Retorts

CO₂ Continues

I've just managed to look up the reference in Nature given by Dr de Freitas in response to my request for evidence of rises in greenhouse gas levels above those at present. I suggested that data from 100 million years ago would not be particularly useful. So Dr de Freitas provides a reference covering the Cretaceous. Only some 60 million years ago, instead, whereas I suggested that back 200,000 years would suffice. I would not mind if he had explained that it was 60 million-year-old data, but anyone reading my comment and his response would imagine that he was producing data for some period in the last 200,000 years.

As the authors of the paper mention, boundary conditions during the Cretaceous may have been very different from today. Dr de Freitas takes great care to avoid comment on the correlation between greenhouse gas levels and global temperatures that is indicated from work on the Vostok and other ice cores that cover more recent times.

P. Waring, Wainuiomata