Berkeley earthquake called off

In a talk at AGU last Fall, Naomi Oreskes criticized the climate science community for being reluctant to take credit for their many successful predictions, so here we are shouting it from the rooftops: The warming trend is something that climate physicists saw coming many decades before it was observed. The reason for interest in the details of the observed trend is to get a better idea of the things we don’t know the magnitude of (e.g. cloud feedbacks), not as a test of the basic theory. If we didn’t know about the CO2-climate connection from physics, then no observation of a warming trend, however accurate, would by itself tell us that anthropogenic global warming is “real,” or (more importantly) that it is going to persist and probably increase.

Muller’s other comments do very little to shed light on climate change, and continue to consist largely of putting down the work of others. “For Richard Muller,” writes Richard Black, “this free circulation also marks a return to how science should be done,” the clear insinuation being that CRU, GISS, and NOAA had all been doing something else. Whatever that “something else” is supposed to be completely eludes us, given that these groups all along have been publishing results in the peer-reviewed literature using methods that proved easy to reproduce using easily available data (and in the GISTEMP case, complete code). In one sense, though, we do agree with Muller’s quote: nobody has stolen his private emails and spun them out of context to make his research look bad.

Laudably, Muller’s group have submitted their research to peer-reviewed journals, and the submitted drafts are available on their website. Amidst a number of verifications of already well-established results on the fidelity of the surface station trends, they also claim to have discovered something new. In their paper Decadal Variations in the Global Atmospheric Land Temperatures, they find that the largest contributor to global average temperature variability on short (2-5 year) timescales in not the El Nino-Southern Oscillation (ENSO) (as everyone else believes), but is actually the Atlantic Multidecadal Oscillation (AMO). This is pretty esoteric stuff, but it would actually be quite interesting if it were true — though we hasten to add that even if true it would have no significant bearing on the interpretation of long term temperature trends. Before anyone gets too excited though, they should take note that the basis for this argument is that the correlation between the global average temperature and a time series that represents the AMO is higher than for one that represents ENSO. But what time series are used? According to the submitted paper, they “fit each record [ENSO and AMO times series] separately to 5th order polynomials using a linear least-­squares regression; we subtracted the respective fits… This procedure effectively removes slow changes such as global warming and the ~70 year cycle of the AMO, and gives each record zero mean.” Beyond the obvious fact that if one removes the low frequencies, than we’re really not talking about the AMO anymore (the “M” in “AMO” stands for “Multidecadal”), one has to be rather cautious about this sort of data analysis. Without getting into the nitty-gritty technical details here, suffice it to say that Muller & Co are proposing a new understanding of global temperature variability, and their statistical approach is — at the very least — poorly described. There is a large literature on how to do this sort of thing, not to mention previous work on the AMO and its relationship to global temperatures (e.g. this or Mann and Park (1999) (pdf), among many others), which the Berkeley group does not cite.

Overall, we are underwhelmed by the quality of Berkeley effort so far — with the exception of the efforts made by Robert Rohde on the dataset agglomeration and the statistical approach. And we remain greatly disappointed by Muller’s public communications (e.g. his WSJ op-ed) which appear far more focused on raising his profile than enlightening the public about the state of the science.

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