323,444 research outputs found
Historic ocean acidification of Loch Sween revealed by correlative geochemical imaging and high-resolution boron isotope analysis of Boreolithothamniom cf. soriferum
No full textOcean Acidification (OA) arises from the increase in atmospheric carbon dioxide concentration following the industrial revolution. The ecological and socio-economic consequences of OA were first identified around 10–15 years ago but remain poorly understood. This is particularly true in coastal regions where local processes can have dramatic consequences on pH trends through time, obscuring and compounding the long-term effects from rising atmospheric CO2. Here we explore the possibility of generating long records of coastal ocean pH using the skeletons of widely distributed coralline algae (CA). The skeletons of these slow growing (<1 mm/year) taxa often contain micron-scale heterogeneities, making sampling for high-resolution climate reconstructions using bulk sampling techniques difficult. Here we use laser ablation coupled to inductively coupled plasma mass spectrometers to generate high-resolution 2D images of the element/calcium ratios and boron isotope composition (δ11B) of a sample of Boreolithothamniom cf. soriferum from Loch Sween in Scotland, UK where we have been monitoring temperature since 2004 and pH during 2014. By carefully correlating the geochemical images with a scanning electron microscopy image we can segment them to remove the marginal portions of the skeleton, isolating the central growth axis to generate an age model and growth rate. The δ11B-pH is significantly elevated above the seawater pH in Loch Sween (8.4 to 8.9 vs. 7.9 to 8.1) consistent with other CA that show internal pH elevation. On a seasonal scale, internal pH is negatively correlated with temperature and also exhibits a long-term decline. By removing this temperature effect, internal pH can be correlated to seawater pH during the 2014 monitoring period allowing us to reconstruct a seawater acidification trend from 2004 to 2018 of -0.018 pH units per year, 10x higher than open ocean trends but consistent with contemporaneous monitoring efforts of UK coastal waters. Reconstructed aqueous CO2 suggests that prior to ∼2008 Loch Sween was a sink of CO2 but after this date, particularly during the early summer, it was a substantial CO2 source. Comparison of reconstructed aqueous CO2 with a record of calcification rate of our sample of Boreolithothamniom cf. soriferum suggests this acidification and associated rise in local seawater pCO2 may have freed this sample from carbon limitation leading to a recent increase in calcification
Optimal monetary policy under low trend inflation
No full textIn the monetary policy literature it is commonly assumed that trend inflation is zero, despite overwhelming evidence that zero inflation is neither empirically relevant nor a practical objective for central bank policy. We therefore extend the standard New Keynesian model to allow for positive trend inflation, showing that even low trend inflation has strong effects on optimal monetary policy and the dynamics of inflation, output, and interest rates. Under discretion, the efficient policy deteriorates and there is no guarantee of determinacy. Even with commitment, targeting non-zero trend inflation leads to substantial welfare losses. Our results serve as a warning against indiscriminate use of models assuming zero trend inflation.Optimal monetary policy, trend inflation
A note on expectational stability under non-zero trend inflation
No full textThis study examines the expectational stability of the rational expectations equilibria (REE) under alternative Taylor rules when trend inflation is non-zero. We find that when trend inflation is high, the REE is likely to be expectationally unstable. This result holds true regardless of the nature of the data (such as contemporaneous data, forecast, and lagged data) introduced in the Taylor rule. Our results suggest that a high macroeconomic volatility during the period of high trend inflation can be well explained by introducing the concept of expectational stability.adaptive learning, E-stability, Taylor rule, trend inflation
A note on expectational stability under non-zero trend inflation
No full textThis study examines the expectational stability of the rational expectations equilibria (REE) under alternative Taylor rules when trend inflation is non-zero. We find that when trend inflation is high, the REE is likely to be expectationally unstable. This result holds true regardless of the nature of the data (such as contemporaneous data, forecast, and lagged data) introduced in the Taylor rule. Our results suggest that a high macroeconomic volatility during the period of high trend inflation can be well explained by introducing the concept of expectational stability.Adaptive learning, E-stability, Taylor rule, trend inflation
Testing for a unit root in the presence of a possible break in trend
No full textIn this paper we consider the issue of testing a time series for a unit root in the possible presence of a break in a linear deterministic trend at some unknown point in the series. We propose a break fraction estimator which, in the presence of a break in trend, is consistent for the true break fraction at rate Op(T^-1) when there is either a unit root or near-unit root in the stochastic component of the series. In contrast to other estimators available in the literature, when there is no break in trend, our proposed break fraction estimator converges to zero at rate Op(T^-1/2). Used in conjunction with a quasi difference (QD) detrended unit root test that incorporates a trend break regressor in the deterministic component, we show that these rates of convergence ensure that known break fraction null critical values are applicable asymptotically. Unlike available procedures in the literature this holds even if there is no break in trend (the true break fraction is zero), in which case the trend break regressor is dropped from the deterministic component and standard QD detrended unit root test critical values then apply. We also propose a second testing procedure which makes use of a formal pre-test for a trend break in the series, including a trend break regressor only where the pre-test rejects the null of no break. Both procedures ensure that the correctly sized (near-) efficient unit root test that allows (does not allow) for a break in trend is applied in the limit when a trend break does (does not) occur.Unit root test; quasi difference de-trending; trend break; pre-test; asymptotic power
Behaviour of Dickey-Fuller Unit Root Tests Under Trend Misspecification
No full textWe analyse the case where a unit root test is based on a Dickey-Fuller regression whose only deterministic term is a fixed intercept. Suppose, however, as could well be the case, that the actual data generating process includes a broken linear trend. It is shown theoretically, and verified empirically, that under the I(1) null and I(0) alternative hypotheses the Dickey-Fuller test can display a wide range of different characteristics depending on the nature and location of the break.
