| 1. |
- van As, Dirk, et al.
(författare)
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Katabatic winds and piteraq storms : observations from the Greenland ice sheet
- 2014
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Ingår i: Geological Survey of Denmark and Greenland Bulletin. - 1811-4598 .- 1604-8156. ; 31, s. 83-86
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Tidskriftsartikel (refereegranskat)abstract
- In 2007 the Programme for Monitoring the Greenland Ice Sheet (PROMICE) was initiated to observe and gain insight into the mass budget of Greenland ice masses. By means of in situ observations and remote sensing, PROMICE assesses how much mass is gained as snow accumulation on the surface versus how much is lost by iceberg calving and surface ablation (Ahlstrøm et al. 2008). A key element of PROMICE is a network of automatic weather stations (AWSs) designed to quantify components of the surface mass balance, including the energy exchanges contributing to surface ablation (Van As et al. 2013).The use of these AWS observations is not limited to studies of ice-sheet mass balance. PROMICE contributes to CryoNet (www.globalcryospherewatch.org/cryonet), the core network of surface measurement sites of the World Meteorological Organization (WMO) Global Cryosphere Watch. By real-time delivery through WMO, PROMICE observations contribute to improve both operational forecasting and climate analysis in the data-sparse Arctic. The Greenlandic population, highly dependent on accurate forecasting of weather conditions, benefits directly from these real-time observations. For instance, extreme surface wind speeds are a high-risk element in Greenland. The third-highest wind speed observed at the surface of the Earth (93 m/s or 333 km/h), was recorded in a 8–9 March 1972 storm at Thule in North-West Greenland (Stansfield 1972).In this paper, we discuss the extent to which the Greenland ice sheet generates its own near-surface wind field. We use PROMICE data to gain insight into the interaction between air temperature, radiation and gravity-driven katabatic winds. We focus on a particularly powerful spring storm in 2013 that contributed to a fatality on an ice-sheet ski traverse attempt (Linden 2013).
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| 2. |
- Andersen, Steffen, et al.
(författare)
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Discounting behavior : A reconsideration
- 2014
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Ingår i: European Economic Review. - : Elsevier. - 0014-2921 .- 1873-572X. ; 71, s. 15-33
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Tidskriftsartikel (refereegranskat)abstract
- We re-evaluate the theory, experimental design and econometrics behind claims that individuals exhibit non-constant discounting behavior. Theory points to the importance of controlling for the non-linearity of the utility function of individuals, since the discount rate is defined over time-dated utility flows and not flows of money. It also points to a menagerie of functional forms to characterize different types of non-constant discounting behavior. The implied experimental design calls for individuals to undertake several tasks to allow us to identify these models, and to several treatments such as multiple horizons and the effect of allowing for a front end delay on earlier payments. The implied econometrics calls for structural estimation of th`e theoretical models, allowing for joint estimation of utility functions and discounting functions. Using data collected from a representative sample of 413 adult Danes in 2009, we draw surprising conclusions. Assuming an exponential discounting model we estimate discount rates to be 9% on average. We find no evidence to support quasi-hyperbolic discounting or "fixed cost" discounting, and only modest evidence to support other specifications of non-constant discounting. Furthermore, the evidence for non-constant discounting, while statistically significant, is not economically significant in terms of the size of the estimated discount rates. We undertake extensive robustness checks on these findings, including a detailed review of the previous, comparable literature.
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| 3. |
- Andersen, Steffen, et al.
(författare)
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Discounting behaviour and the magnitude effect : Evidence from a field experiment in Denmark
- 2013
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Ingår i: Economica. - : Blackwell Publishing. - 0013-0427 .- 1468-0335. ; 80:320, s. 670-697
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Tidskriftsartikel (refereegranskat)abstract
- We evaluate the claim that individuals exhibit a magnitude effect in their discounting behaviour, where higher discount rates are inferred from choices made with lower principals, all else being equal. If the magnitude effect is quantitatively significant, it is not appropriate to use one discount rate that is independent of the scale of the project for cost-benefit analysis and capital budgeting. Using data from a field experiment in Denmark, we find statistically significant evidence of a magnitude effect that is much smaller than is claimed. This evidence surfaces only if one controls for unobserved individual heterogeneity in the population.
