For the first time a record of total solar irradiance covering 9300 years is presented, which covers almost the entire Holocene. This reconstruction is based on a recently observationally derived ...relationship between total solar irradiance and the open solar magnetic field. Here we show that the open solar magnetic field can be obtained from the cosmogenic radionuclide 10Be measured in ice cores. Thus, 10Be allows to reconstruct total solar irradiance much further back than the existing record of the sunspot number which is usually used to reconstruct total solar irradiance. The resulting increase in solar‐cycle averaged TSI from the Maunder Minimum to the present amounts to (0.9 ± 0.4) Wm−2. In combination with climate models, our reconstruction offers the possibility to test the claimed links between climate and TSI forcing.
Since the publication of our first paper devoted to this subject, we have extended our model, using new cosmic ray and nuclear data. Therefore, we revised particle fluxes in the atmosphere and used ...them in concert with experimental or evaluated cross sections to calculate the production rates of 3H, 7Be, 10Be, 14C, and 36Cl. The dependencies of these production rates on solar activity and geomagnetic field intensity were investigated in detail. Our simulations cover a whole range of these two parameters observed in the past. Comparison of the production rates calculated from two of the most frequently used primary galactic cosmic ray spectra showed weak dependence on the shape of the spectra. Alpha particles were included in the simulations for the first time, and we showed that the previously used scheme for estimation of alpha particle contribution to the total production rates is more complicated and latitude dependent. The production rates obtained agree well with most published experimental values.
The risks for several cancer types are increased in people with diabetes. Hyperglycaemia, hyperinsulinaemia, inflammation and altered hormonal concentrations are common characteristics between the ...two diseases and can all be linked to hyperglycaemia.
Here, we use glycated haemoglobin (HbA1c) as a biomarker for chronic hyperglycaemia. We explore whether cancer risk increases with HbA1c, independent of diabetes, and, therefore, if risk is already increased below the diabetic HbA1c range, by analysing data from current studies linking HbA1c to risk of several cancer types.
The data reveal that chronic hyperglycaemia correlates with increased cancer risk for a number of cancers, except prostate cancer. Evidence is also provided that risk is already increased in the pre-diabetic and normal ranges for several cancers.
These results merit urgent investigation into the risks and advantages of updating recommendations for stricter glycaemic control in diabetic and non-diabetic subjects, as this could help reduce the risk of cancer incidence and mortality.
The annual cosmogenic
Be
10
ice-core data from Dye 3 and the North Greenland Ice-core Project (NGRIP), and neutron-monitor data, 1951 – 2014, are combined to yield a record of the annual cosmic-ray ...intensity, 1391 – 2014. These data were then used to estimate the intensity of the heliospheric magnetic field (HMF), 1391 – 1983. All of these annual data are provided in the
Electronic Supplementary Material
. Analysis of these annual data shows that there were significant impulsive increases in
Be
10
production in the year following the very large solar cosmic-ray events of 1942, 1949, and 1956. There was an additional enhancement that we attribute to six high-altitude nuclear explosions in 1962. All of these enhancements result in underestimates of the strength of the HMF. An identification process is defined, resulting in a total of seven impulsive
Be
10
events in the interval 1800 – 1942 prior to the first detection of a solar cosmic-ray event using ionization chambers. Excision of the
Be
10
impulsive enhancements yields a new estimate of the HMF, designated B(PCR-2). Five of the seven
Be
10
enhancements prior to 1941 are well correlated with the occurrence of very great geomagnetic storms. It is shown that a solar cosmic-ray event similar to that of 25 July 1946, and occurring in the middle of the second or third year of the solar cycle, may merge with the initial decreasing phase of the 11-year cycle in cosmic-ray intensity and be unlikely to be detected in the
Be
10
data. It is concluded that the occurrence rate for solar energetic-particle (SEP) events such as that on 23 February 1956 is about seven per century, and that there is an upper limit to the size of solar cosmic-ray events.
