Understanding and modeling the scaling spectrum of climate

2020 ◽  
Author(s):  
Beatrice Ellerhoff ◽  
Kira Rehfeld
Keyword(s):  
Surface Temperature ◽  
Climate Model ◽  
Ice Cores ◽  
Power Laws ◽  
Temperature Spectrum ◽  
Scaling Properties ◽  
Background Continuum ◽  
Temperature Records ◽  
Paleoclimate Records ◽  
Warming World

<p>Modeling climate dynamics in a comprehensive way and improving its predictability in a warming world requires a better understanding of climate variability across scales. However, fundamental mechanisms governing variability on long timescales are still poorly understood. <br>The temporal evolution of climate can be inferred from paleoclimate records, such as ice cores or marine sediments. Power spectra serve to quantify changes of variability over time and to identify timescales associated with periodic or quasi-periodic processes. The spectra of surface temperature not only comprise spectral peaks, but also reveal a continuous part. It was shown that the background continuum exhibits a scale break, following different power-laws on monthly to decadal versus millennial to longer periods. It is yet mostly unexplained, how these power-laws arise and whether a coupling between different timescales can be deduced from it. We study these questions by comparing and applying spectral analyses to paleoclimate records and climate model simulations for the Quaternary. The data is used to reconstruct the temperature spectrum on diurnal to astronomical timescales. We extend previous studies by including climate responses, such as δ<sup>18</sup>O and temperature records, and climate forcings, for example, insolation and volcanic forcing. The emergence of scaling in temperature variability is analyzed by successively accessing the background continuum. Higher order spectra test for correlations between forcings and responses. In particular, the bispectrum and bicoherence is computed for statistical processes and evaluated for temperature records in order to study whether the scaling properties are related to energy transfers between different states in time. We elaborate the potential of these methods to reveal dynamical processes governing the continuous spectrum of surface temperature.</p>

The Continuum of Hydroclimate Variability in Western North America during the Last Millennium

2013 ◽  
Vol 26 (16) ◽  
pp. 5863-5878 ◽  
Author(s):  
Toby R. Ault ◽  
Julia E. Cole ◽  
Jonathan T. Overpeck ◽  
Gregory T. Pederson ◽  
Scott St. George ◽  
...  
Keyword(s):  
North America ◽  
Null Hypothesis ◽  
Climate Model ◽  
Power Spectra ◽  
Low Frequency ◽  
Coupled Model ◽  
Power Laws ◽  
Western North America ◽  
The Future ◽  
Paleoclimate Records

Abstract The distribution of climatic variance across the frequency spectrum has substantial importance for anticipating how climate will evolve in the future. Here power spectra and power laws (β) are estimated from instrumental, proxy, and climate model data to characterize the hydroclimate continuum in western North America (WNA). The significance of the estimates of spectral densities and β are tested against the null hypothesis that they reflect solely the effects of local (nonclimate) sources of autocorrelation at the monthly time scale. Although tree-ring-based hydroclimate reconstructions are generally consistent with this null hypothesis, values of β calculated from long moisture-sensitive chronologies (as opposed to reconstructions) and other types of hydroclimate proxies exceed null expectations. Therefore it may be argued that there is more low-frequency variability in hydroclimate than monthly autocorrelation alone can generate. Coupled model results archived as part of phase 5 of the Coupled Model Intercomparison Project (CMIP5) are consistent with the null hypothesis and appear unable to generate variance in hydroclimate commensurate with paleoclimate records. Consequently, at decadal-to-multidecadal time scales there is more variability in instrumental and proxy data than in the models, suggesting that the risk of prolonged droughts under climate change may be underestimated by CMIP5 simulations of the future.

scholarly journals Evidence for spring mountain snowpack retreat from a Landsat-derived snow cover climate data record

2013 ◽  
Vol 7 (3) ◽  
pp. 2089-2117
Author(s):  
C. J. Crawford
Keyword(s):  
Surface Temperature ◽  
Snow Cover ◽  
Snow Water Equivalent ◽  
Climate Model ◽  
Internal Variability ◽  
Snow Accumulation ◽  
Climate Data ◽  
Data Record ◽  
Temperature Records ◽  
Climate Data Record