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| 4. |
- Andersen, Steffen, et al.
(författare)
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Dual criteria decisions
- 2014
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Ingår i: Journal of Economic Psychology. - : Elsevier. - 0167-4870 .- 1872-7719. ; 41, s. 101-113
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Tidskriftsartikel (refereegranskat)abstract
- The most popular models of decision making use a single criterion to evaluate projects or lotteries. However, decision makers may actually consider multiple criteria when evaluating projects. We consider a dual criteria model from psychology. This model integrates the familiar tradeoffs between risk and utility that economists traditionally assume, allowance for rank-dependent decision weights, and consideration of income thresholds. We examine the issues involved in full maximum likelihood estimation of the model using observed choice data. We propose a general method for integrating the multiple criteria, using the logic of mixture models, which we believe is attractive from a decision-theoretic and statistical perspective. The model is applied to observed choices from a major natural experiment involving intrinsically dynamic choices over highly skewed outcomes. The evidence points to the clear role that income thresholds play in such decision making, but does not rule out a role for tradeoffs between risk and utility or probability weighting.
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| 5. |
- Andersen, Steffen, et al.
(författare)
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Estimating subjective probabilities
- 2014
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Ingår i: Journal of Risk and Uncertainty. - : Springer. - 0895-5646 .- 1573-0476. ; 48:3, s. 207-229
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Tidskriftsartikel (refereegranskat)abstract
- Subjective probabilities play a central role in many economic decisions and act as an immediate confound of inferences about behavior, unless controlled for. Several procedures to recover subjective probabilities have been proposed, but in order to recover the correct latent probability one must either construct elicitation mechanisms that control for risk aversion, or construct elicitation mechanisms which undertake "calibrating adjustments" to elicited reports. We illustrate how the joint estimation of risk attitudes and subjective probabilities can provide the calibration adjustments that theory calls for. We illustrate this approach using data from a controlled experiment with real monetary consequences to the subjects. This allows the observer to make inferences about the latent subjective probability, under virtually any well-specified model of choice under subjective risk, while still employing relatively simple elicitation mechanisms.
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| 6. |
- Andersen, Steffen, et al.
(författare)
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Inferring beliefs as subjectively imprecise probabilities
- 2012
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Ingår i: Theory and Decision. - : Springer Nature. - 0040-5833 .- 1573-7187. ; 73:1, s. 161-184
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Tidskriftsartikel (refereegranskat)abstract
- We propose a method for estimating subjective beliefs, viewed as a subjective probability distribution. The key insight is to characterize beliefs as a parameter to be estimated from observed choices in a well-defined experimental task and to estimate that parameter as a random coefficient. The experimental task consists of a series of standard lottery choices in which the subject is assumed to use conventional risk attitudes to select one lottery or the other and then a series of betting choices in which the subject is presented with a range of bookies offering odds on the outcome of some event that the subject has a belief over. Knowledge of the risk attitudes of subjects conditions the inferences about subjective beliefs. Maximum simulated likelihood methods are used to estimate a structural model in which subjects employ subjective beliefs to make bets. We present evidence that some subjective probabilities are indeed best characterized as probability distributions with non-zero variance.
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| 7. |
- Andersen, Steffen, et al.
(författare)
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Non-linear mixed logit
- 2012
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Ingår i: Theory and Decision. - : Springer Nature. - 0040-5833 .- 1573-7187. ; 73:1, s. 77-96
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Tidskriftsartikel (refereegranskat)abstract
- We develop an extension of the familiar linear mixed logit model to allow for the direct estimation of parametric non-linear functions defined over structural parameters. Classic applications include the estimation of coefficients of utility functions to characterize risk attitudes and discounting functions to characterize impatience. There are several unexpected benefits of this extension, apart from the ability to directly estimate structural parameters of theoretical interest.
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| 8. |
- Andersen, Steffen, et al.
