Terrestrial Physics Research Articles

‘Space Weather Sentinels’: Halley and the evolution of geospace science

The words ‘Antarctic science’ are often synonymous with dramatic, sublime images of penguins and frozen landscapes, but not all Antarctic science looks to the ice or its megafauna. While Antarctica is an important focus of scientific research in its own right, it is also a platform ideally suited to the pursuit of geophysical science—such as solar–terrestrial physics. Investigating the histories of these fields of science contributes not only to our understanding of the history of Antarctic science, but also to the evolution of Antarctic research stations as sites entangled in international networks of people and places beyond Earth's coldest continent. This paper presents the case of Halley VI research station, a British Antarctic Survey station on the Brunt Ice Shelf in East Antarctica, and its co-evolution with geospace science throughout the 1970s and 1980s. Halley's infrastructure and science shaped, and were shaped by, the evolution of geospace science in this period, via Halley's involvement in a series of international geospace collaborations. This co-evolution also affected how the British Antarctic Survey was able to respond to changing UK science policies in later decades. This case demonstrates that Antarctic stations, while physically remote, have historically been entangled in complex networks of people, politics and science that range far beyond Antarctica itself.

Heliophysics Great Observatories and international cooperation in Heliophysics: An orchestrated framework for scientific advancement and discovery

We suggest that the next era of Heliophysics should focus on the Sun–Heliosphere and Geospace as each a system-of-systems, and recommend a coordinated, deliberate, worldwide scientific effort to answer long-standing questions that will remain unanswered without a unified program. Many of the biggest unanswered science questions that remain across Heliophysics center around the interconnectivity of the different physical systems and the role of mesoscale dynamics in modulating, regulating, and controlling that interconnected behavior. Heliophysics has made key progress understanding both the large-scale dynamics and the microphysical processes that occur in these dynamic systems. Such understanding grew out of a systematic approach to study both limits of the system, from global, with the coordinated missions of the International Solar Terrestrial Physics (ISTP) program, to micro, with largely uncoordinated (albeit coincident) missions such as Cluster, Time History of Events and Macroscale Interactions during Substorms (THEMIS), Van Allen Probes, Magnetospheric Multiscale (MMS), Parker Solar Probe, and Solar Orbiter. We suggest that the international Heliophysics community should embark on a grand program to study these system-of-systems holistically, with coordinated, multipoint measurements. We particularly recommend an emphasis on resolving the mesoscale dynamics that links micro to global, and a whole-of-science approach that includes ground-based measurements and advanced numerical modeling. In effect, we propose a mesoscale ISTP type program that would consist of a system of Great Observatories capable of revealing the connections among systems from the solar interior to the top of Earth’s atmosphere. The paradigm and specific approaches outlined in this paper could serve as a strategic imperative and overarching theme that binds our Solar and Space Physics communities together under a common scientific objective. By its very nature, the type of program we argue for would be large, with several coordinated elements, and international in scope. It would include space-borne missions and coordinated ground-based observatories, artificial intelligence/machine learning (AI/ML) methods of analyzing large and complex datasets, and next-generation numerical modeling. The need to coordinate and integrate these different elements is independent of any specific mission implementation. Hence, we suggest the Heliophysics community organize around an ISTP-type program, ISTPNext, with associated Heliophysics “Great Observatories”.

Studying the Impact of the Geospace Environment on Solar Lithosphere Coupling and Earthquake Activity

In solar–terrestrial physics, there is an open question: does a geomagnetic storm affect earthquakes? We expand research in this direction, analyzing the seismic situation after geomagnetic storms (GMs) accompanied by the precipitation of relativistic electrons from the outer radiation belt to form an additional radiation belt (RB) around lower geomagnetic lines. We consider four widely discussed cases in the literature for long-lived (weeks, months) RBs due to GMs and revealed that the 1/GMs 24 March 1991 with a new RB at L~2.6 was followed by an M7.0 earthquake in Alaska, 30 May 1991, near footprint L = 2.69; the 2/GMs 29 October 2003 (Ap = 204) with new RB first in the slot region at L = 2–2.5 cases followed by an M7.8 earthquake on 17 November 2003 at the Aleutian Islands near footprint L = 2.1, and after forming an RB at L~1.5 which lasted for ~26 months, two mega quakes, M9.1 in 2004 and M8.6 in 2005, occurred at the globe; the 3/GMs 3 September 2012 with a new RB at L= 3.0–3.5 was followed by an M7.8 earthquake in Canada near footprint L = 3.2; and the 4/GMs 21 June 2015 with a new RB at L = 1.5–1.8 was followed by an M6.3 earthquake on 7 September 2015 in New Zealand, near footprint L = 1.58. The obtained results suggest that (1) major earthquakes occur near the footprints of geomagnetic lines filled with relativistic electrons precipitating from the outer radiation belt due to geomagnetic storms, and (2) the time delay between geomagnetic storm onset and earthquake occurrence may vary from several weeks to several months. The results may expand the framework for developing mathematical magnetosphere–ionosphere coupling models.

