4,121 research outputs found
Key drivers of ozone change and its radiative forcing over the 21st century
Over the 21st century changes in both tropospheric and stratospheric ozone are likely to have important consequences for the Earthâs radiative balance. In this study, we investigate the radiative forcing from future
ozone changes using the Community Earth System Model (CESM1), with the Whole Atmosphere Community Climate Model (WACCM), and including fully coupled radiation and chemistry schemes. Using year 2100 conditions from the Representative Concentration Pathway 8.5 (RCP8.5) scenario, we quantify the individual contributions to ozone radiative forcing of (1) climate change, (2) reduced concentrations of ozone depleting substances (ODSs), and (3) methane increases. We calculate future ozone radiative forcings and their standard error (SE; associated with inter-annual variability of ozone) relative to year 2000 of (1) 33 Âą 104 m Wmâ² , (2) 163 Âą 109 m Wmâ² , and (3) 238 Âą 113 m Wmâ² due to climate change, ODSs, and methane, respectively. Our best estimate of net ozone forcing in this set of simulations is 430 Âą 130 m Wmâ² relative to year 2000 and 760 Âą 230 m Wmâ² relative to year 1750, with the 95 % confidence interval given by Âą30 %. We find that the overall long-term tropospheric ozone forcing from methane chemistryâclimate feedbacks related to OH and methane lifetime is relatively small (46 m Wmâ²). Ozone radiative forcing associated with climate change and stratospheric ozone recovery are robust with regard to background climate conditions, even though the ozone response is sensitive to both changes in atmospheric composition and climate. Changes in stratospheric-produced ozone account for âź 50 % of the overall radiative forcing for the 2000â2100 period in this set of simulations, highlighting the key role of the stratosphere in determining future ozone radiative forcing
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An Optimisation Model for Designing Social Distancing Enhanced Physical Spaces
YesIn the wake of the COVID-19 pandemic, social distancing has become an essential element of our daily lives. As a result, the development of technological solutions for the design and re-design of physical spaces with the necessary physical distancing measures is an important problem that must be addressed. In this paper, we show how automatic design optimisation can be used to simulate the layout of physical spaces subject to a given social distancing requirement. We use a well known mathematical technique based on the circle packing to address this challenge. Thus, given the dimensions and the necessary constraints on the physical space, we formulate the design as a solution to a constrained nonlinear optimisation problem. We then solve the optimisation problem to arrive at a number of feasible design solutions from which the user can pick the most desirable option. By way of examples, in this paper, we show how the proposed model can be practically applied.University of Bradfordâs COVID-19 Response Fund, the Spanish Ministry of Science, Innovation, and Universities (Computer Science National Program) under grant #TIN2017-89275-R of the Agencia Estatal de Investigacion and European Funds (AEI/FEDER, UE
The Role of Natural Halogens in Global Tropospheric Ozone Chemistry and Budget Under Different 21st Century Climate Scenarios
Funder: NSFFunder: Office of Science of the US Department of EnergyFunder: PICTâ2016â0714 (ANPCyT)Funder: iâCOOPâB20331 (CSICÂ +Â CONICET)Abstract: Tropospheric ozone ( O 3 ) is an important greenhouse gas and a surface pollutant. The future evolution of O 3 abundances and chemical processing are uncertain due to a changing climate, socioeconomic developments, and missing chemistry in global models. Here, we use an Earth System Model with natural halogen chemistry to investigate the changes in the O 3 budget over the 21st century following Representative Concentration Pathway (RCP)6.0 and RCP8.5 climate scenarios. Our results indicate that the global tropospheric O 3 net chemical change (NCC, chemical gross production minus destruction) will decrease âź 50 % , notwithstanding increasing or decreasing trends in ozone production and loss. However, a wide range of surface NCC variations (from â60 % to 150 % ) are projected over polluted regions with stringent abatements in O 3 precursor emissions. Water vapor and iodine are found to be key drivers of future tropospheric O 3 destruction, while the largest changes in O 3 production are determined by the future evolution of peroxy radicals. We show that natural halogens, currently not considered in climate models, significantly impact on the presentâday and future global O 3 burden reducing âź 30â35 Tg (11â15 % ) of tropospheric ozone throughout the 21st century regardless of the RCP scenario considered. This highlights the importance of including natural halogen chemistry in climate model projections of future tropospheric ozone
Very short-lived halogens amplify ozone depletion trends in the tropical lower stratosphere
In contrast to the general stratospheric ozone recovery following international agreements, recent observations show an ongoing net ozone depletion in the tropical lower stratosphere (LS). This depletion is thought to be driven by dynamical transport accelerated by global warming, while chemical processes have been considered to be unimportant. Here we use a chemistryâclimate model to demonstrate that halogenated ozone-depleting very short-lived substances (VSLS) chemistry may account for around a quarter of the observed tropical LS negative ozone trend in 1998â2018. VSLS sources include both natural and anthropogenic emissions. Future projections show the persistence of the currently unaccounted for contribution of VSLS to ozone loss throughout the twenty-first century in the tropical LS, the only region of the global stratosphere not projecting an ozone recovery by 2100. Our results show the need for mitigation strategies of anthropogenic VSLS emissions to preserve the present and future ozone layer in low latitudes
