The Guardian has an amazing series of articles about the Jones 1990 urbanization study that has been quoted by all subsequent IPCC reports as authoritative that urbanization has negligible effect on the historic temperature record. It is pretty clear that while denying the FOI requests and calling skeptics lazy and liars and irritants (etc.) they actually knew full well there were problems with the study. This is what they were saying publicly:

n American colleague, and frequent contributor to the leaked emails, Dr Mike Mann at Pennsylvania State University, advised him: “This crowd of charlatans … look for one little thing they can say is wrong, and thus generalise that the science is entirely compromised. The last thing you want to do is help them by feeding the fire. Best thing is to ignore them completely.” Another colleague, Kevin Trenberth at the National Centre for Atmospheric Research in Boulder, Colorado, urged a fightback. “The response should try to somehow label these guys and [sic] lazy and incompetent and unable to do the huge amount of work it takes to construct such a database.”

This is what they were saying privately:

Those concerns were most cogently expressed to Jones by his ex-boss, and former head of the CRU, Dr Tom Wigley. In August 2007, Wigley warned Jones by email: “It seems to me that Keenan has a valid point. The statements in the papers that he quotes seem to be incorrect statements, and that someone (W-C W at the very least) must have known at the time that they were incorrect.” Wigley was concerned partly because he had been director of the CRU when the original paper was published in 1990. As he told Jones later, in 2009: “The buck should eventually stop with me.” Wigley put to Jones the allegations made by the sceptics. “Wang had been claiming the existence of such exonerating documents for nearly a year, but he has not been able to produce them. Additionally, there was a report published in 1991 (with a second version in 1997) explicitly stating that no such documents exist.” …Wigley, in his May 2009 email to Jones, said of Wang: “I have always thought W-C W was a rather sloppy scientist. I would …not be surprised if he screwed up here … Were you taking W-C W on trust? Why, why, why did you and W-C W not simply say this right at the start? Perhaps it’s not too late.” There is no evidence of any doubts being raised over Wang’s previous work.

Interesting. Intriguingly, Jones did “penance” in some sense for this sloppy work by finding as much as a 1C per century urbanization bias in Chines temperature records in a later study.

Why it matters

The Guardian writes:

t is important to keep this in perspective, however. This dramatic revision of the estimated impact of urbanisation on temperatures in China does not change the global picture of temperature trends. There is plenty of evidence of global warming, not least from oceans far from urban influences.

This is correct. Further, it is absurd to deny the world has warmed over the last 150 years as the little ice age of the 17th and 18th centuries was one of the coldest periods in thousands of years, and thus it is totally natural that we have seen warming in recovery from these frigid times.

But here is what it is important to understand: The real debate between skeptics and alarmists is not over whether the Earth has warmed over the last century or whether CO2 from man contributes incrementally to warming. The real debate is over whether the climate’s sensitivity to CO2 is high or low. Skeptics like me argue for low sensitivity, on the order of 0.5-1.0C per doubling once all feedbacks are taken in to account. Alarmists argue for numbers 3C and higher.

The problem alarmists have is that it is very, very difficult to reconcile past warming to high-sensitivity forecasts. It takes a lot of mathematical contortions, from time-delays to cooling aerosols to ignoring ocean cycles and natural recovery from the little ice age to make the numbers reconcile. Halving the actual historic warming by attributing the other half to measurement biases makes it even, uh, more impossible to reconcile high sensitivity models to actual history.