The Svensmark theory is that variations in the Sun’s electromagnetic behaviour leads to varaiations of the cosmic ray flux reaching earth which in turn impacts cloud formation on earth and that connects to global warming or cooling. A more active sun leads to fewer cosmic rays which gives fewer clouds and more warming on earth.
The CLOUD experiments at CERN have shown that cosmic rays can in fact lead to cloud formation. Now Svensmark and his colleagues have published further evidence from the SKY2 experiments which confirm the connection.
H. Svensmark, Martin B. Enghoff and Jens Olaf Pepke Pedersen, Response of cloud condensation nuclei (>50 nm) to changes in ion-nucleation, Physics Letters A 377 (2013) 2343–2347,
Full paper is available here: svensmark et al 2013
Abstract: In experiments where ultraviolet light produces aerosols from trace amounts of ozone, sulfur dioxide, and water vapor, the relative increase in aerosols produced by ionization by gamma sources is constant from nucleation to diameters larger than 50 nm, appropriate for cloud condensation nuclei. This result contradicts both ion-free control experiments and also theoretical models that predict a decline in the response at larger particle sizes. This unpredicted experimental finding points to a process not included in current theoretical models, possibly an ion-induced formation of sulfuric acid in small clusters.
The Technical University of Denmark has issued a Press Release:
Danish experiment suggests unexpected magic by cosmic rays in cloud formation
Researchers in the Technical University of Denmark (DTU) are hard on the trail of a previously unknown molecular process that helps commonplace clouds to form. Tests in a large and highly instrumented reaction chamber in Lyngby, called SKY2, demonstrate that an existing chemical theory is misleading.
Back in 1996 Danish physicists suggested that cosmic rays, energetic particles from space, are important in the formation of clouds. Since then, experiments in Copenhagen and elsewhere have demonstrated that cosmic rays actually help small clusters of molecules to form. But the cosmic-ray/cloud hypothesis seemed to run into a problem when numerical simulations of the prevailing chemical theory pointed to a failure of growth.
Fortunately the chemical theory could also be tested experimentally, as was done with SKY2, the chamber of which holds 8 cubic metres of air and traces of other gases. One series of experiments confirmed the unfavourable prediction that the new clusters would fail to grow sufficiently to be influential for clouds. But another series of experiments, using ionizing rays, gave a very different result, as can be seen in the accompanying figure.
The reactions going on in the air over our heads mostly involve commonplace molecules. During daylight hours, ultraviolet rays from the Sun encourage sulphur dioxide to react with ozone and water vapour to make sulphuric acid. The clusters of interest for cloud formation consist mainly of sulphuric acid and water molecules clumped together in very large numbers and they grow with the aid of other molecules.
Atmospheric chemists have assumed that when the clusters have gathered up the day’s yield, they stop growing, and only a small fraction can become large enough to be meteorologically relevant. Yet in the SKY2 experiment, with natural cosmic rays and gamma-rays keeping the air in the chamber ionized, no such interruption occurs. This result suggests that another chemical process seems to be supplying the extra molecules needed to keep the clusters growing.
“The result boosts our theory that cosmic rays coming from the Galaxy are directly involved in the Earth’s weather and climate,” says Henrik Svensmark, lead author of the new report. “In experiments over many years, we have shown that ionizing rays help to form small molecular clusters. Critics have argued that the clusters cannot grow large enough to affect cloud formation significantly. But our current research, of which the reported SKY2 experiment forms just one part, contradicts their conventional view. Now we want to close in on the details of the unexpected chemistry occurring in the air, at the end of the long journey that brought the cosmic rays here from exploded stars.”
Simulating what could happen in the atmosphere, the DTU’s SKY2 experiment shows molecular clusters (red dots) failing to grow enough to provide significant numbers of “cloud condensation nuclei” (CCN) of more than 50 nanometres in diameter. This is what existing theories predict. But when the air in the chamber is exposed to ionizing rays that simulate the effect of cosmic rays, the clusters (blue dots) grow much more vigorously to the sizes suitable for helping water droplets to form and make clouds. (A nanometre is a millionth of a millimetre.)