Yesterday, Dutch "astrobiologist" Henrik Svensmark published a groundbreaking new paper in the journal of the Royal Astronomical Society in which he lays out the case that the Earth's climate and biology is driven primarily by supernovae in our galactic neighborhood, plate tectonics and . . . nothing else:
Observations of open star clusters in the solar neighbourhood are used to calculate local supernova (SN) rates for the past 510 Myr. Peaks in the SN rates match passages of the Sun through periods of locally increased cluster formation which could be caused by spiral arms of the Galaxy. A statistical analysis indicates that the Solar system has experienced many large short-term increases in the flux of Galactic cosmic rays (GCR) from nearby SNe. The hypothesis that a high GCR flux should coincide with cold conditions on the Earth is borne out by comparing the general geological record of climate over the past 510 Myr with the fluctuating local SN rates. Surprisingly, a simple combination of tectonics (long-term changes in sea level) and astrophysical activity (SN rates) largely accounts for the observed variations in marine biodiversity over the past 510 Myr. An inverse correspondence between SN rates and carbon dioxide (CO2) levels is discussed in terms of a possible drawdown of CO2 by enhanced bio-productivity in oceans that are better fertilized in cold conditions – a hypothesis that is not contradicted by data on the relative abundance of the heavy isotope of carbon, 13C.
. . .
[I]t was shown that multiple SN sources generate a highly fluctuating GCR signal and that the nearest SNe (closer than ≈300 pc) produce clear spikes in the GCR flux. Those provided the first link to the terrestrial climate noted here, with previously unexplained short-lived falls in sea level accounted for by sudden but brief glaciations caused by the nearest SNe, as in Fig. 16. The match of longer term climate to SN rates, seen in Figs 17 and 18, leaves room only for relatively small or brief climatic influences of all the tectonic, volcanic and other processes discussed in this connection. If the dominant role of the Galaxy in the terrestrial environment is further validated by ongoing studies, cosmic and terrestrial, it promises to simplify Phanerozoic climatology.
As for the palaeobiology, remarkable connections to the long-term histories of life and the carbon cycle have shown up unbidden (Figs 20, 21 and 22). Biodiversity, CO2 and δ13C all appear so highly sensitive to SNe in our Galactic neighbourhood that the biosphere seems to contain a reflection of the sky.
http://onlinelibrary.wiley.com/...
Hopefully, that excerpt wasn't too technically dense for folks. Maybe some of the science-minded Kossacks will chime in to help clarify things. From what I've been able glean from the article so far, the layman's version is that the "swirls" that we have all seen in pictures of the Milky Way galaxy represent "stormy" areas of the galaxy where there are a lot of supernovae (exploding stars) going off. When the Solar System that we inhabit passes through those stormy areas in the galaxy, the bombardment of cosmic rays seeds clouds in our own atmosphere, causing the Earth to cool dramatically (i.e. glaciation). This has all sorts of knock on effects in terms of sea levels, biodiversity, CO2, ultimately, life itself. If his theory stands up to further testing and review over time, it will represent a pretty dramatic rethinking of nearly everything that we think we know about climate and life on Earth.