Estimating Probability Distributions from Complex Models with Bifurcations: The Case of Ocean Circulation Collapse

Abstract in HTML and technical report in PDF available on the Massachusetts Institute of Technology Joint Program on the Science and Policy of Global Change website (http://mit.edu/globalchange/www/).Studying the uncertainty in computationally expensive models has required the development of specialized methods, including alternative sampling techniques and response surface approaches. However, existing techniques for response surface development break down when the model being studied exhibits discontinuities or bifurcations. One uncertain variable that exhibits this behavior is the thermohaline circulation (THC) as modeled in three-dimensional general circulation models. This is a critical uncertainty for climate change policy studies. We investigate the development of a response surface for studying uncertainty in THC using the Deterministic Equivalent Modeling Method, a stochastic technique using expansions in orthogonal polynomials. We show that this approach is unable to reasonably approximate the model response. We demonstrate an alternative representation that accurately simulates the model’s response, using a basis function with properties similar to the model’s response over the uncertain parameter space. This indicates useful directions for future methodological improvements.This research was supported in part by the Methods and Models for Integrated Assessments Program of the National Science Foundation, Grant ATM-9909139, by the Office of Science (BER), U.S. Department of Energy, Grant Nos. DE-FG02-02ER63468 and DE-FG02-93ER61677, and by the MIT Joint Program on the Science and Policy of Global Change (JPSPGC)

Relative Roles of Climate Sensitivity and Forcing in Defining the Ocean Circulation Response to Climate Change

Abstract in HTML and technical report in PDF available on the Massachusetts Institute of Technology Joint Program on the Science and Policy of Global Change website (http://mit.edu/globalchange/www/).The response of the ocean’s meridional overturning circulation (MOC) to increased greenhouse gas forcing is examined using a coupled model of intermediate complexity, including a dynamic 3D ocean subcomponent. Parameters are the increase in CO2 forcing (with stabilization after a specified time interval) and the model’s climate sensitivity. In this model, the cessation of deep sinking in the north “Atlantic” (hereinafter, a “collapse”), as indicated by changes in the MOC, behaves like a simple bifurcation. The final surface air temperature (SAT) change, which is closely predicted by the product of the radiative forcing and the climate sensitivity, determines whether a collapse occurs. The initial transient response in SAT is largely a function of the forcing increase, with higher sensitivity runs exhibiting delayed behavior; accordingly, high CO2-low sensitivity scenarios can be assessed as a recovering or collapsing circulation shortly after stabilization, whereas low CO2-high sensitivity scenarios require several hundred additional years to make such a determination. We also systemically examine how the rate of forcing, for a given CO2 stabilization, affects the ocean response. In contrast with previous studies based on results using simpler ocean models, we find that except for a narrow range of marginally stable to marginally unstable scenarios, the forcing rate has little impact on whether the run collapses or recovers. In this narrow range, however, forcing increases on a time scale of slow ocean advective processes results in weaker declines in overturning strength and can permit a run to recover that would otherwise collapse.This research was supported in part by the Methods and Models for Integrated Assessments Program of the National Science Foundation, Grant ATM-9909139, by the Office of Science (BER), U.S. Department of Energy, Grant No. DE-FG02-93ER61677, and by the MIT Joint Program on the Science and Policy of Global Change (JPSPGC)

Remotely Supported Prehospital Ultrasound : Real-Time Communication Technology for Remote and Rural Communities

Highlands & Islands Enterprise, UK Technology Strategy Board’s Space and Life Sciences Catapult, University of Aberdeen’s dot.rural Digital Economy HubPeer reviewedPublisher PD

Co-producing artistic approaches to social cohesion

This paper examines the potential of co-produced arts-based methodologies through the lens of a social cohesion project, from the perspectives of five artists. Arts methodologies can be useful in working across different disciplines and across university and community boundaries to create equitable knowledge production processes. The ways in which art is used in community settings as a mode of collaboration are explored, using the reflections from five artists who were involved in the social cohesion project together. This paper argues that coproducing artistic approaches to social cohesion is a complex, multilayered and sometimes fragile process, but that recognizing and discussing understandings of the role of power and voice within co-produced projects enables effective team communication

The Ursinus Weekly, December 8, 1966

Two new soloists to appear in Messiah • Tiffany jewels dazzle Prom-goers • Agency brings Odetta to U.C. campus: Contralto to appear here Saturday • Career center • Seasonal festivities include Xmas banquet • Esso foundation grant • Curtain Club scores with The Crucible • Scholarships • Focus prints • Editorial: The Ursinus meal • Go you Bears! Or, glimpses into the rich and varied past of Grizzlies • Letter to the editor: Chapel examined • Book review: Is Bokonon dead? • The Crucible: A play for all seasons • Recent school blaze injures two Ursinus volunteer firemen • Project Earth turnabout is new Ursinus plan to stop Red missiles • Bears top Delval, Campbell scores 25 • Bear Gridders split last two contests; End season 2-5-1 • Wrestling coach Gibson goes for second winning season • Basketball team looks for improvement on 10-6 1965-66 record • Swimming preview • Joan Moser named All-American: Ursinus fares well at hockey tournaments; Linda Nixon and Kim Brown make U.S. Reserve Team • Basketball preview • Perk pollution becoming critical, asseverates Lehigh investigator • Psi Chi - new frat? • Greek gleaningshttps://digitalcommons.ursinus.edu/weekly/1194/thumbnail.jp

BSM integrated PEP with cross-layer improvements

The future development of broadband satellite systems providing services based on the Internet Protocol (IP) needs to be stimulated by means of common standards. This paper presents the ETSI BSM PEP terminal architecture and PEP usage scenarios. In addition this paper shows the benefits of cross-layer improvements, where the TCP traffic sent by STs through an NCC/Gateway that acts as a PEP-spoofer on ACKs going in the opposite direction

An audit of the use of hydroxychloroquine in rheumatology clinics

Objectives To audit the use, indications, complications and patient information regarding hydroxychloroquine (HCQ) treatment in rheumatology clinics in a tertiary referral centre. Methods During a 9-month period, we identified all patients prescribed HCQ and attending rheumatology clinics in one hospital. We established: (1) the indication for HCQ (2) the prevalence of HCQ overdosing based on absolute body weight (ABW) (3) documentation of warning of risk of retinal toxicity (4) systemic and ocular co-morbidities (5) ocular symptoms during treatment (6) reasons for stopping HCQ. Results We identified 427 patients (104 male, 323 female). The cumulative dose of HCQ was lower in rheumatoid arthritis (RA; median 365 g; range 6-1752 g) compared to systemic lupus erythematosus (SLE; 450 g; 66-1788 g) (p = 0.105). The median duration of HCQ therapy was four years (range 0.1-13); 28% of patients with RA and 29% with SLE continued HCQ beyond five years. After adjusting for ABW and renal function, 10% (31/312) had been prescribed doses exceeding recommendations. Formal documentation of counselling on ocular complications was only found in one third of patients. Three cases of HCQ retinopathy were identified (all of whom had RA). Conclusion HCQ therapy is being used for more than five years in 29% of patients with rheumatic diseases, with higher than recommended doses in approximately 10% of patients. We recommend more rigorous scrutiny of the use of HCQ to reduce the risk of retinopathy