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Modeling temporal fluctuations in avalanching system
(Working paper; Arbeidsnotat, 20080722)
We demonstrate how to model the toppling activity in avalanching systems by stochastic differential
equations (SDEs). The theory is developed as a generalization of the classical mean field
approach to sandpile dynamics by formulating it as a generalization of Itoh’s SDE. This equation
contains a fractional Gaussian noise term representing the branching of an avalanche into small
active clusters, ...
A stochastic theory for temporal fluctuations in selforganized critical systems
(Working paper; Arbeidsnotat, 20080722)
A stochastic theory for the toppling activity in sandpile models is
developed, based on a simple meanfield assumption about the toppling process. The
theory describes the process as an antipersistent Gaussian walk, where the diffusion
coefficient is proportional to the activity. It is formulated as a generalization of the Itˆo
stochastic differential equation with an antipersistent fractional ...
Spatiotemporal LongRange Persistence in Earth’s Temperature Field: Analysis of StochasticDiffusive Energy Balance Models
(Journal article; Tidsskriftartikkel; Peer reviewed, 20151101)
A twodimensional stochastic–diffusive energy balance model (EBM) formulated on a sphere by G. R. North
et al. is explored and generalized. Instantaneous and frequencydependent spatial autocorrelation functions and
local temporal power spectral densities are computed for local sites and for spatially averaged surface temperature
signals up to the global scale. On time scales up to the relaxation ...
Late quaternary temperature variability described as abrupt transitions on a 1/f noise background
(Journal article; Tidsskriftartikkel, 20151109)
We show that in order to have a scaling description of the climate system that is not
inherently nonstationary, the rapid shifts between stadial and interstadial conditions
during the last glaciation cannot be included in the scaling law. The same is true for the
5 shifts between the glacial and interglacial states in the quaternary climate. When these
events are omitted from a scaling analysis ...
Global warming projections derived from an observationbased minimal model
(Journal article; Tidsskriftartikkel, 20150918)
A simple conceptual model for the global mean surface temperature (GMST) response
to CO2 emissions is presented and analysed. It consists of linear longmemory models
for the GMST anomaly response ∆T to radiative forcing and atmospheric CO2

5 concentration response ∆C to emission rate. The responses are connected by the
standard logarithmic relation between CO2 concentration and its radiative ...
Attribution in the presence of a longmemory climate response
(Journal article; Tidsskriftartikkel; Peer reviewed, 20151118)
Multiple, linear regression is employed to attribute variability in the global surface temperature to
various forcing components and prominent internal climatic modes. The purpose of the study is to assess how sensitive attribution is to longrange memory (LRM) in the model for the temperature response. The model response to a given forcing component is its fingerprint and is different for a zero ...
Longmemory effects in linear response models of Earth's temperature and implications for future global warming
(Journal article; Tidsskriftartikkel; Peer reviewed, 20140715)
A linearized energybalance model for global temperature is formulated, featuring a scaleinvariant longrange
memory (LRM) response and stochastic forcing representing the influence on the ocean heat reservoir
from atmospheric weather systems. The model is parameterized by an effective response strength, the stochastic
forcing strength, and the memory exponent. The instrumental global surface ...
A stochastic theory for temporal fluctuations in selforganized critical systems
(Journal article; Tidsskriftartikkel; Peer reviewed, 2008)
Burst statistics of fluctuations in a simple magnetized torus configuration
(Working paper; Arbeidsnotat, 20090419)
In a toroidal plasma confined by a purely toroidal magnetic field the plasma transport is governed by electrostatic turbulence driven by the flute interchange instability on the lowfield side of the torus cross section. In this paper we revisit experimental data obtained from the Blaamann torus at the University of Tromso. On timescales shorter than the poloidal rotation time, the time series of ...
Stretchedexponential decay functions from a selfconsistent model of dielectric relaxation
(Working paper; Arbeidsnotat, 20070722)
There are many materials whose dielectric properties are described by a stretched
exponential, the socalled KohlrauschWilliamsWatts (KWW) relaxation function.
Its physical origin and statisticalmechanical foundation have been a matter of debate
in the literature. In this paper we suggest a model of dielectric relaxation,
which naturally leads to a stretched exponential decay function. Some ...