Reconstruction of the Earth’s surface temperature based on data of deep boreholes,global warming in the last millennium,and long-term solar cyclicity. Part 1. Experimental data

The most reliable pattern of climate changes is obtained using data of instrumental observations at the network of meteorological stations. However, the series of such data have short timescales (about 150 years). Indirect data from natural archives make it possible to judge specific features of climate changes in the more distant past. In contrast to indirect methods, when data are related to temperature through statistical correlations with air temperature, the borehole geothermal method makes it possible to directly determine the surface air temperature. The reconstructions of the temperature obtained using different indirect data for the Northern Hemisphere have been compared with the surface air temperature reconstructions based on the data of borehole thermometry and solar activity variations, and the possibilities of using the method in order to reconstruct long-term trends in climate changes have been indicated.     

Reconstruction of the Earth’s surface temperature based on data of deep boreholes,global warming in the last millennium,and long-term solar cyclicity. Part 2. Experimental data analysis

The most reliable pattern of climate changes is obtained using data of instrumental observations at the network of meteorological stations. However, the series of such data have short timescales (about 150 years). Indirect data from natural archives make it possible to judge specific features of climate changes in the more distant past. In contrast to indirect methods, when data are related to temperature through statistical correlations with air temperature, the borehole geothermal method makes it possible to directly determine the surface air temperature. The reconstructions of the temperature obtained using different indirect data for the Northern Hemisphere have been compared with the surface air temperature reconstructions based on the data of borehole thermometry and solar activity variations, and the possibilities of using the method in order to reconstruct long-term trends in climate changes have been indicated.     

Impact of the geomagnetic field and solar radiation on climate change

Recent studies have shown that, in addition to the role of solar variability, past climate changes may have been connected with variations in the Earth??s magnetic field elements at various timescales. An analysis of variations in geomagnetic field elements, such as field intensity, reversals, and excursions, allowed us to establish a link between climate changes at various timescales over the last millennia. Of particular interest are sharp changes in the geomagnetic field intensity and short reversals of the magnetic poles (excursions). The beginning and termination of the examined geomagnetic excursions can be attributed to periods of climate change. In this study, we analyzed the possible link between short-term geomagnetic variability (jerks) and climate change, as well as the accelerated drift of the north magnetic pole and surface temperature variations. The results do not rule out the possibility that geomagnetic field variations which modulate the cosmic ray flux could have played a major role in climate change in addition to previously induced by solar radiation.     

Total solar irradiance variations

Total solar irradiance has been monitored from space for nearly two decades. These space-borne observations have established conclusively that total solar irradiance changes over a wide range of periodicities—from minutes to the 11-year solar cycle. Since the total energy flux of the Sun is the principal driver for all Earths atmospheric phenomena, the accurate knowledge of the solar radiation received by the Earth and its variations is an extremely important issue. In this paper we review the long-term variations of total solar irradiance during solar cycles 21 and 22. We conclude that, within the current accuracy and precision of the measurements, the minimum level of total solar irradiance is about the same for both solar cycles 21 and 22.     

Advances in Understanding Top-of-Atmosphere Radiation Variability from Satellite Observations

This paper highlights how the emerging record of satellite observations from the Earth Observation System (EOS) and A-Train constellation are advancing our ability to more completely document and understand the underlying processes associated with variations in the Earth’s top-of-atmosphere (TOA) radiation budget. Large-scale TOA radiation changes during the past decade are observed to be within 0.5?Wm^?2 per decade based upon comparisons between Clouds and the Earth’s Radiant Energy System (CERES) instruments aboard Terra and Aqua and other instruments. Tropical variations in emitted outgoing longwave (LW) radiation are found to closely track changes in the El Ni?o-Southern Oscillation (ENSO). During positive ENSO phase (El Ni?o), outgoing LW radiation increases, and decreases during the negative ENSO phase (La Ni?a). The coldest year during the last decade occurred in 2008, during which strong La Nina conditions persisted throughout most of the year. Atmospheric Infrared Sounder (AIRS) observations show that the lower temperatures extended throughout much of the troposphere for several months, resulting in a reduction in outgoing LW radiation and an increase in net incoming radiation. At the global scale, outgoing LW flux anomalies are partially compensated for by decreases in midlatitude cloud fraction and cloud height, as observed by Moderate Resolution Imaging Spectrometer and Multi-angle Imaging SpectroRadiometer, respectively. CERES data show that clouds have a net radiative warming influence during La Ni?a conditions and a net cooling influence during El Ni?o, but the magnitude of the anomalies varies greatly from one ENSO event to another. Regional cloud-radiation variations among several Terra and A-Train instruments show consistent patterns and exhibit marked fluctuations at monthly timescales in response to tropical atmosphere-ocean dynamical processes associated with ENSO and Madden–Julian Oscillation.     