Abstract. A Landsat snow cover climate data record (CDR) of visible mountain snow-covered area (SCA) across interior northwestern USA during spring was compared with ground-based snow telemetry (SNOTEL) snow-water-equivalent (SWE) measurements and mean surface temperature and total precipitation observations. Landsat spring SCA on 1 June was positively correlated with 15 May and 1 June SWE, negatively correlated with spring temperatures (April–June), and positively correlated with March precipitation. Using linear regression with predicted residual error sum-of-squares (PRESS) cross-validation, spring SCA was reconstructed (1901–2009) for the mountains of central Idaho and southwestern Montana using instrumental spring surface temperature records. The spring SCA reconstruction shows natural internal variability at interannual to decadal timescales including above average SCA in the 1900s, 1910s, 1940s-1970s, and below average SCA in the 1920s, 1930s, and since the mid 1980s. The reconstruction also reveals a~centennial trend towards decreasing spring SCA with estimated losses of −36.2 % since 1901. Based on the inferred thermal relationship between temperature and snow, strong evidence emerges for mountain snowpack retreat triggered by spring warming, a signal that includes both feedback and response mechanisms. Expanding snow cover CDRs to include additional operational satellite retrievals will add temporal SCA estimates during other snow accumulation and melt intervals for improved satellite-instrumental climate model calibration. Merging Landsat snow cover CDRs with instrumental climate records is a formidable method to monitor climate-driven changes in western US snowpack extent over 20th and 21st centuries.

scholarly journals Sea-surface temperature records of Termination 1 in the Gulf of California: Challenges for seasonal and interannual analogues of tropical Pacific climate change

2012 ◽  
Vol 27 (2) ◽  
pp. n/a-n/a ◽  
Author(s):  
Erin L. McClymont ◽  
Raja S. Ganeshram ◽  
Laetitia E. Pichevin ◽  
Helen M. Talbot ◽  
Bart E. van Dongen ◽  
...  
Keyword(s):  
Climate Change ◽  
Surface Temperature ◽  
Sea Surface Temperature ◽  
Gulf Of California ◽  
Tropical Pacific ◽  
Sea Surface ◽  
Temperature Records

Oligocene sea-surface temperature gradients in the Southern Ocean related to Tasmanian Gateway widening: New TEX86 paleothermometry, dinoflagellate cyst data and climate model comparisons

2021 ◽  
Author(s):  
Frida Hoem ◽  
Suning Hou ◽  
Matthew Huber ◽  
Francesca Sangiorgi ◽  
Henk Brinkhuis ◽  
...  
Keyword(s):  
Southern Ocean ◽  
Surface Temperature ◽  
Sea Surface Temperature ◽  
Climate Model ◽  
Temperature Gradients ◽  
Ocean Currents ◽  
Sea Surface ◽  
Dinoflagellate Cyst ◽  
Frontal Systems ◽  
Dsdp Site

<p>The opening of the Tasmanian Gateway during the Eocene and further deepening in the Oligocene is hypothesized to have reorganized ocean currents, preconditioning the Antarctic Circumpolar Current (ACC) to evolve into place. However, fundamental questions still remain on the past Southern Ocean structure. We here present reconstructions of latitudinal temperature gradients and the position of ocean frontal systems in the Australian sector of the Southern Ocean during the Oligocene. We generated new sea surface temperature (SST) and dinoflagellate cyst data from the West Tasman margin, ODP Site 1168. We compare these with other records around the Tasmanian Gateway, and with climate model simulations to analyze the paleoceanographic evolution during the Oligocene. The novel organic biomarker TEX<sub>86</sub>- SSTs from ODP Site 1168, range between 19.6 – 27.9°C (± 5.2°C, using the linear calibration by Kim et al., 2010), supported by temperate and open ocean dinoflagellate cyst assemblages. The data compilation, including existing TEX<sub>86</sub>-based SSTs from ODP Site 1172 in the Southwest Pacific Ocean, DSDP Site 274 offshore Cape Adare, DSDP Site 269 and IODP Site U1356 offshore the Wilkes Land Margin and terrestrial temperature proxy records from the Cape Roberts Project (CRP) on the Ross Sea continental shelf, show synchronous variability in temperature evolution between Antarctic and Australian sectors of the Southern Ocean. The SST gradients are around 10°C latitudinally across the Tasmanian Gateway throughout the early Oligocene, and increasing in the Late Oligocene. This increase can be explained by polar amplification/cooling, tectonic drift, strengthening of atmospheric currents and ocean currents. We suggest that the progressive cooling of Antarctica and the absence of mid-latitude cooling strengthened the westerly winds, which in turn could drive an intensification of the ACC and strengthening of Southern Ocean frontal systems.</p>