Optical Identification and Spectroscopic Redshift Measurements of 216 Galaxy Clusters from the SRF/eROSITA All-Sky Survey

We present the results of the optical identification and spectroscopic redshift measurements of216 galaxy clusters detected in the SRG/eROSITA all-sky X-ray survey. The spectroscopic observationswere performed in 2020–2023 with the 6-m BTA telescope at the Special Astrophysical Observatory ofthe Russian Academy of Sciences, the 2.5-m telescope at the Caucasus Mountain Observatory of theSternberg Astronomical Institute of the Moscow State University, the 1.6-m AZT-33IK telescope atthe Sayan Solar Observatory of the Institute of Solar–Terrestrial Physics of the Siberian Branch of theRussian Academy of Sciences, and the 1.5-m Russian–Turkish telescope (RTT-150) at the TU¨ BI˙ TAKObservatory. For all of the galaxy clusters presented here the spectroscopic redshift measurements havebeen obtained for the first time. Of these, 139 galaxy clusters have been detected for the first time in theSRG/eROSITA survey and 22 galaxy clusters are at redshifts zspec 0.7, including three at zspec 1.Deep direct images with the rizJK filters have also been obtained for four distant galaxy clusters atzspec 0.7. For these observations we chose the most massive clusters and, therefore, most of the galaxyclusters presented here with the spectroscopic redshifts measured by us will most likely enter in future intothe cosmological samples of galaxy clusters from the SRG/eROSITA survey.

A Catalog of Geoefficient Flare Events of the Current 25th Solar Cycle in a Modern Presentation

To study the phenomena occurring on the Sun and in interplanetary space and their influence on near-Earth space and on processes in the outer and inner shells of the Earth, the results of continuous long-term observations of solar activity become very valuable. A representative collection of such long-term homogeneous series of systematic observations obtained by the worldwide network of solar and astronomical observatories, as well as by spacecraft, has been collected at the World Data Center for Solar–Terrestrial Physics in Moscow. The article describes a cumulative interactive catalog of the main characteristics of significant solar-flare events of the current 25th cycle of solar activity.

The Short Time Prediction of the Dst Index Based on the Long-Short Time Memory and Empirical Mode Decomposition–Long-Short Time Memory Models

The Dst index is the geomagnetic storm index used to measure the energy level of geomagnetic storms, and the prediction of this index is of great significance for geomagnetic storm studies and solar activities. In contrast to traditional numerical modeling techniques, machine learning, which emerged decades ago based on rapidly developing computer hardware and software and artificial intelligence methods, has been unprecedentedly developed in geophysics, especially solar–terrestrial space physics. This study uses two machine learning models, the LSTM (Long-Short Time Memory, LSTM) and EMD-LSTM models (Empirical Mode Decomposition, EMD), to model and predict the Dst index. By building the Dst index data series from 2018 to 2023, two models were built to fit and predict the data. Firstly, we evaluated the influences of the learning rate and the amount of training data on the prediction accuracy of the LSTM model, and finally, 10−3 was thought to be the optimal learning rate. Secondly, the two models were used to predict the Dst index in the solar active and quiet periods, respectively, and the RMSE (Root Mean Square Error) of the LSTM model in the active period was 7.34 nT and the CC (correlation coefficient) was 0.96, and those of the quiet period were 2.64 nT and 0.97. The RMSE and CC of the EMD-LSTM model were 8.87 nT and 0.93 in the active period and 3.29 nT and 0.95 in the quiet period. Finally, the prediction accuracy of the LSTM model in the short time period was slightly better than the EMD-LSTM model. However, there will be a problem of prediction lag, which the EMD-LSTM model can solve and better predict the geomagnetic storm.

