Joined: Sun May 29, 2011 7:48 am
Posts: 619
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Continuing... http://www.pnas.org/content/97/23/12433.fullCurrent global warming commonly is attributed to increased CO2 concentrations in the atmosphere (3). However, geophysical, archaeological, and historical evidence is consistent with warming and cooling periods during the Holocene as indicated by the solar-output model. The current warm period is thought to have not reached the level of warmth of the previous warm period (A.D. 800-1200), when the Vikings raised wheat and livestock in Greenland. Therefore, the magnitude of the modern temperature increase being caused solely by an increase in CO2 concentrations appears questionable. The contribution of solar-output variations to climate change may be significant. http://www.agu.org/pubs/crossref/2002/2 ... 0336.shtmlFrom the frequencies of sunspot and aurora sightings, abundance of carbon-14 in the rings of long-lived trees, and beryllium-10 in the annual ice layers of polar ice cores, we have reconstructed the history of a variable Sun. In the last 1,800 years, the Sun has gone through nine cycles of changes in brightness. While these long-term variations account for less than 1%of the total irradiance, there is clear evidence that they affect the Earth's climate. http://geology.gsapubs.org/content/37/1/71.abstractSome studies indicate that the solar modulation of galactic cosmic ray (GCR) particles has profound consequences for Earth's climate system. A corollary of the GCR-climate theory involves a link between Earth's magnetic field and climate, since the geomagnetic field also modulates the GCR flux reaching Earth's atmosphere. In this study, we explore this potential geomagnetic-climate link by comparing a new reconstruction of the Holocene geomagnetic dipole moment with high-resolution speleothem data from China and Oman. The speleothem δ18O data represent proxy records for past precipitation in low-latitude regions, which is a climate parameter that is likely to have been sensitive to variations in the GCR flux modulated by the dipole moment. Intriguingly, we observe a relatively good correlation between the high-resolution speleothem δ18O records and the dipole moment, suggesting that Earth's magnetic field to some degree influenced low-latitude precipitation in the past. In addition to supporting the notion that variations in the geomagnetic field may have influenced Earth's climate in the past, our study also provides some degree of support for the controversial link between GCR particles, cloud formation, and climate. http://rspa.royalsocietypublishing.org/ ... /1221.fullGalactic cosmic ray (GCR) changes have been suggested to affect weather and climate, and new evidence is presented here directly linking GCRs with clouds. Clouds increase the diffuse solar radiation, measured continuously at UK surface meteorological sites since 1947. The ratio of diffuse to total solar radiation—the diffuse fraction (DF)—is used to infer cloud, and is compared with the daily mean neutron count rate measured at Climax, Colorado from 1951–2000, which provides a globally representative indicator of cosmic rays. Across the UK, on days of high cosmic ray flux (above 3600×102 neutron counts h−1, which occur 87% of the time on average) compared with low cosmic ray flux, (i) the chance of an overcast day increases by (19±4) %, and (ii) the diffuse fraction increases by (2±0.3) %. During sudden transient reductions in cosmic rays (e.g. Forbush events), simultaneous decreases occur in the diffuse fraction. The diffuse radiation changes are, therefore, unambiguously due to cosmic rays. Although the statistically significant nonlinear cosmic ray effect is small, it will have a considerably larger aggregate effect on longer timescale (e.g. centennial) climate variations when day-to-day variability averages out. http://ppg.sagepub.com/content/23/2/181.abstractCurrent concern over ‘greenhouse’ warming and possible human influence upon global climate has been countered by claims that recent advances in solar theory demonstrate a greater role than previously thought for solar forcing in recent climate change. This is still disputed for this century, but new evidence from a range of palaeoenvironmental indicators lends strong support to the notion that not only the long-term (105 to 103 years) climate changes of the Pleistocene but also short-term (101 to 102 years) climate changes in the Holocene may derive in large or small part from solar variability. Evidence from recent research into proxy climate records is reviewed and set in the context of recent advances elsewhere in studies of late Quaternary palaeoenvironments and in solar science.
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