The Maunder minimum (1645–1715) was indeed a grand minimum: A reassessment of multiple datasets
TL;DR: In this article, the authors revisited all existing evidence and datasets, both direct and indirect, to assess the level of solar activity during the Maunder minimum, and concluded that solar activity was indeed at an exceptionally low level during this period.
Abstract: Aims. Although the time of the Maunder minimum (1645–1715) is widely known as a period of extremely low solar activity, it is still being debated whether solar activity during that period might have been moderate or even higher than the current solar cycle #24. We have revisited all existing evidence and datasets, both direct and indirect, to assess the level of solar activity during the Maunder minimum. Methods. We discuss the East Asian naked-eye sunspot observations, the telescopic solar observations, the fraction of sunspot active days, the latitudinal extent of sunspot positions, auroral sightings at high latitudes, cosmogenic radionuclide data as well as solar eclipse observations for that period. We also consider peculiar features of the Sun (very strong hemispheric asymmetry of the sunspot location, unusual differential rotation and the lack of the K-corona) that imply a special mode of solar activity during the Maunder minimum. Results. The level of solar activity during the Maunder minimum is reassessed on the basis of all available datasets. Conclusions. We conclude that solar activity was indeed at an exceptionally low level during the Maunder minimum. Although the exact level is still unclear, it was definitely lower than during the Dalton minimum of around 1800 and significantly below that of the current solar cycle #24. Claims of a moderate-to-high level of solar activity during the Maunder minimum are rejected with a high confidence level.
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TL;DR: The United Nations Framework Convention on Climate Change (UNFCCC) process agreed in Paris to limit global surface temperature rise to “well below 2°C above pre-industrial levels. But what period is preindustrial? Somewhat remarkably, this is not defined within the UNFCCCs many agreements and protocols as mentioned in this paper.
Abstract: The United Nations Framework Convention on Climate Change (UNFCCC) process agreed in Paris to limit global surface temperature rise to “well below 2°C above pre-industrial levels.” But what period is preindustrial? Somewhat remarkably, this is not defined within the UNFCCC’s many agreements and protocols. Nor is it defined in the IPCC’s Fifth Assessment Report (AR5) in the evaluation of when particular temperature levels might be reached because no robust definition of the period exists. Here we discuss the important factors to consider when defining a preindustrial period, based on estimates of historical radiative forcings and the availability of climate observations. There is no perfect period, but we suggest that 1720–1800 is the most suitable choice when discussing global temperature limits. We then estimate the change in global average temperature since preindustrial using a range of approaches based on observations, radiative forcings, global climate model simulations, and proxy evidence. Our assessment is that this preindustrial period was likely 0.55°–0.80°C cooler than 1986–2005 and that 2015 was likely the first year in which global average temperature was more than 1°C above preindustrial levels. We provide some recommendations for how this assessment might be improved in the future and suggest that reframing temperature limits with a modern baseline would be inherently less uncertain and more policy relevant.
223 citations
TL;DR: In this article, the authors reconstructed the sunspot-group count by re-assessment of original sources, and the resulting series is a pure solar index and does not rely on input from other proxies, e.g. radionuclides, auroral sightings, or geomagnetic records.
Abstract: We have reconstructed the sunspot-group count, not by comparisons with other reconstructions and correcting those where they were deemed to be deficient, but by a re-assessment of original sources. The resulting series is a pure solar index and does not rely on input from other proxies, e.g. radionuclides, auroral sightings, or geomagnetic records. “Backboning” the data sets, our chosen method, provides substance and rigidity by using long-time observers as a stiffness character. Solar activity, as defined by the Group Number, appears to reach and sustain for extended intervals of time the same level in each of the last three centuries since 1700 and the past several decades do not seem to have been exceptionally active, contrary to what is often claimed.
195 citations
University of Leeds1, Goethe University Frankfurt2, CERN3, Paul Scherrer Institute4, University of Helsinki5, Harvard University6, Carnegie Mellon University7, Finnish Meteorological Institute8, Helsinki Institute of Physics9, Max Planck Society10, California Institute of Technology11, University of Innsbruck12, Lebedev Physical Institute13, Leibniz Association14, Cooperative Institute for Research in Environmental Sciences15, University of Vienna16
TL;DR: In this article, the authors assess the importance of new particle formation (NPF) for both the present-day and the pre-industrial atmospheres using a global aerosol model with parametrizations of NPF from previously published CLOUD chamber experiments involving sulfuric acid, ammonia, organic molecules and ions.
