Wednesday, September 26, 2012

New paper finds that a solar proton event could cause global cooling of more than 3C

A paper published today in Atmospheric Chemistry and Physics finds that "a solar proton event, if it took place in the near future with an intensity similar to that ascribed to the Carrington Event of 1859, must be expected to have a major impact on atmospheric composition throughout the middle atmosphere, resulting in significant and persistent decrease in total ozone," resulting in a "significant [global] cooling of more than 3C". The Carrington Event of 1859 lasted only 2 days, but caused persistent changes in ozone lasting up to several months. The authors predict such an event could cause a "cooling of up to 5 K in eastern Europe and Russia to a somewhat smaller decrease of about 3 K for the Southern Hemisphere in Argentina."

Atmos. Chem. Phys., 12, 8679-8686, 2012

Influence of a Carrington-like event on the atmospheric chemistry, temperature and dynamics

M. Calisto1, P. T. Verronen2, E. Rozanov3,4, and T. Peter4
1International Space Science Institute (ISSI), Bern, Switzerland
2Finnish Meteorological Institute, Helsinki, Finland
3Physical-Meteorological Observatory/World Radiation Center, Davos, Switzerland
4Institute for Atmospheric and Climate Science ETH, Zurich, Switzerland

 Abstract. We have modeled the atmospheric impact of a major solar energetic particle event similar in intensity to what is thought of the Carrington Event of 1–2 September 1859. Ionization rates for the August 1972 solar proton event, which had an energy spectrum comparable to the Carrington Event, were scaled up in proportion to the fluence estimated for both events. We have assumed such an event to take place in the year 2020 in order to investigate the impact on the modern, near future atmosphere. Effects on atmospheric chemistry, temperature and dynamics were investigated using the 3-D Chemistry Climate Model SOCOL v2.0. We find significant responses of NOx, HOx, ozone, temperature and zonal wind. Ozone and NOx have in common an unusually strong and long-lived response to this solar proton event. The model suggests a 3-fold increase of NOx generated in the upper stratosphere lasting until the end of November, and an up to 10-fold increase in upper mesospheric HOx. Due to the NOx and HOx enhancements, ozone reduces by up to 60–80% in the mesosphere during the days after the event, and by up to 20–40% in the middle stratosphere lasting for several months after the event. Total ozone is reduced by up to 20 DU in the Northern Hemisphere and up to 10 DU in the Southern Hemisphere. Free tropospheric and surface air temperatures show a significant cooling of more than 3 K and zonal winds change significantly by 3–5 m s−1 in the UTLS region. In conclusion, a solar proton event, if it took place in the near future with an intensity similar to that ascribed to of the Carrington Event of 1859, must be expected to have a major impact on atmospheric composition throughout the middle atmosphere, resulting in significant and persistent decrease in total ozone.

 Full paper here:Final Revised Paper (PDF, 1740 KB)   Discussion Paper (ACPD)   


  1. GuarionexSandoval said:

    This has probably happened before:

    "Evidence for a Solar Flare Cause of the Pleistocene Mass Extinction". Paul LaViolette. June 1 2011. Radiocarbon (vol. 53 no. 2, pp. 303-323)

    Paper abstract: The hypothesis is presented that an abrupt rise in atmospheric radiocarbon concentration evident in the Cariaco Basin varve record at 12,837A+-10 cal yrs BP contemporaneous with the Rancholabrean termination, may have been produced by a super-sized solar proton event (SPE) having a fluence of ~1.3 X 10^11 protons/cm^2. A SPE of this magnitude would have been large enough to deliver a lethal radiation dose of at least 3 - 6 Sv to the Earth's surface, and hence could have been a principal cause of the final termination of the Pleistocene megafauna and several genera of smaller mammals and birds. The event time-correlates with a large magnitude acidity spike found at 1708.65 m in the GISP2 Greenland ice record, which is associated with high NO^-3 ion concentrations and a rapid rise in ^10Be deposition rate, all of which are indicators of a sudden cosmic ray influx. The depletion of nitrate ion within this acidic ice layer suggests that the snowpack surface at that time was exposed to intense UV for a prolonged period which is consistent with a temporary destruction of the polar ozone layer by solar cosmic rays. The acidity event also coincides with a large magnitude, abrupt climatic excursion and is associated with elevated ammonium ion concentrations, an indicator of global fires.

    Below is a summary of the paper's principal findings:

    *The proposed super SPE is estimated to have been roughly 125 times more intense than the February 1956 SPE. On the assumption that its cosmic ray energy spectrum had a hardness comparable to the 1956 event, it is estimated to have produced a ground level radiation exposure ranging from 3 Sieverts (Sv) to over 6 Sv delivered over a two-day period. By comparison, LD-100 (lethal exposure) for most mammals is in the range of 3 to 8 Sv. Lethal dose for humans is 3.5 Sv.

    *Correlations made between the Cariaco Basin climate profile and the GISP2 Greenland ice core climate profile show that this candidate radiocarbon spurt correlates with an acidity spike present in the Greenland ice record at a depth of 1708.65 meters, and which is the largest acidity spike to occur during the Younger Dryas period. Also this spike is found to be flanked by two nitrate ion concentration peaks which are the highest of the Younger Dryas period. It is also spanned by a large increase in beryllium-10 concentration. All of these are good indicators for the occurrence of a solar proton event.

    *The acidity spike event is found to coincide with a nitrate ion minimum, which indicates that the nitrate ions were photolytically dissociated by exposure to intense UV radiation at the time of their deposition. This strongly suggests that the 12,837 years BP super SPE likely destroyed the polar ozone layer for a period of several years following its impact. This ozone hole may even have extended to mid latitudes allowing harmful UV radiation to penetrate through the Earth's atmosphere.

    *The Greenland ice record suggests that an abrupt climatic cooling occurred at the time of the 12,837 years BP super SPE acidity spike, which is an expected consequence of the generation of high concentrations of condensation nuclei in the stratosphere. The event is also found to be flanked by two very warm episodes separated from one another by about one solar cycle period. The warming following the SPE was one of the most pronounced Dansgaard/Oeschger climatic events of the entire Younger Dryas with polar temperatures reaching Allerod levels. High ammonium ion concentrations, occurring during each of these warm periods, indicate the occurrence of widespread wildfires. Hazards associated with these fires as well as the associated destruction of food supplies and habitats would have been a contributing factor in megafaunal termination.

    1. Yikes, I'll add that to the seemingly infinite list of things more worrisome than AGW.