Reconstruction of solar activity for the last millennium using 10^{10}Be data

In a recent paper (Usoskin et al., 2002a), we have reconstructed the concentration of the cosmogenic $^{10}$Be isotope in ice cores from the measured sunspot numbers by using physical models for $^{10}$Be production in the Earth's atmosphere, cosmic ray transport in the heliosphere, and evolution of the Sun's open magnetic flux. Here we take the opposite route: starting from the $^{10}$Be concentration measured in ice cores from Antarctica and Greenland, we invert the models in order to reconstruct the 11-year averaged sunspot numbers since 850 AD. The inversion method is validated by comparing the reconstructed sunspot numbers with the directly observed sunspot record since 1610. The reconstructed sunspot record exhibits a prominent period of about 600 years, in agreement with earlier observations based on cosmogenic isotopes. Also, there is evidence for the century scale Gleissberg cycle and a number of shorter quasi-periodicities whose periods seem to fluctuate in the millennium time scale. This invalidates the earlier extrapolation of multi-harmonic representation of sunspot activity over extended time intervals.Comment: Submitted to A&

Climate change: where is the hockey stick? evidence from millennial-scale reconstructed and updated temperature time series.

The goal of this paper is to test on a millennial scale the magnitude of the recent warmth period, known as the “hockey-stick”, and the relevance of the causative anthropogenic climate change hypothesis advanced by several academics and worldwide institutions. A select batch of ten long-term climate proxies, included in the NOAA 92 PCN dataset all of which running well into the nineties, is updated to the year 2011 by means of a Time-Varying Parameter Kalman Filter SISO model for state prediction. This procedure is applied by appropriately selecting as observable one out of the HADSST2 and of the HADCRUT3 series of instrumental temperature anomalies available since the year 1850. The updated proxy series are thereafter individually tested for the values and time location of their four maximum non-neighboring attained temperatures. The results are at best inconclusive, since three of the updated series, including Michael Mann’s celebrated and controversial tree-ring reconstructions, do not refute the hypothesis, while the others quite significantly point to different dates of maximum temperature achievements into the past centuries, in particular those associated to the Medieval Warm Period.Climate Change; Hockey Stick Controversy; Time Series; Kalman Filter

Towards a long-term record of solar total and spectral irradiance

The variation of total solar irradiance (TSI) has been measured since 1978 and that of the spectral irradiance for an even shorter amount of time. Semi-empirical models are now available that reproduce over 80% of the measured irradiance variations. An extension of these models into the more distant past is needed in order to serve as input to climate simulations. Here we review our most recent efforts to model solar total and spectral irradiance on time scales from days to centuries and even longer. Solar spectral irradiance has been reconstructed since 1947. Reconstruction of solar total irradiance goes back to 1610 and suggests a value of about 1-1.5 Wm$^{-2}$ for the increase in the cycle-averaged TSI since the end of the Maunder minimum, which is significantly lower than previously assumed but agrees with other modern models. First steps have also been made towards reconstructions of solar total and spectral irradiance on time scales of millennia

Reply to comment on the paper “ on a role of quadruple component of magnetic field in defining solar activity in grand cycles” by Usoskin (2017)

In this communication we provide our answers to the comments by Usoskin (2017) on our recent paper (Popova et al, 2017a). We show that Principal Component Analysis (PCA) allows us to derive eigen vectors with eigen values assigned to variance of solar magnetic field waves from full disk solar magnetograms obtained in cycles 21–23 which came in pairs. The current paper (Popova et al, 2017a) adds the second pair of magnetic waves generated by quadruple magnetic sources. This allows us to recover a centennial cycle, in addition to the grand cycle, and to produce a closer fit to the solar and terrestrial activity features in the past millennium

Dynamic GMM Estimation With Structural Breaks. An Application to Global Warming and its Causes.

In this paper I propose a nonstandard t-test statistic for detecting level and trend breaks of I(0) series. Theoretical and limit-distribution critical values obtained from Montecarlo experimentation are supplied. The null hypothesis of anthropogenic versus natural causes of global warming is then tested for the period 1850-2006 by means of a dynamic GMM model which incorporates the null of breaks of anthropogenic origin. World average temperatures are found to be tapering off since a few decades by now, and to exhibit no significant breaks attributable to human activities. While these play a minor causative role in climate changes, most natural forcings and in particular solar sunspots are major warmers. Finally, in contrast to widely held opinions, greenhouse gases are in general temperature dimmers.Generalized Method of Moments, Multiple Breaks, Principal Component Analysis, Global Warming

Dynamic Econometric Testing of Climate Change and of its Causes

The goal of this paper is to empirically test for structural breaks of world mean temperatures that may have ignited at some date the phenomenon known as “Climate Change” or “Global Warming”. Estimation by means of the dynamic Generalized Method of Moments is conducted on a large dataset spanning the recordable period from 1850 until present, and different tests and selection procedures among competing model specifications are utilized, such as Principal Component and Principal Factor Analysis, instrument validity, overtime changes in parameters and in shares of both natural and anthropogenic forcings. The results of estimation unmistakably show no involvement of anthropogenic forcings and no occurrence of significant breaks in world mean temperatures. Hence the hypothesis of a climate change in the last 150 years, suggested by the advocates of Global Warming, is rejected. Pacific Decadal Oscillations, sunspots and the major volcanic eruptions play the lion’s share in determining world temperatures, the first being a dimmer and the others substantial warmers.Generalized Method of Moments, Global Warming, Principal Component and Factor Analysis, Structural Breaks.

Climate change: where is the hockey stick? evidence from millennial-scale reconstructed and updated temperature time series.

The goal of this paper is to test on a millennial scale the magnitude of the recent warmth period, known as the “hockey-stick”, and the relevance of the causative anthropogenic climate change hypothesis advanced by several academics and worldwide institutions. A select batch of ten long-term climate proxies, included in the NOAA 92 PCN dataset all of which running well into the nineties, is updated to the year 2011 by means of a Time-Varying Parameter Kalman Filter SISO model for state prediction. This procedure is applied by appropriately selecting as observable one out of the HADSST2 and of the HADCRUT3 series of instrumental temperature anomalies available since the year 1850. The updated proxy series are thereafter individually tested for the values and time location of their four maximum non-neighboring attained temperatures. The results are at best inconclusive, since three of the updated series, including Michael Mann’s celebrated and controversial tree-ring reconstructions, do not refute the hypothesis, while the others quite significantly point to different dates of maximum temperature achievements into the past centuries, in particular those associated to the Medieval Warm Period

Testing the hockey-stick hypothesis by statistical analyses of a large dataset of proxy records.

This paper is a statistical time-series investigation addressed at testing the anthropogenic climate change hypothesis known as the “hockey-stick”. The time-series components of a select batch of 258 long-term yearly Climate Change Proxies (CCP) included in 19 paleoclimate datasets, all of which running back as far as the year 2192 B.C., are reconstructed by means of univariate Bayesian Calibration. The instrumental temperature record utilized is the Global Best Estimated Anomaly (BEA) of the HADCRUT4 time series readings available yearly for the period 1850-2010. After performing appropriate data transformations, Ordinary Least Squares parameter estimates are obtained, and subsequently simulated by means of multi-draw Gibbs sampling for each year of the pre-1850 period. The ensuing Time-Varying Parameter sequence is utilized to produce high-resolution calibrated estimates of the CCP series, merged with BEA to yield Millennial-scale Time Series (MTS). Finally, the MTS are individually tested for temperature single break date and multiple peak dates. As a result, the estimated temperature breaks and peaks suggest widespread rejection of the hockey-stick hypothesis since they are mostly centered in the Medieval Warm Period