A Significant Component of Unforced Multidecadal Variability in the Recent Acceleration of Global Warming

2011 ◽  
Vol 24 (3) ◽  
pp. 909-926 ◽  
Author(s):  
Timothy DelSole ◽  
Michael K. Tippett ◽  
Jagadish Shukla
Keyword(s):  
Twentieth Century ◽  
Time Scales ◽  
Time Scale ◽  
Atlantic Multidecadal Oscillation ◽  
Warming Trend ◽  
Short Term ◽  
The Past ◽  
Climate Simulations ◽  
Internal Component ◽  
Long Time

Abstract The problem of separating variations due to natural and anthropogenic forcing from those due to unforced internal dynamics during the twentieth century is addressed using state-of-the-art climate simulations and observations. An unforced internal component that varies on multidecadal time scales is identified by a new statistical method that maximizes integral time scale. This component, called the internal multidecadal pattern (IMP), is stochastic and hence does not contribute to trends on long time scales; however, it can contribute significantly to short-term trends. Observational estimates indicate that the trend in the spatially averaged “well observed” sea surface temperature (SST) due to the forced component has an approximately constant value of 0.1 K decade−1, while the IMP can contribute about ±0.08 K decade−1 for a 30-yr trend. The warming and cooling of the IMP matches that of the Atlantic multidecadal oscillation and is of sufficient amplitude to explain the acceleration in warming during 1977–2008 as compared to 1946–77, despite the forced component increasing at the same rate during these two periods. The amplitude and time scale of the IMP are such that its contribution to the trend dominates that of the forced component on time scales shorter than 16 yr, implying that the lack of warming trend during the past 10 yr is not statistically significant. Furthermore, since the IMP varies naturally on multidecadal time scales, it is potentially predictable on decadal time scales, providing a scientific rationale for decadal predictions. While the IMP can contribute significantly to trends for periods of 30 yr or shorter, it cannot account for the 0.8°C warming that has been observed in the twentieth-century spatially averaged SST.

Piecing Together a Past

2015 ◽  
Author(s):  
Richard Bradley
Keyword(s):  
Twentieth Century ◽  
Present Account ◽  
The Past ◽  
Single Period ◽  
Previous Decade ◽  
Long Time ◽  
Single Method ◽  
Century Thought ◽  
With Memory ◽  
As If

Piecing Together the Past was one of the last books by Gordon Childe. It was published in 1955 and drew on a series of lectures he had given over the previous decade. Every chapter asked a question. The most difficult was: ‘What happened in prehistory?’ There might be disagreements over particular answers, but they would be based on a single method of analysis, for it seemed as if there was only one past to study. The authors of the present volume take a different view, for, no matter which monuments they consider, they find evidence of many separate pasts. Some of those histories were invoked at different times, and others were advocated simultaneously but by different groups of people. There was far more diversity than Childe allowed. It may have happened because his account was concerned exclusively with prehistory and with its significance for twentieth-century thought. What took place in between was overlooked, for in 1955 few scholars envisaged a past within the past. Those who did so were more concerned with the development of archaeology as a discipline. Childe’s procedure was like that of field projects which disregard later structures to focus on a single period. Childe was concerned with artefacts as well as monuments, but the present account considers the evidence of buildings and related structures. It is a vital distinction. Small objects might have been discovered by chance or could have circulated for a long time as heirlooms. Monuments, however, were impossible to overlook. They might be ignored as unacceptable beliefs were rejected, they might even be destroyed, but in every case their presence demanded some response. It is conventional to associate monuments with memory, as that invokes the Latin verb monere, to remind. This equation is problematical. It is implausible that a single version of the past would remain unaltered for long and more likely that it was revised as circumstances changed. At the same time, forgetting is an important cultural process (Forty and Küchler 1999) and ideas could lose their force surprisingly quickly.

scholarly journals Stratified Flows over and around Long Dynamically Tall Mountain Ridges

2019 ◽  
Vol 76 (5) ◽  
pp. 1265-1287 ◽  
Author(s):  
Arjun Jagannathan ◽  
Kraig Winters ◽  
Laurence Armi
Keyword(s):  
Time Scales ◽  
Time Scale ◽  
Stratified Flows ◽  
Half Width ◽  
Short Time Scale ◽  
Late Time ◽  
Low Level ◽  
Long Time ◽  
Flow Splitting ◽  
Short Time