Multivariate trend comparisons between autocorrelated climate series with general trend regressors
No full textInference regarding trends in climatic data series, including comparisons across different data sets as well as univariate trend significance tests, is complicated by the presence of serial correlation and step-changes in the mean. We review recent developments in the estimation of heteroskedasticity and autocorrelation robust (HAC) covariance estimators as they have been applied to linear trend inference, with focus on the Vogelsang-Franses (2005) nonparametric approach, which provides a unified framework for trend covariance estimation robust to unknown forms of autocorrelation up to but not including unit roots, making it especially useful for climatic data applications. We extend the Vogelsang-Franses approach to allow general deterministic regressors including the case where a step-change in the mean occurs at a known date. Additional regressors change the critical values of the Vogelsang-Franses statistic. We derive an asymptotic approximation that can be used to simulate critical values. We also outline a simple bootstrap procedure that generates valid critical values and p-values. The motivation for extending the Vogelsang-Franses approach is an application that compares climate model generated and observational global temperature data in the tropical lower- and mid-troposphere from 1958 to 2010. Inclusion of a mean shift regressor to capture the Pacific Climate Shift of 1977 causes apparently significant observed trends to become statistically insignificant, and rejection of the equivalence between model generated and observed data trends occurs for much smaller significance levels (i.e. is more strongly rejected).Autocorrelation; trend estimation; HAC variance matrix; global warming; model comparisons
Trend-resistant design of experiments under budget constraints.
No full textWhen experiments are to be performed in a time sequence, the observed responses are affected by a time trend. The construction of trend-resistant run orders is extensively described in the literature. However, run orders that are optimally balanced for time trends usually involve huge costs and they are often of low practical value in view of economical considerations. This paper presents a design algorithm for the construction of trend-resistant run orders under budget constraints. The algorithm offers the experimenter a general method for solving a wide range of practical design problems.
Trend Estimation
No full textTrend estimation deals with the characterization of the underlying, or long–run, evolution of a time series. Despite being a very pervasive theme in time series analysis since its inception, it still raises a lot of controversies. The difficulties, or better, the challenges, lie in the identification of the sources of the trend dynamics, and in the definition of the time horizon which defines the long run. The prevalent view in the literature considers the trend as a genuinely latent component, i.e. as the component of the evolution of a series that is persistent and cannot be ascribed to observable factors. As a matter of fact, the univariate approaches reviewed here assume that the trend is either a deterministic or random function of time.Time series models; unobserved components.
Partial Indexation, Trend Inflation, and the Hybrid Phillips Curve
No full textThis paper proposes a full description of the Calvo price-setting model based on partial prices indexation and studies the interaction between partial indexation and trend inflation. We show that using a hybrid version of the Phillips curve partly decreases the risks of overestimate due to the omission of trend inflation. We also provide new evidence on the fit of the hybrid Phillips curve for the Euro area and the United States over the period 1970-2002. The GMM-West estimates suggest that (i) a full indexation scheme is not data consistent whereas a partial indexation scheme allows a good fit and (ii) forgetting trend inflation induces overestimating by approximately 3-4 percent of the probability to not change the price, for reasonable values of trend inflation.Phillips curve ; Inflation inertia ; Trend inflation ; Degree of indexation
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