Solar Magnetic Activity Linked to Climate Via Cosmic Rays

A new paper published in Journal of Geophysical Research links the solar magnetic field to Earth's climate via cosmic rays.  For years, a strong correlation between high solar magnetic activity (i.e. sunspots) and higher global temperatures has been observed, but given the very small increase in total solar irradiation involved, the causative link has been obscure. It has been hypothesized that when the solar magnetic field is high, it shields the Earth more effectively against cosmic rays.  Cosmic rays striking the Earth's atmosphere create ions which act as seeds for clouds.  Thus high solar activity leads to less cloud formation and greater penetration of the Sun's light and heat to the surface and a cooler climate.

For the first time, this paper shows a solid link between the cosmic rays and formation of aerosols that lead to cloud formation:

With the new results just published in the recognised journal Geophysical Research Letters, scientists have succeeded for the first time in directly observing that the electrically charged particles coming from space and hitting the atmosphere at high speed contribute to creating the aerosols that are the prerequisites for cloud formation.

The more cloud cover occurring around the world, the lower the global temperature – and vice versa when there are fewer clouds. The number of particles from space vary from year to year – partly controlled by solar activity. An understanding of the impact of cosmic particles – consisting of electrons, protons and other charged particles – on cloud formation and thereby the number of clouds, is therefore very important as regards climate models.

With the researchers’ new knowledge, it is now clear that here is a correlation between the Sun’s varying activity and the formation of aerosols in the Earth’s atmosphere. Initially, the researchers have demonstrated that there is a correlation, and they will therefore now carry out systematic measurements and modellings to determine how important it is to the climate.

In recent years the Sun has gone through a period of high solar activity unprecedented during our ability to monitor sunspots, a period during which global temperatures soared.  More recently, the sun appears to be slipping into a period of relative quiescence, and global temperatures have remained approximately constant for the past 10 years or so.