Tropical Stratospheric Circulation and Ozone Coupled to Pacific Multi-Decadal Variability
Observational and modeling evidence suggest a recent acceleration of the stratospheric Brewer-Dobson circulation (BDC), driven by climate change and stratospheric ozone depletion. However, slowly varying natural variability can compromise our ability to detect such forced changes over the relatively short observational record. Using observations and chemistry-climate model simulations, we demonstrate a link between multi-decadal variability in the strength of the BDC and the Interdecadal Pacific Oscillation (IPO), with knock-on impacts for composition in the stratosphere. After accounting for the IPO-like variability in the BDC, the modeled trend is approximately 7%â10% decâ1 over 1979â2010. Furthermore, we find that sea surface temperatures explain up to 50% of the simulated decadal variability in tropical mid-stratospheric ozone. Our findings demonstrate strong links between low-frequency variability in the oceans, troposphere and stratosphere, as well as their potential importance in detecting structural changes in the BDC and future ozone recovery
Natural short-lived halogens exert an indirect cooling effect on climate
Observational evidence shows the ubiquitous presence of ocean-emitted short-lived halogens in the global atmosphere1,2,3. Natural emissions of these chemical compounds have been anthropogenically amplified since pre-industrial times4,5,6, while, in addition, anthropogenic short-lived halocarbons are currently being emitted to the atmosphere7,8. Despite their widespread distribution in the atmosphere, the combined impact of these species on Earthâs radiative balance remains unknown. Here we show that short-lived halogens exert a substantial indirect cooling effect at present (â0.13âÂąâ0.03âwatts per square metre) that arises from halogen-mediated radiative perturbations of ozone (â0.24âÂąâ0.02âwatts per square metre), compensated by those from methane (+0.09âÂąâ0.01âwatts per square metre), aerosols (+0.03âÂąâ0.01âwatts per square metre) and stratospheric water vapour (+0.011âÂąâ0.001âwatts per square metre). Importantly, this substantial cooling effect has increased since 1750 by â0.05âÂąâ0.03âwatts per square metre (61âper cent), driven by the anthropogenic amplification of natural halogen emissions, and is projected to change further (18â31âper cent by 2100) depending on climate warming projections and socioeconomic development. We conclude that the indirect radiative effect due to short-lived halogens should now be incorporated into climate models to provide a more realistic natural baseline of Earthâs climate system
Survey of the Human Pancreatic β-Cell G1/S Proteome Reveals a Potential Therapeutic Role for Cdk-6 and Cyclin D1 in Enhancing Human β-Cell Replication and Function In Vivo
Identification of a Novel Risk Locus for Multiple Sclerosis at 13q31.3 by a Pooled Genome-Wide Scan of 500,000 Single Nucleotide Polymorphisms
Multiple sclerosis is a chronic inflammatory demyelinating disease of the central nervous system with an important genetic component and strongest association driven by the HLA genes. We performed a pooling-based genome-wide association study of 500,000 SNPs in order to find new loci associated with the disease. After applying several criteria, 320 SNPs were selected from the microarrays and individually genotyped in a first and independent Spanish Caucasian replication cohort. The 8 most significant SNPs validated in this cohort were also genotyped in a second US Caucasian replication cohort for confirmation. The most significant association was obtained for SNP rs3129934, which neighbors the HLA-DRB/DQA loci and validates our pooling-based strategy. The second strongest association signal was found for SNP rs1327328, which resides in an unannotated region of chromosome 13 but is in linkage disequilibrium with nearby functional elements that may play important roles in disease susceptibility. This region of chromosome 13 has not been previously identified in MS linkage genome screens and represents a novel risk locus for the disease
Search for the standard model Higgs boson in the H to ZZ to 2l 2nu channel in pp collisions at sqrt(s) = 7 TeV
A search for the standard model Higgs boson in the H to ZZ to 2l 2nu decay
channel, where l = e or mu, in pp collisions at a center-of-mass energy of 7
TeV is presented. The data were collected at the LHC, with the CMS detector,
and correspond to an integrated luminosity of 4.6 inverse femtobarns. No
significant excess is observed above the background expectation, and upper
limits are set on the Higgs boson production cross section. The presence of the
standard model Higgs boson with a mass in the 270-440 GeV range is excluded at
95% confidence level.Comment: Submitted to JHE
Combined search for the quarks of a sequential fourth generation
Results are presented from a search for a fourth generation of quarks
produced singly or in pairs in a data set corresponding to an integrated
luminosity of 5 inverse femtobarns recorded by the CMS experiment at the LHC in
2011. A novel strategy has been developed for a combined search for quarks of
the up and down type in decay channels with at least one isolated muon or
electron. Limits on the mass of the fourth-generation quarks and the relevant
Cabibbo-Kobayashi-Maskawa matrix elements are derived in the context of a
simple extension of the standard model with a sequential fourth generation of
fermions. The existence of mass-degenerate fourth-generation quarks with masses
below 685 GeV is excluded at 95% confidence level for minimal off-diagonal
mixing between the third- and the fourth-generation quarks. With a mass
difference of 25 GeV between the quark masses, the obtained limit on the masses
of the fourth-generation quarks shifts by about +/- 20 GeV. These results
significantly reduce the allowed parameter space for a fourth generation of
fermions.Comment: Replaced with published version. Added journal reference and DO
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