Abstract: New particle formation has been estimated to produce around half of cloud-forming particles in the present-day atmosphere, via gas-to-particle conversion. Here we assess the importance of new particle formation (NPF) for both the present-day and the preindustrial atmospheres. We use a global aerosol model with parametrizations of NPF from previously published CLOUD chamber experiments involving sulfuric acid, ammonia, organic molecules, and ions. We find that NPF produces around 67% of cloud condensation nuclei at 0.2% supersaturation (CCN0.2%) at the level of low clouds in the preindustrial atmosphere (estimated uncertainty range 45–84%) and 54% in the present day (estimated uncertainty range 38–66%). Concerning causes, we find that the importance of biogenic volatile organic compounds (BVOCs) in NPF and CCN formation is greater than previously thought. Removing BVOCs and hence all secondary organic aerosol from our model reduces low-cloud-level CCN concentrations at 0.2% supersaturation by 26% in the present-day atmosphere and 41% in the preindustrial. Around three quarters of this reduction is due to the tiny fraction of the oxidation products of BVOCs that have sufficiently low volatility to be involved in NPF and early growth. Furthermore, we estimate that 40% of preindustrial CCN0.2% are formed via ion-induced NPF, compared with 27% in the present day, although we caution that the ion-induced fraction of NPF involving BVOCs is poorly measured at present. Our model suggests that the effect of changes in cosmic ray intensity on CCN is small and unlikely to be comparable to the effect of large variations in natural primary aerosol emissions.
186 citations
TL;DR: A review of the development of cloud condensation nuclei can be found in this paper, where the authors provide a brief history, synthesize recent significant progresses, and outlines the challenges and future directions for research relevant to new particle formation.
Abstract: New particle formation (NPF) represents the first step in the complex processes leading to formation of cloud condensation nuclei. Newly formed nanoparticles affect human health, air quality, weather, and climate. This review provides a brief history, synthesizes recent significant progresses, and outlines the challenges and future directions for research relevant to NPF. New developments include the emergence of state‐of‐the‐art instruments that measure prenucleation clusters and newly nucleated nanoparticles down to about 1 nm; systematic laboratory studies of multicomponent nucleation systems, including collaborative experiments conducted in the Cosmics Leaving Outdoor Droplets chamber at CERN; observations of NPF in different types of forests, extremely polluted urban locations, coastal sites, polar regions, and high‐elevation sites; and improved nucleation theories and parameterizations to account for NPF in atmospheric models. The challenges include the lack of understanding of the fundamental chemical mechanisms responsible for aerosol nucleation and growth under diverse environments, the effects of SO2 and NOx on NPF, and the contribution of anthropogenic organic compounds to NPF. It is also critical to develop instruments that can detect chemical composition of particles from 3 to 20 nm and improve parameterizations to represent NPF over a wide range of atmospheric conditions of chemical precursor, temperature, and humidity.
164 citations
TL;DR: In this paper, a revised collection of the number of sunspot groups from 1610 to the present is presented, based on the work of Hoyt and Schatten (Solar Phys. 179, 189, 1998).
Abstract: We describe a revised collection of the number of sunspot groups from 1610 to the present. This new collection is based on the work of Hoyt and Schatten (Solar Phys. 179, 189, 1998). The main changes are the elimination of a considerable number of observations during the Maunder Minimum (hereafter, MM) and the inclusion of several long series of observations. Numerous minor changes are also described. Moreover, we have calculated the active-day percentage during the MM from this new collection as a reliable index of the solar activity. Thus, the level of solar activity obtained in this work is greater than the level obtained using the original Hoyt and Schatten data, although it remains compatible with a grand minimum of solar activity. The new collection is available in digital format.
