A recent PhD thesis from James Cook University has been receiving a reasonable amount of attention on sites that either dispute anthropogenic global warming (AGW), or its significance (I won’t link to them, but you can probably find them if you want). The PhD is by someone called John McLean. His PhD supervisor was initially Bob Carter, who died a couple of years ago (Stoat’s post about his death caused a bit of a furore). After Bob Carter’s death, he was then supervised by Peter Ridd, who was fired earlier this year by James Cook University.
If you really want to read the thesis, you can download it here. It has two main parts, one of which considers problems with the HadCRUT4 data, and the other considers alternative causes for the warming, and that bleaching on the Great Barrier Reef has happened before. It’s all very amateurishly written; it’s more like blog science, than something that could be submitted for a PhD.
The discussion of problems with the HadCRUT4 data is very odd. It’s well known that HadCRUT4 suffers from coverage bias. However, there are a number of other global temperature datasets that account for this issue and produce results that are broadly consistent with the HadCRUT4 data (HadCRUT4’s coverage bias actually leads to it showing slightly less warming than those datasets that do account for this). It’s possible that there are problems with some of the actual data, but there is lots of data, so a problem with a small fraction of this data is almost certainly of negligible significance. It seems highly unlikely that those who work with these datasets haven’t checked to see how the results might be impacted by potential data issues. You can also sample subsets of the full dataset. Doing so produces results that are consistent with the full dataset.
The next part of the thesis suggests that the observed warming is a consequence of a combination of ENSO events and changes in cloud cover. This appears to be based on a paper he published in 2009 and one he published in 2014 (I had a link to this, but it was giving warnings when some tried to access it, so I’ve removed it). Turns out that I’ve already discussed the latter. Essentially, it ignores that clouds are a feedback not a forcing, so it’s just nonsense. I don’t think anyone ever published a response, but it seems to have been mostly ignored.
There was, however, a response published to the first paper which says
The suggestion in their conclusions that ENSO may be a major contributor to recent trends in global temperature is not supported by their analysis or any physical theory presented in their paper, especially as the analysis method itself eliminates the influence of trends on the purported correlations.
Essentially, the analysis removed the trend, so couldn’t say anything about what might be causing the long-term warming. As far as I can see, the thesis makes no mention of this response.
I’ve probably already wasted enough of my time discussing this thesis, so will stop here. I don’t know how theses are examined at James Cook university, but it would be quite interesting to know who the examiners were. I’ll finish by posting a Media Matters video that discusses McLean’s work.