Aims. Miyake et al. (2012, Nature, 486, 240, henceforth M12) recently reported, based on 14C data, an extreme cosmic event in about AD775. Using a simple model, M12 claimed that the event was too ...strong to be caused by a solar flare within the standard theory. This implied a new paradigm of either an impossibly strong solar flare or a very strong cosmic ray event of unknown origin that occurred around AD775. However, as we show, the strength of the event was significantly overestimated by M12. Several subsequent works have attempted to find a possible exotic source for such an event, including a giant cometary impact upon the Sun or a gamma-ray burst, but they are all based on incorrect estimates by M12. We revisit this event with analysis of new datasets and consistent theoretical modelling. Methods. We verified the experimental result for the AD775 cosmic ray event using independent datasets including 10Be series and newly measured 14C annual data. We surveyed available historical chronicles for astronomical observations for the period around the AD770s to identify potential sightings of aurorae borealis and supernovae. We interpreted the 14C measurements using an appropriate carbon cycle model. Results. We show that: (1) The reality of the AD775 event is confirmed by new measurements of 14C in German oak; (2) by using an inappropriate carbon cycle model, M12 strongly overestimated the event’s strength; (3) the revised magnitude of the event (the global 14C production Q = (1.1 − 1.5) × 108 atoms/cm2) is consistent with different independent datasets (14C, 10Be, 36Cl) and can be associated with a strong, but not inexplicably strong, solar energetic particle event (or a sequence of events), and provides the first definite evidence for an event of this magnitude (the fluence >30 MeV was about 4.5 × 1010 cm-2) in multiple datasets; (4) this interpretation is in agreement with increased auroral activity identified in historical chronicles. Conclusions. The results point to the likely solar origin of the event, which is now identified as the greatest solar event on a multi-millennial time scale, placing a strong observational constraint on the theory of explosive energy releases on the Sun and cool stars.
Hospital populations are vulnerable to COVID-19, but the relative severity of hospital acquisition compared to community is unknown. We investigated differences in mortality between hospital and ...community acquired cases in Wales.
Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) polymerase chain reaction tests from February 2020 to March 2022 were linked with hospital admissions to identify likely hospital-acquired cases. All-cause mortality within 28 days of a positive SARS-CoV-2 were measured by source of acquisition. Multi-variable logistic regression was used to compare mortality by source of acquisition, adjusting for confounders, computing adjusted odds ratios (aOR) with 95% confidence intervals (CI).
There were 25,263 hospital-acquired cases of COVID-19 and 5490 (22%) deaths in the study period. Although significant on univariate analysis, adjustment for confounding showed no association with increased mortality for hospital-acquired cases compared with cases admitted with COVID-19 (aOR 0.8, 95% CI 0.7-0.8). Vaccination (aOR 0.6, 95% CI 0.5-0.7) and infection in later pandemic waves (aOR 0.5, 95% CI 0.4-0.6) were associated with lower mortality; older age (≥85 vs <25 years: aOR 76.4, 95% CI 41.8-160.5) and male sex (aOR 1.5, 95% CI 1.4-1.6) were associated with higher mortality.
One in five hospitalised COVID-19 cases died within a month of infection. Mortality in nosocomial cases was not worse than those admitted with COVID-19, possibly reflecting early identification of nosocomial cases through screening.
The old question of whether the solar dynamo is synchronized by the tidal forces of the orbiting planets has recently received renewed interest, both from the viewpoint of historical data analysis ...and in terms of theoretical and numerical modeling. We aim to contribute to the solution of this longstanding puzzle by analyzing cosmogenic radionuclide data from the last millennium. We reconsider a recent time series of
14
C-inferred sunspot data and compare the resulting cycle minima and maxima with the corresponding conventional series down to 1610 A.D., enhanced by Schove’s data before that time. We find that, despite recent claims to the contrary, the
14
C-inferred sunspot data are well compatible with a synchronized solar dynamo, exhibiting a relatively phase-stable period of 11.07 years, which points to a synchronizing role of the spring tides of the Venus-Earth-Jupiter system.
SOLAR INFLUENCES ON CLIMATE Gray, L. J.; Beer, J.; Geller, M. ...