Extrema of long-term modulation of the cosmic ray intensity in the last five solar cycles

Modulation of galactic cosmic rays in cycles 19–23 of solar activity has been determined based on observations of their long-term variations on the ground and in the near-Earth space. The extreme values of long-term variations in cosmic rays, obtained from the data of continuous cosmic radiation monitoring on the ground and in the near-Earth space in the last five solar cycles, have been analyzed. The results are compared with the extrema in the characteristics of solar magnetic fields and the sunspot numbers in these cycles. The similarities and differences in cosmic ray modulation between different cycles are discussed.     

Solar–terrestrial,ionospheric and natural phenomena studies using the South America VLF network (SAVNET)

The South America VLF Network (SAVNET) has been installed in April 2009, and is composed of eight tracking receivers spread over South America, in Brazil, Peru and Argentina, and the Antarctica Peninsula. SAVNET is monitoring the properties of subionospheric propagating waves that reveal changes of the electrical properties of the ionospheric diurnal D-region or nocturnal E-region. In this paper, we will show the ability of the diagnostic obtained by SAVNET to discuss the monitoring of the solar activity on short timescales related to ionization due to solar flares. The sensitivity of flare detection as a function of the solar activity level will be discussed. On longer timescales related to the solar cycle, SAVNET is also able to provide information on the solar Lyman-α radiation. Finally we show that the VLF technique is well suited to search for of seismic-electromagnetic effects, and to provide a genuine diagnostic of high-energy astrophysical phenomena.     

Numerical modelling of spectral sky radiance during a total solar eclipse

Ground-based observations of the spectral sky radiance within the totality region during a total solar eclipse are of significant interest because the contribution from direct and single scattered light from the solar disk is eliminated. In the present paper, we develop a numerical model of the spectral sky radiance during totality, evaluate the contribution of double scattered sunlight to the sky radiance at totality and compare it to solar corona emissions. The results show that the single scattered coronal light is the major contaminant in ground-based observations of the corona, opposite to what was believed before. For observation directions outside the corona the double scattered sun radiation dominates over the single scattered coronal light.     

Evidence for solar forcing of climate variation from δ18O of peat cellulose

There have been a number of investigations for examining the possible link between long-term climate variability and solar activity.A continuous δ18O record of peat cellulose covering the past 6000 years and the response of climate variation inferred from the proxy record to solar forcing are reported.Results show that during the past 5000 years the abrupt climate variations,including 17 warming and 17 cooling,and a serious of periodicities,such as 86,101,110,127,132,140,155,207,245,311,820 and 1050 years,are strikingly correlative to the changes of solar irradiation and periodicity.These observations are considered as further evidence for a close relationship between solar activity and climate variations on time scales of decades to centuries.     

Long-term modulation of galactic cosmic rays at solar activity minimums

Based on observations of long-term variations in galactic cosmic rays (CRs) on Earth and in the near-Earth space, we have determined, using our own semiempirical model, modulation of galactic CRs during solar cycles 19–23. The modulation model relates CR variations to the characteristics of the solar magnetic field obtained for the surface of the solar wind source at distances of 2.50 and 3.25 solar radii. The main focus is CR behavior at the minimums of cycles 19–23 and specific features of CR modulation at a prolonged (as compared to previous cycles) minimum of cycle 23, which is still ongoing. CR modulation at minimums related to a change in the solar field dipole component during this period of the cycle has been considered. It is indicated that the long-term variations in CRs are better described if the last two years (2007 and 2008) of cycle 23 with anomalously low solar activity (SA) are included in the model. The role and value of the contribution of the cyclic variations in each index used in the proposed CR modulation model to the observed CR modulation have been estimated.     