Probing nuclear equation of state with the cdm3y version of B3y-fetal effective interaction

This paper is a study of the nuclear Equation of State (EOS) of cold nuclear matter with the B3Y-Fetal effective interaction in its CDM3Y density-dependent version within the framework of Hartree-Fock approximation. The well-known saturation properties of both symmetric and asymmetric nuclear matter are well-reproduced in this work. Using the CDM3Y-K approach, this study has evolved a new set of user interactions, some of which are CDB3Y1-, CDB3Y2-, CDB3Y3-, CDB3Y4-, CDB3Y5-, CDB3Y6-Fetal interactions with corresponding incompressibilities K0 = 188, 204, 217,228, 241 and 252 MeV respectively, in excellent agreement with those of the M3Y-Paris and M3Y-Reid effective interactions. For asymmetric nuclear matter, the new set of interactions has produced the symmetry energy Esym = 32.00 MeV with an associated slope parameter L = 55 MeV at a saturation density ρ = 0.17fm−3 and asymmetry parameter δ = 1.00 (pure neutron matter) in good agreement with the standard values obtained from coupled channel analysis of charge exchange reactions, statistical multifragmentation model and terrestrial Nuclear Physics experimental analyses. Furthermore, the new set of interactions has been found to have bright prospects in a nuclear reaction as the real folded potential computed with the CDB3Y6-Fetal interaction within the framework of double folding potential has been found to be good and similar to that of CDB3Y6-Paris whose optical potential has a repulsive direct component.

First Analysis of In Situ Observation of Surface Alfvén Waves in an ICME Flux Rope

Alfvén waves (AWs) are ubiquitous in space and astrophysical plasma. Their crucial role in various physical processes has triggered intense research in solar–terrestrial physics. Simulation studies have proposed the generation of AWs along the surface of a cylindrical flux rope, referred to as surface AWs (SAWs); however, the observational verification of this distinct wave has been elusive to date. We report the first in situ observation of SAWs in a flux rope of an interplanetary coronal mass ejection. We apply the Walén test to identify them. We have used Elsässer variables to estimate the characteristics of SAWs. They may be excited by the movement of the flux rope’s footpoints or by instabilities along the boundaries of the plasma magnetic cloud. Here, the change in plasma density or field strength in the surface-aligned magnetic field may trigger SAWs.

New Active Galactic Nuclei Detected by the ART-XС and eROSITA Telescopes during the First Five SRG All-Sky X-ray Surveys

We present the results of our identification of 14 X-ray sources detected in the eastern Galactic sky ( $$0^{\circ}<l<180^{\circ}$$ ) in the 4–12 keV energy band on the combined map of the first five all-sky surveys (from December 2019 to March 2022) with the Mikhail Pavlinsky ART-XC telescope onboard the SRG observatory. All 14 sources are reliably detected by the SRG/eROSITA telescope in the 0.2–8 keV energy band. Six of them have been detected in X-rays for the first time, while the remaining ones have already been known previously as X-ray sources, but their nature has remained unknown. We have taken optical spectra for 12 sources with the 1.6-m AZT-33IK telescope at the Sayan Observatory (the Institute of Solar–Terrestrial Physics, the Siberian Branch of the Russian Academy of Sciences). For two more objects we have analyzed the archival spectra taken during the 6dF survey. All objects have turned out to be Seyfert galaxies (one NLSy1, three Sy1, four Sy1.9, and six Sy2) at redshifts $$z=0.015$$ –0.238. Based on data from the eROSITA and ART-XC telescopes onboard the SRG observatory, we have obtained X-ray spectra for all objects in the energy range 0.2–12 keV. In four of them the intrinsic absorption exceeds $$N_{\textrm{H}}>10^{22}$$ cm $${}^{-2}$$ at a 90 $${\%}$$ confidence level, with one of them being probably heavily obscured ( $$N_{\textrm{H}}>5\times 10^{22}$$ cm $${}^{-2}$$ with 90 $${\%}$$ confidence). This paper continues our series of publications on the identification of hard X-ray sources detected during the all-sky survey with the SRG orbital X-ray observatory.

