Solar flares: a study evokes a notable effect on clouds and the climate

According to recent work by researchers from the Technical University of Denmark (DTU) and the Hebrew University of Jerusalem, solar flares have a substantial influence on clouds and the Earth's radiation budget. The results were published Oct. 11 in the journal Scientific Reports.

The hypothesis worked by the scientists is not new in itself. Indeed, when solar activity increases or decreases, the strength of the solar wind does the same and the amount of galactic cosmic rays reaching the Earth therefore also varies. However, the protons and other helium nuclei that make up this radiation act like small germs facilitating the growth of water droplets forming clouds. It is in this context that the CLOUD experience was born.

Thus, in theory, we can expect to observe a correlation between fluctuations in the Earth's cloud cover and the variability of our star. Moreover, as clouds in the liquid phase are very good reflectors of solar radiation, a relationship should also exist between the global temperature and the fluctuations of the latter. While the significance of the hypothesis remains controversial and lacks observational support, research on the issue continues.

What influence do solar flares have on the Earth's radiation balance?

In their study, the researchers now announce that they have found strong evidence in satellite data acquired by NASA's Clouds and the Earth's Radiant Energy System (CERES) program. More specifically, by studying five solar bursts, they observed that during the five to seven days following the eruption and the consecutive minimum in galactic cosmic rays, the Earth absorbed between 1 and 2 W/m² more. The reason ? A decrease in low clouds in ocean areas with little pollution particles.

“The solar effects studied are too short-lived to have a lasting effect on the climate. However, they support the mechanism between clouds and cosmic rays, which operates more slowly on longer time scales. The hope is that this result will help to rethink the long-term effect of solar activity and cosmic rays on the climate," says Henrik Svensmark, lead author of the paper and quite a controversial figure in the science community. climate.

"We now have simultaneous observations of decreases in cosmic rays, aerosols, clouds and energy balance, which is quite amazing," adds Nir Shaviv, one of the co-authors involved in the work.