Press release 14.10.2014

Nature Communications: Solar activity impacts polar ozone

Increase in greenhouse gases explains, to a large extent, the rise in the average temperature of the Earth. According to the research study published in Nature Communications today, the Sun affects middle atmosphere ozone with potential implications on smaller scale to regional, but not global, climate.
Photo: NASA

Mankind is responsible for the global warming of our climate by increasing the amount of greenhouse gases in the atmosphere. However, according results published today, fluctuations in the activity of the Sun impact middle atmosphere ozone, providing a potential link to regional scale climate variability. This climate variability is not a trend, like climate change, but rather year-to-year fluctuations following solar activity. "The detected ozone variation may in part help understand the alternation of local mild and cold winter seasons, as hints have been obtained in previous research that the ozone changes in the middle atmosphere may link as far as the surface of the Earth and affect, among other things, polar wind streams," Finnish Meteorological Institute researcher Dr Pekka Verronen reflects.

The research team was able to confirm, for the first time, the long-term implications of solar-driven electron impact on the upper middle atmosphere ozone. The results showed strong effects in the polar latitudes. The amount of ozone at 70-80 km altitude was found to vary more than 30 percent during a solar cycle, a period of approximately 11 years. The ozone variation between the extremes of the Sun's activity is so great that it is likely to impact the temperature balance of the atmosphere. These temperature changes can in turn have an effect on atmospheric winds.

Electrons from space: Auroras and ozone loss

According to the research study conducted by the Finnish Meteorological Institute, University of Otago and the British Antarctic Survey, the electrons, similar to those behind the aurora, cause significant solar cycle variation in the polar mesosphere ozone. The amount of ozone is smaller when more electrons enter the atmosphere. "These results are only the first step but an important one, allowing us to better understand the long-term impacts of this type of solar activity, and its role in regional climate variability," says Dr Monika Andersson who lead the study at Finnish Meteorological Institute.

The Earth's radiation belts are regions in near-Earth space that contain vast quantities of solar energetic electrons, trapped there by the Earth's magnetic field. During magnetic storms, which are solar wind-driven, the electrons accelerate to high speeds and enter the atmosphere in the polar regions. In the atmosphere, the electrons ionize gas molecules, leading to the production of ozone-depleting catalyst gases. Based on currently available satellite observations, electron precipitation may, during solar storms lasting a few days, reduce ozone in the upper atmosphere (60–80 km) as much as 90 per cent on a momentary basis.

The international group of researchers used ozone observations from an 11-year period from 2002 to 2012. The observations were make by three individual satellite instruments: GOMOS/Envisat (Global Ozone Monitoring by Occultation of Stars), SABER/TIMED (Sounding of the Atmosphere using Broadband Emission Radiometry) and MLS/Aura (Microwave Limb Sounder). In addition, electron measurements from MEPED/POES Medium-Energy Proton and Electron Detectors were used in the study.

The results were published in Nature Communications, 14th October 2014 issue. The research was largely funded by the Academy of Finland.

Additional information:

Monika Andersson, tel. +358 (0)50 380 2160,
Pekka Verronen, tel. +358 (0)29 539 4642,