Newcomb–Benford Law as a generic flag for changes in the derivation of long-term solar terrestrial physics timeseries

AbstractThe Newcomb–Benford Law (NBL) prescribes the probability distribution of the first digit of variables which explore a broad range under conditions including aggregation. Long-term space weather relevant observations and indices necessarily incorporate changes in the contributing number and types of observing instrumentation over time and we find that this can be detected solely by comparison with the NBL. It detects when upstream solar wind magnetic field high resolution OMNI interplanetary magnetic field incorporated new data from the WIND and Advanced Composition Explorer spacecraft after 1995. NBL comparison can detect underlying changes in the geomagnetic auroral electrojet index (activity-dependent background subtraction) and the SuperMAG electrojet index (different station types) that select individual stations showing the largest deflection, but not where station data are averaged, as in the SuperMAG ring-current index. As composite indices become more widespread across the geosciences, the NBL may provide a generic, data processing-independent flag indicating changes in the constituent raw data, calibration, or sampling method.

An Overview of Sunspot Observations in 1727–1748

Solar activity generally exhibits cyclic behavior in terms of sunspot group number and sunspot positions every ≈11 yr. These sunspot data have therefore played key roles in numerous analyses of solar–terrestrial physics. However, their reconstructions prior to the 1830s have remained controversial and included significant data gaps, especially from the 1720s to the 1740s. Therefore, this study reviewed contemporary sunspot observations for 1727–1748 to add several forgotten records by Van Coesfelt in 1728–1729, Dûclos in 1736, Martin in 1737, and Cassini and Maraldi in 1748. On the basis of these records, this study revised the sunspot group number and newly derived the sunspot positions in this interval. The results show clearer solar cycles in sunspot group number than those of previous studies and indicate regular solar cycles with limited hemispheric asymmetry over Solar Cycles 0 to −2. The sunspot positions also show sunspot groups mostly at heliographic latitude φ fulfilling ∣φ∣ < 35° in both solar hemispheres, with slight equatorward motions. Furthermore, the solar minima between Solar Cycles −2 and −1 and between Solar Cycles −1 and 0 have been located around 1733.5 ± 0.5 and 1743 ± 0.5, indicating cycle lengths of 11.7 ± 0.5 yr and 10.0 ± 1.0 yr, respectively. Our results provide a chronological missing link between the Maunder Minimum and the regular solar cycles observed since Staudach’s observations from 1749 onward. This lets us better understand the transition of solar activity from the grand minimum to the regular solar cycles.

The Distant Action of the Heavens in Girolamo Borri’s Tidal Theory

Abstract The Aristotelian professor of natural philosophy and courtier at the Medici in Florence, Girolamo Borri, developed a theory based on heat to explain the tidal motions of the sea. In his dialogues on this phenomenon, he deemed that tides follow from the ‘moderate’ simmering of the waters as an effect of lunar light. His tidal theory displaced the theory of the Moon’s distant action on terrestrial waters from its traditionally astrological connotation. Moreover, his theory was not ‘empirical’ but rather inserted in a broad natural philosophical and cosmological framework. Although Galileo Galilei later dismissed heat-based explanations of the tides, such explanations are historically relevant as part of the larger scientific picture, in which controversies over the phenomenon of the tides of the sea fuelled cosmological, even post-Copernican assessments of the connection between terrestrial physics and incipient celestial physics.

