Peter Guttorp - Academia.edu (original) (raw)

Papers by Peter Guttorp

The process of moving from an ensemble of global climate model temperature projections to local s... more The process of moving from an ensemble of global climate model temperature projections to local sea level projections requires several steps. We estimate sea level in Olympia, Washington (a city quite concerned with sea level rise[1] since parts of downtown are barely above highest high tide) by relating global mean temperature to global sea level, global sea level to sea levels at Seattle, Washington, and finally relating Seattle to Olympia. There has long been a realisation that accurate assessment of the precision of projections is needed for science-based policy decisions . When a string of statistical and/or deterministic models is connected, the uncertainty of each individual model needs to be accounted for. Here we quantify uncertainty for each model in our system, and assess the total uncertainty in a cascading effect throughout the system. We then visualise the projected sea level rise over time with its total estimated uncertainty simultaneously for the years 2000-2100, the increased uncertainty due to each of the component models at a particular projection year, and estimates of the time a certain sea level rise will first be reached.

For a statistician, climate is the distribution of weather and other variables that are part of t... more For a statistician, climate is the distribution of weather and other variables that are part of the climate system. This distribution changes over time. This paper considers some aspects of climate data, climate model assessment, and uncertainty estimation pertinent to climate issues, focusing mainly on temperatures.. There are some interesting methodological needs that arise from these issues.

Vermeer and Rahmstorf (2009) proposed an empirical model relating global temperature to global se... more Vermeer and Rahmstorf (2009) proposed an empirical model relating global temperature to global sea level. The fitting of this model did not take proper account of the dependence structure of the data. We show how their model in fact has a superfluous dependence on temperature change. In addition, we demonstrate how the smoothing procedure the authors used can be avoided, develop a fitted model using updated data, and apply the fitted model to calculate confidence intervals for projected sea level rise under different scenarios using the latest modelling experiment for the new IPCC assessment report.

Journal of The American Statistical Association, 1988

Proceedings of The National Academy of Sciences, 1995

We used stochastic modeling and computer simulation to study the replication, apoptosis, and diff... more We used stochastic modeling and computer simulation to study the replication, apoptosis, and differentiation of murine hemopoietic stem cells (HSCs) in vivo. This approach allows description of the behavior of an unobserved population (ie, HSCs) on the basis of the behavior of observed progeny cells (ie, granulocytes and lymphocytes). The results of previous limiting-dilution, competitive-repopulation studies in 44 mice were compared with the results of simulated transplantation studies to identify parameters that led to comparable outcomes. Using this approach, we estimated that murine HSCs replicate (on average) once every 2.5 weeks and that the frequency of murine HSCs is 8 per 10 5 nucleated marrow cells. If it is assumed that short-term repopulating cells are distinct from HSCs, that they contribute to hemopoiesis early after transplantation, and that they are independently regulated, a frequency of 4 HSCs per 10 5 nucleated marrow cells also allows simulations that best approximate the observed data. When stochastic modeling and computer simulation were applied to limiting-dilution, autologous-trans-plantation studies in cats heterozygous for glucose-6-phosphate-dehydrogenase, different estimates of HSC replication rate (1 per 8.3-10 weeks) and frequency (6 per 10 7 cells) were derived. Therefore, it appears that these parameters vary inversely with increased longevity, size, or both. An implication of these data is that human HSCs may be less frequent and replicate more slowly. These findings on cell kinetics have several implications.

Handbook of Statistics, 1994

A variety of statistical methods for meteorological adjustment of ozone have been proposed in the... more A variety of statistical methods for meteorological adjustment of ozone have been proposed in the literature over the last decade or so. These can be broadly classified into regression methods, extreme value methods, and space-time methods. We describe and offer a critical review of the approaches, discuss questions of variable selection and trend estimation, and compare selected methods as applied to ozone time series from the Chicago area. 6/2/99 2 2 6/2/99 3 3 A further context for assessing the relationship between ozone and meteorology, which we do not specifically consider, is the analysis of ozone and meteorology jointly in the determination of potential ozone-related health effects . The statistical issues in the analysis of health effects are different from those considered here because ozone is a predictor rather than an outcome in the modeling and the impact of meteorology would be considered in the context of epidemiological confounding, such as temperature affecting both ozone production and hospital admissions.

Environmental and Ecological Statistics, 1998

We present an approach to estimate hourly grid-cell surface ozone concentrations based on observa... more We present an approach to estimate hourly grid-cell surface ozone concentrations based on observations from point monitoring sites in space, for comparison with grid-based results from the SARMAP photochemical air-quality model for a region of northern California. Statistical estimation is carried out on a transformed (square root) scale, followed by back-transforming to the original scale of ozone in parts per billion, adjusting for bias and variance. We estimate a spatially-varying diurnal mean structure and a non-separable space-time correlation structure on the transformed scale. Temporal pre-whitening is followed by modelling of a spatially non-stationary, diurnally-varying spatial correlation structure using a spatial deformation approach. Comparisons of SARMAP model results with the estimated grid-cell ozone levels are presented.

Journal of The American Statistical Association, 1992

Environmetrics, 1994

We examine hourly ozone data collected in connection with a model evaluation study for ozone tran... more We examine hourly ozone data collected in connection with a model evaluation study for ozone transport in the San Joaquin Valley of California. A space-time analysis of a subset of the data, 17 sites concentrated around the Sacramento area, indicates a relatively simple spatial covariance structure at night-time, while the afternoon readings show a more complex spatial covariance, which is partly explained by observations from a single station with suspicious data. Simple separable space-time covariance models do not appear applicable to these data.

Atmospheric Environment, 2001

Journal of Geophysical Research, 1993

Long term memory has frequently been observed in physical time series. Statistical theory for lon... more Long term memory has frequently been observed in physical time series. Statistical theory for long term memory stochastic processes is radically different from the standard time series analysis, which assumes short term memory. The Allen variance is a particular measure of variability developed for long term memory processes. This variance can be interpreted as a Haar wavelet coefficient variance, suggesting an approach towards assessing the variability of general wavelet classes. The theory is applied to a 'time' series of vertical ocean shear measurements for which some drawbacks with the Haar wavelets are observed.

Journal of Geophysical Research, 2000