Cosmic rays, clouds and climate

I much enjoyed Henr ik Svensmark’s contribution Cosmic Rays, Clouds and Climate in number 2 of volume 46. Indeed, we desperately try to quantify manmade climate changes, without understanding much larger climate changes in our past, not manmade, with 'ice ages', and possibly also with 'desert ages'. In other words, we do not yet fully understand all the different heating and cooling mechanisms of our planet. Svensmark mentions heating by infalling 'cosmic rays' and 'gamma-rays', from both our Sun and our Galaxy. (The cosmic-ray energy spectrum extends from thermal energies, of order eV/particle, up to extreme values of 1020.5 eV, with its dominant share below 1GeV). He also mentions observed fluctuations thereof, on timescales between hours, and hundreds of Megayears. Ideally, we should like to know the power spectra of their fluctuations, between years and Megayears, and the precise screening mechanisms of our atmosphere against them, via aerosols and clouds. Svensmark mentions 'Forbush decreases', during hours, and oceans as calorimeters, on timescales of kyr, via varying isotopic-rate distributions, and measured (varying) supernova rates. So which of all the aforementioned inputs into our terrestrial temperature balance are the dominant ones? Starlight, supernova explosions, and/or active galactic nuclei and their twin-jets? I have never seen a curve like Svensmark’s Fig.2 drawn for all the above inputs, on timescales of yrs to kyrs. It could be useful to try and draw such curves. A problem for this may be our as yet poor understanding. For instance, mainstream knowledge talks of Galactic rays and cosmic rays, meaning that the highest-energy CRs came from beyond our Galaxy – an energetically unfeasible task, among others because of propagation losses – or of their shock-wave acceleration in SN remnants – a violation of the Second Law (cf. Physikalische Mythen auf dem Pruefstand by W. Kundt & O. Marggraf, Springer, 2014). Many of our astrophysical insights are as yet preliminary, because they are untested. So there remains a lot to be explored by the next generation. n