Variations of solar radiation input to the lower atmosphere associated with different helio/geophysical factors

The influence of helio/geophysical factors on the solar energy input to the lower atmosphere has been studied at the network of actinometric stations of Russia in different latitudinal belts. It was found that there are appreciable changes in the half-yearly values of total radiation associated with galactic cosmic ray (GCR) variations in the 11-yr solar cycle, the increase of GCR flux being accompanied by a decrease of the total radiation at higher latitudes and by its increase at lower latitudes. Auroral phenomena and solar flare activity are likely to affect the solar radiation input to the high-latitudinal belt together with GCR variations, the increase of both these factors resulting in the decrease of total radiation. The changes found in the total radiation fluxes in the lower atmosphere seem to be related to the cloud cover variations associated with the solar and geophysical phenomena under study. The variations of the solar radiation input in the 11-yr-cycle amounting to ±4–6% may be an important factor affecting tropospheric dynamics.     

Solar and geomagnetic activity effects on climate at regional and global scales: Case study—Romania

We analyze 100–150 years-long temperature and precipitation records from 14 meteorological stations in Romania, in connection with long-term trends in solar and geomagnetic activities. The comparison of solar (sunspot number) and geomagnetic (aa index) parameters with the mean air temperature over the Romanian territory, at interdecadal timescales, shows positive correlation coefficients, while the comparison with the mean precipitation shows negative correlation coefficients. The correlation of climatic parameters seems to be stronger for geomagnetic activity than for solar activity. The Romanian temperature series are examined in the context of other European stations and of averages on the European, northern hemisphere, and global scale, respectively. Long-term (interdecadal and centennial) trends and differences between local trends and average trends for larger areas are discussed. The study indicates that solar and geomagnetic activity effects are present on the 22-year Hale cycle timescale. The temperature variation on this timescale lags the solar/geomagnetic ones by 5–9 years.     

Solar EUV Flux Variations in 11–Year Solar Activity Cycle According to Measurements On-Board PROGNOZ Satellite Series, INTERBALL-1 and ELECTRO Satellites during 1978–1997 Period

The paper presents data on flux variations of ionizing EUV radiation for wavelengths shorter than 130 nm and in L-alpha hydrogen line on the basis of measurements performed on-board a Russian Earth-orbiting and interplanetary spacecrafts in the period since 1978 to 1997. These data were received by using common heritage instrumentation installed on four PROGNOZ satellites, INTERBALL-1, PHOBOS, and the geosynchronous meteorological satellite ELECTRO. Though the time series of observations is not continuous, it gives a possibility to estimate flux variations in certain periods of time and during 11–year cycle. During quiet periods of solar activity (except for flares) a level of diurnal variations is rather low, it being equal to about 3%. Radiation changes in L-alpha line from maximum to minimum in an 11–year cycle of solar activity achieves 200% and increases in the range of short waves. Data measured onboard the Russian satellites are compared with data obtained by Solar Mesospheric Explorer.     

Global magnetic field of the Sun and long-term variations of galactic cosmic rays

The paper deals with the relation of long-term variations of 10 GV galactic cosmic rays (GCR) to the global solar magnetic field and solar wind parameters. This study continues previous works, where the tilt of the heliospheric current sheet (HCS) and other solar-heliospheric parameters are successfully used to describe long-term variations of cosmic rays in the past two solar cycles. The novelty of the present work is the use of the HCS tilt and other parameters reconstructed from Hα observations of filaments for the period when direct global solar magnetic field observations were unavailable. Thus, we could extend the GCR simulation interval back to 1953. The analysis of data for 1953–1999 revealed a good correlation (the correlation coefficient >0.88) between the solar-heliospheric parameters and GCR in different cycles of solar activity. Moreover, the approach applied makes it possible to describe the behavior of cosmic rays in the epochs of solar maxima, which could not be done before. This indicates both the adequacy of the model and the reliability of the reconstructed global solar magnetic field parameters.     