North Atlantic jet stream projections in the context of the past 1,250 years

2021 ◽  
Vol 118 (38) ◽  
pp. e2104105118
Author(s):  
Matthew B. Osman ◽  
Sloan Coats ◽  
Sarah B. Das ◽  
Joseph R. McConnell ◽  
Nathan Chellman
Keyword(s):  
21St Century ◽  
North Atlantic ◽  
Climate Model ◽  
Ice Cores ◽  
Natural Variability ◽  
Jet Stream ◽  
Early 21St Century ◽  
The North ◽  
North Atlantic Jet ◽  
Water Isotope

Reconstruction of the North Atlantic jet stream (NAJ) presents a critical, albeit largely unconstrained, paleoclimatic target. Models suggest northward migration and changing variance of the NAJ under 21st-century warming scenarios, but assessing the significance of such projections is hindered by a lack of long-term observations. Here, we incorporate insights from an ensemble of last-millennium water isotope–enabled climate model simulations and a wide array of mean annual water isotope (δ18O) and annually accumulated snowfall records from Greenland ice cores to reconstruct North Atlantic zonal-mean zonal winds back to the 8th century CE. Using this reconstruction we provide preobservational constraints on both annual mean NAJ position and intensity to show that late 20th- and early 21st-century NAJ variations were likely not unique relative to natural variability. Rather, insights from our 1,250 year reconstruction highlight the overwhelming role of natural variability in thus far masking the response of midlatitude atmospheric dynamics to anthropogenic forcing, consistent with recent large-ensemble transient modeling experiments. This masking is not projected to persist under high greenhouse gas emissions scenarios, however, with model projected annual mean NAJ position emerging as distinct from the range of reconstructed natural variability by as early as 2060 CE.

scholarly journals Synchronizing the Greenland ice core and radiocarbon timescales over the Holocene – Bayesian wiggle-matching of cosmogenic radionuclide records

2016 ◽  
Vol 12 (1) ◽  
pp. 15-30 ◽  
Author(s):  
F. Adolphi ◽  
R. Muscheler
Keyword(s):  
Statistical Approach ◽  
Ice Core ◽  
Ice Cores ◽  
The Holocene ◽  
Counting Error ◽  
Climate Reconstructions ◽  
Uncertainty Measurement ◽  
Uncertainty Estimates ◽  
Paleoclimate Records ◽  
Cosmogenic Radionuclide

Abstract. Investigations of past climate dynamics rely on accurate and precise chronologies of the employed climate reconstructions. The radiocarbon dating calibration curve (IntCal13) and the Greenland ice core chronology (GICC05) represent two of the most widely used chronological frameworks in paleoclimatology of the past  ∼  50 000 years. However, comparisons of climate records anchored on these chronologies are hampered by the precision and accuracy of both timescales. Here we use common variations in the production rates of 14C and 10Be recorded in tree-rings and ice cores, respectively, to assess the differences between both timescales during the Holocene. Compared to earlier work, we employ a novel statistical approach which leads to strongly reduced and yet, more robust, uncertainty estimates. Furthermore, we demonstrate that the inferred timescale differences are robust independent of (i) the applied ice core 10Be records, (ii) assumptions of the mode of 10Be deposition, as well as (iii) carbon cycle effects on 14C, and (iv) in agreement with independent estimates of the timescale differences. Our results imply that the GICC05 counting error is likely underestimated during the most recent 2000 years leading to a dating bias that propagates throughout large parts of the Holocene. Nevertheless, our analysis indicates that the GICC05 counting error is generally a robust uncertainty measurement but care has to be taken when treating it as a nearly Gaussian error distribution. The proposed IntCal13-GICC05 transfer function facilitates the comparison of ice core and radiocarbon dated paleoclimate records at high chronological precision.

scholarly journals Atmospheric circulation and hydroclimate impacts of alternative warming scenarios for the Eocene

2017 ◽  
Vol 13 (8) ◽  
pp. 1037-1048 ◽  
Author(s):  
Henrik Carlson ◽  
Rodrigo Caballero
Keyword(s):  
Surface Temperature ◽  
Radiative Forcing ◽  
Climate Models ◽  
Climate Model ◽  
Regional Climate ◽  
Warm Season ◽  
Cloud Albedo ◽  
Cloud Properties ◽  
Atmospheric Co2 Concentrations ◽  
Global Mean