Reviews of geophysics (1985),
December 2010, Letnik:
48, Številka:
4
Journal Article
Recenzirano
Odprti dostop
Understanding the influence of solar variability on the Earth's climate requires knowledge of solar variability, solar‐terrestrial interactions, and the mechanisms determining the response of the ...Earth's climate system. We provide a summary of our current understanding in each of these three areas. Observations and mechanisms for the Sun's variability are described, including solar irradiance variations on both decadal and centennial time scales and their relation to galactic cosmic rays. Corresponding observations of variations of the Earth's climate on associated time scales are described, including variations in ozone, temperatures, winds, clouds, precipitation, and regional modes of variability such as the monsoons and the North Atlantic Oscillation. A discussion of the available solar and climate proxies is provided. Mechanisms proposed to explain these climate observations are described, including the effects of variations in solar irradiance and of charged particles. Finally, the contributions of solar variations to recent observations of global climate change are discussed.
Context. Understanding the Sun’s magnetic activity is important because of its impact on the Earth’s environment. Direct observations of the sunspots since 1610 reveal an irregular activity cycle ...with an average period of about 11 years, which is modulated on longer timescales. Proxies of solar activity such as 14C and 10Be show consistently longer cycles with well-defined periodicities and varying amplitudes. Current models of solar activity assume that the origin and modulation of solar activity lie within the Sun itself; however, correlations between direct solar activity indices and planetary configurations have been reported on many occasions. Since no successful physical mechanism was suggested to explain these correlations, the possible link between planetary motion and solar activity has been largely ignored. Aims. While energy considerations clearly show that the planets cannot be the direct cause of the solar activity, it remains an open question whether the planets can perturb the operation of the solar dynamo. Here we use a 9400 year solar activity reconstruction derived from cosmogenic radionuclides to test this hypothesis. Methods. We developed a simple physical model for describing the time-dependent torque exerted by the planets on a non-spherical tachocline and compared the corresponding power spectrum with that of the reconstructed solar activity record. Results. We find an excellent agreement between the long-term cycles in proxies of solar activity and the periodicities in the planetary torque and also that some periodicities remain phase-locked over 9400 years. Conclusions. Based on these observations we put forward the idea that the long-term solar magnetic activity is modulated by planetary effects. If correct, our hypothesis has important implications for solar physics and the solar-terrestrial connection.
The most powerful explosions on the Sun – in the form of bright flares, intense storms of solar energetic particles (SEPs), and fast coronal mass ejections (CMEs) – drive the most severe ...space‐weather storms. Proxy records of flare energies based on SEPs in principle may offer the longest time base to study infrequent large events. We conclude that one suggested proxy, nitrate concentrations in polar ice cores, does not map reliably to SEP events. Concentrations of select radionuclides measured in natural archives may prove useful in extending the time interval of direct observations up to ten millennia, but as their calibration to solar flare fluences depends on multiple poorly known properties and processes, these proxies cannot presently be used to help determine the flare energy frequency distribution. Being thus limited to the use of direct flare observations, we evaluate the probabilities of large‐energy solar events by combining solar flare observations with an ensemble of stellar flare observations. We conclude that solar flare energies form a relatively smooth distribution from small events to large flares, while flares on magnetically active, young Sun‐like stars have energies and frequencies markedly in excess of strong solar flares, even after an empirical scaling with the mean coronal activity level of these stars. In order to empirically quantify the frequency of uncommonly large solar flares extensive surveys of stars of near‐solar age need to be obtained, such as is feasible with the Kepler satellite. Because the likelihood of flares larger than approximately X30 remains empirically unconstrained, we present indirect arguments, based on records of sunspots and on statistical arguments, that solar flares in the past four centuries have likely not substantially exceeded the level of the largest flares observed in the space era, and that there is at most about a 10% chance of a flare larger than about X30 in the next 30 years.
Key Points
Solar, stellar, lunar, and terrestrial data need to be combined
Radionuclide data and ice cores do not tell us much about largest solar flares
We argue for an upper limit for the largest solar flares of about X30
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