Been working on this for a while, and got the final piece in an interview with Gavin Schmidt at the American Geophysical Union convention early this month. (see that whole – brief – interview on this page)
The “cosmic ray – climate” connection is a perrenial favorite on the denial circuit. It sounds cool, and there is some effect at the tiny level, too tiny to matter.
As far as effects on climate – it’s probably more likely that cosmic rays will make you super-strong, invisible, or really, really stretchy – than it is that they have a ruling effect on climate.
See full Gavin Schmidt interview, and Potholer’s Useful take below…
Gavin’s Realclimate post on what’s useful and what’s not in the research.
We were clear in the 2006 post that establishing a significant GCR/cloud/climate link would require the following steps (given that we have known that ionisation plays a role in nucleation for decades). One would need to demonstrate:
- … that increased nucleation gives rise to increased numbers of (much larger) cloud condensation nuclei (CCN)
- … and that even in the presence of other CCN, ionisation changes can make a noticeable difference to total CCN
- … and even if there were more CCN, you would need to show that this actually changed cloud properties significantly,
- … and that given that change in cloud properties, you would need to show that it had a significant effect on radiative forcing.
Of course, to show that cosmic rays were actually responsible for some part of the recent warming, you would need to show that there was actually a decreasing trend in cosmic rays over recent decades – which is tricky, because there hasn’t been (see the figure).
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