Abstract Uniformly stratified flows approaching long and dynamically tall ridges develop two distinct flow components over disparate time scales. The fluid upstream and below a “blocking level” is stagnant in the limit of an infinite ridge and flows around the sides when the ridge extent is finite. The streamwise half-width of the obstacle at the blocking level arises as a natural inner length scale for the flow, while the excursion time over this half-width is an associated short time scale for the streamwise flow evolution. Over a longer time scale, low-level horizontal flow splitting leads to the establishment of an upstream layerwise potential flow beneath the blocking level. We demonstrate through numerical experiments that for sufficiently long ridges, crest control and streamwise asymmetry are seen on both the short and long time scales. On the short time scale, upstream blocking is established quickly and the flow is well described as a purely infinite-ridge overflow. Over the long time scale associated with flow splitting, low-level flow escapes around the sides, but the overflow continues to be hydraulically controlled and streamwise asymmetric in the neighborhood of the crest. We quantify this late-time overflow by estimating its volumetric transport and then briefly demonstrate how this approach can be extended to predict the overflow across nonuniform ridge shapes.

scholarly journals Short-Term and Long-Term Surface Soil Moisture Memory Time Scales Are Spatially Anticorrelated at Global Scales

2019 ◽  
Vol 20 (6) ◽  
pp. 1165-1182 ◽  
Author(s):  
Kaighin A. McColl ◽  
Qing He ◽  
Hui Lu ◽  
Dara Entekhabi
Keyword(s):  
Soil Moisture ◽  
Time Scales ◽  
Time Scale ◽  
Surface Soil ◽  
Satellite Observations ◽  
Surface Soil Moisture ◽  
Short Term ◽  
Term Memory ◽  
Memory Time

Abstract Land–atmosphere feedbacks occurring on daily to weekly time scales can magnify the intensity and duration of extreme weather events, such as droughts, heat waves, and convective storms. For such feedbacks to occur, the coupled land–atmosphere system must exhibit sufficient memory of soil moisture anomalies associated with the extreme event. The soil moisture autocorrelation e-folding time scale has been used previously to estimate soil moisture memory. However, the theoretical basis for this metric (i.e., that the land water budget is reasonably approximated by a red noise process) does not apply at finer spatial and temporal resolutions relevant to modern satellite observations and models. In this study, two memory time scale metrics are introduced that are relevant to modern satellite observations and models: the “long-term memory” τL and the “short-term memory” τS. Short- and long-term surface soil moisture (SSM) memory time scales are spatially anticorrelated at global scales in both a model and satellite observations, suggesting hot spots of land–atmosphere coupling will be located in different regions, depending on the time scale of the feedback. Furthermore, the spatial anticorrelation between τS and τL demonstrates the importance of characterizing these memory time scales separately, rather than mixing them as in previous studies.

The Age of the Earth in the Twentieth Century

1989 ◽  
Vol 8 (2) ◽  
pp. 170-182 ◽  
Author(s):  
Stephen Brush
Keyword(s):  
Nineteenth Century ◽  
Twentieth Century ◽  
Time Scales ◽  
Time Scale ◽  
Molten State ◽  
Expanding Universe ◽  
New Science ◽  
Upper Limit ◽  
The Earth ◽  
Age Determinations

At the end of the nineteenth century, Lord Kelvin's upper limit of only 20 or 30 million years for the age of the Earth was challenged by the American geologist T. C. Chamberlin, who showed that Kelvin's model of an Earth gradually cooling from an initial molten state was not the only possible one. Kelvin's limit was soon afterwards repealed by the new science of radioactivity, which yielded ages of a few billion years. While some geologists resisted this expanded time-scale, Chamberlin was the only one who could provide a comprehensive cosmogonical theory that did not submit to the epistemological superiority of physics and astronomy. In the 1940s, as radiometric age determinations improved in accuracy, they came into conflict with the expanding-universe cosmology — a conflict which the cosmologists eventually avoided by expanding their distance and time scales. In 1953, Patterson announced the result 4.5 billion years, which is still accepted as the best estimate for the age of the Earth. But geologists, liberated from Kelvin's limit, define the epoch of the Earth's formation as being outside the scope of their science, and their textbooks rarely give credit to the person who established the number that once seemed so important to accounts of the Earth's history.

scholarly journals Features of Neuralization Diagnostics Transitor-Ischemic Attacks

2021 ◽  
Vol 8 (7) ◽  
pp. 670
Author(s):  
Tursunova M. O ◽  
Abdullaeva M. B ◽  
Kalanov A. B ◽  
Aktamova M.U
Keyword(s):  
Statistical Data ◽  
Current Knowledge ◽  
Educational Programs ◽  
Transient Ischemic Attacks ◽  
Short Term ◽  
Important Place ◽  
The Past ◽  
The Us ◽  
Long Time ◽  
The Brain