On the Nature and Origin of Atmospheric Annual and Semi-Annual Oscillations

This paper proposes a joint analysis of variations of global sea-level pressure (SLP) and of Earth’s rotation (RP), expressed as the coordinates of the rotation pole (m1, m2) and length of day (lod). We retain iterative singular spectrum analysis (iSSA) as the main tool to extract the trend, periods, and quasi periods in the data time series. SLP components are a weak trend, seven quasi-periodic or periodic components (∼130, 90, 50, 22, 15, 4, 1.8 years), an annual cycle, and its first three harmonics. These periods are characteristic of the space-time evolution of the Earth’s rotation axis and are present in many characteristic features of solar and terrestrial physics. The amplitudes of the annual SLP component and its three first harmonics decrease from 93 hPa for the annual to 21 hPa for the third harmonic. In contrast, the components with pseudo-periods longer than a year range between 0.2 and 0.5 hPa. We focus mainly on the annual and, to a lesser extent, the semi-annual components. The annual RP and SLP components have a phase lag of 152 days (half the Euler period). Maps of the first three components of SLP (that together comprise 85% of the data variance) reveal interesting symmetries. The trend is very stable and forms a triskeles structure that can be modeled as Taylor–Couette flow of mode 3. The annual component is characterized by a large negative anomaly extending over Eurasia in the NH summer (and the opposite in the NH winter) and three large positive anomalies over Australia and the southern tips of South America and South Africa in the SH spring (and the opposite in the SH autumn), forming a triskeles. The semi-annual component is characterized by three positive anomalies (an irregular triskeles) in the NH spring and autumn (and the opposite in the NH summer and winter), and in the SH spring and autumn by a strong stable pattern consisting of three large negative anomalies forming a clear triskeles within the 40–60∘ annulus formed by the southern oceans. A large positive anomaly centered over Antarctica, with its maximum displaced toward Australia, and a smaller one centered over Southern Africa, complement the pattern. Analysis of iSSA components of global sea level pressure shows a rather simple spatial distribution with the principal forcing factor being changes in parameters of the Earth’s rotation pole and velocity. The flow can probably best be modeled as a set of coaxial cylinders arranged in groups of three (triskeles) or four and controlled by Earth topography and continent/ocean boundaries. Flow patterns suggested by maps of the three main iSSA components of SLP (trend, annual, and semi-annual) are suggestive of Taylor–Couette flow. The envelopes of the annual components of SLP and RP are offset by four decades, and there are indications that causality is present in that changes in Earth rotation axis lead force pressure variations.

Eastern Approaches: Interball in the International Solar‐Terrestrial Program

AbstractProgress in space plasma physics, or Heliophysics, necessarily requires the combined efforts of scientists in many nations employing observations from many spacecraft and ground‐based observatories. This article describes some of my efforts to integrate the Soviet missions Interball‐1 and ‐2 missions into the International Solar Terrestrial Physics program during the 1990's, with a focus on studies concerning the interaction of the solar wind with the Earth's dayside magnetosphere.

Tools for the Long Run

AbstractThe first discovery of the space age was in the field of space physics and occurred with the Explorer 1 launch in 1958 and its observations of the radiation belts encircling Earth. Space physics remained a young science into 1981 when I started graduate school, so young that there were no comprehensive textbooks on the subject. It evolved quickly with missions such as Voyager, Interplanetary Monitoring Platform‐8, Hawkeye, Active‐Magnetospheric‐Particle‐Tracer‐Experiment, and ISEE in the early years. The International Solar Terrestrial Physics mission focused part of solar and space physics into Sun‐Earth‐Connections (SECs) to understand the chain of events in the Sun‐Earth system. Heliophysics was an extension and evolution of SEC, combining all of solar and space physics, maturing the whole and the individual parts into an established science.

Machine learning in the search for new fundamental physics

Compelling experimental evidence suggests the existence of new physics beyond the well-established and tested standard model of particle physics. Various current and upcoming experiments are searching for signatures of new physics. Despite the variety of approaches and theoretical models tested in these experiments, what they all have in common is the very large volume of complex data that they produce. This data challenge calls for powerful statistical methods. Machine learning has been in use in high-energy particle physics for well over a decade, but the rise of deep learning in the early 2010s has yielded a qualitative shift in terms of the scope and ambition of research. These modern machine learning developments are the focus of the present Review, which discusses methods and applications for new physics searches in the context of terrestrial high-energy physics experiments, including the Large Hadron Collider, rare event searches and neutrino experiments.

Hybrid Method for Detecting Anomalies in Cosmic ray Variations Using Neural Networks Autoencoder

