Update: The gross divergence in October data reported below between the various metrics is explained by an error, as reported at the bottom. The basic premise of the post, that real scientific work should go into challenging these measurement approaches and choosing the best data set, remains.
The October global temperature data highlights for me that it is time for scientists to quit wasting time screwing around with questions of whether global warming will cause more kidney stones, and address an absolutely fundamental question: Just what is the freaking temperature?
Currently we are approaching the prospect of spending hundreds of billions of dollars, or more, to combat global warming, and we don't even know its magnitude or real trend, because the major temperature indices we possess are giving very different readings. To oversimplify a bit, there are two competing methodologies that are giving two different answers. NASA's GISS uses a melding of surface thermometer readings around the world to create a global temperature anomaly. And the UAH uses satellites to measure temperatures of the lower or near-surface troposhere. Each thinks it has the better methodology (with, oddly, NASA fighting against the space technology). But they are giving us different answers.
For October, the GISS metric is showing the hottest October on record, nearly 0.8C hotter than it was 40 years ago in 1978 (from here).
However, the satellites are showing no such thing, showing a much cooler October, and a far smaller warming trend over the last 40 years (from here)
So which is right? Well, the situation is not helped by the fact that the GISS metric is run by James Hansen, considered by skeptics to be a leading alarmist, and the UAH is run by John Christy, considered by alarmists to be an arch-skeptic. The media generally uses the GISS data, so expect stories in the next day or so trumpeting "Hottest October Ever," which the Obama administration will wave around as justification for massive economic interventions. But by satellite it will only be the 10th or so hottest in the last 30, and probably cooler than most other readings this century.
It is really a very frustrating situation. It is as if two groups in the 17th century had two very different sets of observations of planetary motions that resulted in two different theories of gravity,
Its amazing to me the scientific community doesn't try to take this on. If the NOAA wanted to do something useful other than just creating disaster pr0n, it could actually have a conference on the topic and even some critical reviews of each approach. Why not have Christy and Hansen take turns in front of the group and defend their approaches like a doctoral thesis? Nothing can replace surface temperature measurement before 1978, because we do not have satellite data before then. But even so, discussion of earlier periods is important given issues with NOAA and GISS manual adjustments to the data.
Though I favor the UAH satellite data (and prefer a UAH - Hadley CRUT3 splice for a longer time history), I'll try to present as neutrally as possible the pros and cons of each approach.