Skip to main content

Thank you for visiting You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

Causes of an ad 774–775 14C increase



Arising from F. Miyake, K. Nagaya, K. Masuda & T. Nakamura Nature 486, 240–242 (2012)10.1038/nature11123

Atmospheric 14C production is a potential window into the energy of solar proton and other cosmic ray events. It was previously concluded that 14C results from ad 774–775 would require solar events that were orders of magnitude greater than known past events1. We find that the coronal mass ejection energy based on 14C production is much smaller than claimed in ref. 1, but still substantially larger than the maximum historical Carrington Event of 18592,3,4. Such an event would cause great damage to modern technology5,6, and in view of recent confirmation of superflares on solar-type stars7,8, this issue merits attention.

This is a preview of subscription content

Access options

Buy article

Get time limited or full article access on ReadCube.


All prices are NET prices.

Figure 1: Percentage change in globally averaged O3 column density.


  1. Miyake, F., Nagaya, K., Masuda, K. & Nakamura, T. A signature of cosmic-ray increase in AD 774–775 from tree rings in Japan. Nature 486, 240–242 (2012)

    ADS  CAS  Google Scholar 

  2. Melott, A. L. & Thomas, B. C. Astrophysical ionizing radiation and the Earth: a brief review and census of intermittent intense sources. Astrobiology 11, 343–361 (2011)

    ADS  CAS  Article  Google Scholar 

  3. Clauer, C. R., Siscoe, G., eds. The great historical geomagnetic storm of 1859: a modern look. Adv. Space Res. 38, 115–388 (2006)

    Article  Google Scholar 

  4. Thomas, B. C., Jackman, C. H. & Melott, A. L. Modeling atmospheric effects of the September 1859 solar flare. Geophys. Res. Lett. 34 L06810, (2007)

    ADS  Google Scholar 

  5. National Research Council Space Studies Board. Severe Space Weather Events — Understanding Societal and Economic Impacts (National Academies Press, 2008); available at = 12507&page = R1

  6. Hapgood, M. Astrophysics: prepare for the coming space weather storm. Nature 484, 311–313 (2012)

    ADS  CAS  Article  Google Scholar 

  7. Schaefer, B. E., King, J. R. & Deliyannis, C. P. Superflares on ordinary solar-type stars. Astrophys. J. 529, 1026–1030 (2000)

    ADS  Article  Google Scholar 

  8. Maehara, H. et al. Superflares on solar-type stars. Nature 485, 478–481 (2012)

    ADS  CAS  Article  Google Scholar 

  9. Reedy, R. C. in Solar Drivers of Interplanetary and Terrestrial Disturbances: Proceedings of the 16th International Workshop (eds Balasubramaniam, K. S., Keil, S. L. & Smartt, R. N. ) 429–436 (ASP Conf. Ser. Vol. CS-94, Astronomical Society of the Pacific, 1996)

    Google Scholar 

  10. Schrijver, C. J. Eruptions from solar ephemeral regions as an extension of the size distribution of coronal mass ejections. Astrophys. J. 710, 1480–1485 (2010)

    ADS  Article  Google Scholar 

  11. Love, J. J. Credible occurrence probabilities for extreme geophysical events: earthquakes, volcanic eruptions, magnetic storms. Geophys. Res. Lett.. 39, L10301, (2012)

    ADS  Google Scholar 

  12. Ejzak, L. M., Melott, A. L., Medvedev, M. V. & Thomas, B. C. Terrestrial consequences of spectral and temporal variability in ionizing photon events. Astrophys. J. 654, 373–384 (2007)

    ADS  CAS  Article  Google Scholar 

  13. Calisto, M., Verronen, P. T., Rozanov, E. & Peter, T. Influence of a Carrington-like event on the atmospheric chemistry, temperature and dynamics. Atmos. Chem. Phys. 12, 8679–8686 (2012)

    ADS  CAS  Article  Google Scholar 

  14. Schrijver, C. J. et al. Estimating the frequency of extremely energetic solar events, based on solar, stellar, lunar, and terrestrial records. J. Geophys. Res.. 117, A08103, (2012)

    ADS  Article  Google Scholar 

Download references

Author information

Authors and Affiliations



A.L.M. planned and wrote the paper with the assistance of B.C.T. B.C.T. performed the atmospheric computations and made the plot.

Corresponding author

Correspondence to Adrian L. Melott.

Ethics declarations

Competing interests

Declared none.

PowerPoint slides

Rights and permissions

Reprints and Permissions

About this article

Cite this article

Melott, A., Thomas, B. Causes of an ad 774–775 14C increase. Nature 491, E1–E2 (2012).

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI:

Further reading


By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.


Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing