Just imagine they’re saying “intragalactic”
While we’re on the topic, one of the proposed mechanisms of the alleged cosmic ray-climate connection, championed by Shaviv and Svensmark among others, is the supposed connection between the solar system’s path through our galaxy’s spiral arms and past climate changes. Overholt et al. examine the evidence in a paper entitled Testing the link between terrestrial climate change and galactic spiral arm transit and surprise surprise, find it wanting [abstract, all emphases in this post mine]:
We re-examine past suggestions of a close link between terrestrial climate change and the Sun’s transit of spiral arms in its path through the Milky Way galaxy. These links produced concrete fits, deriving the unknown spiral pattern speed from terrestrial climate correlations. We test these fits against new data on spiral structure based on CO data that do not make simplifying assumptions about symmetry and circular rotation. If we compare the times of these transits with changes in the climate of Earth, the claimed correlations not only disappear, but we also find that they cannot be resurrected for any reasonable pattern speed.
And their conclusion:
Although previous work found a correlation between the 140 Myr climate cycle on the Earth and the intersection with spiral arms (Shaviv 2003, Shaviv & Veizer 2003; Svensmark 2006), with new data on the structure of the Galaxy, this correlation disappears. We have used a new model of the large-scale gas distribution in the Galaxy, using a velocity deconvolution of CO and Hi line data based on self-consistently computed, non-circular gas flows in the inner Galaxy (Bissantz et al. 2003; Pohl et al. 2008; Englmaier et al. 2009). In contrast to many published studies, this model does not force azimuthal symmetry into the spiral-arm structure. The asymmetry of the arms near the solar circle erases any correlation to the 140 Myr cycle and any periodic trend less than the orbital period of our solar system relative to the spiral pattern as a whole. This would be greater than 500 Myr for the previously fit pattern speed. Even if we allow the pattern speed to vary, it will not be less than the orbital period of the Sun, which is still longer than the 140 Myr cycle in question. The asymmetry of the new galactic picture could create a correlation between the spiral-arm crossings and any non-periodic event by varying the pattern speed. We conclude that, based on these new data, there is no evidence to suggest any correlation between the transit of our solar system through the spiral arms of our Galaxy and the terrestrial climate.