appeared in nature. In it, Kanipe explains the solar → cosmic-ray → climate connection, and the planned CLOUD experiment in CERN, expected to finally resolve the issue. Given that my work is mentioned in the review, I through I should mention a few relevant points.
- Other galactic/climate mechanisms: Kanipe mentions the work of Shapely, in 1921, who speculated that passing through a dense molecular cloud would make earth colder. Other ideas include accretion of interstellar dust, which would block sun light, periodic perturbation of the Oort cloud and subsequent atmospheric accretion of disintegrated comets, as well as other mechanisms. The problem with them is that they simply don't work. They require extreme parameters which current day data does not support. In particular, you don't see evidence for very large variations in the accreted interplanetary dust (e.g., through geochemical records in sea floor sediments), or clear variations in the cratering record on Earth. The only mechanism which is in fact supported by data, is the spiral arms → cosmic-rays → climate scenario.
Kanipe mentions several critiques raised following the Shaviv & Veizer (2003) paper. Most of the criticism was of course politically motivated. Here is a full list of the scientific (and pseudo-scientific) attacks:
- Critique by Rahmstorf et al.: No point to dwell on that for too long. Here we show why their first attack is baseless, and why their rebuttal attack only demonstrates their ignorance in statistics.
- Critique by Royer et al.: It is funny that the only critique which may contain real science was not mentioned! In it, it was argued that atmospheric CO2 offsets the δ18O paleoclimate data, a point which may have merit to it. Alas, it doesn't change the main conclusion of Shaviv & Veizer (2003), namely, that cosmic rays are the primary climate driver over geological time scales (and not CO2), and that Earth's climate sensitivity is on the low side (roughly that of a black body Earth, and not much more as often suggested). More about it here.
- Critique by Jahnke: Last year, a critique by Knud Jahnke appeared on the astro-ph preprint arXiv, in which the meteoritic-based reconstruction of the cosmic ray flux was heavily criticized. Given that it didn't receive attention (and the fact that I was a somewhat lazy to write a reply) I thought I should not waste too much of my precious time on it. However, just this week it received prime real-estate on nature, and mentioned on the ever popular Motl's blog, leaving me with no real choice but to explain the reasons why this criticism is simply baseless. In fact, using a better statistical analysis of the meteoritic data, one which also quantifies the periodic signal in the errors, I demonstrate that a 143 Myr periodicity exists in the meteoritic data with high statistical certainty, while the null hypothesis can be ruled at least at the 99.8% level. Incidentally, if you're wondering why an astrophysicist would try to attack me in such a way, look at his previous affiliation. In fact, he wrote me himself that he was approached by my dear friend Rahmstorf.