14.10.2014 8:59

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.

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,
[email protected]

Pekka Verronen, tel. +358 (0)29 539 4642,
[email protected]