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Statistical significance of rising and oscillatory trends in global ocean and land temperature in the past 160 years
(Journal article; Tidsskriftartikkel, 2014-03-20)
Various interpretations of the notion of a trend in the context of global warming are discussed, contrasting the difference between viewing a trend as the deterministic response to an external forcing and viewing it as a slow variation which can be separated from the background spectral continuum of long-range persistent climate noise. The emphasis in this paper is on the latter notion, and a general ...
A stochastic theory for temporal fluctuations in self-organized critical systems
(Journal article; Tidsskriftartikkel; Peer reviewed, 2008)
Evidence of low-dimensional chaos in magnetized plasma turbulence
(Working paper; Arbeidsnotat, 2008-03-10)
We analyze probe data obtained from a toroidal magnetized plasma configuration
suitable for studies of low-frequency gradient-driven instabilities. These instabilities give
rise to field-aligned convection rolls analogous to Rayleigh-Benard cells in neutral fluids,
and may theoretically develop similar routes to chaos. When using mean-field dimension
analysis, we observe low dimensionality, but ...
Kayas identitet og valgets kval
(Chronicle; Kronikk, 2017-08-21)
<i>Ingress</i>: Det Kayas identitet viser oss er for det første at for å redusere utslippene må vi gjøre noe med befolkningsveksten og/eller en eller flere av de tre intensitetene.
Statistical significance of rising and oscillatory trends in global ocean and land temperature in the past 160 years
(Preprint; Manuskript, 2014-10-30)
Various interpretations of the notion of a trend
in the context of global warming are discussed, contrasting
the difference between viewing a trend as the deterministic
response to an external forcing and viewing it as a slow
variation which can be separated from the background spectral
continuum of long-range persistent climate noise. The
emphasis in this paper is on the latter notion, and a ...
Long-range memory in internal and forced dynamics of millennium-long climate model simulations
(Journal article; Tidsskriftartikkel; Peer reviewed, 2014)
Northern Hemisphere (NH) temperature records from a palaeoclimate reconstruction and a number
of millennium-long climate model experiments are investigated for long-range memory (LRM). The models are
two Earth system models and two atmosphere–ocean general circulation models. The periodogram, detrended
fluctuation analysis and wavelet variance analysis are applied to examine scaling properties ...
Late Quaternary temperature variability described as abrupt transitions on a 1/f noise background
(Journal article; Tidsskriftartikkel; Peer reviewed, 2016-03-31)
In order to have a scaling description of the climate system that is not inherently non-stationary, the
rapid shifts between stadials and interstadials during the last glaciation (the Dansgaard-Oeschger events) cannot be included in the scaling law. The same is true for the shifts between the glacial and interglacial states in the Quaternary climate. When these events are omitted from a scaling ...
Global warming projections derived from an observation-based minimal model
(Journal article; Tidsskriftartikkel; Peer reviewed, 2016-01-29)
A simple conceptual model for the global mean surface temperature (GMST) response to CO2 emissions
is presented and analysed. It consists of linear long-memory models for the GMST anomaly response 1T
to radiative forcing and the atmospheric CO2-concentration response 1C to emission rate. The responses are
connected by the standard logarithmic relation between CO2 concentration and its radiative ...
Comment on "Scaling regimes and linear/nonlinear responses of last millennium climate to volcanic and solar forcing" by S. Lovejoy and C. Varotsos (2016)
(Journal article; Tidsskriftartikkel; Peer reviewed, 2016-07-13)
Lovejoy and Varotsos (2016) (L&V) analyse the temperature response to solar, volcanic, and solar
plus volcanic forcing in the Zebiak–Cane (ZC) model, and to solar and solar plus volcanic forcing in the Goddard
Institute for Space Studies (GISS) E2-R model. By using a simple wavelet filtering technique they conclude that
the responses in the ZC model combine subadditively on timescales from 50 to ...
Spectral characteristics of instrumental and climate model surface temperatures
(Journal article; Tidsskriftartikkel; Peer reviewed, 2016-02-05)
The spatiotemporal temperature variability for several gridded instrumental and general circulation climate model data is characterized, contrasting power spectra of local and global temperatures, land and sea temperatures, and temperatures of different regions. There is generally a high degree of agreement between the spectral characteristics of instrumental and climate model data. All but the ...