The Galactic Cosmic Ray (GCR) hypothesis is a "skeptic" argument that global warming is caused by periods of high solar activity when strong solar magnetic fields protect the Earth from GCRs. Some hypothesize that GCRs seed clouds and therefore fewer of them lead to less reflective clouds and more global warming, so strong solar activity with low GCR counts should correlate with increasing global temperature. This graphic debunks that myth without even needing to address the questionable hypothesis, by simply looking at the measured relationship between global temperature and GCR counts. Shown are annual average GCR counts per minute (blue, left axis) from the Neutron Monitor Database, along with the annual average global surface temperature (red, right axis) from NOAA NCDC, both with second order polynomial fits. In recent decades when global temperature has been increasing, GCR counts have also increased (note inverted Cosmic Ray scale). Higher GCR counts should correspond to more reflective clouds and therefore global cooling rather than the observed global warming, so GCRs cannot be responsible for the observed temperature increase (also see this graphic). Similarly, direct solar activity isn't causing global warming either.
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