Abstract. Recent work in modelling the warm climates of the early Eocene shows that it is possible to obtain a reasonable global match between model surface temperature and proxy reconstructions, but only by using extremely high atmospheric CO2 concentrations or more modest CO2 levels complemented by a reduction in global cloud albedo. Understanding the mix of radiative forcing that gave rise to Eocene warmth has important implications for constraining Earth's climate sensitivity, but progress in this direction is hampered by the lack of direct proxy constraints on cloud properties. Here, we explore the potential for distinguishing among different radiative forcing scenarios via their impact on regional climate changes. We do this by comparing climate model simulations of two end-member scenarios: one in which the climate is warmed entirely by CO2 (which we refer to as the greenhouse gas (GHG) scenario) and another in which it is warmed entirely by reduced cloud albedo (which we refer to as the low CO2–thin clouds or LCTC scenario) . The two simulations have an almost identical global-mean surface temperature and equator-to-pole temperature difference, but the LCTC scenario has  ∼  11 % greater global-mean precipitation than the GHG scenario. The LCTC scenario also has cooler midlatitude continents and warmer oceans than the GHG scenario and a tropical climate which is significantly more El Niño-like. Extremely high warm-season temperatures in the subtropics are mitigated in the LCTC scenario, while cool-season temperatures are lower at all latitudes. These changes appear large enough to motivate further, more detailed study using other climate models and a more realistic set of modelling assumptions.

A Percolation Equation for Modeling Experimental Results for Continuum Percolation Systems

2001 ◽  
Vol 699 ◽  
Author(s):  
D.S. McLachlan ◽  
C. Chiteme ◽  
W.D. Heiss ◽  
Junjie Wu
Keyword(s):  
Experimental Data ◽  
Ac Conductivity ◽  
Volume Fraction ◽  
Power Laws ◽  
Second Order ◽  
Experimental Results ◽  
Analytical Equation ◽  
Scaling Properties ◽  
First Order ◽  
Dc And Ac Conductivity

AbstractThe standard percolation equations or power laws, for dc and ac conductivity (dielectric constant) are based on scaling ansatz, and predict the behaviour of the first and second order terms, above and below the percolation or critical volume fraction (øc), and in the crossoverregion. Recent experimental results on ac conductivity are presented, which show that these equations, with the exception of real σm above øc and the first order terms in the crossover region, are only valid in the limit σi/σc = 0, where for an ideal dielectric σi=ωε0εr.A single analytical equation, which has the same parameters as the standard percolation equations, and which, for ac conductivity, reduces to the standard percolation power laws in the limit σi(ωε0εr)/σc = 0 for all but one case, is presented. The exception is the expression for real σm below øc, where the standard power law is always incorrect. The equation is then shown to quantitatively fit both first and second order dc and ac experimental data over the entire frequency and composition range. This phenomenological equation is also continuous, has the scaling properties required at a second order metal-insulator and fits scaled first order dc and ac experimental data. Unfortunately, the s and t exponents that are necessary to fit the data to the above analytical equation are usually not the simple dimensionally determined universal ones and depend on a number of factors.

scholarly journals The impact of climate model sea surface temperature biases on tropical cyclone simulations

2018 ◽  
Vol 53 (1-2) ◽  
pp. 173-192 ◽  
Author(s):  
Wei-Ching Hsu ◽  
Christina M. Patricola ◽  
Ping Chang
Keyword(s):  
Tropical Cyclone ◽  
Surface Temperature ◽  
Sea Surface Temperature ◽  
Climate Model ◽  
Sea Surface ◽  
The Impact

scholarly journals Multi-periodic climate dynamics: spectral analysis of long-term instrumental and proxy temperature records

2013 ◽  
Vol 9 (1) ◽  
pp. 447-452 ◽  
Author(s):  
H.-J. Lüdecke ◽  
A. Hempelmann ◽  
C. O. Weiss
Keyword(s):  
Pearson Correlation ◽  
Temperature Drop ◽  
Ice Cores ◽  
Climate Dynamics ◽  
Fluctuation Analysis ◽  
Harmonic Decomposition ◽  
The Mean ◽  
Temperature Records ◽  
Instrumental Records

Abstract. The longest six instrumental temperature records of monthly means reach back maximally to 1757 AD and were recorded in Europe. All six show a V-shape, with temperature drop in the 19th and rise in the 20th century. Proxy temperature time series of Antarctic ice cores show this same characteristic shape, indicating this pattern as a global phenomenon. We used the mean of the six instrumental records for analysis by discrete Fourier transform (DFT), wavelets, and the detrended fluctuation analysis (DFA). For comparison, a stalagmite record was also analyzed by DFT. The harmonic decomposition of the abovementioned mean shows only six significant frequencies above periods over 30 yr. The Pearson correlation between the mean, smoothed by a 15-yr running average (boxcar) and the reconstruction using the six significant frequencies, yields r = 0.961. This good agreement has a > 99.9% confidence level confirmed by Monte Carlo simulations. It shows that the climate dynamics is governed at present by periodic oscillations. We find indications that observed periodicities result from intrinsic dynamics.

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