Galactic cosmic rays, high-energy particles flying from space, have the effect of inducing cloud formation and increasing the amount of clouds (Svensmark effect).

 This time, a research group led by Professor Masayuki Hyodo of the Center for Environmental Education and Research in the Inland Sea of ​​Kobe University was in the middle of the geomagnetic reversal 78 years ago when galactic cosmic rays were increasing. He found evidence of increased seasonal winds and showed that galactic cosmic rays can be a factor in climate change.

 It has long been suggested that galactic cosmic rays may affect the climate due to the Svensmark effect.However, recent verifications using meteorological observation data have not provided clear evidence because changes in galaxy cosmic dose and cloud cover are small.

 Therefore, in this study, we focus on about 50 years ago, 78 years ago, when galactic cosmic rays increased by more than 5000% due to the decrease in geomagnetic strength due to the geomagnetic reversal.During the period when galactic cosmic rays increased significantly, the amount of clouds also increased significantly, and it was hypothesized that the winter monsoon should have been strengthened by the strong cloud sunshade effect. The changes in the particle size and deposition rate of the dust layer) were investigated.

 As a result, we found traces that the grain size of the dust was coarse and the deposition rate increased more than three times during about 5000 years during the geomagnetic reversal.This suggests that the parasol effect of the clouds strongly cooled the continent and strengthened the Siberian High, which strengthened the winter monsoon.

 At the same time, analysis of the Osaka Bay sediment core suggests that the annual average temperature has decreased and the annual temperature range has increased. Is almost certain to be the cause of these climate changes.

 The results of this research are likely to be an opportunity to review the effects of clouds on the climate.For example, if the number of galactic cosmic rays decreases, the number of lower clouds also decreases, so there is a possibility that warming will occur due to the reverse parasol effect, and it can be said that the cloud parasol effect is important for understanding the current global warming.

Paper information:[Scientific Reports] Intensified East Asian winter monsoon during the last geomagnetic reversal transition

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