Transient-ischemic attacks (TIA) as precursors of cerebral strokes occupy an important place among all forms of cerebrovascular insufficiency. With regard to the epidemiology of transient ischemic attacks (TIA), most countries do not have accurate data. So, in the US, they carry up to 5 million adult citizens per year, with many TIAs remaining undiagnosed. These episodes of sudden and short-term neurological deficit were considered benign and harmless for a long time. Most general practitioners and patients incorrectly or insufficiently understand the nature and significance of TIA, perhaps this can explain the small interest of doctors and the lack of statistical data on this nosological unit. Transient ischemic attacks (TIA) are defined clinically as rapidly occurring focal and less commonly diffuse (cerebral) dysfunctions of the brain that are caused by local ischemia and disappear within one day (Gafurov: 2006). Over the past two decades, many views on TIA have changed significantly; approaches to the diagnosis and treatment of patients have become much more intense and more aggressive. Current knowledge of TIA is of great importance both for the proper organization of patient care and for educational programs among the population, the importance of which cannot be overestimated.

Variations of interplanetary magnetic field on various long time-scales

2019 ◽  
Vol 492 (2) ◽  
pp. 1914-1918
Author(s):  
Yury A Nagovitsyn ◽  
Aleksandra A Osipova
Keyword(s):  
Magnetic Field ◽  
Solar Activity ◽  
Interplanetary Magnetic Field ◽  
Time Scales ◽  
Sunspot Number ◽  
Time Scale ◽  
Wavelet Transformation ◽  
B Values ◽  
Group Sunspot Number ◽  
Long Time

ABSTRACT The IDV index of geomagnetic activity is used by many researchers as a proxy of the interplanetary magnetic field (IMF) strength B. Using the original multiscale regression (MSR) method based on wavelet transformation, we obtained a long series of B values starting from 1845. Then, based on the new 2.0 versions of the sunspot number and group sunspot number and using MSR method and this series as a reference, we reconstructed IMF strength B starting from 1610. Further extension of the reconstruction is associated with radiocarbon reconstructions of solar activity at a time-scale of up to several millennia. It is shown that in the last 3200 yr the IMF strength has been experiencing a downward trend of −(0.39 ± 0.17) · 10−3 nT· yr−1.

scholarly journals Photometric and H-Alpha Variability in Some Be Stars

1987 ◽  
Vol 92 ◽  
pp. 101-103
Author(s):  
S. Catalano ◽  
G. Umana
Keyword(s):  
Magnetic Fields ◽  
Time Scales ◽  
Time Scale ◽  
Small Amplitude ◽  
Rotation Period ◽  
Light Curves ◽  
Radial Pulsation ◽  
Be Stars ◽  
Relative Movement ◽  
Short Term

Short-term variations, typically with small amplitude (Δm < 0.1 mag.), time-scales of hours or near one day and in many cases correlated with the rotation period have been found to be commonplace among Be stars (see Harmanec and Pavlovski 1983 for review and papers). Radial and non-radial pulsation modes have been proposed to explain this variability. However, the light curves are often double-peaked, at first suggesting the stars may have large organized dipole magnetic fields and spots not unlike those in the Ap or Bp stars (Harmanec 1983). These rotationally modulated variations are not stable, and seem to vary in both amplitude and period in the sense that intervals with well defined light curves alternate with intervals when variations are absent. This phenomenon is very reminiscent of formation and apparent relative movement in longitude of spots (groups) in some RS CVn binaries (Catalano 1983, Rodono 1986), but on a much more rapid time scale.

A Study of Impacts of Coupled Model Initial Shocks and State–Parameter Optimization on Climate Predictions Using a Simple Pycnocline Prediction Model

2011 ◽  
Vol 24 (23) ◽  
pp. 6210-6226 ◽  
Author(s):  
S. Zhang
Keyword(s):  
Time Scales ◽  
Parameter Optimization ◽  
Time Scale ◽  
Model Simulation ◽  
Coupled Model ◽  
State Parameter ◽  
Model Parameters ◽  
Forecast Errors ◽  
Long Time ◽  
The Impact

