Investigating bias in the application of curve fitting programs to atmospheric time series

The decomposition of an atmospheric time series into its constituent parts is an essential tool for identifying and isolating variations of interest from a data set, and is widely used to obtain information about sources, sinks and trends in climatically important gases. Such procedures involve fitting appropriate mathematical functions to the data. However, it has been demonstrated that the application of such curve fitting procedures can introduce bias, and thus influence the scientific interpretation of the data sets. We investigate the potential for bias associated with the application of three curve fitting programs, known as HPspline, CCGCRV and STL, using multi-year records of CO2, CH4 and O3 data from three atmospheric monitoring field stations. These three curve fitting programs are widely used within the greenhouse gas measurement community to analyse atmospheric time series, but have not previously been compared extensively. The programs were rigorously tested for their ability to accurately represent the salient features of atmospheric time series, their ability to cope with outliers and gaps in the data, and for sensitivity to the values used for the input parameters needed for each program. We find that the programs can produce significantly different curve fits, and these curve fits can be dependent on the input parameters selected. There are notable differences between the results produced by the three programs for many of the decomposed components of the time series, such as the representation of seasonal cycle characteristics and the long-term (multi-year) growth rate. The programs also vary significantly in their response to gaps and outliers in the time series. Overall, we found that none of the three programs were superior, and that each program had its strengths and weaknesses. Thus, we provide a list of recommendations on the appropriate use of these three curve fitting programs for certain types of data sets, and for certain types of analyses and applications. In addition, we recommend that sensitivity tests are performed in any study using curve fitting programs, to ensure that results are not unduly influenced by the input smoothing parameters chosen. Our findings also have implications for previous studies that have relied on a single curve fitting program to interpret atmospheric time series measurements. This is demonstrated by using two other curve fitting programs to replicate work in Piao et al. (2008) on zero-crossing analyses of atmospheric CO2 seasonal cycles to investigate terrestrial biosphere changes. We highlight the importance of using more than one program, to ensure results are consistent, reproducible, and free from bias

Trade-offs and synergies in the ecosystem service demand of urban brownfield stakeholders

Brownfield site redevelopment presents an opportunity to create urban green spaces that provide a wide range of ecosystem services. It is important, therefore, to understand which ecosystem services are demanded by stakeholders and whether there are trade-offs or synergies in this demand. We performed a quantitative survey of ecosystem service demand from brownfield sites that included all major stakeholder groups. Results showed that there was a strong trade-off between demand for services related to property development (e.g. ground strength and low flood risk) and all other services, which were linked to vegetated sites. There was a secondary, but weak, trade-off between demand for services of more ‘natural’ vegetated sites (e.g. with a biodiversity protection role) and those linked to aesthetics and recreation. Stakeholders with a strong preference for biodiversity protection formed a distinct group in their ecosystem service demands. While a ‘development’ vs ‘green space’ trade-off may be unavoidable, the general lack of strong trade-offs in demand for other services indicated that the creation of multifunctional greenspaces from former brownfield sites would be desirable to most stakeholders, as long as these are biophysically possible

Geothermal exploration in the Fell Sandstone Formation (Mississippian) beneath the city centre of Newcastle upon Tyne, UK: the Newcastle Science Central Deep Geothermal Borehole

The postulate that geothermal energy might be recoverable from strata laterally equivalent to the Fell Sandstone Formation (Carboniferous: Mississippian) beneath Newcastle upon Tyne has been examined by the drilling and testing of the 1821 m deep Newcastle Science Central Deep Geothermal Borehole. This proved 376.5 m of Fell Sandstone Formation below 1400 m, much of which resembled braided river deposits found at outcrop, although some lower portions were reddened and yielded grains of aeolian affinity. Downhole logging after attainment of thermal equilibrium proved a temperature of 73°C at 1740 m, and allowed estimation of heat flow at about 88 mW m−2. This relatively high value probably reflects deep convective transfer of heat over a distance of >8 km from the North Pennine Batholith, along the Ninety Fathom Fault. The Fell Sandstone traversed by the borehole proved to be of low hydraulic conductivity (c. 7×10−5 m d−1). The water that entered the well was highly saline, with a Na–(Ca)–Cl signature similar to other warm waters encountered in the region. It remains for future directional drilling to establish whether sufficient natural fracture permeability can be encountered, or wells stimulated, to support commercial heat production

Comment on ‘Repurposing Hydrocarbon Wells for Geothermal Use in the UK: The Onshore Fields with the Greatest Potential. Watson et al. (2020)’

Comment: We wish to comment on factual inaccuracies around the purpose of the UK Geoenergy Observatory in Glasgow (GGERFS) in the recent Energies paper by Watson et al [...

