We need to and are, doing much more work to explore these questions and Hoyt's simplistic statement about borehole data reflecting only temperature forcing simply shows a naive at best and dishonest at worst attitude to the many problems that afflict these , and all ,palaeodata. I for one still believe that we are seeing the manifestation of greenhouse warming but I know the evidence presented to date leves many questions still unanswered . I too believe that solar variabilty is a potential forcing factor that has likely contributed to the variability of 19th and 20th century observations . The extent of the effect surely requires much more model-based research. Simply correlating Hoyt's series against observations or reconstructed temperatures does not get us far. I also believe we have major uncertainty surrounding global or hemispheric estimates of centennial or millennial reconstructions , and real problems with spacial patterns on long timescales. Saying this does not make me an outlaw in the palaeo family - I hope! - just someone anxious to maintain our objectivity. We should all resist the attempts of those who try to push us into the pro or anti greenhouse camps. I think Hoyt's comments betray someone who is perhaps lacking the degree of objectivity I had previously thought him to have.
Save the world with internal combustion engines
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