133 citations
References
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Queen's University Belfast1, Collège de France2, English Heritage3, University of Arizona4, University of Sheffield5, University of Oxford6, University of Minnesota7, University of Hohenheim8, University of Kiel9, Lawrence Livermore National Laboratory10, University of Bergen11, ETH Zurich12, University of Waikato13, Woods Hole Oceanographic Institution14, Swiss Federal Institute for Forest, Snow and Landscape Research15, Cornell University16, University of Bristol17, University of Glasgow18, University of California, Irvine19, University of New South Wales20
TL;DR: In this paper, Heaton, AG Hogg, KA Hughen, KF Kaiser, B Kromer, SW Manning, RW Reimer, DA Richards, JR Southon, S Talamo, CSM Turney, J van der Plicht, CE Weyhenmeyer
Abstract: Additional co-authors: TJ Heaton, AG Hogg, KA Hughen, KF Kaiser, B Kromer, SW Manning, RW Reimer, DA Richards, JR Southon, S Talamo, CSM Turney, J van der Plicht, CE Weyhenmeyer
13,605 citations
Journal Article•
5,701 citations
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TL;DR: In the years around a sunspot maximum there is seldom a day when a number of spots cannot be seen, and often hundreds are present.
Abstract: zero. In contrast, in the years around a sunspot maximum there is seldom a day when a number of spots cannot be seen, and often hundreds are present. Past counts of sunspot number are readily available from the year 1700 (3), [m and workers in solar and terrestrial studies often use the record as though it were of of uniform quality. In fact, it is not. Thus it is advisable, from time to time, to
1,853 citations
"The Maunder minimum (1645–1715) was..." refers background in this paper
...These reports (see details in Riley et al. 2015) suggest that the solar corona was reddish and unstructured, which was interpreted (Eddy 1976) as the F-corona (or zodiacal light) in the absence of the K corona....
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...The more thorough surveys by Lovering (1860), Fritz (1873, 1881) and Link (1964, 1978) have all confirmed this conclusion (see Eddy 1976)....
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...It is a common present-day paradigm that the Maunder minimum (MM), occurring during the interval 1645–1715 (Eddy 1976), was a period of greatly suppressed solar activity called a grand minimum....
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...As shown already by Eddy (1976) and re-analyzed recently by Riley et al. (2015), recorded observations of solar eclipses suggest the virtual absence of the bright structured solar corona during the MM....
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TL;DR: In this article, it was proposed that the semiannual variation in geomagnetic activity is caused by a semiannually variation in the effective southward component of the interplanetary field.
Abstract: It is proposed that the semiannual variation in geomagnetic activity is caused by a semiannual variation in the effective southward component of the interplanetary field. The southward field arises because the interplanetary field is ordered in the solar equatorial coordinate system, whereas the interaction with the magnetosphere is controlled by a magnetospheric system. Several simple models utilizing this effective modulation of the southward component of the interplanetary field are examined. One of these closely predicts the observed phase and amplitude of the semiannual variation. This model assumes that northward interplanetary fields are noninteracting and that the interaction with southward fields is ordered in solar magnetospheric coordinates. The prediction of the diurnal variation of the strength of the interaction at the magnetopause by this model, does not, however, match the diurnal variation of geomagnetic activity as derived from ground-based data.
943 citations
"The Maunder minimum (1645–1715) was..." refers background in this paper
...…open flux in the magnetosphere-ionosphere system (Lockwood 2013) and so are more likely to be caused by the effect of Earth’s dipole tilt on solar wind-magnetosphere coupling and, in particular the magnetic reconnection in the magnetopause that generates the open flux (Russell & McPherron 1973)....
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15 Mar 2000-Philosophical transactions - Royal Society. Mathematical, physical and engineering sciences
TL;DR: In this article, the authors present a new model of the magnetic › eld at the core{mantle boundary for the interval 1590{1990] to 1990, called gufm1, which is based on a massive new compilation of historical observations.
Abstract: We present a new model of the magnetic › eld at the core{mantle boundary for the interval 1590{1990. The model, called gufm1, is based on a massive new compilation of historical observations of the magnetic › eld. The greater part of the new dataset originates from unpublished observations taken by mariners engaged in merchant and naval shipping. Considerable attention is given to both correction of data for possible mislocation (originating from poor knowledge of longitude) and to proper allocation of error in the data. We adopt a stochastic model for uncorrected positional errors that properly accounts for the nature of the noise process based on a Brownian motion model. The variability of navigational errors as a function of the duration of the voyages that we have analysed is consistent with this model. For the period before 1800, more than 83000 individual observations of magnetic declination were recorded at more than 64000 locations; more than 8000 new observations are for the 17th century alone. The time-dependent › eld model that we construct from the dataset is parametrized spatially in terms of spherical harmonics and temporally in B-splines, using a total of 36512 parameters. The model has improved the resolution of the core › eld, and represents the longest continuous model of the › eld available. However, full exploitation of the database may demand a new modelling methodology.
932 citations