Benny Peiser last week sent ’round a note on his CCNet list about a study just published by Hai Xu and colleagues from the Chinese Academy of Sciences on the solar-climate link. “New study – Solar Activity is Primary Driving Force of Climate Change” was Benny’s subject line.
The paper wasn’t on line for free, so it took me a few days to swing by the university library and pick up a copy. It was worth it – a very interesting paper, suggesting some tantalizing long-term climate-solar links. But it doesn’t say what Benny and the other climate skeptics who have been so approvingly linking to it seem to think it says.
Xu and his colleagues used oxygen isotopes in peat bogs as a temperature proxy for the last 6,000 years at two sites in China. They compared this with models of solar output over the last 6,000 years and found that “temperature events … correspond well to solar perterubations during the last 6,000 years.” The problem, when I picked up the paper, is that the time scale did not appear fine enough to tease out the temperature increase of the last 100 years, and Xu et al., in the paper’s text, were silent on the question. So I wrote him and asked if he felt their work supported a solar explanation for the warming of the last 100 years. His response:
As you have noticed, because the time resolution of peat deposition (in our study) is not high enough to discuss the dynamic of temperatures on interannual/interdecadal scales, we did not address the cause of the ongoing global warming in the past century.
The paper is “Temperature responses to quasi-100-yr solar variability during the past 6000 years based on delta 18 O of peat cellulose in Hongyuan, eastern Qinghai-Tibet plateau, China,” by Hai Xua, Yetang Hong, Qinghua Lin, Yongxuan Zhu, Bing Hong and Hongbo Jiang, Palaeogeography, Palaeoclimatology, Palaeoecology, Volume 230, Issues 1-2 , 17 January 2006, Pages 155-164