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“Looking at a single, noisy 10-year period is cherry picking.”
~Benjamin Santer
Land surface temperatures are depicted in this NASA Earth Observatory map. Click on the image for more information.
By Summit Voice
SUMMIT COUNTY — Scientists with Lawrence Livermore National Laboratory directly addressed the issue of data cherry picking in a recent paper, suggesting that it takes at least 17 years worth of temperature records to separate human-caused global warming from the “noise” of purely natural climate fluctuations.
To address criticism of the reliability of thermometer records of surface warming, the scientists analyzed satellite measurements of the temperature of the lower troposphere (the region of the atmosphere from the surface to roughly five miles above) and saw a clear signal of human-induced warming of the planet.
Satellite measurements of atmospheric temperature are made with microwave radiometers, and are completely independent of surface thermometer measurements. The satellite data indicate that the lower troposphere has warmed by roughly 0.9 degrees Fahrenheit since the beginning of satellite temperature records in 1979. This increase is entirely consistent with the warming of Earth’s surface estimated from thermometer records.
Recently, a number of global warming critics have focused attention on the behavior of Earth’s temperature since 1998. They have argued that there has been little or no warming over the last 10 to 12 years, and that computer models of the climate system are not capable of simulating such short “hiatus periods” when models are run with human-caused changes in greenhouse gases.
“Looking at a single, noisy 10-year period is cherry picking, and does not provide reliable information about the presence or absence of human effects on climate,” said Benjamin Santer, a climate scientist and lead author on an article in the Nov. 17 online edition of the Journal of Geophysical Research (Atmospheres).
Many scientific studies have identified a human “fingerprint” in observations of surface and lower tropospheric temperature changes. These detection and attribution studies look at long, multi-decade observational temperature records. Shorter periods generally have small signal to noise ratios, making it difficult to identify an anthropogenic signal with high statistical confidence, Santer said.
“In fingerprinting, we analyze longer, multi-decadal temperature records, and we beat down the large year-to-year temperature variability caused by purely natural phenomena (like El Niños and La Niñas). This makes it easier to identify a slowly-emerging signal arising from gradual, human-caused changes in atmospheric levels of greenhouse gases,” Santer said.
The research shows that climate models can and do simulate short, 10- to 12-year “hiatus periods” with minimal warming, even when the models are run with historical increases in greenhouse gases and sulfate aerosol particles. They find that tropospheric temperature records must be at least 17 years long to discriminate between internal climate noise and the signal of human-caused changes in the chemical composition of the atmosphere.
“One individual short-term trend doesn’t tell you much about long-term climate change,” Santer said. “A single decade of observational temperature data is inadequate for identifying a slowly evolving human-caused warming signal. In both the satellite observations and in computer models, short, 10-year tropospheric temperature trends are strongly influenced by the large noise of year-to-year climate variability.”
The research team is made up of Santer and Livermore colleagues Charles Doutriaux, Peter Caldwell, Peter Gleckler, Detelina Ivanova, and Karl Taylor, and includes collaborators from Remote Sensing Systems, the National Center for Atmospheric Research, the University of Colorado, the Canadian Centre for Climate Modeling and Analysis, the National Oceanic and Atmospheric Administration, the U.K. Meteorology Office Hadley Centre, and Lawrence Berkeley National Laboratory.
Filed under: climate and weather, El Niño, Environment, global warming, La Niña, Summit County news Tagged: | Benjamin D. Santer, climate, global warming, land surface temperatures, Lawrence Livermore National Laboratory, National Center for Atmospheric Research
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Cherry picking, should be left to the orchard, not the data to prove a point. But, as with all subjects, that pile evidence against a given theory, there comes a time to let the ego go, or in this case, deniability. Of course, for some, that doesn’t seem possible, for perhaps to do so, would also end the financial backing from sources that profit from said position. Food for thought, on a Saturday morning.
Have these “researchers” mentioned about oscillation that may be the factor?
The climate system is vast (includes the “ocean”) and many factors are in ploy here.
NCARs head, Kevin Trenberth wrote in October 2009 – in a climategate email – that the pause in warming was a “travesty” because “we [climate scientists] can’t explain it.”
Now comes along career climate modeler (actually, an applied mathematician – my college roommate became one at MIT after his doctorate at the University of Minnesota), Ben Santer, to explain these inconvenient facts all away. Thus, we find the goal posts suddenly moved.
What will Santer say when 2013-14 come along and 1998s record high El Nino year isn’t surpassed? I bet Santer’s goal posts will move AGAIN!
Hard data and facts are so inconvenient to a theory that MUST be true, like the idea that CO2 is the main climate control knob. Too many careers ride on the theory’s “truth,” not to mention the $78 billion already “invested.”
But CO2 levels have increased about 5%, while temps have not climbed according to satellites with REAL global coverage. THAT’S really inconvenient.
Thus, the goal posts HAVE to be uprooted and moved again.
I’m wondering how they came up with the 17-year figure. That seems somewhat random, but I’m not a mathematician.
But nobody has ever claimed that, just because CO2 concentrations are increasing at 5 percent per year, that temps will go up at exactly the same rate. We all know the climate system is more complicated than that.
You call it moving the goalposts, I see genuine effort to try and explain and understand the differences between climate models and observational daya.
As for your other comment, I’m not even going to go there. If you have links to some credible peer-reviewed research suggesting that the Earth’s surface and atmosphere are NOT getting warmer, please send them to me and I’m happy to report on them. I’m not posting links to cherry-picked data, charts and graphs that are designed only to confuse and mislead.
Trenberth said nothing of the sort. Why lie when it’s a matter of record what he said?
He was bemoaning the then lack of instruments to measure deeper ocean temperatures. That has now been remedied and we now know that the oceans are warming at depth.
Thank you for the summary article on the LLNL assessment of the debate about the last ten year temperature history and what it says (or doesn’t say). I enjoy quiet thoughtful articles like that one.
I am tired of loud voices that try to dismiss the science of global warming with simplist claims lacking in substance. Please keep up the reporting of similar studies. The public needs clear honest reporting on this subject.
And by the way; ‘climategate’ has been shown to be a complete sham.
It was and is a pathetic failed smear campaign – as every single inquiry revealed. Not that anyone who isn’t a bigot needed 6 inquiries – you just need to read the e-mails.