Cosmic rays were discovered by the Austrian physicist Victor Hess in 1912 in a series of balloon experiments performed between 1911 and 1912. Cosmic rays are an integral part of fundamental and applied research in the field of solar–terrestrial physics and space weather. Cosmic ray data are applied in different fields from the discovery of high-energy particles coming to Earth from space, and new fundamental symmetries in the laws of nature, to the knowledge of residual matter and magnetic fields in interstellar space. The properties of interplanetary space are determined from intensity variations, angular distribution, and other characteristics of galactic cosmic rays. The measure of cosmic ray flux intensity variability is used as one of the significant space weather factors. The negative impact of cosmic rays is also known. The negative impact can significantly increase the level of radiation hazard and pose a threat to astronauts, crews, and passengers of high-altitude aircraft on polar routes and to modern space equipment. Therefore, methods aimed at timely detection and identification of anomalous manifestations in cosmic rays are of particular practical relevance. The article proposes a method for analyzing cosmic ray variations and detecting anomalous changes in the rate of galactic cosmic ray arrival to the Earth. The method is based on a combination of the Autoencoder neural network with wavelet transform. The use of non-linear activation functions and the ability to flexibly change the structure of the network provide the ability of the Autoencoder to approximate complex dependencies in the recorded variations of cosmic rays. The article describes the numerical operations of the method implementation. Verification of the adequacy of the neural network model is based on the use of Box–Ljung Q-statistics. On the basis of the wavelet transform constructions, data-adaptive operations for detecting complex singular structures are constructed. The parameters of the applied threshold functions are estimated with a given confidence probability based on the α-quantiles of Student’s distribution. Using data from high-latitude neutron monitor stations, it is shown that the proposed method provides efficient detection of anomalies in cosmic rays during increased solar activity and magnetic storms. Using the example of a moderate magnetic storm on 10–11 May 2019, the necessity of applying different methods and approaches to the study of cosmic ray variations is confirmed, and the importance of taking them into account when making space weather forecast is shown.

Predictability of variable solar–terrestrial coupling

Abstract. In October 2017, the Scientific Committee on Solar-Terrestrial Physics (SCOSTEP) Bureau established a committee for the design of SCOSTEP's Next Scientific Programme (NSP). The NSP committee members and authors of this paper decided from the very beginning of their deliberations that the predictability of the Sun–Earth System from a few hours to centuries is a timely scientific topic, combining the interests of different topical communities in a relevant way. Accordingly, the NSP was christened PRESTO – PREdictability of the variable Solar–Terrestrial cOupling. This paper presents a detailed account of PRESTO; we show the key milestones of the PRESTO roadmap for the next 5 years, review the current state of the art and discuss future studies required for the most effective development of solar–terrestrial physics.

Quiet-Filament Eruptions and Coronal Jets as Causes of Depressions in Microwave Radio Emission

Several solar events with different types of negative microwave bursts have been studied using data from different spectral ranges. The total radio flux data obtained at the Ussuriysk Observatory, the Nobeyama Observatory, the US Air Force Radio Solar Telescope Network (RSTN), and the spectropolarimeter of the Institute of Solar–Terrestrial Physics, Siberian Branch of the Russian Academy of Sciences (ISTP SB RAS) were used. The images were analyzed using data from the SDO/AIA space observatory in the 304 Å channel and the Nobeyama radio heliograph at a frequency of 17 GHz. It was shown that the “isolated” depressions of radio emission were caused by the absorption of radiation from radio sources and/or vast regions of the quiet Sun by low-temperature material of a large eruptive filament in the absence of flares. This confirmed the conclusions of the previous studies. It was revealed that the cause of negative bursts of the “pre-burst depression” type was the screening of a near-limb radio source by the material of coronal jets. In the case of a weak flare accompanying the jet, the negative burst could also be of the “isolated” type. A case of a previously unreported occurrence of a deeper depression of radio emission at high frequencies as compared to low frequencies was considered. It was shown that negative bursts are not as rare phenomena as previously thought.

Cosmic connections: James Croll's influence on his contemporaries and his successors

ABSTRACTThis paper examines the astronomical theory of ice ages of James Croll (1821–1890), its influence on contemporaries John Tyndall, Charles Lyell, and Charles Darwin, and the subsequent development of climate change science, giving special attention to the work of Svante Arrhenius, Nils Ekholm, and G. S. Callendar (for the carbon dioxide theory), and Milutin Milanković (for the astronomical theory). Croll's insight that the orbital elements triggered feedbacks leading to complex changes – in seasonality, ocean currents, ice sheets, radiative forcing, plant and animal life, and climate in general – placed his theory of the Glacial Epoch at the nexus of astronomy, terrestrial physics, and geology. He referred to climate change as the most important problem in terrestrial physics, and the one which will ultimately prove the most far reaching in its consequences. He was an autodidact deeply involved in philosophy and an early proponent of what came to be called ‘cosmic physics’ – later known as ‘Earth-system science.’ Croll opened up new dimensions of the ‘climate controversy’ that continue today in the interplay of geological and human influences on climate.