Evidence for solar forcing of climate variation from δ18O of peat cellulose

There have been a number of investigations for examining the possible link between long-term climate variability and solar activity. A continuous δ¹⁸O record of peat cellulose covering the past 6 000 years and the response of climate variation inferred from the proxy record to solar forcing are reported. Results show that during the past 5 000 years the abrupt climate variations, including 17 warming and 17 cooling, and a serious of periodicities, such as 86, 101, 110, 127, 132, 140, 155, 207, 245, 311, 820 and 1 050 years, are strikingly correlative to the changes of solar irradiation and periodicity. These observations are considered as further evidence for a close relationship between solar activity and climate variations on time scales of decades to centuries.     

Correlation between Long-Term Variations in the Vertical Component of the Electric Field in Baikal and Solar Activity

The vertical component of the electric field along the surface–bottom baseline was measured for several years in the southwestern part of Baikal. The measurements revealed a correlation between long-term variations in the field that were interpreted as variations in the current in the hydrospheric segment of the global electric circuit with intermittent variations in the solar activity. However, the continuous measurement series were no longer than a year, which is shorter than the maximal quasi-period of the alternating variations. The first continuous two-year measurement series was made in 2014–2016. Its analysis shows quite strong variations with quasi-periods of up to 320 days, which correlate with variations in the solar X-ray flux. The effective delay of the correlation is about four days, which is evidence of an indirect effect of solar activity on the vertical current in the hydrosphere by rather slow atmospheric processes.     

Cosmic ray modulation during the solar activity growth phase of cycle 24

Recent years allowed us to study long-term variations in the cosmic ray (CR) intensity at an unusually deep solar activity (SA) minimum between cycles 23 and 24 and during the SA growth phase in cycle 24, which was the cycle when SA was the lowest for the epoch of regular ground-based CR observations since 1951. The intensity maximum, the value of which depends on the particle energy, was observed in CR variations during the period of an unusually prolonged SA minimum: the CR density during the aformentioned period (2009) is higher than this density at previous CR maxima in cycles 19–23 for low-energy particles (observed on spacecraft and in the stratosphere) and medium-energy particles (observed with neutron monitors). After 2009 CR modulation at the SA growth phase was much weaker over three years (2010–2012) than during the corresponding SA growth periods in the previous cycles. The possible causes of this anomaly in CR variations, which are related to the CR residual modulation value at a minimum between cycles 23 and 24 and to variations in SA characteristics during this period, were examined. The contribution of different solar magnetic field characteristics and indices, taking into account sporadic solar activity, has been estimated.     

Measurements of total solar radiation at Giza

Summary Records of total solar radiation on a horizontal surface has been obtained at the Agro-meteorological Station at Giza continuously since December 1, 1955 by means of a Robitzsch actinograph. The difficulties in obtaining precise measurements were described. The results of the first three years of record were discussed and summarized in tabular and graphical form. To such few years of observations, a 15 days moving average was applied. The new data were plotted so as to obtain the solar radiation pattern, which has been compared with the radiation received at the outer limits of the atmosphere and with the maximum probable radiation expected at the Station.     

Variations in the solar fluxes of helium and protons on the long-term scale

A reconstruction of data on ancient (to ～600 Ma ago) solar fluxes of protons and helium has been performed on the basis of isotopic investigations of helium and neon in lunar soil samples from columns delivered by the automatic stations Luna-16 and Luna-24 in 1970 and 1976. Recent investigations have shown the presence of long-term climate variations, which can be explained in the context of solar-terrestrial links. However, the “space” impact, simultaneously with the Sun’s influence on the Earth, takes place in the form of cosmic ray irradiation and as an influence on the Earth that is exerted by the flux of cosmic dust and meteorites (including the very large ones at the early stage of the Earth evolution). Therefore the existence of long-term variability of solar corpuscular fluxes may serve as direct evidence of the manifestation of solar-terrestrial links. The possibility of finding these links appears on the basis of the revealed variations of solar wind fluxes with an age from the contemporary level to the level of ～600 Ma ago.