(författare)
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When the Field Is Not Enough : Using Complementary Field and Lab Experiments to Investigate Congestion Pricing Responses
- 2014
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- We use data from a field experiment collecting route choices using GPS recorders and a lab experiment eliciting risk attitude characteristics of drivers. We find that drivers behave in predicted ways in response to variations in average travel times, and in response to manipulations of route pricing. Demand functions are downward sloping in tolls and in travel times. We do not find that drivers respond to variations in the unreliability of travel times, but this is not due to their risk attitudes. Almost all drivers are risk averse, and express a revealed preference in favor of the relatively safe route that is increasing in risk aversion. Because the alternate routes are located at some distance apart, we suspect that the lack of response to travel time unreliability is to be found in biases in drivers expectations of unreliability.
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| 9. |
- Gjelstrup, Louise Carstensen, et al.
(författare)
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The role of higher-order protein structure in supporting binding by heteroclitic monoclonal antibodies: The monoclonal antibody KIM185 to CD18 also binds C4-binding protein
- 2011
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Ingår i: Molecular Immunology. - : Elsevier BV. - 1872-9142 .- 0161-5890. ; 49:1-2, s. 38-47
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Tidskriftsartikel (refereegranskat)abstract
- Heteroclitic monoclonal antibodies are characterized by the ability to bind multiple epitopes with little or no similarity. Such antibodies have been reported earlier, but insight into to the molecular basis of this propensity is limited. Here we report that the KIM185 antibody to human CD18 reacts with the plasma protein C4b-binding protein (C4BP). This was revealed during affinity purification procedures where human serum was incubated with surfaces coated with monoclonal antibodies to CD18. Other monoclonal antibodies to CD18 (KIM127 and TS1/18) showed no such interaction with C4BP. We constructed a sandwich-type time-resolved immunofluorometric assay using KIM185 both as capture and developing antibody. By use of proteolytic fragments of KIM185 and recombinant deletion mutants of C4BP the interaction sites were mapped to the variable region of KIM185 and the oligomerization domain of C4BP, respectively. C4BP is a large oligomeric plasma protein that binds activated complement factor C4b and other endogenous ligands as well as microorganisms. By use of the recent crystallographic data on the structure of CD11c/CD18 and prediction of the secondary structure of the C4BP oligomerization domain, we show that epitopes bound by KIM185 in these proteins are unlikely to share any major structural similarity. However, both antigens may form oligomers that would enable avid binding by the antibody. Our report points to the astonishing ability of heteroclitic antibodies to accommodate the binding of multiple proteins with no or little structural similarity within the confined space of the variable regions. (C) 2011 Elsevier Ltd. All rights reserved.
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| 10. |
- Kaislahti Tillman, Päivi, et al.
(författare)
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Stable isotopes in Sphagnum fuscum peat as late-Holocene climate proxies in northeastern European Russia
- 2013
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Ingår i: The Holocene. - : SAGE Publications. - 0959-6836 .- 1477-0911. ; 23:10, s. 1381-1390
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Tidskriftsartikel (refereegranskat)abstract
- The environment of the northern taiga to tundra transition is highly sensitive to climate fluctuations. In this study from northeastern European Russia, stable carbon and oxygen isotope ratios (δ13C, δ18O) in α-cellulose of Sphagnum fuscum stems subsampled from hummocks and peat plateau profiles have been used as climate proxies. The entire isotope time series, dated by lead (210Pb), caesium (137Cs) and AMS-radiocarbon (14C) dating, spans the past 2500 years. Plant macrofossil analyses were used as an aid in single species selection, but are also helpful in identifying past surface moisture conditions. The most significant relationships were found between the recent δ13C record and summer (July–August) temperatures (R 2 = 0.58, p < 0.01), and the recent δ18O record and winter (October–May) precipitation anomalies in the tundra region (R 2 = 0.36, p < 0.01). The study demonstrates that stable isotopes preserved in northern peat deposits are useful indicators for summer temperature and winter precipitation at decadal to millennial timescales.
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| 11. |
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