosol Emissions

Limiting global warming to 1.5 or 2.0°C requires strong mitigation of anthropogenic greenhouse gas (GHG) emissions. Concurrently, emissions of anthropogenic aerosols will decline, due to coemission with GHG, and measures to improve air quality. However, the combined climate effect of GHG and aerosol emissions over the industrial era is poorly constrained. Here we show the climate impacts from removing present-day anthropogenic aerosol emissions and compare them to the impacts from moderate GHG-dominated global warming. Removing aerosols induces a global mean surface heating of 0.5–1.1°C, and precipitation increase of 2.0–4.6%. Extreme weather indices also increase. We find a higher sensitivity of extreme events to aerosol reductions, per degree of surface warming, in particular over the major aerosol emission regions. Under near-term warming, we find that regional climate change will depend strongly on the balance between aerosol and GHG forcing

An investigation into linearity with cumulative emissions of the climate and carbon cycle response in HadCM3LC

We investigate the extent to which global mean temperature, precipitation, and the carbon cycle are constrained by cumulative carbon emissions throughout four experiments with a fully coupled climate-carbon cycle model. The two paired experiments adopt contrasting, idealised approaches to climate change mitigation at different action points this century, with total emissions exceeding two trillion tonnes of carbon in the later pair. Their initially diverging cumulative emissions trajectories cross after several decades, before diverging again. We find that their global mean temperatures are, to first order, linear with cumulative emissions, though regional differences in temperature of up to 1.5K exist when cumulative emissions of each pair coincide. Interestingly, although the oceanic precipitation response scales with cumulative emissions, the global precipitation response does not, due to a decrease in precipitation over land above cumulative emissions of around one trillion tonnes of carbon (TtC). Most carbon fluxes and stores are less well constrained by cumulative emissions as they reach two trillion tonnes. The opposing mitigation approaches have different consequences for the Amazon rainforest, which affects the linearity with which the carbon cycle responds to cumulative emissions. Averaged over the two fixed-emissions experiments, the transient response to cumulative carbon emissions (TCRE) is 1.95 K TtC-1, at the upper end of the IPCC’s range of 0.8-2.5 K TtC-1