How Hot IS It?
The records tell unsettling tales.
By anybody’s definition, Tucson, Arizona, is a warm place. The question of just how warm started attracting special attention about 20 years ago when the government’s official climate-monitoring station began racking up a series of daily record high temperatures, with a greater number of new records set each year.
Tucson observed 21 new record daily highs in 1986 and 23 in 1987. For 1988, the number climbed again, to 38 record highs, and it jumped to 59 the following year. Remarkably, in 1988 and ’89 all but one of these milestones were achieved on days when no other station within a thousand miles set a record of its own.
The growing pile of record daily highs from the National Weather Service (NWS) office at Tucson International Airport—and the absence of corresponding new records from Davis-Monthan Air Force Base on very similar terrain just three miles away—suggested a problem with NWS monitoring equipment, specifically with a device called the HO-83 hygrothermometer, newly installed at the airport in 1986.
By itself, misleading data from one temperature sensor would be of little if any consequence. But in the early 1990s, articles in the scientific and technical literature began examining design flaws that might cause any HO-83 to read significantly higher than the real ambient air temperature and to produce higher readings the longer it remained in service. The earliest of these papers seen by Wisconsin Energy Cooperative News appeared in the American Meteorological Society’s Journal of Climate in June 1992. Author Robert Gall of the National Center for Atmospheric Research and three co-authors noted that by comparison with the equipment it replaced, the instrument at NWS Tucson tended to report daytime temperatures 2 to 3 degrees higher.
Since NWS records “are often the first that researchers turn to when studying climate changes,” the authors wrote, “It is important that biases in the data be identified and corrected before the record is hopelessly contaminated with errors and before small changes that are being searched for are lost.”
They went on to write that if there is a design problem with the HO-83, “then it is serious because these instruments have been installed at all first-order sites [weather stations operated directly by the NWS] around the country, and all of these could be providing erroneous readings.”
Dueling Data
Since Gall and his coauthors published their findings more than 15 years ago, at least a half-dozen other papers have noted HO-83 problems, with the focus on an aspiration fan intended to draw outside air into the sensor enclosure but performing poorly at the outset and deteriorating as the instrument gets dirty over time. It is common practice for records of the U.S. Historical Climatology Network (USHCN) to be adjusted to account for biasing factors such as differing times of recording data or changes in the location of monitoring equipment. But the USHCN records are evidently not adjusted to compensate for measurement errors introduced by the HO-83.
One reason for that could be that the HO-83 is installed at just 5 percent of the USHCN’s 1,221 monitoring stations, the vast majority of which are not NWS offices but rather are sited on private property and operated by citizen volunteers. Even so, in 1995 Thomas Karl, current head of the USHCN’s parent organization, the National Climatic Data Center (NCDC), and a strong proponent of the theory of human-induced climate change, authored a paper indicating replacement of older equipment with the HO-83 may have polluted the record of U.S. maximum temperature averages since the 1980s, raising them by an error of as much as 0.5 degree, Celsius.
That works out to nine-tenths of one degree, Fahrenheit, but small numbers loom large in what could be the nation’s most crucial public policy choices in a very long time. Climate science is generally agreed that the global average temperature increase since the mid-19th century is approximately 0.7 degrees Celsius or 1.26 degrees Fahrenheit.
A further reason for curiosity about what’s being measured—and how—is a temperature-sensing device called the MMTS. Far more common than the HO-83, it’s now installed at more than half the network of stations from which the USHCN compiles the nation’s temperature history.
Watts Burning?
Theoretically, the electronic MMTS should represent progress. But concerns are cropping up over a design feature that amounts to a built-in inducement to locate the instrument in places inherently biased toward warmer readings.
Published NWS siting guidelines require temperature sensors to be mounted four to six feet above ground on a level, open clearing, “so the thermometers are freely ventilated by air flow.” The guidelines state that the sensor “should be no closer than four times the height of any obstruction (tree, fence, building, etc.)” and, “The sensor should be at least 100 feet from any paved or concrete surface.”
Lots of sites don’t come close to meeting those standards, and it appears the MMTS sensors—by a recent count 55 percent of the entire network—could be part of the reason.
One key MMTS component is a cable that needs to be buried, and ongoing site surveys reveal quite a few short cables. This translates almost automatically into sensors mounted close to artificial heat sources like buildings, air conditioner exhausts, and pavement.
Anthony Watts of Chico, California, suggests a straightforward explanation. “It’s easier to dig a short trench than a long one, easier than going under sidewalks and parking lots, and that brings sensors closer to buildings and violates the 100-foot rule,” he told Wisconsin Energy Cooperative News.
Watts is in the business of selling weather station equipment and related services. A former television meteorologist, he took note of climatologist Roger Pielke Sr. lamenting the absence of comprehensive data on the physical characteristics of USHCN monitoring sites. An emeritus professor at Colorado State University–Boulder, Pielke has advocated systematic documentation of the condition of these stations and their surrounding environment. Heeding the call in June of this year, Watts launched a web site (www.surfacestations.org) and began recruiting volunteers to photograph all 1,221 sites.
