Watts up with GCRs

Posted by John Byatt (swat team)

Today Anthony watts posts what he describes as a game changing admission from the IPCC AR5.
Lead story from the Second Order Draft: strong evidence for solar forcing beyond TSI now acknowledged by IPCC
Compared to the First Order Draft, the SOD now adds the following sentence, indicated in bold (page 7-43, lines 1-5, emphasis added):
Many empirical relationships have been reported between GCR or cosmogenic isotope archives and some aspects of the climate system (e.g., Bond et al., 2001; Dengel et al., 2009; Ram and Stolz, 1999). The forcing from changes in total solar irradiance alone does not seem to account for these observations, implying the existence of an amplifying mechanism such as the hypothesized GCR-cloud link. We focus here on observed relationships between GCR and aerosol and cloud properties.

First Point Anthony
:
Its only a “game changing admission” if you ignore the following four paragraphs. e.g.:
.
7.4.5.3 Synthesis
Although there is some evidence that ionization from cosmic rays may enhance aerosol nucleation in the free troposphere, there is medium evidence and high agreement that the cosmic ray-ionization mechanism is too weak to influence global concentrations of CCN or their change over the last century or during a solar cycle in any climatically significant way. The lack of trend in the cosmic ray intensity over the last 50 years (Agee et al., 2012; McCracken and Beer, 2007) provides another strong arguement against the hypothesis of a major contribution of cosmic rays to ongoing climate change.”

second point Anthony

You do :realize that amplifying a negative number just gives you a bigger negative number, right? In other words, you’re arguing for bigger solar cooling since 1980.

Third and final point Anthony
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 any

Acknowledgements . Dana, Zeke and Gavin

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