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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)
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 ...
Are there multiple scaling regimes in Holocene temperature records?
(Journal article; Tidsskriftartikkel; Peer reviewed, 2016-04-28)
In this article it is discussed how temperature variability on centennial timescales and longer can be described in a simplistic way. By analysing the scaling in late Holocene temperature reconstructions and longer temperature records from Greenland and Antarctic ice cores, we find that the choice of model depends heavily on the data material and timescale one chooses to emphasize. Ignoring data ...
Long-range memory in Earth's surface temperature on time scales from months to centuries
(Journal article; Tidsskriftartikkel; Peer reviewed, 2013)
The paper explores the hypothesis that the temporal global temperature response can be modeled as a long-range memory (LRM) stochastic process characterized by a Hurst exponent 0.5 < H≲1.0 on time scales from months to decades. The LRM is a mathematical representation of the multitude of response times associated with the various subsystems. By analysis of instrumental and reconstructed temperature ...
The Life and Death of the Recent Global Warming Hiatus Parsimoniously Explained
(Journal article; Tidsskriftartikkel; Peer reviewed, 2018-07-21)
The main features of the instrumental global mean surface temperature (GMST) are reasonably well described by a simple linear response model driven by anthropogenic, volcanic and solar forcing. This model acts as a linear long-memory filter of the forcing signal. The physical interpretation of this filtering is the delayed response due to the thermal inertia of the ocean. This description is ...