Visuals Abound
It didn’t take long to collect photos of stations virtually guaranteed to produce inflated temperature readings: sensors mounted among air conditioner exhausts on flat, downtown rooftops, on brick walls above paved parking lots, on a heat-absorbing wooden deck no more than 20 feet from both an air-conditioner exhaust and the asphalt tie-down area of the local airport. One hilarious example showed a sensor (not an MMTS) a few yards from paved tennis courts and five feet from a steel burn barrel used to incinerate rubbish.
It’s not hard to imagine enthusiasts for such a survey being inclined to gather the most absurd examples possible (where’s the fun in documenting that something’s the way it’s supposed to be?) so we asked Watts if he was concerned about oversampling deficient stations.
“There’s a built-in element of randomness that I have no control over,” Watts replied. “I have no control over who collects the data or what stations they choose to document,” he said. Watts reasons that those who defend the quality of network data have just as much opportunity as do critics to furnish examples that support their views.
In any case, Watts seems to take very seriously his goal of surveying all 1,221 stations. In June, he welcomed our initial interview request, but said speculating on outcomes would be “completely wrong until a large enough sample of stations is in place.”
That doesn’t mean he’s liking what he’s seen so far. One recurring feature is the siting of temperature sensors at wastewater treatment plants. Those are troublesome sites, Watts says, “and yet it appears that there are at least a hundred throughout the USHCN record, just based on an eyeball count of my own.
“A sewage treatment plant is a heat bubble, especially in the winter,” he explains, because it’s processing vast quantities of water that’s been artificially heated and is virtually certain, especially in cold weather, to warm the surrounding air.
Watts documented 404 stations by mid-September, with 87 percent flunking published NCDC standards for error-free measurement. Fifty-five percent have site conditions associated with errors exceeding 3.6 degrees, Fahrenheit. Fifteen percent have a nine-degree error potential. Watts told us “The majority of the biases would be positive,” that is, most temperatures would read too high.
No New Problem
That temperature monitoring falls short of what’s needed to confidently assess climate trends is not a new idea. Ten years ago, participants in a United Nations conference on the World Climate Research Program expressed concern about deterioration of monitor networks worldwide, saying that absent corrective action, “The ability to characterize climate change and variations over the next 25 years will be even less than during the past quarter-century.”
The U.N.’s worries had to do in large part with a declining number of active monitoring stations, much of this resulting from the collapse of the Soviet Union. And, the U.S. network is regarded as the world’s best. Nevertheless, this summer Thomas Karl’s NCDC was still citing the 1997 U.N. conference finding that “the ability to monitor the global climate was inadequate and deteriorating,” by way of describing the NCDC’s current effort to better detect problems within U.S. monitoring systems.
In March of this year, the American Association of State Climatologists addressed an open letter to Congress saying, “All federal modernization plans proposed during the last 14 years have floundered from lack of specific funding direction and insufficient funds.” The letter warned of “the slow collapse” of the nation’s climate monitoring network, “documented in numerous professional reports during the past two decades.”
A new high-tech system called the U.S. Climate Reference Network (CRN), overseen by the NCDC, has 116 stations operating as of this year. The CRN raises high hopes for future collection of uncorrupted data, but can’t do much to resolve past problems.
Well-adjusted or Maladjusted?
Apart from any controversy over instrumentation, the USHCN mathematically adjusts temperature records for urban influences (heat from buildings, pavement, and vehicle traffic), station moves, and data-recording conducted at different times of day through history. But this begs the question: To construct long-term national temperature averages, is it necessary to use data our best scientific minds believe needs adjustment to make it truer than what the thermometers say?
Wisconsin Energy Cooperative News posed the question to Watts and to Prof. Gavin Schmidt of the Goddard Institute for Space Studies (GISS) at Columbia University in New York. Schmidt has said this summer’s correction of the GISS’ previously published U.S. temperature averages for 2000-2006—lowering them by 0.15 Celsius—is insignificant.
He told us adjustments are necessary in identifying long-term climate trends, because “we need information for as long back as possible, so while going forward, it’s important to uphold standards, we still need to be able to process the data we already have.” Urban heat effects, Schmidt added, “are not representative of regional climate change, so some adjustments are needed to deal with that,” along with station moves and different observation times.
Watts told us he believes his survey will identify enough stations producing clean data to be able to say with confidence and without introducing adjustments what the historical temperature trend has been in the United States—up, down, or neutral. And as far as the ultimate findings are concerned, he says he doesn’t have a horse in the race.
“I’m not in anyone’s employ. I don’t have a budget. I don’t have any funding. I don’t have any donations. I don’t have any connection with any organizations whatsoever,” he says. “This is just me, a guy who saw something that I thought was out of whack.”
And what if it isn’t out of whack?
“I’m not out to disprove global warming. I’m not out to do that at all. What I am out to do is to understand what we really have in this record,” Watts told us, adding that weather monitoring technology is “just something that I know and understand, so it’s an area that I could contribute to, and you know if we get down to it at the very end and we find all the good stations and their data reflects a significant positive trend, I’ll be satisfied, knowing that we can trust the data. Right now I’m not sure we can.”—Dave Hoopman, photos courtesy of Anthony Watts, www.surfacestations.org