Continuous measurements of greenhouse gases and atmospheric oxygen at the Namib Desert atmospheric observatory

A new coastal background site has been established for observations of greenhouse gases (GHGs) in the central Namib Desert at Gobabeb, Namibia. The location of the site was chosen to provide observations for a data-poor region in the global sampling network for GHGs. Semi-automated continuous measurements of carbon dioxide, methane, nitrous oxide, carbon monoxide, atmospheric oxygen, and basic meteorology are made at a height of 21 m a.g.l., 50 km from the coast at the northern border of the Namib Sand Sea. Atmospheric oxygen is measured with a differential fuel cell analyzer (DFCA). Carbon dioxide and methane are measured with an early-model cavity ring-down spectrometer (CRDS); nitrous oxide and carbon monoxide are measured with an off-axis integrated cavity output spectrometer (OA-ICOS). Instrument-specific water corrections are employed for both the CRDS and OA-ICOS instruments in lieu of drying. The performance and measurement uncertainties are discussed in detail. As the station is located in a remote desert environment, there are some particular challenges, namely fine dust, high diurnal temperature variability, and minimal infrastructure. The gas handling system and calibration scheme were tailored to best fit the conditions of the site. The CRDS and DFCA provide data of acceptable quality when base requirements for operation are met, specifically adequate temperature control in the laboratory and regular supply of electricity. In the case of the OA-ICOS instrument, performance is significantly improved through the implementation of a drift correction through frequent measurements of a reference cylinder

Statistical mechanics of triangulated ribbons

We use computer simulations and scaling arguments to investigate statistical and structural properties of a semiflexible ribbon composed of isosceles triangles. We study two different models, one where the bending energy is calculated from the angles between the normal vectors of adjacent triangles, the second where the edges are viewed as semiflexible polymers so that the bending energy is related to the angles between the tangent vectors of next-nearest neighbor triangles. The first model can be solved exactly whereas the second is more involved. It was recently introduced by Liverpool and Golestanian Phys.Rev.Lett. 80, 405 (1998), Phys.Rev.E 62, 5488 (2000) as a model for double-stranded biopolymers such as DNA. Comparing observables such as the autocorrelation functions of the tangent vectors and the bond-director field, the probability distribution functions of the end-to-end distance, and the mean squared twist we confirm the existence of local twist correlation, but find no indications for other predicted features such as twist-stretch coupling, kinks, or oscillations in the autocorrelation function of the bond-director field.Comment: 10 pages, 13 figures. submitted to PRE, revised versio

Fertility, Living Arrangements, Care and Mobility

There are four main interconnecting themes around which the contributions in this book are based. This introductory chapter aims to establish the broad context for the chapters that follow by discussing each of the themes. It does so by setting these themes within the overarching demographic challenge of the twenty-first century – demographic ageing. Each chapter is introduced in the context of the specific theme to which it primarily relates and there is a summary of the data sets used by the contributors to illustrate the wide range of cross-sectional and longitudinal data analysed

Atmospheric Methane : Comparison Between Methane's Record in 2006–2022 and During Glacial Terminations

Atmospheric methane's rapid growth from late 2006 is unprecedented in the observational record. Assessment of atmospheric methane data attributes a large fraction of this atmospheric growth to increased natural emissions over the tropics, which appear to be responding to changes in anthropogenic climate forcing. Isotopically lighter measurements of (Figure presented.) are consistent with the recent atmospheric methane growth being mainly driven by an increase in emissions from microbial sources, particularly wetlands. The global methane budget is currently in disequilibrium and new inputs are as yet poorly quantified. Although microbial emissions from agriculture and waste sources have increased between 2006 and 2022 by perhaps 35 Tg/yr, with wide uncertainty, approximately another 35–45 Tg/yr of the recent net growth in methane emissions may have been driven by natural biogenic processes, especially wetland feedbacks to climate change. A model comparison shows that recent changes may be comparable or greater in scale and speed than methane's growth and isotopic shift during past glacial/interglacial termination events. It remains possible that methane's current growth is within the range of Holocene variability, but it is also possible that methane's recent growth and isotopic shift may indicate a large-scale reorganization of the natural climate and biosphere is under way

Saartjie Baartman, Nelisiwe Xaba, and me: the politics of looking at South African bodies

Dance Artist/Choreographer Nelisiwe Xaba’s They Look at Me and That Is All They Think (2006) ‘refers to the story of Sara[tjie] Baartman […] the “Hottentot Venus”’ (2006. 9th Jomba! Contemporary dance experience 2006 programme, p. 7) who was taken from her homeland South Africa, and exhibited in Europe in the nineteenth century. After Baartman died in 1815, her remains were displayed in a museum in Paris until 1982. Xaba parallels the story of Baartman to her own experience of performing in Europe as a black South African woman. This article considers how They Look at Me and That Is All They Think exposes the politics surrounding the act of looking at a particular racial and gendered body in both the historical and contemporary context, and how the concept and articulation of the ‘superior’ European subject was dependent on the classification of Baartman, and other black Africans, as exotic others. In my practice-based research project How I Chased a Rainbow And Bruised My Knee (2007), which was a choreographic response to Xaba’s work, I theatricalize my identity as a white South African woman to make visible whiteness, its associated privilege, and how it is dependent on the representation of a particular type of blackness