Abstract A skillful decadal prediction that foretells varying regional climate conditions over seasonal–interannual to multidecadal time scales is of societal significance. However, predictions initialized from the climate-observing system tend to drift away from observed states toward the imperfect model climate because of the model biases arising from imperfect model equations, numeric schemes, and physical parameterizations, as well as the errors in the values of model parameters. Here, a simple coupled model that simulates the fundamental features of the real climate system and a “twin” experiment framework are designed to study the impact of initialization and parameter optimization on decadal predictions. One model simulation is treated as “truth” and sampled to produce “observations” that are assimilated into other simulations to produce observation-estimated states and parameters. The degree to which the model forecasts based on different estimates recover the truth is an assessment of the impact of coupled initial shocks and parameter optimization on climate predictions of interests. The results show that the coupled model initialization through coupled data assimilation in which all coupled model components are coherently adjusted by observations minimizes the initial coupling shocks that reduce the forecast errors on seasonal–interannual time scales. Model parameter optimization with observations effectively mitigates the model bias, thus constraining the model drift in long time-scale predictions. The coupled model state–parameter optimization greatly enhances the model predictability. While valid “atmospheric” forecasts are extended 5 times, the decadal predictability of the “deep ocean” is almost doubled. The coherence of optimized model parameters and states is critical to improve the long time-scale predictions.

scholarly journals Detecting isolated stellar-mass black holes in the absence of microlensing parallax effect

2020 ◽  
Vol 498 (1) ◽  
pp. L25-L30
Author(s):  
Numa Karolinski ◽  
Wei Zhu(祝伟)
Keyword(s):  
Black Holes ◽  
Time Scales ◽  
Time Scale ◽  
Stellar Mass ◽  
Population Synthesis ◽  
Dominant Form ◽  
Gravitational Microlensing ◽  
Long Time

ABSTRACT Gravitational microlensing can detect isolated stellar-mass black holes (BHs), which are believed to be the dominant form of Galactic BHs according to population synthesis models. Previous searches for BH events in microlensing data focused on long time-scale events with significant microlensing parallax detections. Here we show that, although BH events preferentially have long time-scales, the microlensing parallax amplitudes are so small that in most cases the parallax signals cannot be detected statistically significantly. We then identify OGLE-2006-BLG-044 to be a candidate BH event because of its long time-scale and small microlensing parallax. Our findings have implications to future BH searches in microlensing data.

scholarly journals Multidecadal Trends in Instrumental SST and Coral Proxy Sr/Ca Records

2010 ◽  
Vol 23 (5) ◽  
pp. 1017-1033 ◽  
Author(s):  
Robert B. Scott ◽  
Christina L. Holland ◽  
Terrence M. Quinn
Keyword(s):  
Nineteenth Century ◽  
Twentieth Century ◽  
Standard Deviation ◽  
Time Scales ◽  
Pearson Correlation ◽  
Statistical Significance ◽  
Warming Trend ◽  
Poor Quality ◽  
Seasonal Effects ◽  
Factors Affecting

Abstract Historical ship observations of sea surface temperature (SST) from 1850 to present were used to compute linear 40-yr trends for all 5° latitude by 5° longitude grid cells with sufficient data. Trends from throughout the twentieth century were centered about a 7 mK yr−1 warming trend with standard deviation 14 mK yr−1. Although different with high statistical significance from a distribution with zero mean, the warming trends were not unusual in amplitude compared to the available nineteenth-century trends. Trends at the same grid points from the latter half of the nineteenth century were distributed about near-zero mean with standard deviation 17 mK yr−1. The shift in mean is robust to accounting for the biases arising from differing observational methods prior to 1942. The 40-yr trends from the latter half of the twentieth century were centered about 10 ± 4 mK yr−1 and more clearly distinct from earlier trends. Linear 40-yr trends were computed at different locations and times from all publicly available coral skeleton records of the concentration ratio of Sr to Ca. The pre-twentieth-century distribution of 40-yr trends in the Sr/Ca ratio was significantly different from the twentieth-century trends, consistent with the warming found in the instrumental SST. The interpretation of the coral Sr/Ca 40-yr trends cannot yet be reduced to a single factor. Major uncertainties were due to (i) the correlation of modern Sr/Ca records with instrumental SST being dominated by seasonal effects, with correlations on time scales longer than the annual cycle much lower, and (ii) the poor quality instrumental SST on long time scales in remote locations. Based on the NOAA extended reconstructed instrumental SST dataset since 1870 and 499 yr of Sr/Ca data from 13 different coral records, the authors found a Pearson correlation coefficient r = −0.77 for 40-yr low-pass-filtered times series. Interpreting the change in distribution of trends in Sr/Ca will require further study of the factors affecting Sr/Ca on time scales longer than seasonal.

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