• Kayas identitet og valgets kval 

      Rypdal, Kristoffer (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.
    • Klimakrisen og økonomisk politikk 

      Rypdal, Kristoffer (Chronicle; Kronikk, 2015-11-14)
    • Late Quaternary temperature variability described as abrupt transitions on a 1/f noise background 

      Rypdal, Kristoffer; Rypdal, Martin Wibe (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 ...
    • Late quaternary temperature variability described as abrupt transitions on a 1/f noise background 

      Rypdal, Martin Wibe; Rypdal, Kristoffer (Journal article; Tidsskriftartikkel, 2015-11-09)
      We show that in order to have a scaling description of the climate system that is not inherently non-stationary, 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 ...
    • The Life and Death of the Recent Global Warming Hiatus Parsimoniously Explained 

      Rypdal, Kristoffer (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 ...
    • Long-memory effects in linear response models of Earth's temperature and implications for future global warming 

      Rypdal, Martin Wibe; Rypdal, Kristoffer (Journal article; Tidsskriftartikkel; Peer reviewed, 2014-07-15)
      A linearized energy-balance model for global temperature is formulated, featuring a scale-invariant 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 ...
    • Long-range memory in Earth's surface temperature on time scales from months to centuries 

      Rypdal, Kristoffer; Østvand, Lene; Rypdal, Martin wibe (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 ...
    • Long-range memory in internal and forced dynamics of millennium-long climate model simulations 

      Østvand, Lene; Nilsen, Tine; Rypdal, Kristoffer; Divine, Dmitry, V.; Rypdal, Martin wibe (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 ...
    • Low-dimensionality and predictability of solar wind and global magnetosphere during magnetic storms 

      Zivkovic, Tatjana; Rypdal, Kristoffer (Journal article; Tidsskriftartikkel; Peer reviewed, 2011)
      The storm index SYM-H, the solar wind velocity v, and interplanetary magnetic field Bz show no signatures of low-dimensional dynamics in quiet periods, but tests for determinism in the time series indicate that SYM-H exhibits a significant low-dimensional component during storm time, suggesting that self-organization takes place during magnetic storms. Even though our analysis yields no discernible ...
    • Modeling temporal fluctuations in avalanching system 

      Rypdal, Martin; Rypdal, Kristoffer (Working paper; Arbeidsnotat, 2008-07-22)
      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, ...
    • Modelling suggests limited change in the reproduction number from reopening Norwegian kindergartens and schools during the COVID-19 pandemic 

      Rypdal, Martin Wibe; Rypdal, Veronika Gjertsen; Jakobsen, Per Kristen; Ytterstad, Elinor; Løvsletten, Ola; Klingenberg, Claus; Rypdal, Kristoffer (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-02-25)
      <i>Background</i> - To suppress the COVID-19 outbreak, the Norwegian government closed all schools on March 13, 2020. The kindergartens reopened on April 20, and the schools on April 27 and May 11 of 2020. The effect of these measures is largely unknown since the role of children in the spread of the SARS-CoV-2 virus is still unclear. There are only a few studies of school closures as a separate ...
    • Organization of the magnetosphere during substorms 

      Zivkovic, Tatjana; Rypdal, Kristoffer (Journal article; Tidsskriftartikkel; Peer reviewed, 2012)
      The change in degree of organization of the magnetosphere during substorms is investigated by analyzing various geomagnetic indices, as well as interplanetary magnetic field z-component and solar wind velocity x-component. We conclude that the magnetosphere self-organizes globally during substorms, but neither the magnetosphere nor the solar wind become more predictable in the course of a substorm. ...
    • Paris-toppmøtet og spillet om CO2-kvotene 

      Rypdal, Kristoffer (Chronicle; Kronikk, 2015-11-25)
    • A Parsimonious Description and Cross-Country Analysis of COVID-19 Epidemic Curves 

      Rypdal, Kristoffer; Rypdal, Martin (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-09-06)
      In a given country, the cumulative death toll of the first wave of the COVID-19 epidemic follows a sigmoid curve as a function of time. In most cases, the curve is well described by the Gompertz function, which is characterized by two essential parameters, the initial growth rate and the decay rate as the first epidemic wave subsides. These parameters are determined by socioeconomic factors and ...
    • Scale-free vortex cascade emerging from random forcing in a strongly coupled system 

      Rypdal, Kristoffer; Ratynskaia, Svetlana; Kozelov, Boris; Klumov, Boris; Knapek, Christina (Working paper; Arbeidsnotat, 2008-03-04)
      The notions of self-organised criticality (SOC) and turbulence are traditionally considered to be applicable to disjoint classes of phenomena. Nevertheless, scale-free burst statistics is a feature shared by turbulent as well as self-organised critical dynamics. It has also been suggested that another shared feature is universal non-gaussian probability density functions (PDFs) of global fluctuations. ...
    • Scaling of global temperatures explained by linear energy balance models 

      Rypdal, Kristoffer; Fredriksen, Hege-Beate (Journal article; Tidsskriftartikkel; Peer reviewed, 2017-12)
      <i>Introduction</i>: Scale invariance of natural variability of global surface temperatures is often interpreted as a signature of nonlinear dynamics. However, the observed scaling can be adequately explained by linear energy balance involving subsystems with different response times.
    • Spatial scaling of optical fluctuations during substorm-time aurora 

      Kozelov, Boris V; Rypdal, Kristoffer (Journal article; Tidsskriftartikkel; Peer reviewed, 2007)
    • Spatiotemporal Long-Range Persistence in Earth’s Temperature Field: Analysis of Stochastic-Diffusive Energy Balance Models 

      Rypdal, Kristoffer; Rypdal, Martin Wibe; Fredriksen, Hege-Beate (Journal article; Tidsskriftartikkel; Peer reviewed, 2015-11-01)
      A two-dimensional stochastic–diffusive energy balance model (EBM) formulated on a sphere by G. R. North et al. is explored and generalized. Instantaneous and frequency-dependent 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 ...
    • Spectral characteristics of instrumental and climate model surface temperatures 

      Fredriksen, Hege-Beate; Rypdal, Kristoffer (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 ...
    • Spillet om CO2-kvotene - et drama i tre akter 

      Rypdal, Kristoffer (Conference object; Konferansebidrag, 2015-12-28)